Kirk Wallace wrote: > Jon, how hard would it be to get a current output (SPI?) from your PWM > amps? I guess remote reset would be good too, but that's easy. > Pretty hard. You really don't want to mess with the high-current loop. There might be a couple things you could do. There are a pair of low-side current sense resistors, depending on which polarity is selected, current flows through one or the other. You could tap an op-amp circuit on there to sense the voltage across the resistors. However, they are .005 Ohm (5 milli-Ohm) so the developed voltage is pretty small, and subject to a lot of interference from the switched currents.
You could rig an OP620 instrumentation amp with 1% or better resistor voltage dividers to bring the voltage down to +15 V. I used these in the current/torque loop of my analog servo amps, and they work astonishingly well in an extreme environment. (Before the voltage divider, they are looking at signals less than 100 mV with 70 V square wave common-mode pulses at 100 KHz, and there must be 70+ dB attenuation of the common-mode component!) A current-sense resistor could be added outside the amp in series with the motor wires, and then you'd get both polarities of motor current. That would be an analog signal, then you could feed it to whatever ADC you like. Jon ------------------------------------------------------------------------------ Colocation vs. Managed Hosting A question and answer guide to determining the best fit for your organization - today and in the future. http://p.sf.net/sfu/internap-sfd2d _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
