This is a project I'm currently working on for my local combat robotics club. It is an LED light system that will signal the drivers when the match will start. Here are the goals I was aiming for:

- Physically appear similar to an older style traffic light that suspends in the middle of the intersection.
- Be controlled without a microprocessor (i.e. no Arduino)
- Internal power supply that can run the system for several days.
- Be protected from shrapnel and flying robots.
- Incorporate sounds as well as lights.
- Be very bright and look cool!

Testing at home:

A video of it in action (with brightness toned down):

Step 1: Circuit Design

Like I said earlier I wanted to accomplish the timing control without the use of a microprocessor. I'm using the 555 timer IC as it is simple to use and also very inexpensive as well.

The circuit is designed to have a momentary switch trigger the first light, and the next light is triggered when the first light shuts off. Repeat as necessary.

The schematic I've hacked together here (props to kpsec.freeuk.com) shows how I've wired the red and yellow portions of the circuit. You have to add an additional 555 timer 'section' for each light.

I used 100k resistors to get an approximate time of 1.1 seconds for each cycle. If you replace R1/R2 with a 1 megaohm pot you can easily vary the timing of your circuit.

A typical 555 timer can sink up to 200mA of current which is more than enough for a handful of LEDs. In my case I am using 36 LEDs per 555 timer which draw approximately 120mA.

Step 2: Building the Circuit.

To solder my circuit I picked up a proto board from the local electronic supply store. Cost me about $5 and I could probably fit about 3 of these circuits onto it. I cut out the chunk that I needed with a dremel.

I tested the PCB with some single LEDs and it works quite well. The measured the circuit drawing about 30mA as it 'idles' with no lights on.

Step 3: The Control Box

To house the circuit board, switches, and battery I picked up a plastic project box from the local electronic supply store for about $5 as well. The various parts you see inside:

The large red "start" button switch that is meant for arcade/pinball machines. Got it from the Electronic Goldmine.

11.1V 1000mAh Li-poly battery which I got from Hobby King.

15A toggle switch that will be the master power switch, got it from a local auto parts store.

5kohm pot that was supposed to act as a brightness adjustor. I included it as I had a few laying around but it ended up being pretty useless as the value was much too high.

12V beeper module from local electronic supply store.

Step 4: The LEDs

The LEDs I'm using are a little special. An older project of mine was building LED interior lights for my car. I'm using 5mm 'super flux' LEDs and even had custom PCBs made up for them. I special ordered some green and yellow LEDs for this project and soldered up all the light boards I needed.

Each board has 9 LEDs. (3 strands of 3 wired in series)

The run off 11-15V and have an input diode (reverse voltage protection) and 3 surface mount resistors.

Step 5: The LED Housing

To mount the LED boards I'm using a chunk of 2.5" aluminum tubing which is the same stuff I used in my RC Nerf Tank project. I drilled and tapped holes for 4-40 screws. The larger holes are for running the wires through.

Step 6: Protective Case

To keep the LEDs safe from damage I'm encasing them in a clear polycarbonate box. Some of it is 1/8" and some is 1/4" thick. Tapped and screwed together with countersunk screws.

Step 7: Assembly and Wiring and Trying It Out

I wired the LEDs to the control box temporarily, I will need to make a much longer cable when it is hooked up the arena. It seems to work well except I had to remove the beeper. I think perhaps it may draw too much current as the last 55 timer died when I first tried it out. I replaced it and disconnected the beeper and now it works quite well.