[blockquote]Barry Li said:
Would really love to be able to control individual LED of a PF light.
That will be a great feature for vechile signal lights.
[/blockquote]
I had the same idea. It is not as easy as some thing. My first idea when I saw the diode bridge was to basically bridge it and reverse the polarity of one LED. Bad Idea, said Frank, as the cut-off voltage of 9V for the "off" LED would just burn it.
So I removed the board and made a "floating", simplified circuit: GND from the power side to the cathode (-) of both LEDs, and C1 respectively C2 via 4.7k to the LEDs anodes (+). I left the capacitors off, and also the 150k signaling resistor for the WeDo.
Made four of them as switch indicators or signal lights, might build more.
Philo's work may help: http://www.philohome.com/pf/pflights.htm
The 9V and GND lines are present, 9V is not used, GND is used but not for the LEDs (theres is a 150K resistor from C1 to GND, it's used by LEGO WeDo USB Hub as a signature ID to detect the presence of the PF Lights, has to be a high value so that many PF Lights can be used in parallel ans still be recognized as one - if total value drops to 3K9 the WeDO considers it a WeDo tilt sensor).
Christian: such hack is indeed possible.
The SBrick's ports can be in four diferent states:
- Off: C1 & C2 pins are floating: both LEDs are off.
- Turn CW / CCW: one of the control pins is high, other is grounded: one LED on, other is OFF
- Break: C1 & C2 is high (connected to the power supply. This is just a distant memory, I need to check this, as it's possible that both are grounded): Both LEDs ON, currently the firmeware can't do PWM in this mode however.
[blockquote]Barry Li said:Would really love to be able to control individual LED of a PF light.[/blockquote]
As far as I know this is not possible, as both are connected to the same power lines. But I'm considering to hack the black "distribution box" to switch on either one or the other based on the polarity. This would save a lot of materials with traffic lights, switch indicators, etc.
[blockquote]Barry Li said:That will be a great feature for vechile signal lights.[/blockquote]
Not only for that...
Leg bedre,
Christian
