Would this work?

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Well-Known Member
Jan 18, 2009
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I'm not much of an electrician and less of a schematistician.
Would this work for a launch controller?
Would I need some other electrical thingees to get the current to flow where it is needed? Or something like that.
More complicated than necessary, but looking for a bit of a cool factor.
Idea is-
1. put the key in and turn it, yellow light comes on.
2. flip the switch and the red light comes on.
3. push the two buttons and the rocket goes bye-bye.
Have to have the key turned and switch flipped to be able to launch.
Can use the test light to test the controller and the launch cables.
Not sure what to use for batteries, probably 12 volt.
Maybe a sealed gel cell, or just two of the square 6 volt lantern batteries.
Be housed in an old ammo can, that will hold batteries, board, and rolled/wadded cables.

Thanks for any help,


Just a couple of thoughts.

First, with the double pushbutton, the arm switch is a little redundant, I think that the main key switch would be enough, that is unless you like seeing the lights;) .

Second, there is no continuity check in your diagram. Without a continuity check you have no idea if your ignitor is connected.

You might want to search on other launch controllers and see what they have done for a continuity check

Continuity check you say? Hhmm. Hadn't thunked of that.
Will do.
Yeah I know, but-
1. have the parts laying around
2. lots of switches and lights increase coolness
3. I really don't like things happening before I want them to

Thanks for the input,
Have a good one,
The controller I built ... when you turn the key. the continuity light(green) comes on... then you just push the fire button to launch...

Then again... if I had them I would probably wire a bunch of lights into it... Heck... everyone like lights...LOL

since you have a lot of switches, how about using one of the momentary ones for a continuity check? That adds another switch and light/buzzer. Also you could add a warning buzzer on the arming switch, that would give you a positive indication of being ready to launch, and be really obnoxious so that you don't leave it on long...:D

the two 6V batteries would probably work fine. I have had
some trouble using them in the past, and I avoided using them whenI built my controller. They last about a year, and if they go dead, you need to buy another one. I went to Mouser and ordered a 12V 7AH Gel-Cell, and charger. I believe it cost me $40 6 years ago, but I haven't had to buy another battery since. All I have to do is charge it and I am ready to go for the next launch.

Good luck on your build, and oh yes... Pictures, we like pictures....


Here's some recent threads tha might be useful.






I don't recommend lantern batteries unless you got them for nothing, and then they might work. Use a 7 AH lead acid gell cell or 12 volt NiMH rechargable pack.

Also the use of two launch buttons is not necessary and in the excitment of a launch you might lift off one finger.

You really do want a continuity check light to make sure your ignitor is good before you launch. A 12 volt led plug in checker is ok, but it won't pass more than 20 ma so you don't know if you have high resistance in your clips or launch wires (and it's another thing to loose), whereas the continuity check circuit does the same thing and checks the entire circuit.

Bob Krech
Ok, is this better?


With a panel that looks something like this-

You're sure that testing the circuit via the continuity test will not launch the rocket?
Most likely not going to use LEDs, too hard to find the 12v in all three colors; I'll just use regular lights.
I really wanted to go with a sealed gel cell from the get go, but have some of the 6v lantern batteries around.
Easier to build it once than to change things later, so go with the sealed batteries from the start.
Especially with the limited space in the ammo can.
The lamps won't actually say "Warning", "Danger", & "Go". Or maybe they will?
If you'll notice, I still have TWO launch buttons, because I WANT two launch buttons, so :p.
{Since I'm new around here I'll point out for clarity that the preceding comment and "pppttt" were meant in good nature with no offense meant}

And if I do say so myself, one can actually get pretty good results using the ole MS Paint program for these kind of purposes.

Thanks for the help, you guys may actually enable me to do this,
Greg, Looking Good!!!

Just a couple more suggestions, If you are wanting the two launch buttons for two handed operation, you should space them as far apart as possible on the box.

Also, you will want to put the continuity light and buzzer in parallel, not in series as you have shown. You might also think about having the buzzer on the switch for continuity, with the LED wired without a switch for a continuous readout.

Looks good, keep up the good work.

When you pick out those momentary switches for the launcher, make sure you get 12V DC rated switches and not switches only rated for AC at low amp loads.
Ooohhh, good call.
Just checked, and...
YES, the ones I have are in fact the low amp versions.
Have to get new ones,
Thanks much for saving me the trouble of having to figure that out later,

I did my controller with low amp Radio Shack AC switches at first so I figured I would bring it up in case you did something similar. After reading up on it, seems like the switches were doomed to fail (but would work fine for a while until they did). I took one of the AC switches apart for kicks and there really was not much to it. The switch was just a metal washer that pushed down onto two tiny contact areas to make a connection. I took apart the DC switch I got and it had much more contact area and a very solid connection that snapped into place with a click.

Automotive shops are a good place to get 12V DC rated switches.
Originally posted by grimlock3000
Automotive shops are a good place to get 12V DC rated switches.
I do quite a bit of shopping at NAPA, AutoZone, and the like.
And, they have better stuff than Radio Shack(RS); like the butt connectors that have something like hot glue in them that you crimp on then heat up and they get waterproof.
I've really always thought that RS has kind of chinchy stuff to be honest.
Biggest problem with the RSs in my area is that they always have 2 out of 3 or 3 out of 5 things that I need.
But still a fun place to go nose around.

I've really always thought that RS has kind of chinchy stuff to be honest.
Biggest problem with the RSs in my area is that they always have 2 out of 3 or 3 out of 5 things that I need.

No doubt much of what RS sells is not designed to be used in high stress situations. I can not really complain, my options for electronics supplies are really limited in Maine :p

Luckily both the RS locations in my area are within 4 miles of my house. I have not looked for anything yet that has been out of stock in both locations. On the other hand, I have bought a lot of stuff that never got used or was wrong. The RS employees never knew enough to tell me something was a good idea/bad idea once I told them what I was doing.
Originally posted by grimlock3000
I did my controller with low amp Radio Shack AC switches at first so I figured I would bring it up in case you did something similar. ....

Automotive shops are a good place to get 12V DC rated switches.

How many amps are you talking about them needing to be rated for? 10? 15? 30? 60? What are we talking?
The one I have is (man, I'm only 33 and that is some SMALL writing they have there :eek: got to get out the magnifying glass) 1 amp @ 125v DC - 1/2 amp @250v DC. Not sure how that works out at 12v DC.
Maybe I just need another one of these.

Went to an electrical supply place and they didn't have any. The could get them for me for about $5.00 apiece. No wait, they only special order for business, not individuals. :mad:
Radio Shack nada tambien. :rolleyes:
Went to a fleet store; they had 60amp starter buttons for $5.95 each. Picked up two. If they can't handle the current, well.... :D
Only things now needed besides the battery is a green lamp and the actual panel itself.