avr_fred:
Changing the drive is no help, it still needs a 10V speed reference.I'd like to know, what's wrong with the high voltage digital potentiometer that I suggested? That will work and it is by far the simplest solution. Is the problem that you cannot handle the surface mount aspect of the part?
I have ordered some, so i can try them out. I do not know yet where everything gets wired (thats why i got extras). From what i can tell so far:
(1) Vcl
(2) SCL --> PinA4*
(3) A1
(4)SDA --> PinA5*
(5) A0
(6)Vlat
(7)NC
(08)SHDN
(09)DGND --> GND
(10)V- --> GND
(11)Pa --> S1 from drive
(12)Wiper --> S2 From drive
(13)Pb --> S0 from drive
(14)V+ --> 5V+
*These pins use a 4.7KΩ pull up resistor to 5v
PinA4 goes high to indicate selected chip and PinA5 handles the communication
Is this everything? I also ordered a TSSOP to Din breakout board to handle the connections.
Abandoning the digital pot idea and doing this with op amps is easy so long as you have a 12 to 15 volt power supply. A simple LM358 with a gain of two and a low pass filter (one resistor and one capacitor) should suffice to convert the PWM to an analog output of 10 volts.
I am also looking at this as a possible solution as well since i do have an adequate power supply on this machine. I have LM358 OpAmps on the way. Do you have a diagram for the circuit i would have to build?
You'd only need about 50 ma of current. Using the drives +/-10 volt reference as the supply requires a high voltage rail-to-rail op amp and those don't come easy or cheap as I pointed out in post #8.
PS: Isolation is not a factor here, it's not required. MarkT's original comment was about the drive's lack of a PWM input which is the Arduino native analog output method. This is not a surprise in the motor drive world as +/-10 volts has been the standard for the speed command since drives became solid-state devices.
Got it, thanks