DIY controller project

Feedback or comments are fine.

I just went to "The Shack" to pick up parts to build a new launch controller as the older home-built one I have isn't up to regulations (no removable safety key).

I was trying to beat what I would spend on a new Pratt Hobbies Go Box but I didn't do it; ended up being about the same but with a few extra parts and no shipping so maybe I didn't do all bad.

It'll end up with a few extra features too. I have LED's for both a power indicator and a continuity indicator (both have resistors built in). Using an audio jack for the safety key (sales guys were familiar with rockets and thought that was cool).

I wanted to be able to use either battery clips to go to something bigger (daisy chain a couple 6v lantern batteries) or use internal batteries (2x9v) for more simple launches. Do acomplish this I added a toggle switch right next to the 9v battery connectors so I can cut them out of the circut.

Launch and continuity check switches are both momentary switches. Due to the fact that I might be hooking up 2 6v lantern batteries the guys suggested I add a fuse to protect the whole system (keep from blowing switches or the LED's). They recomended the same kind of fuse you'd put into a car, 20 amp fuses that way if anything spikes the fuse goes and everything else is fine. That would be my first question, was that really necessary? Would that size fuse keep from lighting a cluster of Quest igniters? I'm not the most knowledgable on that type of electrical work but I have a soldering iron and I know how to use it.

I guess my other question is whether or not I might need more of a resistor in the continuity circut to keep it from igniting. The only resistor on that circut is the one that came with the LED.

I've attached a basic diagram that I downloaded from an older thread on this forum. Changes will be battery clips comming off the back end of the square, the switch next to the power source to cut out batteries if I'm using the clips. I may eliminate the power LED to keep from popping it if I'm using the 2 6v lantern batteries. The fuse would be mounted opposite the safety key switch.

The fuse can't and won't protect the LEDs. That's what the resistors are for.
The fuse is a good idea but it is used to protect the wiring, from internal construction shorts or operator error. Example: accidentally short the clips together on the blast deflector plate then press the launch button. Hold it long enough and the lantern batteries may start smoking the wiring. If the 9 volt batteries in series don't pop the LED then the lantern batteries won't either.

What voltage are these LEDs (with built in resistor) rated for ?

I also would not bother using the nine volt batteries.
Spend more money for AA batteries and holders.

The LED's are rated 12.0 typical 16.0 max for voltage and 12mA typical 20mA max for current.

The primary reason I'm using the 9v batteries is I already have 2 connectors for those from my old controller that isn't regulation (and is huge and made of wood). I haven't had any trouble with that setup but the safety switch is a lighted rocker switch, maybe that needed more juice.

I like the thought that the fuse wasn't a waste of money...

I'm not sure I'd use the 9v batteries. If you wire them in series, you double the voltage but halve the current. If, however, you wire them in parallel, your voltage stays the same, but you double the current. That would probably be fine for single Estes or Quest ignitors, but I wouldn't use it for a cluster.

Well, make sure the resisters on the leds are below the current needed to ignite your lowes resistance ignitor.

otherwise you could launch under detection of current.

I used a 12volt cigarette lighter from radio shack. for power with a 25ft lead... (works perfect) i also made a battery clip lead..

I thought about using a battery like a lipo, but thougth that was needless in a personal launcher where i could get my car within 25' of me...
I used audio disconect to and from the controller (just for packing)
i can coil the battery leads and launch leads...
Problem is on the recieving end of the audio (microphone plugs) some are not a full circuit..and the ones i bought i kept bending the clip, and havign to take it apart to fix it..
My next launcher will use automotive trailer connectors...(easier) and more durable...

qquake2k said:

I'm not sure I'd use the 9v batteries. If you wire them in series, you double the voltage but halve the current. If, however, you wire them in parallel, your voltage stays the same, but you double the current. That would probably be fine for single Estes or Quest ignitors, but I wouldn't use it for a cluster.

Click to expand...

Same current in series, not half.

qquake2k said:

If, however, you wire them in parallel, your voltage stays the same, but you double the current. That would probably be fine for single Estes or Quest ignitors, but I wouldn't use it for a cluster.

Click to expand...

I don't intend to use the 9v setup for clusters, I would cut the power from them and hook up the battery clips up to something more powerful for that.

No one seems to like use of 9v batteries, I'm not sure how they're wired in my current setup but I've had 0 ignition failures with only Estes igniters. I'd only use the 9v to check continuity or for launching single motors.

At first I thought 6v lantern batters wired in series would work for clusters but they're about $5 each and I can get a nice 12v 7Ah hobbyco battery locally for about $20.... hmmmmmm....

The 12v battery wouldn't fry any of my components would it?

The stronger battery will do no harm to the components.
But stronger battery makes it even more important to use a fuse to protect the wiring against shorts.

Dale Saukerson said:

The stronger battery will do no harm to the components.
But stronger battery makes it even more important to use a fuse to protect the wiring against shorts.

Click to expand...

An autoreset thermal breaker is more convenient than a fuse. It protects the wiring from dead shorts without having to replace a fuse. I've been using them for 15 years in launch systems. Only a couple bucks. Just wire them inside without needing access to a fuse.

I'll be doing something similar with my system under development.
I mention fuse simply because it's more familiar to most folks.

Peregrine Falcon said:

I don't intend to use the 9v setup for clusters, I would cut the power from them and hook up the battery clips up to something more powerful for that.

No one seems to like use of 9v batteries, I'm not sure how they're wired in my current setup but I've had 0 ignition failures with only Estes igniters. I'd only use the 9v to check continuity or for launching single motors.

At first I thought 6v lantern batters wired in series would work for clusters but they're about $5 each and I can get a nice 12v 7Ah hobbyco battery locally for about $20.... hmmmmmm....

The 12v battery wouldn't fry any of my components would it?

Click to expand...

i dont use a fuse at all.. its fine.. MOMENTARY SWITCH... if it starts smoking, and your not pushing the button . un plug it... if you dont light after 5seconds, let off the button... duh...

if you use a car cigarette lighter,,, and plug it into a car, it has a 20a fuse already...

i also use a Black and decker battery pack for jumpstarting cars, has a max 5a output ciggarete plug in it.. if i dont want to move the car and the wind moves the pad to a corner of the yard... 60 bucks rechargable forever, and a good thing to have anyway.....

the little orage box to the left is the best power supply.. i have lauched 8 motor clusters with estes ignitors.., and mid power copperheads...
also comes with an air comppressor and a 500amp car jumpstart....

Well I went ahead and put it all togther today, tested with a single Estes igniter and all worked well. Continuity circut didn't set off the igniter, launch button did, light and audio plug/safety key worked. I don't have any Quest igniters to test it with so that will have to come later.

I still have to wire the larger battery clips to the 2nd audio plug for use with my larger additional battery but the interior of the box is done. The audio jack on the box is wired properly so I shouldn't have to do any more than wire up the plug correctly and I'll be good to go.

If I get time I'll upload a few pictures...

(for those that followed it yes I am going to finish my AMRAAM build thread...too cold to paint...even if the paint would be fine it's still cold enough I don't look forward to being outside right now)

Pictures, yes please!
Since I am attempting the same project, did the earlier posted schematic prove to be the way it was built?