I'm working on a machine that has a master drive that outputs a 0-10 Vdc signal based on machine speed. The machine has 40+ secondary motor drives grouped in quantities of 4 to 8. Each group will take the base 0-10 Vdc signal and an additional adjuster signal to allow for group speed adjustment.
Given the limitations of the current sourcing of the main drive signal I had planned on using a series of Op-amp non inverting voltage followers with NPN transistors to drive the roughly 70mA of current that the 8 ganged drives will require.
So far so good, where I'm drawing a blank is how to handle the individual group offsets. I was thinking about a potentiometer tied to the Op-amp supplies to give me a +/- signal fed into the Op-amp input as a summing signal.
Question 1: I'm guessing I need to drop a small signal diode and resistor on the the master drive analog signal to prevent circuit cross talk?
Question 2: How would I ensure the offset voltage doesn't load the master drive signal if the offset signal is lower than the master drive signal?
Please forgive the format of the questions, I'm a practicing controls electrician whose electronics training is 30+ years out of date. I was originally trained on vacuum tubes if that gives anyone here an idea how out of date I am.
Given the limitations of the current sourcing of the main drive signal I had planned on using a series of Op-amp non inverting voltage followers with NPN transistors to drive the roughly 70mA of current that the 8 ganged drives will require.
So far so good, where I'm drawing a blank is how to handle the individual group offsets. I was thinking about a potentiometer tied to the Op-amp supplies to give me a +/- signal fed into the Op-amp input as a summing signal.
Question 1: I'm guessing I need to drop a small signal diode and resistor on the the master drive analog signal to prevent circuit cross talk?
Question 2: How would I ensure the offset voltage doesn't load the master drive signal if the offset signal is lower than the master drive signal?
Please forgive the format of the questions, I'm a practicing controls electrician whose electronics training is 30+ years out of date. I was originally trained on vacuum tubes if that gives anyone here an idea how out of date I am.