- 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
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.
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
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
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.