Designing a custom launch controller?

Ok...I've worked out testing the Aerotech Interlock and got it working. Now I've moved on to assembling my own basic one for fun, so I'm editing the title and first post of this thread.






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I have the Aerotech Interlock Controller:

View attachment 107398

And a few months ago the button mechanism fell apart when I was out in the field launching. I cut the wires and just launched for the rest of the morning by touching bare wire to my battery leads. Now that I'm fixing it, it seems to be having problems off an on. My question is...what is the best way to test these kinds of things without wasting precious igniters? Is it ok to simply connect the two alligator clips (it doesn't have the Aerotech Copperhead clips anymore) together and see if I get the test tone when it's armed?

Thanks

A seed light (small incandescent light with leads) - or a spare Christmas tree light - would probably work well. Continuity should result in a dim light, and brighter when you "launch." I'm guessing you don't have a voltmeter, or you would have just hooked it up to that.

edit - on re-reading, yes, just shorting the circuit by clipping the leads together should give you the test tone. Low current igniters are less than an ohm - you can have more resistance in your leads than in the igniter, so shorting should be fine.

Don't feel bad. I only do electrical with things having two leads. Anything with less than two (antennas) or more than two (transistors, etc) is dark magic.

Make sure it's rated for 12v. Wattage doesn't matter, that's just how bright it will be (kinda).

If you have alligator clips for the connectors just hooked them to a paper clip to complete the circuit.

Shorting the leads (clips) is okay to test for continuity (light or buzzer) but DO NOT press the launch button-- that creates a dead short which will do one of two things-- burn up the battery or fry something (wires, contacts, whatever.

Electricity really isn't that hard... I mean, it CAN be... solid state circuits are hard... digital stuff is hard. Three phase AC power is hard. Regular DC low-voltage (what most of us will ever see that's battery powered) is easy... AC is easy up to 240 volts... high voltage AC is harder... but then most of us will never have to mess with that anyway.

Basically, everything electrical is ruled by Ohm's Law-- I (current in amperes)= V (volts) divided by R (resistance in ohms). Shortened, that's I=V/R... or transposing mathematically, V=I x R, (V=IR), or R=V/I...
Think of electricity in terms of water usually helps people to be able to relate to the terms better and visualize what's actually going on... For instance, current... measured in Amperes or Amps for short... You have two hoses and want to fill your swimming pool. Which will fill it faster, a garden hose, or a fire hose?? The fire hose of course, because it's bigger... it delivers more water in a given amount of time because of that. The garden hose is smaller and can't carry as much water per unit of time. This is amps.

Volts is the pressure in the hose. If you have low water pressure, water is going to come out of the hose much slower than if the water pressure was high, regardless of whether it's a big hose or small one. By the same token, higher voltage pushes more electrical energy through a circuit than lower voltage.

Resistance, measured in Ohms, is the "load" on the circuit... it's the resistance of electricity to flow through the circuit. If you measure the pressure of the water going into one end of a very large pipe, and measure the pressure of the water near the outlet end of the pipe, the pressure will have a very small difference... a pressure drop, due to resistance of the water flowing through the pipe. If you have a very long but very small pipe and measure the same pressure at the inlet, you will have a much lower pressure at the outlet, which is to say a much bigger pressure drop-- due to the internal resistance of the smaller pipe to the flow of water... so it is with electricity-- the bigger the wire, the less internal resistance there is, and the less voltage drop... and it, like the fire hose, can carry more water per unit time than the smaller hose, just as the larger wire can deliver more power (amps) than a smaller wire, which has higher internal resistance, and cannot carry as much current (amps), just like a smaller garden hose.

Might as well mention that electricity has to flow through a complete circuit, which most of us know... and that electricity comes in two basic forms in usage... Direct Current, or DC, and Alternating Current, or AC. DC is the type produced by all batteries... electrons flow from one terminal of the battery, through the circuit, to the other end of the battery. AC is what we have in homes, where the current flows forward, then backward, 60 times a second (60 Hertz). AC can have its voltage converted easily via transformers, whereas DC cannot (without switching it to collapse the magnetic field and induct current in the secondary windings-- IE how car spark plugs fire). AC isn't used in rocketry, except in power tools. Everything powered by a battery is DC (unless there's an inverter involved to change it into AC, but that's very rare).

Launch controllers basically have a very simple circuit... you have a power source (battery or batteries) providing anywhere from 6 volts (poor) to 12 volts (fine) to more (unnecessary) and conductors to connect them to the switching components to form a circuit, that circuit then extends out one launch lead, to the microclip, through the ignitor, back through the other microclip, thru the second lead, back to the other battery post. The hardest part is the switching. You have first a safety key switch which, when opened (removed) totally isolates the battery from the rest of the circuit (breaks the circuit, or "opens" it). When the key is installed, battery power flows though it into the circuit. Here the circuit branches in two-- one side goes through the continuity device (light, LED, or buzzer), then to the launch lead going to the clip and ignitor. The continuity device restricts the current due to its internal resistance (light bulbs have low resistance since they need a lot of current to produce light via incandescence of a wire filament, heating it up enough to glow-- which is why light bulbs aren't suitable for use with low-current ignitors-- they will allow SO much current through them they'll fire the ignitor the instant the key is inserted! Hence why you don't want to use stock Estes controllers with Quest Q2G2 low current ignitors). Solid state devices that use a semiconductor bridge have a resistor wired in series (placed in the circuit either ahead or behind the solid state component, such as an LED or piezo buzzer, to restrict the current and prevent too much power from flowing through it, which would burn up the LED or buzzer... this also restricts how much current flows through the ignitor, making it "low current ignitor safe"... but always test to make sure-- some ematches are EXTREMELY sensitive, sorta like flashbulb ignition systems from decades ago). In the case of an LED or buzzer continuity device, the power flows from the key, through the resistor, through the LED semiconductor bridge (which of course must observe the correct polarity, since it will allow electricity to flow in one direction, but NOT in the other (hence, light emitting DIODE (LED), then the small amount of current will go on to the lead and clip to the ignitor... buzzers work the same way.

The OTHER branch of the circuit bypasses the continuity device... basically it creates a "short circuit" for the electricity to "go around" the bulb, LED, or buzzer, and allow FULL BATTERY POWER to go DIRECTLY to the clips and ignitor(s). This is called a "normally open" (n.o.) switch, which is a push-button switch which is spring loaded to hold the contacts open, breaking this part of the circuit, which forces the electricity to flow through the other branch, the continuity device. This is called a PARALLEL circuit... it is in parallel, or beside, the other branch of the circuit. The safety key, which is between the battery and the point where the circuits branch apart (or it can be placed between the launch lead and where the point where the two branches come back together again, either way it prevents power from flowing from the battery thru the components to the launch lead) is wired in SERIES, meaning power must flow from one part to the next to the next. When the launch button is pressed, the contacts close, completing that branch of the circuit, allowing full battery power to flow through the switch and out the launch lead to the ignitor(s) and back to the battery, bypassing the resistance provided by the bulb, LED, or buzzer in the continuity device. The battery voltage pushes electricity through the ignitor(s) with as much current as the ignitor can pass, causing it to heat up, until it ignites the pyrogen and burns the bridgewire through (a very thin peice of wire in the ignitor which heats up due to resistance to the amps being pushed through it by the voltage from the battery...igniting the pyrogen and then usually burning through (on 12 volt systems anyway-- 6 volt systems often don't push enough current through to melt the bridge wire). Once the wire melts, power stops flowing through the circuit.

Which brings us to ignitors on clusters... remember old Christmas tree lights back in the day, where one bulb burned out and the whole string would go dark?? That's called a SERIES circuit... it was wired so electricity went through the wire, through the first bulb, out from it thru a wire to the next bulb, thru it, out thru a wire to the third bulb, etc... If one bulb burned out, it breaks the circuit and power cannot flow, even though the other bulbs are still good. That whole "complete circuit" requirement, remember?? If we wire our ignitors like this on a cluster, once the first one burns through, even if the others are really close and very hot, but haven't ignited yet, the power will stop flowing, and the others will rapidly cool down-- NO ignition on the other motors! What we need is a PARALLEL circuit... one where every ignitor is connected to the power supply wire (clip) on ONE SIDE of the ignitor, and the power return clip/wire going back to the battery on the other... that way, when the first ignitor burns through, only current through THAT ignitor stops... and the electricity that had been flowing through it continues on to the REMAINING ignitors, and, along with the electricity which had already been flowing through them, helps them heat up and ignite EVEN FASTER...

Anyway, that's a basic primer on electricity in launch controllers... hope it helps yall out... Do a search, because this has been discussed at length before, and I've posted some circuit diagrams showing how the controllers are wired and discussed how to modify controllers in other threads... back before my hard drive melted down and ate my diagrams and drawings...

Later and good luck! OL JR

It looks like the contacts on the green sliding piece are bent back, have you verified that they touch the contacts when pressed in with the red key? Sorry you're having trouble with this, is this the one I sold you?

chadrog said:

It looks like the contacts on the green sliding piece are bent back, have you verified that they touch the contacts when pressed in with the red key? Sorry you're having trouble with this, is this the one I sold you?

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Hey Chad. Yeah it's the one that was yours. The green contacts for the arming key are bent back, but they are kinda supposed to be as they get pressure from the key. Anyway, they make plenty of good strong contact with the leads as done the red fire button.

Green Jello said:

Ok, nevermind. I ended up taking the whole thing apart and putting it back together again. One of the screw connections inside must have been making bad contact with the wire. Anyway...I didn't change anything, but it work now. Thanks for all your help guys.

While I have you here....seeing how ridiculously simple these things really are, does anyone have good plans for a home made controller. It might be a fun project.

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Let me be the first to say "glad it works!" Building one is a great winter project, not that there's any winter in Reno. As you've noticed, there's not much to them - it's easy to cob one together for a few bucks at Radio Shack. Here's mine:

chadrog said:

Let me be the first to say "glad it works!" Building one is a great winter project, not that there's any winter in Reno. As you've noticed, there's not much to them - it's easy to cob one together for a few bucks at Radio Shack. Here's mine:
View attachment 108120

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I'm originally from Chicago and I know what winter is in your part of the country, but Reno does have some winter. It's not like Vegas. It's at 5,500' and is a high desert very similar to Denver. In fact.....it's lightly snowing outside as we speak.

My duh, thought it was all desert-ee out there. Got a trace of snow here today, already gone. Lovin' it.

Green Jello said:

Yeah, I meant to say that. I don't own a volt meter and I have no clue about all things electricity.

I considered buying a cheap one from Harbor Freight, but I'm afraid I would have no idea what to do with it.

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Here's a crash course, free to download and read:

https://learn.adafruit.com/downloads/pdf/multimeters.pdf

It's worth it to get an inexpensive multimeter and start learning what you do with it. There are a surprising number of situations when you'll be glad to have one as your rocketry projects get more complex.

A multimeter is a great tool to have, not just for rockets but other household fix-it chores.
It will certainly help determine if the controller works or not.
But it will not test the launch battery under load.

Here is what I use for that:
A common # 1157 automobile tail light bulb.

It has two filaments. Wire them together and it will draw about 2.6 amps at 14 volts.

If your launch system can light the bulb to full brightness--it will certainly fire an igniter.

Green Jello said:

Yeah, I meant to say that. I don't own a volt meter and I have no clue about all things electricity.

I considered buying a cheap one from Harbor Freight, but I'm afraid I would have no idea what to do with it.

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Youtube is your friend. There are tutorials there.

If I make one....I'm pretty sure it has to have one of these:

https://www.mindkits.co.nz/store/co...ds/electrical-components/Missile-Switch-Cover

Green Jello said:

Ok...I finally got around to trying to get this thing to work with all the advice you guys gave me. Here are some detail pics so you can see what I am dealing with:

View attachment 108105View attachment 108106View attachment 108107View attachment 108108View attachment 108109

No matter what I do, I can't get this thing to work. I tried getting a seed light and even just connecting with a piece of metal to just test for continuity. Here is what I have found:

• All of the wire connections APPEAR to be good and strong
• All of the brass contacts APPEAR to be connecting the leads when the buttons are pressed.
• The car jump battery I use has good power and I clicked the leads of it together and got some healthy sparks
• The audible "armed" tone will not sound no matter what.
• The seed light or even igniter will not fire.

So...any ideas before I attempt to contact Aerotech about it?

Thanks

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Sounds like you have a broken wire or bad connection somewhere that's keeping the circuit completely open regardless. It could be a broken wire in the leads somewhere between the battery and controller, or between the controller and the clips. Could also be a faulty "safety key" contacts/parts not making contact when the key is installed...

What you have is called an "open circuit". From the description you gave, I'd tend to think it's somewhere either in the safety key area not working correctly, or a broken lead... (the wires CAN break inside the insulation and the wire still appear to be intact... testing can determine if this is so). The reason I think this is because you said when you hook up a good battery and short the ignitor clips (hooking up metal between them to act as a low-resistance conductor in lieu of the ignitor), when you install the safety key, the beeper should go off. Now, it COULD be a faulty beeper, but if hit the launch button, electricity should flow (which isn't a good thing with a shorting bar (piece of metal) in between the clips) but if you installed an ignitor or test light between the clips, it should fire or light up... which you said it is not... therefore, the problem must be in a "common" area of the circuit, one which is in common to both the "continuity test" configuration of the circuit (when the key is installed and the launch button is not depressed, ie, the leads from the battery to the controller, through the buzzer, to the safety key, though the key, out the launch lead to one clip, thru the ignitor (or shorting bar, test lamp, etc) back through the other clip, back through the second lead, which usually goes straight through the controller or hooks directly to the second lead going back to the battery...

I don't have an interlock, but it works the same as an Estes controller, just slightly different parts... the buzzer is the small white 'can' connected by the thin leads to the two screws on either side of the launch button... With an ignitor (or shorting bar) hooked up, and the battery leads correctly hooked up (make sure you observe polarity, since most solid-state components like LED's and piezo buzzers usually will work when hooked up with the correct polarity, and WILL NOT if hooked up backwards... they act as a diode, which is a 'one way check valve' for electricity). When the safety key is installed, power should flow from the battery, in through one battery lead, to the screw on one side of the launch button, thru the buzzer, back to the other screw on the other side of the launch button, to one side of the safety key, through it, out the other side of the safety key, out thru one of the launch leads to the clip, thru the ignitor, back thru the other clip, then back to the controller thru the other launch lead, which should connect up with the second lead going back from the controller to the battery... trace the circuit and you'll see what I mean. If it doesn't do that (and if you've removed some of the wires and reinstalled them, you might have hooked it back up incorrectly... double check the circuit paths and make sure the electricity flows as I described... if you took any screws or wires loose in there). It's hard to tell exactly, because I cannot see the leads going out to the battery in any of your pictures, and I don't have an interlock of my own to compare it against.

The launch button on this one is very simple... when you press the launch button, the brass strip attached to the plastic button comes down and shorts the little angled posts sticking up from the screws on either side of the button, allowing electricity to flow unimpeded between them, through the brass metal bar, which "bypasses" the buzzer, allowing full battery power to go to the safety key, through it, out the other side, thru the lead and clip, thru the ignitor, back into the other clip and back thru the other lead, which should connect inside the controller to the second lead going back to the battery. Trace the circuit and you'll see what I mean...

If I could clearly see the battery leads, I could troubleshoot it for you from here...

The safety key on these controllers is unusual... Estes uses a metal "pin" (the actual metal "key") which is inserted between two narrowly spaced but seperate contacts on either side, which when the key is removed, creates a break in the circuit and isolates the battery, button, and continuity light from one of the launch leads, creating an "open circuit". When the key is installed, the metal key bridges the gap between the two contacts, allowing power to flow unimpeded to the ignitor, first thru the continuity light, and full power to the ignitor when the launch button is depressed, bypassing the continuity light. This is basically how all controllers work, to a point. I'm not exactly sure how the new Estes controllers with the "push in and hold" safety keys work-- I presume they bridge the gap in the same way as the old metal keys (since they use a metal pin) but have a rubber ring to "pop them out" unless held down to keep contact (added safety feature so you don't leave the key in and the circuit remain "hot" when hooking up the next rocket). Apparently the interlock uses some sort of a plastic "interlocking key" which is inserted to complete the circuit, probably by forcing two spring-loaded contacts together to bridge the circuit, which spring apart and open the circuit when the plastic key is removed... Not sure since I haven't worked on one, but it's reasonable... there's only so many ways these things can work. This is the first thing I would check.

Now, how can you test this to find out what's wrong?? You'll have to do some "investigating" and systematically prove each component is 'good' to find the problem. Start by tracing the circuits, as I described above, looking for any broken wires, loose wires, faulty connections, incorrect connections, shorts, opens, etc... anything that would allow the power to not go where it's supposed to, jump paths, or follow an incorrect path, or any spots where there is poor or no contact which would prevent power from flowing AT ALL. I'm about 95% sure you have an open circuit problem, probably in the safety key, or in one of the battery or launch leads... I'd probably wager on the safety key mechanism contacts... Once you've done a visual check of the circuit paths and the contacts and their conditions, if nothing has caught your eye, you'll have to start testing components. Unhook the battery from the controller, and remove the ignitor or shorting bar from the clips... you want open circuits for testing so you can test each branch of the circuit, each component or set of contacts, individually. For this you'll need a POWERED test light... Don't worry, it's not hard to do... all you need is a regular test light and a JUMPER WIRE, which is basically a piece of wire with a clip on each end... You can either make test jumper wires using extra wire and extra clips, or get pre-made ones for a couple bucks or so at the auto supply... to make your test light a POWERED test light, simply hook a GOOD 9 volt battery between one lead of your test light (I usually use an automotive test light which has a sharp pointy probe on one end and a wire with a clip on the other end, used to ground the test lamp when checking automotive circuits energized by the car battery.) If you have this type test light, connect one side of the test lamp to the 9 volt, and use the jumper wire to connect the other side of the battery to one side of the component being tested. Then touch the probe of the test light to the other side of the component-- say the buzzer... if the buzzer is good, it should either buzz, or the test light should come on. To test the launch button, connect the ground jumper wire to the batter to one screw on one side of the button, depress the launch button, and touch the test light lead to the other side (same as you would to test the buzzer-- Oh, BTW, reverse the test leads on the buzzer and test it BOTH WAYS to ensure that you get the correct polarity!) With the launch button held down and the battery ground jumper wire clipped on to the screw on one side, and the test light probe touched to the other side (and of course the test light ground or second lead clipped to the other battery post securely to form a complete circuit) the light should glow brightly. If it doesn't, make sure all the connections are good (test the test light and battery by touching it to the other screw (the one that the jumper wire is already connected to-- this should complete the circuit from the battery thru the jumper wire, to the probe, thru the test light bulb, and back thru the ground lead of the test light back to the battery-- if it doesn't light, figure out why-- dead battery or bad test light, or incorrect polarity (reverse the battery and try again).

If the buzzer and launch button check out okay, you know the problem isn't there... so you can ignore those parts from now on. Now hook the battery jumper wire ground to one side of the safety key contacts/switch. Make sure the test light ground is securely attached to the other side of the battery, and then touch the test light probe to the other side of the safety key switch where power goes out to the launch lead... with the key removed, the light should NOT be on. Insert the safety key (and hold down if necessary-- again, I don't have an interlock so I'm not sure if you have to do that). With the key securely installed, the light SHOULD be on... if it's not, double check your jumper wire/battery connections, and test again... if not, check the contacts and stuff inside the safety switch for bent, broken, or corroded parts. Fix and repeat-- Assuming that checks out as good, now you have to start testing the leads. Start with the battery lead from one battery clip connected to one lead wire going into the controller... clip the ground wire to this clip, make sure it's not touching anything else, and follow that wire with the probe, up it's length and into the case, to where it should connect up to a screw... touch the light probe to that screw... the test light should lite up... (again, make sure the jumper wire and battery and test light ground connections to the 9 volt are all good-- you MUST make a complete circuit). If the lite does NOT light (and you're ABSOLUTELY SURE that you've followe d the RIGHT wire, and didn't jump to the other one at some point accidentally) then you have a broken wire somewhere in the insulation. Check the second battery lead wire the exact same way, move the battery jumper ground to the other battery clip, trace the wire to its other end (whatever it connects to-- it could go straight through the controller out to one of the launch clips). Test probe the other end... lamp should lite-- if so, you're good... if not, check your test circuit, double test, and if still no light, you've probably found you're broken wire. Test the launch leads the same way... clip the battery jumper ground to one ignitor clip and trace the wire back to whatever it connect to, and then probe that end. It should light. Same thing with the other ignitor clip and lead. Then, test the wire connecting the launch button with the safety key switch-- clip the ground to one end, and probe the other end. It should light up.

Do the tests systematically and follow the electricity as it would flow through the circuit, and I'm sure you'll find the problem. If you have more problems, PM me and I'll walk you through it...

later and Good luck! OL JR

Green Jello said:

Thanks Luke. As per usual, your help posts go above and beyond. Not sure if you read above that I already fixed it though. Either way...I read all that and did learn a bit. Thanks!

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Hehehe... yeah, I read it... AFTER I posted how to troubleshoot it... spent about a half hour or so thinking that one through and putting it into words...

Oh well, maybe it'll end up as a sticky...

Glad you found the problem... figured it was something like that.

Later! OL JR

Green Jello said:

I was killing some time at lunch looking at Radio Shack and a local electronics parts supplier here looking at all the fun switched and lights, etc. So without starting a new thread for this purpose, maybe I can ask you guys here.

For the toggle switches....most of them are rated for 125V. Should I be looking for all 12V stuff?

I found tons of options, but none with the fun "arming cover" like this:

https://www.mindkits.co.nz/store/co...oards/toggle-switch-and-cover-illuminated-red

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No, 125 V (110/120, it's all the same-- household AC power) will work fine... as long as you're not trying to RUN something that takes household AC current... but you wouldn't be doing that anyway with a launch controller...

In fact, I modified my stock Estes "Electron Beam" controller from back in the 80's to run off a car jumper pack, using lamp cord to feed the power in from the "battery charger" clamps that I got at the auto supply (I just clip the jumper back clamps over them, and if I *wanted* to run off a regular car battery, the controller has its own "battery charger" type clamps to clip directly to the car battery). I installed an "LED indicator" that I got from Radio Shack (essentially, an LED in a housing with a button lens and a threaded back to install in a hole, with a resistor already soldered in it to protect the semiconductor bridge of the LED at 12 volts to keep it from passing too much current and burning out. They cost about $3-4 bucks and come in numerous colors, and work great for this application-- already has two wires (red and black) coming out about four inches to connect up with your wiring inside the controller, observing the correct polarity of course). I had a "Pola Pulse" Estes controller that I really liked, except it used those stupid flat Polaroid camera batteries which were already expensive and hard to get even back in the late 80's... So I rewired that one with lamp cord to use a car battery almost as soon as I got it. One thing that always ticked me off about Estes controllers were, that, even using a car battery, you were never really sure if you had a "no continuity" that it wasn't one of three things-- 1) the key not making good contact (those stupid steel keys would rust a little and wouldn't pass current even though the ignitor and clips and batteries were good), 2) the batteries weren't making good contact (either the dinky "AA's" had lost contact or corroded a bit or were dead, or if it was wired for a car battery, the clips weren't making good contact with the battery post and thus not delivering current to the controller), 3) the dinky light bulb lost contact and needed a little "massaging" in the socket to get it to come on, showing the ignitor was good), 4) the clips were dirty or the ignitor was indeed bad, which is really what the stupid continuity light is SUPPOSED to tell you!

SO, when I rewired my controllers, I installed an AMBER LED indicator connected to the two battery leads coming in to the case from the battery clips... Red to red, black to black, for polarity... I attached the wires under the screw where the wire from the battery attached to the launch switch/continuity flashlight bulb brass contact, and the other where the wire coming in from the ground ignitor clip and the lead going back out to the battery ground (negative) were wired together under a screw...) This LED indicator glows whenever the battery is connected to the launcher and the controller is getting power... IOW, if the amber light isn't on, jimmy the battery clips until it DOES come on!)

Next, I installed a SECOND LED indicator, this one RED, to indicate ignitor continuity and a hot firing circuit ready for launch. First I unscrewed the stupid light bulb and tossed it... they were worthless anyway. Next, I attached the red wire under the same screw that attaches the battery wire to the brass launch switch/light bulb contact... the other (black) wire from the LED indicator attaches to the other brass contact on the other side of the ignition switch, just like the buzzer is attached in your interlock controller. This serves the same function as the buzzer or light bulb in the Estes controller... it allows a little current to "bypass" the launch switch when the key is inserted, flow through the leads and ignitor, and back to the battery, showing that the clips and ignitor are indeed good and ready to launch. The stupid steel key I replaced with some homemade keys, made from a piece of scrap household Romex wiring (12 or 14 guage IIRC, about 2 inches long) stripped completely of insulation and having one end wrapped around into a loop with a pair of pliers, and then soldering the loop closed, since the copper wire is soft and bends easily). The copper key can pass a LOT more current with a LOT less resistance than a stupid steel key, and it doesn't corrode as easily. The safety key contacts are left as-is. Lamp cord replaces the dinky bell wire Estes uses in their controllers, to carry more current to the ignitor with less resistance, and I soldered on some small copper-clad microclips I got from Radio Shack. Later I removed the bulk of the lamp cord, and installed a female 110 volt plug (available in the electrical section of the hardware store or big box store-- commonly used to repair extension cords) about 2 feet from the end of the lamp cord coming out of the controller going to the ignitor clips. I cut about 3 feet of cord back from the clips, and installed a MALE cord end onto it... (if you have an old toaster or VCR (or something similar) you're going to throw away, you can cut the cord off it and solder microclips on the end of it for your launch leads... works great and costs nothing!) THEN, this allows me to use a STANDARD 110 volt extension cord, either from say 25-50 feet, for launch leads between the controller and the pad... the extension cord plugs into the controller female socket, and the male end of the clips plugs into the female end of the extension cord... the fine-wire multistrand conductor carries a LOT of current and it works great!

If you build your own controller, here's a couple things you need to keep in mind:

The safety code says you have to have a safety "key" which basically is a removable circuit bridge, IE that COMPLETELY OPENS the circuit when removed... a toggle switch or "normally open" push button switch is NOT acceptable for use as a safety key, because it cannot be removed. If you use a "lawn mower" type key switch, the switch MUST be INCAPABLE of having the key removed with the switch left in the "on" position (circuit closed). And yes, there are plenty of cheapy lawnmower switches which you CAN remove the key with the switch left "on"...

The ignition switch should be of the "normally open" type. While the "guard switches" look really cool and very "NASA-like", they are an ordinary toggle, just with a "lock off" guard installed... technically speaking, this ensures that if the guard is "closed" the switch is "locked OFF"-- ie the circuit is LOCKED OPEN. Technically speaking, however, this is NOT a "normally open" switch, which is defined as one which is spring-loaded to the circuit open (off) position when the switch is not being pushed or pressed... IE a doorbell button, or a press type button, is "normally open" versus a "regular two-position" switch like a knob switch, rocker switch, or toggle switch... (including the locking toggles, which are a "two position" switch). This might not pass muster at your local launches, depending on how hard your RSO is to deal with... a guarded switch SHOULD NOT pass muster as a "safety switch" because it is non-removable-- IE someone technically COULD pick up a controller equipped with a guard switch, flip it open, flip the toggle, and press the launch button while you're hooking up your rocket and launch it with you under it... NOT GOOD. A REMOVABLE safety key prevents this, because per the code you SHOULD have the key with you at the pad... A "suitable" switch for launching that won't raise any eyebrows for a launch switch would be a normally open "push button" type switch....

The most easily obtained and widely used type of "circuit opening safety switch" is a shorted jack plug or bananna plug... a 110 volt outlet, with a shorted "male plug" would do the same thing... basically a shorted jack plug would be like a microphone or headphone jack plug, with the two wires coming out of it stripped and twisted together, and then taped up with electrical tape... The wire coming in from the battery would attach to one side of the jack plug socket, and the wire going out to the launch switch button/continuity indicator would attach to the other connection... If one used a 110 volt household outlet type plug/socket for a safety key, the battery wire would attach to one side of the outlet, the launch button/continuity indicator to the other side, and a replacement male plug end from the hardware store would be used for a "Safety key"-- (or a spare bit of cord off an old toaster or VCR) with the wires stripped and twisted together, and taped up...

Hope this helps! Later! OL JR

Green Jello said:

Ok....if I make one of these things (for fun) my first one will be very simple and basically a copy of the Aerotech one in a different case with better and more fun switches. So here is a crude diagram of how I understand it to be:

View attachment 108256

Does this look correct to you guys?

What I want to get is probably a key for the arming switch and a push "momentary" button for the launch switch. If this is correct, I guess the main thing I'm wondering how to do it adding small lights for arming, continuity, etc.

Click to expand...

Here you go... Modded your drawing to show where the LED indicators would be wired in, and how they would work... You can delete the buzzer if you wanted... I personally don't like them, but some folks don't like the LED indicators... Totally your choice...

Later! OL JR

PS. Okay, one slight tweak (and no I'm not bothering to fight the stupid new totally F-ed up version of "Paint" that came with Windoze 7 on our fairly new laptop... how they managed to take a totally easy and good program like PAINT and managed to SCREW IT UP ROYALLY so that it's a total PITA to use, I'll never know, but the geniuses at Windoze managed to accomplish it! Guess I'll have to go find some freeware someplace to replace it with something that WORKS!) Anyway, the "battery power" LED will only work with the ignitor hooked up in this configuration... basically it should be wired between the battery clamps... just inside the case... hard to do with the way this is drawn... anytime the battery is hooked up and the system is getting power, the LED would be on that way, regardless of if the key is inserted, there's an ignitor in the clips, whatever... Just so ya know... Basically if you reversed the locations of your battery and ignitor in the diagram, this would work.

Radio Shack is great if you have one locally. I find the clerks in mine are pretty clueless, unless you're buying a cell phone. Don't expect a whole lot of help.

If you have to mail order, I like Jameco.com. they will send you a real paper catalog which is still a nice way to shop. They don't carry every thing, but will have this stuff.

If you have real special needs, digikey.com has like 10,000,000 different things in stock. But unless you know what you want, it'all be hard to find it.

Green Jello said:

Now....I just need to source all the parts. I've noticed Radio Shack actually has most of what I need and it's pretty cheap. Any good online sources you guys recommend?

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Green Jello said:

WTF Luke? The text was 24pt Arial and you totally changed it!

Thanks man. I figured that's where the continuity lamp would go, but I had no idea about the battery power one.

Now....I just need to source all the parts. I've noticed Radio Shack actually has most of what I need and it's pretty cheap. Any good online sources you guys recommend?

Click to expand...

You're welcome... sorry to muss your drawing... flip the locations of the ignitor and battery, and you've got it.

I dunno what the heck is up with the new version of paint on my computer... it S U C K S !!!! I used to be able to knock out fairly high quality diagrams and stuff in paint in nearly no-time, and now this new one seems to fight me every single step of the way...

Typical computer "upgrades"... take something that works perfectly fine and SCREW IT UP!!!

Later! OL JR

PS. as for sources, some stuff you can get at Radio Shack, some stuff you'd be better off at the auto supply or indoor lumberyard type store... lamp cord is cheapest at the dollar store... Good luck!