Sparkfun MOSFET Power Control Kit (https://www.sparkfun.com/products/10256), and clearly the constant-current mode did not like it and the output current did not stay stable.
You do realize that that particular kit is not a constant current driver, right? However, if you add a small npn + a resistor to it, you can easily make it into a constant current drive.
I am not sure what you are trying to do , but you could drive a simple constant current driver with the pwm to vary the brightness while limiting the max current to 20mA
with 16-bit resolution, ...have 32-bit resolution for light intensity.
Quotewith 16-bit resolution, ...have 32-bit resolution for light intensity.A couple of questions:1) What kind of eyes do you have that require that kind of resolution?2) What kind of computing power is required for that kind of resolution?
Uh... Yeah.... Dynamic range is the difference between full-bright and fully-dark. You can't get any more dark than "off", so you can only go brighter ... and you can't (or shouldn't) go over the device's maximum current rating on the bright-end.16-bits (converted to decimal) gives you a range from 0 to 65,535. I'm sure you can't tell the brightness-difference difference between 0 and 1, between 65,534 and 65,535, or between 30,000 and 30,001, etc.!
so not very special hardware would be required
Quoteso not very special hardware would be requiredYou probably want your pwm sessions to end fairly quickly. Say 50hz, or 20ms.Each tick of a 32-bit pwm train would be then 20ms / 2^32 = 5e-6 us. or about 200Ghz.Good luck with that.
// init Timer2 mode and period (PR2) (frequency of 1 / 20 kHz = (3999 + 1) / 80MHz * 1OpenTimer2( T2_ON | T2_PS_1_1 | T2_SOURCE_INT, MAX_DUTY);
4000 duty cycle steps
Quote4000 duty cycle stepsThat's about 12 bits, on a 80Mhz mcu.From there, it goes up exponentially.If I were you, I would try to understand what you are trying to do, and what can be done realistically and decide where to compromise.
16-bits (converted to decimal) gives you a range from 0 to 65,535. I'm sure you can't tell the brightness-difference difference between 0 and 1
, between 65,534 and 65,535, or between 30,000 and 30,001, etc.!
Quote from: DVDdoug on Oct 19, 2012, 01:20 am, between 65,534 and 65,535, or between 30,000 and 30,001, etc.! Brightnesses in that range are a bit more difficult.