Sneak peek at the new launch controller

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Lugnut

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The Watkins Engineering System LCS-300 =) Its a work in progress, but coming along nicely. Don't ask how much I've sunk into the parts, lets just say its more than a standard Estes Solar controller ;)

Basic specs are master key for power (with indicator light), master arming switch, which activates volt panel meter. I have a switchable resistor to simulate a load to do an accurate battery power test on the voltage meter. Continuity test is via LED and piezo buzzer. Red momentary button is launch. Controller will support up to 3 separate pads (next project is an aluminum 3 station launch pad); each independently selectable, though I'm not inclined towards drag race launchs, it is capable. All wires will be connected to front access panel via banana clips and binding posts. Power is via external 12Vgel battery. I will carry the battery and all wires in a plastic tool box, so that way, its easier to transport to the field

Schematic has been altered several times as I've gone through this, but as I had no prior electronics experience, I've done this as much to quell the 'hacker' instinct and try and gut through it as much as anything else. If it looks like a St Joseph controller, its no accident, I saw the picture of theirs on their website, and liked the looks of it. and thought I'd make a 3 station version with a couple extra bells and whistles

Still need to make up all the cabling, find another set of plug posts (RadioShack was out), and do some final testing(haven't tried to light off an ignitor yet).

PS I know its not an NAR compliant keyswitch, thats still to come, so the safety nazis among you can keep your brown shirts on. ;)

Lugnut
 

Lugnut

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random pic: Heres my son with the Super Eagle before launch today.
 

Lugnut

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Here it is (part of it anyway) right after launch
 

grimlock3000

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Looks neat. One thing you will want to look out for, if your momentary switches are these...

https://www.radioshack.com/product.asp?catalog_name=CTLG&product_id=275-609

...you will want to replace them with better DC rated switches. The AC rated Radio Shack ones are not built well enough to hold up to repeated launched and have failed at least a few people. When the cheap switches fail, they get suck in the ON position as well.
 

Lugnut

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Thanks for the heads up on that, i think those are the ones I have. I had originally tried to find a good heavy duty momentary switch, but couldn't locate a suitable one on Ebay at the time, and this was the highest Amp rated one RadioShack had in stock at the time. I'll have to change that one out.
 

Micromeister

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Originally posted by grimlock3000
Looks neat. One thing you will want to look out for, if your momentary switches are these...

https://www.radioshack.com/product.asp?catalog_name=CTLG&product_id=275-609

...you will want to replace them with better DC rated switches. The AC rated Radio Shack ones are not built well enough to hold up to repeated launched and have failed at least a few people. When the cheap switches fail, they get suck in the ON position as well.
Grimlock ya took the words right out of my mouth...off the fingertips I guess would be more accurate;)
I've had many of the RS monentary's weld on various systems over the years. I found a really nice 20amp spst momentary contact swith at Allied Electronics. but it's been discontinued. What did you end up using DC rating wise and where did you pice them up?
Lug nut if you have a plug type disconnect in the circuit, I wouldn't worry about the Key switch problem, it becomes a redundant safety, sort of like this:)
 

Lugnut

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I don't have a plug disconnect, I have a toggle arm switch.

rough description of circut flow is battery> Power (key switch)>arm toggle switch>continuity check (momentary)>momentary launch switch>pad select (on/off)>banana plug to pad

I guess it raises the question, who carries a good 10A-20A momentary pushbutton switch (that doesn't have a $25 minimum order charge, like a Digikey/Mouser)?
 

grimlock3000

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*Momentary launch button* 12V DC @20A, or @40A if wired in parallel. You can also wire this to fire when pressed up, down, or either $4.49:

https://www.radioshack.com/product.asp?catalog_name=CTLG&product_id=275-709

I wired mine up at 20 amps, which really is plenty for most rocket launching needs. You can wire it up at 40 amps for large clusters, just make sure the rest of your wiring can handle that much current. One cool thing about this switch is that it takes a lot of effort to switch it. You really have to push on the thing to get it to click ON so almost no chance of misfire from accidental press or touch unless you manage to kick it. It has a solid click when it goes on too. I took mine apart to check it out, it is many times better than the cheap momentary switches.

In the cheap one, the button presses a small thin metal disc onto two small pieces of metal about as this as a pencil lead. The power goes up one side, through the disc, and back out through two VERY small contact patches which is why they weld themselves together.

Anyway, check out the rest of my controller here:

https://www.rocketryforum.com/showthread.php?s=&threadid=9202
 

Lugnut

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Yeah I had seen that, I was leaning more towards a push button rather than a toggle switch, but if I can locate a suitable one, then I guess beggars can't be choosers.

Lugnut
 

Lugnut

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Well, I got it working last night. I had had a problem with it shorting, it was testing positive for continuity even without clips plugged it. I figured out that when you install the banana clip binding posts on an aluminum face plate, it creates a circuit between both posts. I needed to wrap tape around the posts to create an insulating bushing so there was no metal to metal contact. After that, worked like a charm. I sacrificed an ignitor to test, and it went off in less than a second with a 30' clip.

I still need to wire up the second pad switch and get another set of binding posts for the third, but otherwise it will be done. Once it is I'll take better pictures of the inside and out. If anyone is interested in a schematic, let me know and I'll try to work one up when I get the time.
 

Cajunman06

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Currently, I have my controller built using one of the above mentioned RS push button momentary switches. The difference with my system is that I use a 9V battery within the controller to siganl the relay boxes.

What is the opinion regarding using this "cheap" switch with that sort of set up? I'm not opposed to changing it out, but I would rather not. Seems like there should be some decent momentary push button switch available at an auto parts store.
 

Lugnut

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Question is amperage more so than voltage, they're rated to 3 amps I think. I think you need to consider what guage wire is in the controller, clips, whether your doing clusters, how long the clip length is, plus other things I don't know enough to consider (total resistance of your launch circuit), so you can sit down with Ohms law equation and figure out how much current your pulling.

PS Marine parts store might be a good source too....

Lugnut - who really knows squat about electronics
 
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