So, I want to control 3 or 4 (I'm thinking of supporting 4, but need 3) 4-pin fans (like new CPU fans), and I find that the 28X and 40X only have 2 actual separate PWM outputs! Oh no! But, I've been itching to pick up a PICAXE to play with for awhile, but have not had a good enough excuse...until now!
The idea:
1x knob, 1x SPST momentary button (to handle a simple menu system), 1xLCD display (probably a 20x4 from phanderson), 1x 28X or 40X PICAXE. Must input 3-4 tach signals (knowing approximate RPMs, I should be able to get them recorded right, even if things get weird), output 3-4 PWM signals at 25kHz, must read the knob (probably just a pot) and button. The software in general I have ideas of how to do in my head. Setting up interrupts from input pins should make it even easier to handle, though I'm sure there will be some challenges.
I can test with a single fan and get the general kinks out, but working with several independently that I'm not sure on.
So, I was looking at ways to handle this, and I thought of two possibilities:
1. Some IC that can be set to output multiple PWM signals at 25kHz. I can handle a soldering iron OK, but am otherwise a total n00b. This idea would likely be simpler, but is scary to my n00bish mind . Simpler to wire up, and cheaper. What might such an chip be?
2. Using multiple 08M (continuous PWM outputs) units attached to a 28X or 40X, using serial outs to each 08M.
#2 would seem to me (recall, n00b here) to be easier, as it should be easier to debug. I could have a 28X or 40X starter or proto kit and 08 one to play with, then simply connect the final one to a small PCB with DIP sockets for the 08M units. The 28X or 40X would do the main bits of controlling, and deal with a display.
But, the manual isn't quite clear here...can the 28X and 40X use serial output on any output pins? Nowhere is it said it can't, and the command reference makes it seem that way, but there's a clear set of serial connection pins, too. Also, I'm not really sure how to deal with possible clock differences, if that would be a likely problem (with 28/40 devices, I could probably parallel them to the same resonator, right?).
I'm not necessarily sure that, if an IC that's easy to interface with could be found, that it wouldn't be an easier way to go...both ways seem to have their challenges.
Advice?
The idea:
1x knob, 1x SPST momentary button (to handle a simple menu system), 1xLCD display (probably a 20x4 from phanderson), 1x 28X or 40X PICAXE. Must input 3-4 tach signals (knowing approximate RPMs, I should be able to get them recorded right, even if things get weird), output 3-4 PWM signals at 25kHz, must read the knob (probably just a pot) and button. The software in general I have ideas of how to do in my head. Setting up interrupts from input pins should make it even easier to handle, though I'm sure there will be some challenges.
I can test with a single fan and get the general kinks out, but working with several independently that I'm not sure on.
So, I was looking at ways to handle this, and I thought of two possibilities:
1. Some IC that can be set to output multiple PWM signals at 25kHz. I can handle a soldering iron OK, but am otherwise a total n00b. This idea would likely be simpler, but is scary to my n00bish mind . Simpler to wire up, and cheaper. What might such an chip be?
2. Using multiple 08M (continuous PWM outputs) units attached to a 28X or 40X, using serial outs to each 08M.
#2 would seem to me (recall, n00b here) to be easier, as it should be easier to debug. I could have a 28X or 40X starter or proto kit and 08 one to play with, then simply connect the final one to a small PCB with DIP sockets for the 08M units. The 28X or 40X would do the main bits of controlling, and deal with a display.
But, the manual isn't quite clear here...can the 28X and 40X use serial output on any output pins? Nowhere is it said it can't, and the command reference makes it seem that way, but there's a clear set of serial connection pins, too. Also, I'm not really sure how to deal with possible clock differences, if that would be a likely problem (with 28/40 devices, I could probably parallel them to the same resonator, right?).
I'm not necessarily sure that, if an IC that's easy to interface with could be found, that it wouldn't be an easier way to go...both ways seem to have their challenges.
Advice?