Launch Controller Project Help

Hi all,

I was clearing some stuff out and came across a launch controller project that I started a while back but never finished and I'd like to get it done. I did have plans a friend drew up for me on how to wire this thing up but I've since lost them. I'ts nothing special, just a single pad affair with continuity testing and an internal piezo alarm to alert when the controller is armed. If anyone can help me to figure this thing out it would be much appreciated.

Note; from what I remember I intended to run this off a 2S Lipo.

Thanks,

Karl

Can you provide a photo of what is inside the box? Also details of anything already assembled.

Hi Dave,

It's a total blank canvas underneath, the red cable I soldered on just has a deans plug on the end you can't see. I've dug out some reciepts so here's a list of what I bought for the project.

1x Superbright Green LED 12v
1x Superbright Red LED 12v
2x 12mm Momentary Waterproof ON/OFF Push Button Switch
1x Dual Female Banana Plug Terminal Binding Post (For removable launch cable)
2x 4mm Banana Plugs
1x Key Operated 2 SPST 2 Position Switch
1x 12v 90dB Warning Buzzer
1x ON/OFF Round Rocker Switch 12v
2x 52mm 5A Insulated Crocodile Clips

A blank canvas actually makes things easier. With a couple of additional items of information I could sketch out a schematic if you like.

Specifically what kind of LEDs do you have? You said you have receipts, do you have manufacturer and part number? For an LED you need to either have an internal dropping resistor or supply an external resistor, and the value of this resistor depends on the current needed to light the LED and the supply voltage.

Do you planned to use the "Test" pushbutton for a momentary continuity test?

A schematic would be fantastic thank you. The help is much apprecaited, I thought this thing was going to go back on the 'projects that I will never get around to finishing' pile.

The LED's were from eBay and they didn't really give much information about them other than they are rated for 12v. Here's what else they said about them ;

• Emitting Color: Red/Green/Blue/Yellow/White/Warm White/Orange/Pink/Purple
• Size: 3mm/5mm
• Lens Color: Water Clear
• Forward Voltage (V) : 1.8-3.4V
• Current: 20MA
• View Angle: About 120 degree.
• Luminous Intensity: 4000~20000mcd

Yep the 'test' button was intended to be used as a momentary continuity test with the green LED illuminating to confirm all is good to go.

This is the way I would do it. The resistor on the battery (+) is to protect the LiPo battery (they plump when you cook them). It could be replaced with a fuse. In this configuration switching the power on allows continuity check without arming. This would be consistent with your current markings. You could swap the key switch and power switch, which would do the same thing but the key switch would kill everything and the power switch would actually be more of an arming switch.

I recommend using a 3S rather than a 2S battery. You'll get some extra "oomph" to get past the resistance of the wires. If you're going over 100', you may need a relay box at the far end... but that's a different circuit entirely. I have a box similar to this, using a pizo buzzer instead of the LED, I run it off a car battery. Very old school... but effective.

Thanks Dave! I'm just about to order the extra bits I need and I can find 1.8Ω & 2.2Ω 10W resistors but no 2Ω. I'm guessing the 2.2Ω will be just fine?

Thanks for the input Cerving, I've got plenty of 3S packs handy.

The 2.2 is fine. Just never short a LiPo!

And, if you are going t an S3 or 12 volt battery bump the resistors for the LEDs up to 750-ish Ohms.

DaveW6DPS said:

The 2.2 is fine. Just never short a LiPo!

And, if you are going t an S3 or 12 volt battery bump the resistors for the LEDs up to 750-ish Ohms.

Click to expand...

I decided to go with 3S in the end Dave and upped the resistors up to 750 ohms like you said. Took it out for its first launch today and it worked flawlessly, even with 25m of cable there didn't seem to be much impedance and it lit the igniters up with little to no hesitation.

Thanks for helping me get this project finished I really appreciate it.

I am glad it worked out for you, Karl!