Large Club Control Panel

[Handeman]

Found it! I have nekkid pix and internal rats nest pix also if anyone is interested.

Excellent work!

One question, if you turn on all the circuits, could you have a 32 rocket drag race?

 

[jsdemar]

Here's a simple relay launch controller with some optional parts for safety, such as a stuck relay alarm, and over-current protection:
https://www.thrustgear.com/relayer.pdf

Here's a full multiple pad system I designed in 1996 and redesigned in 2002.
https://www.thrustgear.com/LCS02/
Some of the unique features include: simple rotary encoder to select the pad (no bank of switches); continuity tone is high pitch for good igniter, low pitch for poor igniter; pulsed tone when armed; warning alarm for stuck relay; LED's for each pad that indicate armed and continuity status.

The system I built in 1996 for the MARS(NY) club has been used at all the NYPOWER launches and a few NARAMs and NSLs. The system was copied and built by the WOOSH section also. There may be a couple other ones around that are based on it. I will try to find some photos of the launch controller and boxes.

Feel free to use whatever you see on those pages. If you have questions, just holler.

-John

 

[bobkrech]

John,

Here's a schematic for a simple relay launch controller I built a few years ago. It's for a single pad, but it can be easily scaled up to multiple pads. I put a beeper at the pad instead of at the controller. I thought it was more important to hear the "armed" alarm at the pad then at the launch control point. I use a 4-wire telephone cord to connect between the launch controller and the pad.

If the beeper is placed at the launch controller only one wire in needed per pad plus two wires for power and ground. A 4-wire cable could handle 2 pads, and an 8-wire cable could handle 6 pads.

I'll bring my launch controller the next time I make it to a launch.

Dave

John (JAL#)

1.) Dave's launcher is one of the least expensive implementations of a launcher. It uses only 1 battery, and because it uses a relay, the control cable can be cheap telephone wire as it only needs to carry about 0.1 amps to pull in the launch relay, and the 10+ amps that will be required by a non-relay, 12 volt system.

You can actually use only two wires to connect the controller to the relay box with a slight modification to the circuit and still maintain the same functioality.

2.) Key switches are expensive and in many cases the most probable failure point in the launcher. There is no NAR requirement for a key switch interlock. The NAR launcher requirement calls for a removable interlock to prevent unauthorized or unintentional launches. A simple jack on the controller requiring a shorted plug to be inserted into the controller meets the NAR requirement.

3.) Voltages greater than 12 volts don't buy anything. Current is what activates your igniter, not voltage. And the more voltage you supply, the more current your batteries have to supply. (ohm law: I=V/R)

For example Estes igniters have an all-fire current of 2 amps and a resistance of 0.8 ohm according to the Estes website. TR??? The minimum voltage across the igniter is equal to the resistance times the current or 2 amps x 0.8 ohm = 1.6 volts. If you use a 12 volt battery, the resistance of the wiring must be low enough so you can actually draw 2 or more amps throught the igniter circuit and the igniter. (That 5.2 ohms is the maximum reisistance you can have in a 12 volt circuit for an Estes ingiter, but in reality, you need to have a lower resitance if you want a prompt ignition and that means you will draw more current from the battery.

The power delivered by the ignition system determines how long it takes to activate the igniter. Power is current squared multiplied by the resistance. For an Estes igniter this is 2 amps ^2 x 0.8 ohms = 3.2 watts, however the time to actuate the igniter is not defined, and may be several seconds. To insure a prompt ignition, most folks look for at least currents 2 to 3 times the minimum all-fire current corresponding to a power of 12.8 watts or 28.8 watts respectively. Thisi requires a much lower circuit resistance. You can run 14 gauge wire and use 20 amp switches everywhere or use a relay and 14 gauge wire for the short run igniter cirucit and small gauge wire to activate the relay.

Bob

 

[jsdemar]

It's a very good idea to have a way to disarm at the pad and not count on the switches back at the main controller, especially in a relay system.

Bob's suggestion of only two wires without a second battery had a major vulnerability. Simply shorting the leads anywhere along the way will launch the rocket. No power is needed.

Likewise, with power being back-fed to the main controller from the pad, a short at a connector or a crimped cable could apply power to the relay coil. The savings of eliminating a cheap, low-capacity battery at the main controller doesn't justify the risk, in my opinion.

With only the control voltage and a ground (and an optional continuity signal), a failure in the control cable or the connectors will not launch the rocket.

Some readers may not be aware of how many close calls there have been with relay-based systems that have lit motors as the clips were attached, or when the arming switch is toggled at the pad. Relays get welded shut after use and abuse with no protection. This is why I have added alarms to my circuits for stuck relays. And I've also added a cheap "auto reset thermal breaker" to limit the current during dead shorts. It saves on the relay and the wiring.

-John D.

 

[Bone Daddy]

Yep, that's bright. I noticed those on the breadboard in your earlier pix. Great price.

How do you mount those to a panel?

My fav source is superbright leds dot com. They have T1.75 ~8000 MCD LEDs in colors for about $.50 each. Drive them with about 18ma and fully visible in bright daylight.

I like the low profile panel lenses for mounting but those are getting harder to source.

I use the ubiquitous super glue. May have to rough up the surface a bit. If all else fails I use epoxy.

Yeah, they rock too.

I like (or maybe shouldn't like) EG because I can always find a bunch of cool things to buy. One of my favorites was actual silicon wafers used for ic's. I bought three for a couple of bucks each. Too cool. And then there was the time I buoght the "Instruction and Maintenance Manual" for a 1964 radiological survey meter. Yeah, only the manual but how cool is that? The schematic alone was worth the couple of bucks I paid for it. And the list goes on and on.

 

[Bone Daddy]

I was born with the curse of having both the curiosity and the scientist gene mutation. (On top of that, I’m easily distracted, so the first thing I look at in posts is the pictures. If you suffer from this affliction also, go ahead and jump right down to the picture descriptions. I labeled them so they are easy to find.)

Now that we have all that out in the open, I decided to take an empirical look at the whole resistor/led/igniter thing. Since this discussion is centering on a 12 v system and I still don’t have a 12v battery handy, I decided to up the ante and use 18v. That’s right, 18 v, two 9v batteries in series.

The design goal was simple: swap out the current limiting resistor with a progressively lower value until the igniter is set off or the led melts, which ever comes first.*

Parts list:
18v battery
Run of the mill green led
100K and 560, 330, 220, 100 1/4 watt and 18 ohm 1.5 watt resistors
Standard Estes igniters** (1.2 ohm)

What happened? Cutting right to the chaste, the 10 ohm resistor melted the led. The igniter was never set off. But, the resistors did get a bit toasty towards the lower end of the values. At 12v, a ½ watt resistor would probably be a better choice.

After the led melted, I went ahead and applied the 18v straight to the igniter. Ignition, but unexpectedly, the bridge wire didn’t melt. It must be the heat from the ignited motor that melts the wire. ***

Next question: What would happen if we eliminated the led? **** Same drill as above w/o led.

All the way down to 100 ohm. Nothing. I’m going to get my junk box and pull out some values between 100 and 18. Be right back.

OK, where were we? Oh yeah………….

33 ohm 1 watt: resistor starts getting really hot. Battery still sees a dead short.

6 ohm 3 watt: Bingo. Houston we have liftoff.

Conclusions: A standard Estes igniter has a resistance of about 1.2 ohms (by my measure). To set off the pyrogen, a total resistance somewhere less than 33 ohms is need. A continuity indicator consisting of a led and pretty much any resistor that doesn’t melt it can be safely used. And this is using a standard led, not a low current led.

This makes sense if we look at it though the lens of Ohm’s Law (as stated above).

Let’s assume a .5 (easy math) voltage drop across a typical led (efficient super bright led will drop anywhere from 1.25 or more volts using less current and giving off much more light). With an 18v battery, we now work with 17.5 volts. With a 100 (easier math still) ohm resistor we are only pulling 175 mA or 0.175 amps. Compare to the igniter and 33 ohm which draws 0.530 amps and still doesn’t trip the igniter.

Picture descriptions are here!
Pix 1shows the breadboard setup I used.
Pix 2 is a close up of the source of my 18v.
Pix 3 is a close up of the resistor/led/igniter circuit.


* If you have never looked at an led with a loop or other source of magnification, go ahead. You be astounded at how thin the wire connecting the anode to the cathode is. This is the wire we are protecting from melting. If you do let a bit to much current through the led – oh go ahead and do this too, they’re cheap – this wire will glow red hot for a short period of time before melting. That thing that looks like a bowl? That's the reflector.

** Will someone be nice enough to repeat this experiment with those uppity Quest igniters? My guess is there will be no difference.

*** Admittedly, this was a sample of n=1. It would be great if others repeated this experiment. I had already trashed a slew of igniters getting to this point.

**** Actually did this before when I was designing the touch screen controller. Repeated here anyway.

 

[Bone Daddy]

Jal3

Be careful, electronics is another addictive hobby. You don't need to understand all the physics behind it to design and build all kinds of wonderful things. (I sure as heck don't.)

With that said:

The best book I've found for learning the practical ins and outs is:

Practical Electronics for Inventors
isbn 0-07-058078-2
This book taught me the power of water analogies.

At Radio Shack buy all the Mini-Notebooks by Forrest M. Mims III. If RS no longer carries these then the world really is coming to an end.

Buy a breadboard like the one in my pixs. A breadboard lets you play around with a circuit without soldering. I breadboarded my launch controller before building it even though it's a pretty straightforward circuit. A quick web search will tell you everything you need or PM me.

A whole world of wonder awaits you.

Regarding the voltmeter in your control panel. I wouldn't put one in at this time. It's a level of complexity you just don't need at his point in time. Just buy a cheap VOM (volt ohm meter) and keep it in your range box. Resist the temptation to make things more complicated than they need be. Always start with the minimum needed to get the job done safely. Add features as needed.

And most of all have fun.

 

[Bone Daddy]

I really am still only an idiot.

My new system uses 12v. Just look at the picture. 1,2,3,4,5,6,7,8 batteries. 8 x 1.5 equals 12!

It was the one it replaced that used 9v. Ooooooooops.

I'd redo everything with 12v, but it really doesn't matter does it?

Chagriningly yours

BD

 

[JAL3]

Ok. I'll throw out a few comments for consideration.

I guess I am ok with the voltmeter and lamp1, but not the piezo. The LED inline with the ignitor is ok, you can limit that current by design, but the piezo might draw 50 to 100 milliamps or more and you might light or cook off some low current ignitors like the new Quest ones, or eMatches based ignitors that your members might use. If the purpose of the piezo is to provide audible warning that the panel is armed, then you can just connect it parallel to the lamp1 and voltmeter and that will be good. The pad LEDs will continue to give you pad status.

Now you also want to limit current flow through the LED for the same reason. LEDs can work well with between 8 and 20 milliamps depending on the type, but you'll want to keep that as low as you can and still see it. So a series resistor inline with the LED is a good idea (actually you really do need a resistor). The value will depend on the LED and possibly the length/guage of the other wiring. That can be calculated or even simple trial and error will work (tip: test outdoors in the sunlight).

That said, if you really do need to drive a higher current LED (for visibility in bright sunlight, for example), then you might need to consider adding a simple transistor or darlington transistor type circuit to minimize current through the ignitor. Not too tough but it will add complexity.

Thanks for your commentery.

Here are my response questions:

1. Something I don’t understand about what you say on the piezo: the way I have it right now, current can flow through the piezo when a circuit through an igniter is completed but only through the current limited LED unless Sw3 is closed. How is this a problem?
2. also, if the piezo were hooked up like the voltmeter, it would buzz any time the power is on. I want it to buzz whenever there is a complete circuit through an igniter. How do I accomplish that?
3. I have added a resistor in line with the LED, value to be determined later.
4. Is the LED oriented correctly? I’m fuzzy on the symbols.
5. I do want an ultra bright LED to be visible. Fry catalog “burn out your eyeballs” style. I’m afraid transistor is just a word associated with radios to me and Darlington is just a small town I once visited. Can you elaborate?

 

[JAL3]

OK,John... here's where you might be getting into a bit of trouble/undesired consequences:



Not a bad idea, but you probably want to wire it so that when the user plugs in the remote switch, it cuts out the possibility of the panel-mounted switch from firing - that way there's only one finger that can cause a launch, and everyone should know who it is... its called positive control.



Good idea to be able to read the battery voltage. You might also want to add an current indicator like an micro-amp meter there, as well, to aid in trouble-shooting.



Unintended consequence of this is that the lamp will continually draw power from the battery. That may, or may not, be a problem. You can minimize the current draw by substituting a voltage limiting resistor/LED in series in place of the lamp. Remember the discussions about the new Quest Q2G2 igniters that would pop when put into a circuit that had a little lamp used as the continuity indicator? The lamp allowed a lot more current to be drawn than the LED/resistor combo: the Q2D2's wouldn't fire with a resistor/LED combo as the continuity indicator.



Remember that an LED is just a diode that iluminates. Without some way of limiting the current through the diode, it'll conduct everything you throw at it until it burns up. Thus, a current limiting resistor must be placed in series with the LED so that only a small amount of current (20 ma or less IIRC) is needed to light an LED to it's normal max brightness.

I've just read through the thread for the first time, tonight - a lot of good information there! Thanks for starting, and continuing to feed, the thead!

Wayne

I appreciate your input also and have some questions for you too:

1. I added a rotary switch to choose between launch triggers
2. I added an amp meter. is it in the right place and won’t it read only when current is shot through an igniter? if that is the case, are there any that hold their reading for a while?
3. I understand in general what you say about the lamp drawing current but:
a. I do want to be safe with ematches and the Quest igniters
b. if the lamp is serving as a pilot for the power source and is located where shown, how does current get to the igniter to set it off until the “trigger” switch is closed?
4. an as yet unspecified resistor has been added in line with the LED

 

[JAL3]

John (JAL#)

1.) Dave's launcher is one of the least expensive implementations of a launcher. It uses only 1 battery, and because it uses a relay, the control cable can be cheap telephone wire as it only needs to carry about 0.1 amps to pull in the launch relay, and the 10+ amps that will be required by a non-relay, 12 volt system.

You can actually use only two wires to connect the controller to the relay box with a slight modification to the circuit and still maintain the same functioality.

2.) Key switches are expensive and in many cases the most probable failure point in the launcher. There is no NAR requirement for a key switch interlock. The NAR launcher requirement calls for a removable interlock to prevent unauthorized or unintentional launches. A simple jack on the controller requiring a shorted plug to be inserted into the controller meets the NAR requirement.

3.) Voltages greater than 12 volts don't buy anything. Current is what activates your igniter, not voltage. And the more voltage you supply, the more current your batteries have to supply. (ohm law: I=V/R)

For example Estes igniters have an all-fire current of 2 amps and a resistance of 0.8 ohm according to the Estes website. TR??? The minimum voltage across the igniter is equal to the resistance times the current or 2 amps x 0.8 ohm = 1.6 volts. If you use a 12 volt battery, the resistance of the wiring must be low enough so you can actually draw 2 or more amps throught the igniter circuit and the igniter. (That 5.2 ohms is the maximum reisistance you can have in a 12 volt circuit for an Estes ingiter, but in reality, you need to have a lower resitance if you want a prompt ignition and that means you will draw more current from the battery.

The power delivered by the ignition system determines how long it takes to activate the igniter. Power is current squared multiplied by the resistance. For an Estes igniter this is 2 amps ^2 x 0.8 ohms = 3.2 watts, however the time to actuate the igniter is not defined, and may be several seconds. To insure a prompt ignition, most folks look for at least currents 2 to 3 times the minimum all-fire current corresponding to a power of 12.8 watts or 28.8 watts respectively. Thisi requires a much lower circuit resistance. You can run 14 gauge wire and use 20 amp switches everywhere or use a relay and 14 gauge wire for the short run igniter cirucit and small gauge wire to activate the relay.

Bob

Thanks for the information. I feel lucky that Dave Hein sometimes visits my club and I get to see some of the cool toys he comes up with. It can be intimidating but it is fun.

Right now my ideas for what I want to do are in flux. I am playing out the design process here because I am not qualified to do it myself and I am learning. I have over arching plans for what I want to accomplish but not for most of how I want to do it.

I plan to keep up this process, refining as I go and hopefully understanding more as I go as well. I expect everything to gell eventually and then I will actually start drilling holes is the great big enclosure I bought over a year ago. If I'm feeling lucky, I might even put some wires in it!:y:

 

[JAL3]

Jal3

Be careful, electronics is another addictive hobby. You don't need to understand all the physics behind it to design and build all kinds of wonderful things. (I sure as heck don't.)

With that said:

The best book I've found for learning the practical ins and outs is:

Practical Electronics for Inventors
isbn 0-07-058078-2
This book taught me the power of water analogies.

At Radio Shack buy all the Mini-Notebooks by Forrest M. Mims III. If RS no longer carries these then the world really is coming to an end.

Buy a breadboard like the one in my pixs. A breadboard lets you play around with a circuit without soldering. I breadboarded my launch controller before building it even though it's a pretty straightforward circuit. A quick web search will tell you everything you need or PM me.

A whole world of wonder awaits you.

Regarding the voltmeter in your control panel. I wouldn't put one in at this time. It's a level of complexity you just don't need at his point in time. Just buy a cheap VOM (volt ohm meter) and keep it in your range box. Resist the temptation to make things more complicated than they need be. Always start with the minimum needed to get the job done safely. Add features as needed.

And most of all have fun.

Thanks for the additions to my reading list. I will search them out.

As I told Bob, right now everything is a gedanken experiment. I want to understand why things are the way they are before I go buying any more components than I already have.

 

[JAL3]

Todays contribution to the process includes the following:

1. resistor added inline with the continuity LED
2. a rotary switch to choose between launch ignition switches; the deadman is still under consideration as I mull over a few things
3. an amp meter because you can never have too many guages on your frankenstein monster and because I might actually understand its output someday; be advised, I have not "hooked one up" since undergrad days and I cannot even say if it is in the right place.

I did post some questions to specific suggestions a few posts back. I am having a hard time udnerstanding why the piezo or the lamp would be dangerous to the igniter since current flowing through them does not get to the igniter unless the switch is closed.

Another question that occurs is 1. what is the best way of making connections within the control box? Should they be soldered, crimped, screw down terminal, electricians tape, conducting CA, ?

Inquiring minds want to know

 

[flight4]

Excellent work!

One question, if you turn on all the circuits, could you have a 32 rocket drag race?

Yes, Indeed you can!!!!!

It will also launch some or all pads, sequentially or randomly, at intervals from 100ms and up. That's really cool.

 

[JAL3]

I suppose I am a bit bummed out that most people spent new years day doing things besides reviewing my controller plans but I'm not surprised

I, on the other hand have had a productive day.

I'm still waiting for comments and explanations from previous posts but I have revised my plans so far.

In this installment, the single launch circuit has been replaced by a cluster of 8 pads. This cluster is activated by a single switch and has an LED pilot.

The jack for the single igniter lead pair has been replaced by a yet to be determined connector to run out to the pad.

In addition to the previous questions still outstanding, I submit the following drawing.

On the connector to the pad, I assumed a 10 conductor wire and plug.

the numbers on the plug correspond to the pad number of the cluster. connector 10 is used for the return current and you will notice that I have shorted it to connector 9 since that was not being used for anything. My reason is an assumption that the extra conductor in the wire already exists. Won't doubling the wire lower the resistance at least on the return leg? If so, is it enough to do any good?

I also added an LED and resistor combination to indicate which lead of the rotary switch is active.

 

[n5wd]

I appreciate your input also and have some questions for you too:
1. I added a rotary switch to choose between launch triggers

Well, looking at Rev1.c(#2) OK - looks like it should work. The idea about a deadman switch has a whole lot of merit, espcially if you're going to be handing it to a "guest LCO". One place you can find heavy-duty switches configured in a pistol grip is from an electronics house that deals in traffic control devices (TTI in San Antonio is one source I'd look at).

2. I added an amp meter. is it in the right place and won’t it read only when current is shot through an igniter? if that is the case, are there any that hold their reading for a while?

As you've got it installed, it will continually show how much current is being at all times (when SW1 is closed). There's be a minute amount being drawn through the voltmeter, a fair amount drawn through Lamp1, a little through PZ1 when the igniter leads are attached to an igniter or shorted, plus a little bit through R1/LED1.

3. I understand in general what you say about the lamp drawing current but:
a. I do want to be safe with ematches and the Quest igniters

If you keep your current through the igniter to about 10ma (the R1/LED1 current)you should be fine IIRC - the allfire current on Q2D2 igniters is 20ma (you might want to double check my memory - someone either here or on RP did a bunch of testing to see just when they would always fire and I believe it was at 20ma).

b. if the lamp is serving as a pilot for the power source and is located where shown, how does current get to the igniter to set it off until the “trigger” switch is closed?

I may have confused you when talking about the pilot light. In the original 1.c verion, the lamp does not draw current through the igniter - but it does continually drawn current from the battery, which may not necessarily be what you want.

When I was talking about the current draw through the igniter, I was talking about the fact that, at that time, you did not have a current limiting resistor in series with LED1. That would have allowed max current to flow through the LED and igniter until either (a) the LED blew or (b) the igniter opened up.

4. an as yet unspecified resistor has been added in line with the LED

Somewhere earlier in the thread, someone did the Ohm's law equation - I think it was a 1K ohm resistor sinks limits the current to about 10ma through the LED which should not be enough to set even the Q2D2's off (I don't know, off hand, which ematch you'll be using or what their firing current is).

Sorry we didn't respond earlier - we've got our grand daughter staying with us and at 19 months, she requires constant supervision when awake! :y: so most computer time is scheduled after the little darling is asleep!

 

[flight4]

Thanks for your commentery.

Here are my response questions:

1. Something I don’t understand about what you say on the piezo: the way I have it right now, current can flow through the piezo when a circuit through an igniter is completed but only through the current limited LED unless Sw3 is closed. How is this a problem?
2. also, if the piezo were hooked up like the voltmeter, it would buzz any time the power is on. I want it to buzz whenever there is a complete circuit through an igniter. How do I accomplish that?
3. I have added a resistor in line with the LED, value to be determined later.
4. Is the LED oriented correctly? I’m fuzzy on the symbols.
5. I do want an ultra bright LED to be visible. Fry catalog “burn out your eyeballs” style. I’m afraid transistor is just a word associated with radios to me and Darlington is just a small town I once visited. Can you elaborate?

Ok, I saw your later schematics and also this post. I guess I'm getting a little lost. But that's just me.

1. Yes, now it is current limited, but it wasn't before. With the piezo and the LEDs, even with the resistors, you have a series/parallel circuit. True your limiting resistors will keep the PED current to a safe level, but then maybe your piezo won't sound.

2. I guess I just don't understand why you want to hear when one (or more) ignitors are hooked up. What does it tell you that the continuity LEDs don't? First guy hooks up, piezo sounds. All others hook up, no change. Piezo keeps going until last rocket is launched. It's your circuit.

3. Good.

4. The LEDs are oriented correctly. The bar is the cathode and connects to the more negative voltage. Current flows and the LED lights up.

5. Ultrabright LEDs are great and values to 8000 MCD and higher are readily available. Give them enough current, say 10 to 18 ma, and they will fry your eyeballs. Especially at a night launch. A transistor has many uses but I meant as a switch. The advantage is you can do a lot of work with very little current in. A darlington transistor (also called a darlington pair), is a special kind of transistor or transistor circuit that provides very high gain. Meaning also extremely low input current. Google "transistor circuits" for many examples on the web. transistors require additional resistors and will make the circuit more complicated. Best to leave them out and keep your circuit simple unless you really need them.

 

[flight4]

I suppose I am a bit bummed out that most people spent new years day doing things besides reviewing my controller plans but I'm not surprised

I, on the other hand have had a productive day.

I'm still waiting for comments and explanations from previous posts but I have revised my plans so far.

In this installment, the single launch circuit has been replaced by a cluster of 8 pads. This cluster is activated by a single switch and has an LED pilot.

The jack for the single igniter lead pair has been replaced by a yet to be determined connector to run out to the pad.

In addition to the previous questions still outstanding, I submit the following drawing.

On the connector to the pad, I assumed a 10 conductor wire and plug.

the numbers on the plug correspond to the pad number of the cluster. connector 10 is used for the return current and you will notice that I have shorted it to connector 9 since that was not being used for anything. My reason is an assumption that the extra conductor in the wire already exists. Won't doubling the wire lower the resistance at least on the return leg? If so, is it enough to do any good?

I also added an LED and resistor combination to indicate which lead of the rotary switch is active.

Is the switch labeled SW the deadman switch? Is the intent to disable continuity, the piezo and all (and ignition of course).

 

[JAL3]

Well, looking at Rev1.c(#2) OK - looks like it should work. The idea about a deadman switch has a whole lot of merit, espcially if you're going to be handing it to a "guest LCO". One place you can find heavy-duty switches configured in a pistol grip is from an electronics house that deals in traffic control devices (TTI in San Antonio is one source I'd look at).



As you've got it installed, it will continually show how much current is being at all times (when SW1 is closed). There's be a minute amount being drawn through the voltmeter, a fair amount drawn through Lamp1, a little through PZ1 when the igniter leads are attached to an igniter or shorted, plus a little bit through R1/LED1.



If you keep your current through the igniter to about 10ma (the R1/LED1 current)you should be fine IIRC - the allfire current on Q2D2 igniters is 20ma (you might want to double check my memory - someone either here or on RP did a bunch of testing to see just when they would always fire and I believe it was at 20ma).



I may have confused you when talking about the pilot light. In the original 1.c verion, the lamp does not draw current through the igniter - but it does continually drawn current from the battery, which may not necessarily be what you want.

When I was talking about the current draw through the igniter, I was talking about the fact that, at that time, you did not have a current limiting resistor in series with LED1. That would have allowed max current to flow through the LED and igniter until either (a) the LED blew or (b) the igniter opened up.



Somewhere earlier in the thread, someone did the Ohm's law equation - I think it was a 1K ohm resistor sinks limits the current to about 10ma through the LED which should not be enough to set even the Q2D2's off (I don't know, off hand, which ematch you'll be using or what their firing current is).

Sorry we didn't respond earlier - we've got our grand daughter staying with us and at 19 months, she requires constant supervision when awake! :y: so most computer time is scheduled after the little darling is asleep!

First things first, you have NOTHING to apologize for. In the first place, grandkids take priority over everything. Even I know that! I raised my sister's 3 kids for 12 years at the same time I took care of my mom. 3 grandkids divided into one grandma gives an parental uncle quotient approaching infinity.

Also, I know its a holiday weekend and priorities are elsewhere.

I like the deadman idea and will likely incorporate it. I'm just mulling a few things over in my mind for right now. Thanks for the info about TTI.

I'm fuzzy on what an amp meter can do for me in any event. I understand that it might be handy for troubleshooting but what you described is what I understand based on my drawing. I really don't have a clue.

Can you check me on this: there will be no current through the LED1/resistor even if all switches are closed unless there is an igniter (or something) hooked to the jack to complete the circuit. Is this correct?

Thanks for the other info too. I actually recognized Ohm's law some posts back but have not tried to plug in any number as yet. I want to get clear on my concepts first.

 

[JAL3]

Ok, I saw your later schematics and also this post. I guess I'm getting a little lost. But that's just me.

1. Yes, now it is current limited, but it wasn't before. With the piezo and the LEDs, even with the resistors, you have a series/parallel circuit. True your limiting resistors will keep the PED current to a safe level, but then maybe your piezo won't sound.

2. I guess I just don't understand why you want to hear when one (or more) ignitors are hooked up. What does it tell you that the continuity LEDs don't? First guy hooks up, piezo sounds. All others hook up, no change. Piezo keeps going until last rocket is launched. It's your circuit.

3. Good.

4. The LEDs are oriented correctly. The bar is the cathode and connects to the more negative voltage. Current flows and the LED lights up.

5. Ultrabright LEDs are great and values to 8000 MCD and higher are readily available. Give them enough current, say 10 to 18 ma, and they will fry your eyeballs. Especially at a night launch. A transistor has many uses but I meant as a switch. The advantage is you can do a lot of work with very little current in. A darlington transistor (also called a darlington pair), is a special kind of transistor or transistor circuit that provides very high gain. Meaning also extremely low input current. Google "transistor circuits" for many examples on the web. transistors require additional resistors and will make the circuit more complicated. Best to leave them out and keep your circuit simple unless you really need them.

I'll probably get confused with multiple posts before all this is over with as well!

The purpose of the piezo, in my mind, is not so much a continuity check as it is a warning that there is a "hot" circuit hooked up to one or more igniter. What I want is for the buzzer to sound whenever something is hooked up and ready to fire. If the switch to the individual pad is open or if the switch to a whole cluster of pads is open, it not sound unless, by some path, there is actually an igniter hooked up that is in danger of firing.

EXAMPLE; Everybody goes out and hooks up their rockets on pads 1-8 of cluster A. The controller is safed and the cluster is turned off as are the individual pads. When when everyone is back behind the line and launches are ready to commence, the LCO turns on the controller. No buzzer sounds because the switch to the complex is still open as are the switches for the individual pads. The LCO then activates the switch for cluster A. There is still no tone because the individual pads are safed. He announces the flight on 1A and closes that switch. A tone sounds because pressing the launch button at that point will complete the circuit and fire the igniter. When the rocket is launched, the 1A switch is opened and the tone ceases. Next the same thing happens on 1B and then 1C. The next flight after that is a drag race on 1d, 1E and 1F. All three switches are closed and the tone sounds. It does not tell which pad is ready to fire, it is only a warning that such a pad (in this case 3 of them) is active. They are launched, the switches open and the tone ceases. 1G proves to be problematical. The switch is closed and there is no tone or weak tone. The LCO interprets this as a problem at the pad and scrubs that launch telling the flyer to go check things out when the range is opened again.

Does this make sense?

 

[n5wd]

I'm fuzzy on what an amp meter can do for me in any event. I understand that it might be handy for troubleshooting but what you described is what I understand based on my drawing. I really don't have a clue.

Think of the amp meter as a way of telling when things are going right (by noticing just how much current is being drawn on a normal launch (and again, and again, etc.) so that if something does go wrong (a rocket refuses to launch, no matter what you do, a cluster flyer consistently has problems, etc.) you've got some information instead of just guessing what's going on. For example, I attended a launch where one rack seemed to have a whole lot of problems launching - turns out not much current was being drawn, which was probably due to an incomplete connection (a high resistance). When the current was looked at, it became a matter of quick troubleshooting versus what could have been a long drawn-out affair.

If you don't like extra bells and whistles, though... an amp meter is NOT needed - it's an extra piece of information.

Can you check me on this: there will be no current through the LED1/resistor even if all switches are closed unless there is an igniter (or something) hooked to the jack to complete the circuit. Is this correct?

That's correct - as long as there's nothing that makes the circuit complete (assuming there's no other short, somewhere) no current will be drawn.

 

[JAL3]

Is the switch labeled SW the deadman switch? Is the intent to disable continuity, the piezo and all (and ignition of course).

OOPS. I forgot to label it. That switch is supposed to activate the cluster of pads that are connected to it.

In the grand scheme, there will be several clusters. Each has its own cluster switch and each pad in the cluster has a switch as well. It is the cluster on/off I mentioned in the previous post.

 

[JAL3]

Think of the amp meter as a way of telling when things are going right (by noticing just how much current is being drawn on a normal launch (and again, and again, etc.) so that if something does go wrong (a rocket refuses to launch, no matter what you do, a cluster flyer consistently has problems, etc.) you've got some information instead of just guessing what's going on. For example, I attended a launch where one rack seemed to have a whole lot of problems launching - turns out not much current was being drawn, which was probably due to an incomplete connection (a high resistance). When the current was looked at, it became a matter of quick troubleshooting versus what could have been a long drawn-out affair.

If you don't like extra bells and whistles, though... an amp meter is NOT needed - it's an extra piece of information.

Can you check me on this: there will be no current through the LED1/resistor even if all switches are closed unless there is an igniter (or something) hooked to the jack to complete the circuit. Is this correct? [\QUOTE]

That's correct - as long as there's nothing that makes the circuit complete (assuming there's no other short, somewhere) no current will be drawn.

clear as a bell.

Thanks.

 

[flight4]

I'll probably get confused with multiple posts before all this is over with as well!

The purpose of the piezo, in my mind, is not so much a continuity check as it is a warning that there is a "hot" circuit hooked up to one or more igniter. What I want is for the buzzer to sound whenever something is hooked up and ready to fire. If the switch to the individual pad is open or if the switch to a whole cluster of pads is open, it not sound unless, by some path, there is actually an igniter hooked up that is in danger of firing.

EXAMPLE; Everybody goes out and hooks up their rockets on pads 1-8 of cluster A. The controller is safed and the cluster is turned off as are the individual pads. When when everyone is back behind the line and launches are ready to commence, the LCO turns on the controller. No buzzer sounds because the switch to the complex is still open as are the switches for the individual pads. The LCO then activates the switch for cluster A. There is still no tone because the individual pads are safed. He announces the flight on 1A and closes that switch. A tone sounds because pressing the launch button at that point will complete the circuit and fire the igniter. When the rocket is launched, the 1A switch is opened and the tone ceases. Next the same thing happens on 1B and then 1C. The next flight after that is a drag race on 1d, 1E and 1F. All three switches are closed and the tone sounds. It does not tell which pad is ready to fire, it is only a warning that such a pad (in this case 3 of them) is active. They are launched, the switches open and the tone ceases. 1G proves to be problematical. The switch is closed and there is no tone or weak tone. The LCO interprets this as a problem at the pad and scrubs that launch telling the flyer to go check things out when the range is opened again.

Does this make sense?

Yes, that does make sense. Sorry about all the back and forth.

You still might want to think about the location of that piezo in relation to your continuity LEDs. Since it is in series with the battery and the LEDs it will tend to limit LED current. It will also factor into choosing the LED limiting resistors. The LEDs are parallel so they'll get dimmer and dimmer with more ignitors hooked up, while the piezo gets marginally louder.

I did look up the Quest no fire spec and it is 150ma. Other sources put the Quest fire current at 120ma. According to Quest their all fire current is 350ma. In any case it would appear you are ok if you keep the LED and piezo current below 20ma. Obviously stay away from higher current buzzers and incandescent lamps.

 

[JAL3]

You still might want to think about the location of that piezo in relation to your continuity LEDs. Since it is in series with the battery and the LEDs it will tend to limit LED current. It will also factor into choosing the LED limiting resistors. The LEDs are parallel so they'll get dimmer and dimmer with more ignitors hooked up, while the piezo gets marginally louder.

.

I'm open to suggestions. How would you recommend achieving the stated goal with a different wiring scheme?

 

[jsdemar]

If the purpose of the ammeter is to check continuity, it won't give you any more information than the LED. If the purpose is to read the firing current, it won't be fast enough. If you want to troubleshoot the system, just use an external DVM and not bother with the ammeter. One less thing to fail, too... since it's in series with everything, the system is dead with a bad ammeter.

In your latest schematic (multipad), you may want to think about adding a switch in series with the continuity piezo so that you only hear it when you want to check continuity. It can be distracting running a busy range when a tone is always in your ear. You can also move the continuity beeper to its own series path with its own limiting resistor and bypass all the individual LED circuits per pad. That way, the tone loudness won't change as pads are selected. But, you will have twice the current through an igniter when both the piezo on an LED are switched in. If you limit each to 10mA, then you'll stay below 20mA.

The no-fire current is fairly high for almost all igniters and e-matches (>200mA). A low-current ematch is around 100mA no-fire. Here's some info on e-matches: https://www.vernk.com/Igniters.htm
and igniter firing in general: https://www.vernk.com/Igniters.htm

-John D

 

[Handeman]

I'll probably get confused with multiple posts before all this is over with as well!

The purpose of the piezo, in my mind, is not so much a continuity check as it is a warning that there is a "hot" circuit hooked up to one or more igniter. What I want is for the buzzer to sound whenever something is hooked up and ready to fire. If the switch to the individual pad is open or if the switch to a whole cluster of pads is open, it not sound unless, by some path, there is actually an igniter hooked up that is in danger of firing.

EXAMPLE; Everybody goes out and hooks up their rockets on pads 1-8 of cluster A. The controller is safed and the cluster is turned off as are the individual pads. When when everyone is back behind the line and launches are ready to commence, the LCO turns on the controller. No buzzer sounds because the switch to the complex is still open as are the switches for the individual pads. The LCO then activates the switch for cluster A. There is still no tone because the individual pads are safed. He announces the flight on 1A and closes that switch. A tone sounds because pressing the launch button at that point will complete the circuit and fire the igniter. When the rocket is launched, the 1A switch is opened and the tone ceases. Next the same thing happens on 1B and then 1C. The next flight after that is a drag race on 1d, 1E and 1F. All three switches are closed and the tone sounds. It does not tell which pad is ready to fire, it is only a warning that such a pad (in this case 3 of them) is active. They are launched, the switches open and the tone ceases. 1G proves to be problematical. The switch is closed and there is no tone or weak tone. The LCO interprets this as a problem at the pad and scrubs that launch telling the flyer to go check things out when the range is opened again.

Does this make sense?

Your explanation makes sense, but your circuit doesn't work that way. The way it works is:

• All rockets are loaded and igniters are hooked up.
• The pad is turned on with key switch - No buzzer
• Switch SW is closed. Buzzer sounds because current flows from battery, thru key switch, thru buzzer, thru SW, thru parallel paths of R1/LED1, thru connected igniters and back to pins 9/10 of the connector, thru amp meter, and back to battery. The buzzer will continue to sound until all igniters are removed from the circuit, or SW is opened or key switch is opened.

WARNING Depending on the current draw of the buzzer and the fire current of the igniter, with SW closed, pressing a SW3 could launch the rocket without SW1 or SW2 being closed because the current flows through the buzzer to SW, bypassing the SW1 and SW2 switches.

I'm not sure why you want the buzzer to sound when ignition current is supplied to the igniter. You have LED1 that tells you there is continuity through the igniter. When you push the SW3 button, the rocket launches or it doesn't, that should be plenty of indication that it worked or didn't. I don't understand the value added that the buzzer gives you.


If you want it to work the way you described, you have to use double pole switchs for SW3. One pole is used as your current schematic shows, the second pole would supply voltage to the buzzer making it sound. This would not let the buzzer give an audio indication of igniter status, only the SW3 was closed.

 

[JAL3]

Your explanation makes sense, but your circuit doesn't work that way. The way it works is:

• All rockets are loaded and igniters are hooked up.
• The pad is turned on with key switch - No buzzer
• Switch SW is closed. Buzzer sounds because current flows from battery, thru key switch, thru buzzer, thru SW, thru parallel paths of R1/LED1, thru connected igniters and back to pins 9/10 of the connector, thru amp meter, and back to battery. The buzzer will continue to sound until all igniters are removed from the circuit, or SW is opened or key switch is opened.

WARNING Depending on the current draw of the buzzer and the fire current of the igniter, with SW closed, pressing a SW3 could launch the rocket without SW1 or SW2 being closed because the current flows through the buzzer to SW, bypassing the SW1 and SW2 switches.

I'm not sure why you want the buzzer to sound when ignition current is supplied to the igniter. You have LED1 that tells you there is continuity through the igniter. When you push the SW3 button, the rocket launches or it doesn't, that should be plenty of indication that it worked or didn't. I don't understand the value added that the buzzer gives you.


If you want it to work the way you described, you have to use double pole switchs for SW3. One pole is used as your current schematic shows, the second pole would supply voltage to the buzzer making it sound. This would not let the buzzer give an audio indication of igniter status, only the SW3 was closed.

I appreciate the input. Let me address the reason for the buzzer first. To me, an audible tone is more noticable than an LED, no matter how bright the LED may be and will draw attention that something is amiss (or ready to launch). My assumption in the schema I described is that as rockets are launched the buzzer will stop because either the igniter burned through or the Sw3 is opened after the launch. THe intention is not to let all of them stay closed until everything is launched; the plan is for the switch to the appropriate pad to be closed when needed and then reset after launch. In fact, one of the few pieces of hardware I actually have bought is the switch covers. Closing them opens the switch.

I understand the warning about current flowing through the buzzer to reach the igniter and bypassing Sw1 and Sw. Isn't that handled by the proper choice of the buzzer, a low current one?

 

[JAL3]

As you will see, today's effort is quite a bit more complex looking. It has not yet incorporated stuff that was posted after about 9 this morning.

1. Sw5 has now been labled. There are multiples of this switch because what it does is activate a cluster.

2. Another cluster has been added just like the first to better convey the idea of the cluster

3, a third cluster has been added to maintain the ability to use my clubs extant equipment based on normal extension cords.

4. a deadman launch mode has been added

5. a hypothetical electronic countdown, launch circuit has been added as a black box

6. a speaker and button combo has been added right after the key switch as an attention getter for heads up situations

7. the connection between pins 9 and 10 on the connectors has been severed for reasons which will become apparent in the next post.

I think that does it for this drawing.

 

[JAL3]

Next up is a simple sketch of my club's "legacy" system.

Its what we have now and it works so I assume there is no problem.