I have this drive, that drives a BLDC motor, and it has a 10 k potentiometer which can be used to vary speed,
and i replaced that with DAC(the one on the left in schematic) and it worked fine for a couple of days, but one day opamp U1a heated up, and i replaced it and now the drive shows erratic behaviour,
normally the drive goes to max speed on 0 volts, and stops at 5, when the three pins of potentio are disconnected the signal pin shoes five volts, and now when i connect my dac to it, regardless of dac's output, output voltage is 3.3 V, and only increases when DAC's output is greater than 3.3 Volts.
i though it was a current issue so i replaces the output stage with the one on the right so as to increase the current, but still nothing. What should i do?
And also it is still working fine with potentiometer.
I am no expert, but the port connections on the DAC seem completely wrong.
You have one output going to ground and the other to a 5V rail, whilst you seem to be using the REF input as some sort of driving output.
Either I'm reading things wrong or it is amazing it worked at all.
i used the voltage mode operation mentioned of page 5
http://www.ti.com/lit/ds/slas061d/slas061d.pdfthe one i am using is ad7524, so the max voltage i got was 2.5, i dont know why,must be some sort of resistor divider inside, but this guy had the same design,
http://www.waveguide.se/?article=a-simple-dac-using-the-tlc7524 read the comment thread.
drive works fine with potentiometer, could it be a current issue?
also do you think that it would work fine if i used unipolar circuit operation thingy? also i would need a bipolar supply for it, wouldn't i?
i used the voltage mode operation mentioned of page 5
http://www.ti.com/lit/ds/slas061d/slas061d.pdf
the one i am using is ad7524, so the max voltage i got was 2.5, i dont know why,must be some sort of resistor divider inside, but this guy had the same design,
http://www.waveguide.se/?article=a-simple-dac-using-the-tlc7524
read the comment thread.
drive works fine with potentiometer, could it be a current issue?
also do you think that it would work fine if i used unipolar circuit operation thingy? also i would need a bipolar supply for it, wouldn't i?
Looking at the data sheet, Vref is typically twice Vout so in voltage operation mode I think you need to have the supply voltage greater than the output voltage so I think you need to either make VDD higher than the current 5V or set Out 1 to 2.5V instead of 5V. The test conditions on the data sheet for voltage operation mode have Vref at 5V and Vout at 2.5V so that is probably a good place to start.