We are converting a regular traffic light to a Peace-Love-Linux traffic light.
- 3 * 3W RGB LEDs.
- Controller => Arduino pro mini
- Power Supply DC 5V 50W
- 12 * 10K
- 6 * 5R
- 12 * 3R
- How do we gonna make the images?
Maybe it would be a good thing to make a system to mount it, so it will no longer need to lay stand on the ground.
- Uledr = 2.0->2.5V
- Uledg = 3.2->3.6V
- Uledb = 3.2->3.8V
- I = 350mA
- UR = VCC - UT1 - UT4 - Uled
- URr = 5V - 0.3V - 0.3V - 2.0->2.5V = 2.4->1.9V
- URg = 5V - 0.3V - 0.3V - 3.2->3.6V = 1.2->0.8V
- URb = 5V - 0.3V - 0.3V - 3.2->3.8V = 1.2->0.6V
- R = UR / I
- Rr = 2.4V / 0.3A = 8R
- Rg = 1.2V / 0.3A = 4R
- Rb = 1.2V / 0.3A = 4R
note: we use the highest voltage and a slightly lower current as safety.
The power consumption of the resistors need to be calculated
- PR = UR * I
- PRr = 2.4V * 0.35A = 0.84W
- PRg&b = 1.2V * 0.35A = 0.42W
Conclusion: We will need resistors which be able to consume 2W for red and 1W for green and blue. (according to the safety standard of 25% spare)
Because we use multiplexing...
- Rr = 8R / 3 = 2R666 (We used 2R5 implemented as 2 resistors of 5R 1W in parallel)
- Rg = 4R / 3 = 1R333 (We used 1R5 implemented as 2 resistors of 3R 1W in parallel)
- Rb = 4R / 3 = 1R333 (We used 1R5 implemented as 2 resistors of 3R 1W in parallel)
The base resistors of the transistors we took some basic 10K resistors.
The power of the power supply
LED max current 350mA => 9 LEDs is 3.15A.
P = U * I = 5V * 3.15A = 15.75W (a 25W supply should be enough)
an other less accurate way: we use 3W LEDs so if we have 9 times 3W it should be 27W without other parts of the circuit. This isn't correct because the leds don't consume 3W but if we calculate the power we give the leds it wil be maximum about 3.3V(average max LED forward voltage) * 350mA = 1.155W => 9 times = 10.395W without other parts of the circuit.
Lenses and Images
I was thinking of making a mold out of wood using the CNC and use resin & hardener to make the lenses