Launch Controller Parts Help

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OverTheTop said:
Go with the relay design for long distances. You won't regret it.

Have a good think about the cable you will be using. It is one of the high-maintenance items in the launch kit IMHO. Mishandling is the rule rather than the exception. :(.
Click to expand...

I built a multi-pad system for the local club. Except for the nice slope-faced panel, everything was bought at Radio Shack (they are common parts that can be found elsewhere). The system used two sets of relays; low power inside the launch controller panel box that switched between measuring conductivity and firing, and the pad box that had high power relays to handle firing current. The system also used a pad-located 12v battery. Control wiring to/from pad was done with Cat5 network cable; power from battery at pad was brought to control box by a common extension cable. The only thing that ever wore out or broke was the key switch - I think somebody dropped the control panel.

Since Radio Shack is gone, my favorite place for these sorts of parts is BG Micro in Garland, TX (just East of Dallas); bgmicro.com .
 
Tyler P said:
Also, if I'm reading correctly, minimum distance from the pad has to be 100' from hpr G up to L motors, so 100' for levels 1 and 2.

What gauge is usable for this kind of distance?
Click to expand...

This is incorrect. As per HPR safety code, single motor distances for HPR G to J motors is 100', K is 200' and L is 300'

Tyler P said:
I'm going to revive this thread, as I'm looking to build a 12V controller.

I've looked at a bunch of diagrams and they're starting to make some sense (I'm really not strong with electronic circuits), but I'm missing a bit of information. What is the minimum resistance needed for the continuity check so that the igniter doesn't ignite but the LED will light up?

This will be a simple, single motor launcher but I may want it to be capable of doing 3 motor clusters later.

Thanks in advance!
Click to expand...

If you are doing clusters, add 100' to the HPR G to J distances, now 200', K is 300' and L is 500' I believe that is the total impulse, not the impulse of each of the clustered motors. 3 clustered J motors would likely put you into the L cluster 500' distance.
 
Handeman said:
This is incorrect. As per HPR safety code, single motor distances for HPR G to J motors is 100', K is 200' and L is 300'



If you are doing clusters, add 100' to the HPR G to J distances, now 200', K is 300' and L is 500' I believe that is the total impulse, not the impulse of each of the clustered motors. 3 clustered J motors would likely put you into the L cluster 500' distance.
Click to expand...

Thank you! Somehow I didn’t recognize the incorrect safe distances. I should have.
 
Handeman said:
This is incorrect. As per HPR safety code, single motor distances for HPR G to J motors is 100', K is 200' and L is 300'



If you are doing clusters, add 100' to the HPR G to J distances, now 200', K is 300' and L is 500' I believe that is the total impulse, not the impulse of each of the clustered motors. 3 clustered J motors would likely put you into the L cluster 500' distance.
Click to expand...

Interesting. I don't know how I missed the distances when I looked at the Tripoli HPR chart. Thanks for pointing it out, though!

The good thing about going the relay route is that I can just add more sections to the controller feed without sacrificing power at the pad. So I can start out with 100' for my L1, and can still use it to get my L2. If I progress beyond J motors, I can add in another 100' or 200' to go to the edge of L2 power.
 
Tyler P said:
So, I'm planning on using 3s LiPo packs. In theory, the voltage drop should be less than other traditional cells, as LiPos are known to be able to deliver more current with less voltage drop through their discharge cycle.

The packs in question are 16000mah 11.1V 15C. Again, in theory, these can deliver 240A for the length of their discharge cycle. I have two of them and also have made a parallel harness to use them as a 32000mah pack that I've used to power 35lb thrust trolling motor on my canoe.

Would you say it would make more sense to run a system such as you describe with a control box running to a pad box or could I keep it more simple with a direct run? A direct run will mean running heavier gauge for the whole length. I guess I can calculate the voltage drop by calculating the resistance per foot of the wire in question.

At this point, not even having my L1, but intending to progress to at least L2 over the next couple years, I think I'm okay with limiting this setup to the necessary 100'.

Given what I've seen here in this discussion, and with your help, it looks like a 300 Ohm resistor will suffice ahead of the LED. Now the decision is whether to build it with a relay setup or direct run.
Click to expand...

Say you want to run 100ft of wire to your launch pad, and say you are using typical extension cables from your local big box store.
These are nominally 16 gauge copper wire. A quick look and that will indicate about 0.4 ohms per 100 feet (~4 ohms/1000). With the circuit supply at the control point you are looking at 200ft of wire or a total of 0.8 ohms of wire resistance. Now for a 3S pack you should see 12V. This means if you have a dead short at the pad connections you could only see about 9.6 Amps in the circuit. No need for more batteries in parallel. You should be able to launch a single starter with this configuration. If you double the distance then you will double the resistance and that will halve the current 200ft : 1.6 ohms, 12 V/ 1.6 = 4.8 Amps. This assumes No other connection resistances. This would be considered below marginal for a normal starter.
 

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