G'day All,
In case anyone was looking at making a launch controller, here are some pics and a schematic of one I built as a first attempt. I think it was Tim from the MMRG that said it might be good for me to put some info up on the forum about mine. Maybe I did go a little "over the top" with some of the features, but I was having fun!
The unit is powered by 10 AA Nicad batteries. These have nice low internal resistance so can give out some decent current to the igniters. These are charged by a plugpack that plugs into the mains. Only a simple constant current charge, limited by resistor R1, is used. Overnight charging results in a fairly full set of cells. But don't leave it on for days at a time or the cells will suffer!
The cells have a resettable circuit breaker (see the left side of the box) in series to protect the system from inadvertent shorts anywhere.
The safety key is worn around the neck of the person prepping at the launch pad. When ready to launch, it is put in the switch and turned. Once this is activated it is possible to launch the rocket. Operating the keyswitch turns on an audible beeper that alerts all in the area that something is happening. Power is also fed to the strobe at the launch site so there is no guessing which bird is about to fly!
There is a continuity test circuit that proves there is a return circuit through the igniter. No green is no continuity. This is quite useful to find out if my daughter hasn't plugged the cable in properly!
The actual "Launch" switch is a hooded ("missile launch" style) spring toggle, so there is no chance of bumping it accidentally. The red hood needs to be lifted first, then the toggle can be pushed up to launch.
The cable/connector I used were some parts that I had around already. Multiple cables in parallel are used to reduce voltage drop and to provide some redundancy. The cable is just a little longer than the required safety distance so there is no guessing how far away you need to be from the pad.
Using 4mm banana sockets on the pad end of things give flexibility about whether I use "standard" alligator leads, or add more (piggy-back style), or have a special set of leads for cluster work. They are usually rated for over 10A or more so are a good choice for a few reasons.
The actual pad was machined, drilled and tapped from some scrap I had lying around. It's just a round piece of aluminium with a flat plate screwed on. The launch rod is screwed into this. This allows me to change rods as I need to in the future. The whole thing mounts on a standard camera tripod which makes for great adjustability. It is sporting my daughter's Estes Moondog in the attached picture.
Wiring inside the boxes was just done point-to-point, not using any PCB or veroboard.
I guess when I get some spare time I'll get some nice engraved escutchions for the front, but for now it works. Ah, so much to do, so little time...
Enjoy!
In case anyone was looking at making a launch controller, here are some pics and a schematic of one I built as a first attempt. I think it was Tim from the MMRG that said it might be good for me to put some info up on the forum about mine. Maybe I did go a little "over the top" with some of the features, but I was having fun!
The unit is powered by 10 AA Nicad batteries. These have nice low internal resistance so can give out some decent current to the igniters. These are charged by a plugpack that plugs into the mains. Only a simple constant current charge, limited by resistor R1, is used. Overnight charging results in a fairly full set of cells. But don't leave it on for days at a time or the cells will suffer!
The cells have a resettable circuit breaker (see the left side of the box) in series to protect the system from inadvertent shorts anywhere.
The safety key is worn around the neck of the person prepping at the launch pad. When ready to launch, it is put in the switch and turned. Once this is activated it is possible to launch the rocket. Operating the keyswitch turns on an audible beeper that alerts all in the area that something is happening. Power is also fed to the strobe at the launch site so there is no guessing which bird is about to fly!
There is a continuity test circuit that proves there is a return circuit through the igniter. No green is no continuity. This is quite useful to find out if my daughter hasn't plugged the cable in properly!
The actual "Launch" switch is a hooded ("missile launch" style) spring toggle, so there is no chance of bumping it accidentally. The red hood needs to be lifted first, then the toggle can be pushed up to launch.
The cable/connector I used were some parts that I had around already. Multiple cables in parallel are used to reduce voltage drop and to provide some redundancy. The cable is just a little longer than the required safety distance so there is no guessing how far away you need to be from the pad.
Using 4mm banana sockets on the pad end of things give flexibility about whether I use "standard" alligator leads, or add more (piggy-back style), or have a special set of leads for cluster work. They are usually rated for over 10A or more so are a good choice for a few reasons.
The actual pad was machined, drilled and tapped from some scrap I had lying around. It's just a round piece of aluminium with a flat plate screwed on. The launch rod is screwed into this. This allows me to change rods as I need to in the future. The whole thing mounts on a standard camera tripod which makes for great adjustability. It is sporting my daughter's Estes Moondog in the attached picture.
Wiring inside the boxes was just done point-to-point, not using any PCB or veroboard.
I guess when I get some spare time I'll get some nice engraved escutchions for the front, but for now it works. Ah, so much to do, so little time...
Enjoy!
