My Scrap Pile Launch Controller Project

The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Tobor

Get your peanuts....
TRF Supporter
Joined
Oct 8, 2016
Messages
2,868
Reaction score
1,251
Hello there,

The scrap in the title is a reference to all the "stuff" I have collected from my various hobbies and activities over these many years. Everything from R/C planes and cars, computer case/component modding, and home and car audio to name a few.

Anyhoot, when I started building my first MPR, the upscale of Pem-Tech's Kraken, I realized that NIRA does not have a 1010 pad. At least not that I have seen so far. So a while back I fabbed my version of a JawStand pad w/8' 1010 rail, and needed a LC to go along with it.

My first version of a scratch built LC, using all new parts, priced out to over 200 smackers! As funds are tight atm, I came to the conclusion that I had enough junk, errr collected parts, to hack one together without spending a dime. (Not quite true but close).

At some point in the future I'll get around to the "All new parts" version, but for now the scraps have been dusted off and repurposed for this project. :facepalm:

I started working on this project last Saturday. It is moving along slowly as I tend to do these kind of projects in an "On the fly" or "Seat of the pants" (take your pick) approach.

Schematic
My Scrap Pile Launch Controller.jpg

Sorry about the faded image. I used EagleCAD to draw up the schematic but it's exported image doesn't scale down well.

Initial collection for consideration
My Scrap Pile Launcher - Case_Small.jpgMy Scrap Pile Launcher - Hardware_Small.jpg

The case is from my first 12V cordless drill set I purchased when I used to be a field service tech, installing/servicing PBXs and PC based voice mail systems. The idea is to have everything fit inside the case.

Current state of base unit.
My Scrap Pile Launcher - Case-02_Small.jpg

I am using 0.2" ply as the plate for the base's electronics. The finished product will have everything enclosed but the 12V AGM battery.


Early pic of remote unit
My Scrap Pile Launcher -Remote 02_Small.png

I've made further progress then shown in the pic. Will post updated pic soon.


Power Brick = Battery holder
index.jpg My Scrap Pile Launcher-Remote  03_Small.jpg

I had a dead power brick from my R-Box 32 bitcoin miner laying around, so I am using it's enclosure to make a battery holder for the 4x 18650 cells that will reside in the remote unit.

I will bang out a full parts list and post it soon.

Till next time...
 
Had a 4 day weekend last week so I was able to make good progress on this project and finished my Kraken build!

Completed fabbing the battery holder.
My Scrap Pile Launcher - Remote Battery Holder - Complete_Small.jpg

Finished stuffing bits into Remote
My Scrap Pile Launcher - Remote - Complete_Small.jpg

Pieced together Base's sub-Enclosure
My Scrap Pile Launcher - Base Sub Enclosure_Small.jpg

Not complete but now operational
My Scrap Pile Launcher - Operational_Small.jpg

More to come...
 
Out standing! Always amazing what one can whip up using stuff out of the junk bin.
 
Tobor,

Kinda wondering why you chose to use three sets of batteries. The whole setup can be done with the main 12 volt battery. Don't get me wrong it does look nice and well constructed.

Steve G
 
Out standing! Always amazing what one can whip up using stuff out of the junk bin.

Thank you. I really enjoy coming up with inventive ways of solving problems.

Tobor,

Kinda wondering why you chose to use three sets of batteries. The whole setup can be done with the main 12 volt battery. Don't get me wrong it does look nice and well constructed.

Steve G

Good question, thx for asking.

My reasoning goes like this.

Continuity Tester:
When it comes to Mid/High Power motors, I'm just anal about safety. So, using a single 18650 LiPo caps the voltage to the igniter at 3.7V Max. and the LED/resistor combo limits current. Together, these two restrictions guarantee no misfire will occur while testing continuity. At least with AeroTech igniters.

Edit: Put another way, since the source voltage is 3.7V max., there is no possible way the igniter could ever see 12V at any level of current

Remote:
Using LiPos in the remote offers the main advantage in that it maximizes the AGM battery's available Voltage & Current to the igniter since non of it has to travel the 200 ft of 18G wire. That's 100 ft. over one 18G conductor (to the remote) and down the other 100ft. conductor (back to the Base Unit).
 
Thank you. I really enjoy coming up with inventive ways of solving problems.



Good question, thx for asking.

My reasoning goes like this.

Continuity Tester:
When it comes to Mid/High Power motors, I'm just anal about safety. So, using a single 18650 LiPo caps the voltage to the igniter at 3.7V Max. and the LED/resistor combo limits current. Together, these two restrictions guarantee no misfire will occur while testing continuity. At least with AeroTech igniters.

Edit: Put another way, since the source voltage is 3.7V max., there is no possible way the igniter could ever see 12V at any level of current

Remote:
Using LiPos in the remote offers the main advantage in that it maximizes the AGM battery's available Voltage & Current to the igniter since non of it has to travel the 200 ft of 18G wire. That's 100 ft. over one 18G conductor (to the remote) and down the other 100ft. conductor (back to the Base Unit).

I agree with the battery in the remote, but since the control unit doesn't have to pass much current, it could be powered from the remote unit and not need it's own battery. You still get the power at the igniter without the long run. As for the battery on the continuity test, that is a good idea but the idea is a little faulty. 3.7 V can easily fire a CTI igniter and probably an AT igniter if applied long enough. The bridge wires in the igniters heat from current, the voltage doesn't matter. Think of the current as the size of your water pipe or volume and voltage as the water pressure. The higher the voltage the quicker the volume will arrive but since it's the volume that is required, voltage only affects the timing. It is the LED and resister limiting the current that is the only real safety part of the continuity circuit, not the supplied voltage.

But, hey, build it the way you want. That's what the hobby is all about. There isn't one right way to do anything.

Good luck.
 
I agree with the battery in the remote, but since the control unit doesn't have to pass much current, it could be powered from the remote unit and not need it's own battery. You still get the power at the igniter without the long run. As for the battery on the continuity test, that is a good idea but the idea is a little faulty. 3.7 V can easily fire a CTI igniter and probably an AT igniter if applied long enough. The bridge wires in the igniters heat from current, the voltage doesn't matter. Think of the current as the size of your water pipe or volume and voltage as the water pressure. The higher the voltage the quicker the volume will arrive but since it's the volume that is required, voltage only affects the timing. It is the LED and resister limiting the current that is the only real safety part of the continuity circuit, not the supplied voltage.

But, hey, build it the way you want. That's what the hobby is all about. There isn't one right way to do anything.

Good luck.

Thank you. Yeah, everything you said is correct, of course. What I really wanted to do for continuity testing was build a active circuit that limited current to around 20 µA @1.5V, but that vreg is not among my collection. Maybe next year I'll do some upgrades.
 
Update:
Last Sunday I finally had the chance to use my launch controller along with the 1st use of my JawStand launch pad to sling my upscale Kraken on it's maiden flight. Controller worked flawlessly.

Thx to everyone for all the inspiration slathered throughout these forums.
 
Back
Top