AO Extension - right values



  • Hi, can anyone give me a hint how to control the AO Add-on? I mean, what uint value means +10V at the OUT, what uint value gives 0V at the OUT? right now it feels like jeopardy ^^ ..e.g. if I set the channel to uint=10000, I get 4.4V at the OUT. channel transformation is identity, power supply with 5V and 24V for AO

    thanks in advance


  • administrators

    Which addon is it specifically? Is it the I2C addon from this topic?

    https://forum.unipi.technology/topic/258/ao-out-extension-board

    Apologies for the late reply. I think the input should be 12V instead of 24 though, but if you could take a photo of the device it would be very helpful.



  • Yes, it’s the old AO add on shown in the picture.
    I found out that I can adjust the output voltage from 0-10V with an uint from 0....4095. If I put it 4096 it jumps back to 0V.
    Can you confirm ?

    Also is it allowed to apply 24V as supply or will it damage the unit?

    Right now I am facing the problem of noise injection into the cable at the analog out. Even though I use a PIMPF Cat7 cable (approx 2m long) at the AO, parallel running cables inject a voltage around 0.5...0.6V. I have a LED power supply connected which can be dimmed and which switches on/off at 0.6V and now the LEDs are blinking^^.
    Any idea how to improve ? (I know.. I shouldn’t lay the cat7 along with power cables, but I didn’t expect so huge effects. However, I will try to find an alternative route :) )



  • Found out that EMC was not an issue, but the LED power supply. I added a 10k resistor in parallel to the 0-10V input which fixed the 0V problem.
    Only poor thing now is the bad behaviour of Mervis with the AO extension board. I added a ramp for smooth dimm up and down, but it's actually not smooth but rather stepwise:

    0_1526662741568_upload-fba94365-0a89-44d6-90b0-8fbb5326bd3c

    Any idea how to fix? Maybe the problem comes from the transformation "to_uint(real)" ?
    0_1526662837098_upload-a436bee8-a32a-4d6f-a8c3-69adaea46871