Home Made Controller??

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RobN

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Dec 5, 2014
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Hi all,

Total newbie here thinking about making my own controller. I have been launching a few low power (A-C) rockets (just built a Bid Daddy though) with the cub scouts for a couple of years and thought we needed a multiple rocket controller and something better than the Estes Controller. I know very little about circuits and after much searching and research came up with a schematic that I think will work.

I welcome any thoughts, criticisms and corrections:

3R-Controller-v2snip.png

Thanks in advance,
Rob.
 
Welcome aboard. I don't see anything glaringly wrong with your diagram. Very important that you have your resistor values correct. Do you have an internal and external battery diagramed just so you have options? If you wanted to do just a small battery, like a 9v, for continuity checks, you could then switch over for the big one for launching.
 
Thanks Ton,

I have no clue on resistor size. I did find a parts list for a similar design that used a 470 Ohm resistor, so I tested that with a very simplified mock up and it worked fine. I suspect I will burn out a quite few igniters doing full testing and will test different size resistors to find what works. The external battery was an afterthought as I have an 8 AA battery holder that I was going to use, but after reading that a lot of people use lawn/motorcycle... batteries for all day launches, I decided I would incorporate an external battery as well. Easy enough to have a backup if needed.

So this design should work? I like the idea of single or simultaneous launches as well as continuity lights and the lighted ready/selected switches and my son insists that it have the flip up lighted arming switch.

Thanks, Rob.
 
R= (es-e led)/I led

e LED will depend on the color of the light emitted by the LED's
Red LED 2 v
Green LED 2.1 v
Blue LED 3.2
White LED 3.2 v

Most LED's want 20 to 30 ma

Also use something like 1n4000 series diodes for your blocking diodes.
Are your lighted switches designed for 12 V operation ? I do not notice any current limiting resistors for the LED's associated withe them. Possibly their already included with the switch.
 
Also all your ready lights will be on as soon as the unit is armed the way the circuit is drawn. Probably you want the LED on the other contact of the switch.
 
I have made my own electric controllers since the beginning. My V2 had a standard switch box with a standard off and on switch. It worked good the first few times. The other end went to my dads car battery. One day I forgot to turn off the switch before hooking on the roach clips. My hand was black and and in pain as the rocket motor started upon contact.

OOps - - - I launched several more times in the 60's with this launch controller. My current controller has 8 c-cells soldered together and a toggle switch that is on with pressure and self releases. I got the switch at Maxwell street in the mid 70s.

We recently started up again and are using up our old motors. For some reason we don't have any more hot wires so have launched with cannon fuse. Yeah pretty old school but it lights them up. should get some new motors next week and we will go back to electric.
 
Just for laughs or for use in Estes controllers with Q2G2 igniters there are LED's with current limiting resistors built in. I got these for my Estes controllers when I was considering launching clusters. BA9SF-G-12VAC:Green 180 Degree 12VAC/DC from Super Bright LED's Also I do not see any sneak paths for current in your diagram so you may not need the blocking diodes. Only the igniters that are selected should go off.
 
I just used a variable resistor to find the right value. Enough to light the led but very low mA. You may want to use a pad to drop voltage before through cont and ready leds or you will burn them using 12v for a 2v led.
 
For mounting and seeing LED's I highly recommend the Clear LED Cliplite Lens from All Electronics:

https://www.allelectronics.com/make-a-store/category/340400/leds/mounting-hardware/1.html
480x480-1912.Jpg


I use these in combination with water-clear very bright colored LED's. When the LED is off, all you see is the clear housing. When the LED is on, you see the color of the LED light, and the lens helps make it more visible from a wider viewing angle. This works well even in the brightest of sunlight (One problem with diffused LED's, and/or colored lenses, is you cannot be so sure if the LED is actually lit or if it is the sunlight shining on it).

Here is a short video showing them in operation in a controller I made up. I plug in the arming plug, then off-camera hook up the micro clips (and later unclip them).

[video=youtube;JF8WmMLUuto]https://www.youtube.com/watch?v=JF8WmMLUuto[/video]

Another trick I like to do for controllers, is to wire up a Piezo beeper in series with a blinking LED. I do not even make the blinking LED visible (they typically are diffused and not very bright anyway), as its purpose is to turn the Piezo Beeper on and off to make it beep-beep-beep. That is what you hear in the video when it has continuity.

- George Gassaway
 
Last edited:
As others have said, you need resistors in series with your LEDs--this is important both so that you don't blow out the LEDs, don't short your battery, and don't accidentally fire the ignitors.
The LED datasheet should list a nominal current (as Random said, usually 29 mA) and forward voltage (Vf, usually 1.5-2.0 V). Series Resistance = (Battery Voltage - Forward Voltage) / LED Current.

Robert Briody's work on igniters is a very good resource on the subject (https://www.gwiz-partners.com/igniters.pdf). Essentially you want to be careful when you use igniters that trigger at close to your continuity current (LED Current). OR add a continuity switch so that you can disable that feature for sensitive igniters.

Which brings me to my other two concerns with the circuit:
1) As it is currently, you HAVE to enable continuity to launch
2) With the ability to use different batteries, your continuity current will change depending on battery voltage. Design the circuit using your largest expected battery voltage, and never exceed it.
 
Also, plenty of Engineers on this board, PLEASE ask if you have questions.

We can also give you better advice if you tell us what you want the system to do, specifically.

Have fun, but remember these words of wisdom passed down to me by generations of Electrical Engineers (which, ironically, are probably very aplicable to rockets as well):
"Not only will electricity kill you, it will hurt the whole time you are dying."
 
R= (es-e led)/I led

e LED will depend on the color of the light emitted by the LED's
Red LED 2 v
Green LED 2.1 v
Blue LED 3.2
White LED 3.2 v

Most LED's want 20 to 30 ma

Also use something like 1n4000 series diodes for your blocking diodes.
Are your lighted switches designed for 12 V operation ? I do not notice any current limiting resistors for the LED's associated withe them. Possibly their already included with the switch.

Thanks Random,

I just picked up a pack of 470 Ohm 1/2 Watt carbon fiber resistors from Radio Shack. Is the only difference that the 1n4000 series are 1 Watt?
The switches will be lighted 12v 20A toggle switches. The light is built in to the switch. Sorry, I couldn't figure out how to depict that when creating the schematic.

Thanks, Rob.
 
Also all your ready lights will be on as soon as the unit is armed the way the circuit is drawn. Probably you want the LED on the other contact of the switch.

Ummm, I don't see how that is true, but this is first time I have tried anything like this, so what am I missing? Additionally, the Ready Lights will actually be lighted switches. Sorry, I couldn't figure out how to depict that when creating the schematic.

Thanks, Rob.
 
I just used a variable resistor to find the right value. Enough to light the led but very low mA. You may want to use a pad to drop voltage before through cont and ready leds or you will burn them using 12v for a 2v led.

So I would use the variable resistor just for testing to find the right size? That would require using a multimeter, which I have and have used, but still a little confused on. I will have to do some more research on that.

The Ready LEDs will actually be part of the switch, so should be OK?? Sorry, I couldn't figure out how to depict that when creating the schematic. The Continuity LEDS will be behind the resistors, so should be OK as well??

Thanks, Rob.
 
For mounting and seeing LED's I highly recommend the Clear LED Cliplite Lens from All Electronics:

https://www.allelectronics.com/make-a-store/category/340400/leds/mounting-hardware/1.html
480x480-1912.Jpg


I use these in combination with water-clear very bright colored LED's. When the LED is off, all you see is the clear housing. When the LED is on, you see the color of the LED light, and the lens helps make it more visible from a wider viewing angle. This works well even in the brightest of sunlight (One problem with diffused LED's, and/or colored lenses, is you cannot be so sure if the LED is actually lit or if it is the sunlight shining on it).

Here is a short video showing them in operation in a controller I made up. I plug in the arming plug, then off-camera hook up the micro clips (and later unclip them).

[video=youtube;JF8WmMLUuto]https://www.youtube.com/watch?v=JF8WmMLUuto[/video]

Another trick I like to do for controllers, is to wire up a Piezo beeper in series with a blinking LED. I do not even make the blinking LED visible (they typically are diffused and not very bright anyway), as its purpose is to turn the Piezo Beeper on and off to make it beep-beep-beep. That is what you hear in the video when it has continuity.

- George Gassaway

Thanks for LED lens tip. I really like those and will have to check them out. I have been toying with beeper idea. That sounds like an easy way to make a beeper.

Awesome, thanks Rob.
 
As others have said, you need resistors in series with your LEDs--this is important both so that you don't blow out the LEDs, don't short your battery, and don't accidentally fire the ignitors.
The LED datasheet should list a nominal current (as Random said, usually 29 mA) and forward voltage (Vf, usually 1.5-2.0 V). Series Resistance = (Battery Voltage - Forward Voltage) / LED Current.

Robert Briody's work on igniters is a very good resource on the subject (https://www.gwiz-partners.com/igniters.pdf). Essentially you want to be careful when you use igniters that trigger at close to your continuity current (LED Current). OR add a continuity switch so that you can disable that feature for sensitive igniters.

Which brings me to my other two concerns with the circuit:
1) As it is currently, you HAVE to enable continuity to launch
2) With the ability to use different batteries, your continuity current will change depending on battery voltage. Design the circuit using your largest expected battery voltage, and never exceed it.

Excellent points Zan,

The Ready lights will actually be Illuminated switches. Sorry, I couldn't figure out how to depict that when creating the schematic. So, they should be OK??

Excellent point on battery size. I have an 8 AA battery holder I was going to use for the internal. That should be 12V, but I will make sure I fully test with a 12V motorcycle battery I have as well as the jumper/power pack I have.

Thanks, Rob.
 
Also I do not see any sneak paths for current in your diagram so you may not need the blocking diodes. Only the igniters that are selected should go off.

Here is where my knowledge is severely limited. I saw other designs using Blocking Diodes, so here is my thought process:

With out the Blocking Diodes: is it possible for the R1 Ready light to light up when the Continuity Switch and the R2 Switch are closed??

Thanks, Rob.
 
Rob,

I see a major problem with the schematic depending on the type of lighted switch you are planning on using. When switch R1 is activated (for example) the igniter will short out the "ready" LED when selected. Exactly what model switch are you using?

Steve G
 
Which brings me to my other two concerns with the circuit:
1) As it is currently, you HAVE to enable continuity to launch
.


I originally drew it up so that you didn't HAVE to enable the Continuity to launch, but changed it. What is the concern with having it this way?



Thanks, Rob.
 
Rob,

I see a major problem with the schematic depending on the type of lighted switch you are planning on using. When switch R1 is activated (for example) the igniter will short out the "ready" LED when selected. Exactly what model switch are you using?

Steve G


The Red toggle switches I have are Borg-Warner #S7012 (Red Lighted) Toggle Switches, 12 volt - 20 amp.
The green toggle switch is just listed as 20 AMP - 12 VDC, 3 Pole - SPST.

Will those work?


Thanks, Rob.
 
Probably not as the internal LED is not isolated from the switch contacts. There's no way to illuminate the LEDs as wired currently. You would need DPST switches at minimum.

Heading out to work at the moment.

Steve G
 
Last edited:
These are a couple circuit diagrams of simple controller I posted previously.

Modified Rocket-launcher-circuit-diagram.jpg Multipad-Rocket-launcher-circuit-diagram.jpg

The LHS single pad controller can be replicated n times through a pad select switching system as shown on the RHS into a multi-pad controller.

Notes: A LED is just like a light bulb except it needs a series current limiting resistor to limit the current so it won't burn out. The maximum safe current of an igniter is ~ 25 ma max so if you have a 12 volt system R = V/I = 12/470 = 0.025 amps. Personally I prefer to use 1000 ohm resistors and limit the current to ~ I = V / R = 12/1000 = 0.012 amps max which reduces the drain on the launch battery.

Bob
 
I originally drew it up so that you didn't HAVE to enable the Continuity to launch, but changed it. What is the concern with having it this way?

Primarily because some igniters will fire with very little current, and there is a chance that the continuity circuit will fire the rocket prematurely--and at a time when there are usually people around the launch pad.

And a secondary benefit is that an active continuity circuit consumes energy from your battery. Granted, this isn't much, but if you're running on AAs, over a few launches this may add up, especially if you have delays on the pad.

I'm using a momentary continuity switch on mine so that I can't accidentally leave it in the "on" position and have an igniter fire upon connection.
 
Also all your ready lights will be on as soon as the unit is armed the way the circuit is drawn. Probably you want the LED on the other contact of the switch.

The way your schematic is drawn the ready lights will only light when the fire button is pressed.

I don't see how either of these is true. I agree that his ready light position needs refinement, but currently they turn on when a channel's ready switch is thrown, and the continuity switch is pressed.
 
At the risk of innundating you with information, I have uploaded the third revision of my controller. This design is relay-based (as is generally recommended with 12V systems). As you are a bit unfamiliar with circuit design, I encourage you to read and understand as many similar diagrams as possible. Once you are familiar with the different approaches, and what they allow or simplify, you will be able to plan your controller better.

Things to pay attention to in my schematic:
- Launch power and continuity power are kept very separate
- All LEDs have series resistors to limit current
- I'm allowing channel selection at the remote, which is convenient, but requires a higher signal count on the wire connecting it to the controller (CAT-5 in this case)
- Individual continuity switches per channel, allowing for different igniter types on each channel (for a drag race situation, for example)
- The 1M resistors are to keep the relays quiet and grounded until a launch signal is sent, as these are the primary firing mechanisms, I didn't want to leave them floating.

Launch Controller Mk3 - Schematic.jpg
 
I don't see how either of these is true. I agree that his ready light position needs refinement, but currently they turn on when a channel's ready switch is thrown, and the continuity switch is pressed.

zanfar that's only correct if the ignitor is not connected. As I stated previously the igniter ,which is only a couple of ohms at best, will short out the "ready" LED.:(
The only way I see to use the existing switches is to add relays as in this edited schematic.

Steve G

Robn launch controller.jpg
 
Last edited:
Primarily because some igniters will fire with very little current, and there is a chance that the continuity circuit will fire the rocket prematurely--and at a time when there are usually people around the launch pad.

And a secondary benefit is that an active continuity circuit consumes energy from your battery. Granted, this isn't much, but if you're running on AAs, over a few launches this may add up, especially if you have delays on the pad.

I'm using a momentary continuity switch on mine so that I can't accidentally leave it in the "on" position and have an igniter fire upon connection.

Thanks Zan,

My thought was to have the Green LEDs stay on and and have both a Green and Red light on for those rockets you want launched. More lights the better, right. LOL. I guess now I know why most of the designs I have seen don't have it this way.

Thanks, Rob.
 
At the risk of innundating you with information, I have uploaded the third revision of my controller. This design is relay-based (as is generally recommended with 12V systems). As you are a bit unfamiliar with circuit design, I encourage you to read and understand as many similar diagrams as possible. Once you are familiar with the different approaches, and what they allow or simplify, you will be able to plan your controller better.

Things to pay attention to in my schematic:
- Launch power and continuity power are kept very separate
- All LEDs have series resistors to limit current
- I'm allowing channel selection at the remote, which is convenient, but requires a higher signal count on the wire connecting it to the controller (CAT-5 in this case)
- Individual continuity switches per channel, allowing for different igniter types on each channel (for a drag race situation, for example)
- The 1M resistors are to keep the relays quiet and grounded until a launch signal is sent, as these are the primary firing mechanisms, I didn't want to leave them floating.

View attachment 248364



Definitely over my head, but I will study and figure it out. I love a challenge.

Thanks, Rob.
 
zanfar that's only correct if the ignitor is not connected. As I stated previously the igniter ,which is only a couple of ohms at best, will short out the "ready" LED.:(
The only way I see to use the existing switches is to add relays as in this edited schematic.

Steve G


Thank you VERY much for the edit. Not sure exactly how the relays works, but I will do some research, try and figure it out, and come back with questions.

I do have one question now though: What do mean when you say the ingitor will short out the "ready" LED? Are you saying that no current will get to the "ready" LED so it won't light? Sorry, but this is all new to me.


Thanks, Rob.
 
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