LPR/MPR Launch Controller Build

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Yes, you would only need to use a 10 A fuse, typically. My homemade controller uses a 10 A resettable circuit breaker and it’s never blown, but it would if there had been a dead short for a few seconds. The ones you’ve identified look ok. I also use the 7 Ah SLA batteries on my standard controller.

I saw the 30A fuse in this build and thought it was a bit large as well. I put a 10A resettable fuse on my wireless relay launcher also. I just built it, and don't have many cycles on it, but the fuse has yet to blow in my tests. However, I did blow the 10A fast-blow fuse in my multimeter while trying to measure the amperage through a Copperhead igniter!
 
@Mike Haberer - The 30 amp breaker you refer to seems like a lot for the 12 volt on your relay, or is the '12 SLA batteries' you mention actually 12 batteries of the SLA type?

I'm looking at a single, external 12 volt 7Ah SLA battery connected to the controller with 10 feet of 18AWG zip wire. The run out to the pad is a 100-foot 16/2 medium-duty extension cord. Could I get away with something along the lines of a 10 or 15 amp breaker? I'm thinking of just putting it inline on the positive lead coming from the battery, before the controller, using these:

https://powerwerx.com/atc-ato-inline-fuse-holder-18-gauge-redhttps://powerwerx.com/resettable-atc-blade-circuit-breakers
@Voyager1 - Your thoughts?

Thanks.
One 12V SLA battery, 12aH on the relay box, 7aH on the controller box.

At the time I built the relay system I was relying on things I was reading when I was doing the design. The design I stole mine from (it was 10 years old and all of the parts were Radio Shack, so I had to research equivalent parts) used a 30A breaker, so I cloned it.

The thing that has not been mentioned to this point is that my relay system can fire 4 pads at the same time, so it could generate a fair amount of current. The launch controller on that system only has a 10A breaker, but the relay box has a 30A. I used automotive relays that are also fused at 30A. Since a fused relay could be disastrous in a relay system, I overbuilt it on purpose. So, in theory, no relay in that system should ever become fused due to overcurrent, nor should the entire relay box melt down if the combined draw of the relays exceeds 30A.

In retrospect I may have foregone the individually fused relays and used low voltage relays instead. When I did my testing, only one of the 4 relays would fire due to the voltage drop over the 100-foot distance (again, I didn't calculate voltage drop ahead of time, lesson learned). The choice was to either go to 24v or use a bigger wire gauge on the cable. Since the box was built, switching to 24v wasn't really an option, plus the fact that 24v batteries aren't easily had. If I had known more at the time, I could have switched to using a 6S LiPo, but I was LiPo illiterate at the time. Consequently, since I was using DB-9 connectors on the cable and there were no standard DB-9 cables that were not small gauge wire, I bought 100-foot rolls of 18-gauge wire and built my own.

My docs for the relay system are attached below.

P.S. I did not put continuity checks on the relay pad at the time because I couldn't figure it out in my head but have designed that in now. I haven't made the mod yet but intend to. The docs include the design with and without and the BOM includes the necessary add-on components. The .dsn file is a TinyCad file.
 

Attachments

  • Launcher & Relay Design Components.xlsx
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  • Launch Controller & Pad Relay Circuit Design.dsn.txt
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  • Relay Box Cover Design.pdf
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  • Relay Box Internal Design.pdf
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  • Relay Box Side Designs.pdf
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  • Relay Launch Controller Cover Design.pdf
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  • Relay Launch Controller Internal Design.pdf
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@Mike Haberer - The 30 amp breaker you refer to seems like a lot for the 12 volt on your relay, or is the '12 SLA batteries' you mention actually 12 batteries of the SLA type?

I'm looking at a single, external 12 volt 7Ah SLA battery connected to the controller with 10 feet of 18AWG zip wire. The run out to the pad is a 100-foot 16/2 medium-duty extension cord. Could I get away with something along the lines of a 10 or 15 amp breaker? I'm thinking of just putting it inline on the positive lead coming from the battery, before the controller, using these:

https://powerwerx.com/atc-ato-inline-fuse-holder-18-gauge-redhttps://powerwerx.com/resettable-atc-blade-circuit-breakers
@Voyager1 - Your thoughts?

Thanks.
Would definitely work. Thanks for posting. I may add this to my LPR controller.
 
My docs for the relay system are attached below.

The docs include the design with and without and the BOM includes the necessary add-on components. The .dsn file is a TinyCad file.

Not familiar with TinyCAD. If it is not too much trouble, can you post an image of the relay system wiring schematic?
 
Not familiar with TinyCAD. If it is not too much trouble, can you post an image of the relay system wiring schematic?

It's not one diagram, it's 4. One for the launch controller. One for the relay box without continuity checking (built & tested). One for the relay box with continuity checking (not tested). One for the serial cable design that matches the specs of the controller and relay boxes.

TinyCad is free. Download and install it, download the .dsn file and drop the .txt extension. Open the file.
 
Would definitely work. Thanks for posting. I may add this to my LPR controller.
I received the 10A circuit breaker and blade fuse holder I referenced above. Be warned if you order this that the holder is designed for the short blade fuses, not the breaker, which is taller. The breaker fits fine, but the cap won't completely cover it. Other than that, this will work perfectly for inline protection.
 
Since the holder is in the box the cap isn't needed and would actually be a detriment to doing a reset if and when needed. I would just cut it off......
 
Since the holder is in the box the cap isn't needed and would actually be a detriment to doing a reset if and when needed. I would just cut it off......
I kept the cap, but separated it from the housing and cut an opening in the top. That way the cap can help keep things clean down inside, but not interfere with resetting the breaker.

This is on 10ft of 18 gauge zip wire, connected with a heat shrinkable butt connector.

IMG_0555.jpg IMG_0556.jpg IMG_0558.jpg IMG_0559.jpg
 
The TinyCad file I posted above had a tab with continuity checking added to my relay controller. My wiring design was wrong. I've revised it, accordingly. One design uses one LED per pad to show continuity. Then I figured out the design for using one buzzer for all four pads. Both are included.
 

Attachments

  • Launch Controller & Pad Relay Circuit Design.dsn.txt
    780.3 KB · Views: 15
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The last step was to run a test. On the first try the amber Power On LED did not light up. Breaking out the multi-meter showed the LED was fine, but the connection at the busbar was broken. The post on the keyed switch was right over that connection and broke it when the lid closed. Snip, re-make and move it over one position on the busbar to the left. Time to re-test.

Keyed Switch on...

View attachment 498692

Armed switch toggled on, no continuity...

View attachment 498693

Armed switch on with continuity (second green LED connected to the output leads) ...

View attachment 498694

Launch button pressed (box LED goes out, continuity LED gets brighter) ...

View attachment 498695
Nice build! Good work!
 
I used the final 25' of 14 gauge wire I had remaining and built a wire lead with banana plugs on the controller end and alligator clips on the other. The final step will be to print and attach labels to the switches and LEDs.

All-in-all, a challenging and fun build. This will be easy to carry to the field and use. Now I'm itching to use it. Oh, it's winter in the Midwest and it's -2 degrees outside. The grandsons are 1,000 miles away in Denver (another really deep sigh). I guess I have to go back to building rockets....
Thanks for the work you've put into this. I've been looking for a solid, thought out, well-engineered LPR/MPR controller design and am going to use your basic design; it's really one of the best laid-out builds I have seen. I am considering some changes and will likely use a Harbor Freight Pelican clone as the case and a 12v 5.5A SLA, and so will have room to surface mount a breaker and buzzer.

I'm close to green-lighting this little project, and now that it's all said and done is there anything you might have done differently in the design or basic build?
 
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