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?
Found it! I have nekkid pix and internal rats nest pix also if anyone is interested.
John (JAL#)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
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.
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.
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
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
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.
Excellent work!
One question, if you turn on all the circuits, could you have a 32 rocket drag race?
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
Thanks for your commentery.
Here are my response questions:
1. Something I dont 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? Im fuzzy on the symbols.
5. I do want an ultra bright LED to be visible. Fry catalog burn out your eyeballs style. Im afraid transistor is just a word associated with radios to me and Darlington is just a small town I once visited. Can you elaborate?
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.
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!
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.
JAL3 said: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.
JAL3 said: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?
Is the switch labeled SW the deadman switch? Is the intent to disable continuity, the piezo and all (and ignition of course).
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.
JAL3 said: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.
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?
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'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:
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.
- 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.
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.
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