paradigm wrote:Don't know about using LCDC to address a custom 1-wire applicaiton. You'd have to ask mat-d-rat in the software section. However anything that can send/receive commands via RS232 can access the 1-wire bus. I think I posted a tutorial on the MX2 1-wire bus. I'll look around for it, and if I can't find it, I'll post another one.
Could you post that tutorial on the MX2 1-wire bus ?
Sorry about the delay. I just got back from holidays. The second one is inactive. And yes you could use it for a similar cirtuit, or whatever else you wanted to use it for. Anything else?
James McTavish, P.Eng
Director of Engineering
Matrix Orbital
Edit: Oh, by the way: my friend just commented on the circuit. He said it is not exactly his field, but passed it on to colleagues who deal with this more often. They say the diagram is OK (with the TCA0372 in stead of the LM741).
Wow! I guess my memory isn't that bad after all. I haven't dealt with op-amps for a long time (hence the LM741 screw-up). Good to hear you got it reviewed. I might just have to move it to it's own thread. I'm working on that 1-wire tutorial. Look for it on Monday.
James McTavish, P.Eng
Director of Engineering
Matrix Orbital
paradigm wrote:Wow! I guess my memory isn't that bad after all. I haven't dealt with op-amps for a long time (hence the LM741 screw-up). Good to hear you got it reviewed. I might just have to move it to it's own thread. I'm working on that 1-wire tutorial. Look for it on Monday.
I found some references in the manual for the LK204-24-USB_01 (pdf, but also on the maxic site (in the specs of the digital pot)). There is a section on the 1-wire control, with some basic commands and how to use them. This appears to be the statement to send commands over the 1-wire:
Transaction command (254 C8 1 [fags] [Send Bits] [Recieve bits]
[Send data])
If LCDC could send commands like these, it ought to be usable for sending the 1-wire commands. LCDC already has some basic functionality regarding 1-wire interfaces: http://www.lcdc.cc/help/configuration.htm#amxxd1w
The digital pot, I doubt it. Because it is a resistor dividor, there will be a constant current of 12/200000 A or 6uA. Not much. And by definition the input of an opamp draws an extremely small current. The opamp on the otherhand might require something to help get rid of excess heat. I would take the wait and see approach. Assemble it, run it with low current loads at first and work your way up. Just stick your finger on top of the package and see if it gets too hot to the touch. If you can't touch it, it needs help.
James McTavish, P.Eng
Director of Engineering
Matrix Orbital
As soon as I have the display (am
awaiting the MX4, doubting between
this - 4 lines offer much more
possibilities - and the MX2), I'll
get working on it.
If I want RPM monitoring of a fan connected to a digital pot, is it sufficiant to connect the RPM wire to the correct pin of a fanheader of the MX, split the ground wire and also have one of the parts going to the same fanheader (groundpin) of the MX (the other part connected to the pot) ?
The MX series doesn't care if the PWM signal it's delivering is used. So just the RPM should be fine. If you have problems, get a ground from the fan to the display too. If you have to do that, I would reccommend that you use the ground from the low power GPOs (bottom right pin of the 2x5 header).
James McTavish, P.Eng
Director of Engineering
Matrix Orbital
paradigm wrote:The MX series doesn't care if the PWM signal it's delivering is used. So just the RPM should be fine. If you have problems, get a ground from the fan to the display too. If you have to do that, I would reccommend that you use the ground from the low power GPOs (bottom right pin of the 2x5 header).
Ah, so I only should connect the RPM wire to the fan (just one of the 3 wires )
and have a common ground to that low power ground pin in case the first scenario doesn't work...
That's right. The problem is that we've had noise issues when only the RPM pin is connected. The resistance between the RPM pin and ground becomes too much. So connecting a direct ground will help that.
James McTavish, P.Eng
Director of Engineering
Matrix Orbital
I guess my memory isn't that bad after all. I haven't dealt with op-amps for a long time (hence the LM741 screw-up). Good to hear you got it reviewed. I might just have to move it to it's own thread. I'm working on that 1-wire tutorial. Look for it on Monday.
) 
I'll get the one wire tutorial up sometime this week. I'm a little back logged at the moment.
They say the diagram is OK (with the TCA0372 in stead of the LM741).