Relay launch controller design help needed.

I had a thread on the old forum about this but it is now lost.

I want to finish building my 12V relay launch controller for HPR. I want continuity check at the pad as well as an alert in case the relay is bad.

I think we came up with the design I attached but I can't remember exactly.

Will this work?

Thanks!

So far, the only change I would make is to connect b2 to the other side of the ignitor. You need to complete a circuit from the both sides of the battery to both sides of the ignitor, with one side having the switch and buzzer in series. Also the bulb across the battery will just waste power, unless you want to show the battery is live. And, the bulb in the controller isn't doing anything important, other than stealing current from the relay coil.

falingtrea is right about the continuity buzzer, it won't work. The way you have it drawn, the circuit goes from the battery, through he normally closed (NC) relays contacts, through the switch when closed, through the buzzer and back to the battery. It never goes through the igniter.

I would put the buzzer between the relay contacts and the continuity switch. Then the switch closes to the lead going to the igniter, through the igniter and back to the battery.

He's also right about the bulb on the controller. It can only light when the safety key is in and the launch switch is closed. The only thing it does for you is to show you that the current is flowing through the relay coil, not if the coil is pulling the relay closed. It's basically a bad relay/dead battery indicator if it doesn't light.

heres one I've been using for about the last 25years without any problems at all. I think it has everything you were looking for.

I've used the same basic scheme in two different launchers, one strictly for 2 to 12motor clusters. the other combined with an on-board Solar cap-discharge system to allow use with single or cluster models with the addition of an external 12V Gelcell battery.
Both have been in pretty much monthly used since the early 80's

Hope this helps a bit.

Micromeister said:

heres one I've been using for about the last 25years without any problems at all. I think it has everything you were looking for.

I've used the same basic scheme in two different launchers, one strictly for 2 to 12motor clusters. the other combined with an on-board Solar cap-discharge system to allow use with single or cluster models with the addition of an external 12V Gelcell battery.
Both have been in pretty much monthly used since the early 80's

Hope this helps a bit.

Click to expand...

I have to say that I have been using Micromeisters relay launcher for quite awhile now and it works very very well.

Luv2launch said:

I have to say that I have been using Micromeisters relay launcher for quite awhile now and it works very very well.

Click to expand...

Thanks Andy,
It's so nice to hear positive feedback, and that others enjoying success with a system thats given me so much joy over the years

Attached is a schematic for a relay launcher that was posted on TRF by Guy Smith about a year ago, that I redrew. It has most of what you want, except that the welded relay contact detector is a "safe" indicator when they are not welded rather than an "unsafe" indicator when welded. Not as desirable, as it requires active attention by the user to check for safe, but MUCH simpler to implement. My own relay launcher has an "unsafe" audible alarm, but it required a transistor and a Schottky diode and some fiddling with resistor values to make the alarm sound only when it was supposed to. Perhaps the solution to Guy's circuit is as simple as adding a high impedance beeper between the + side and the NO contact on the relay. It would sound whenever the relay was activated intentionally, but that's probably a don't care or even a feature (you know the relay is activated). I'd have to think about that one some more.

I like having the "armed" indicator on the control box (not included in Guy's design) lit only when the safety key is inserted. To me, that is the meaning of "armed". A separate indicator (light or meter) to show that the system is powered is a plus.

View attachment Relay_Launcher simple.bmp