Post by thread:PWM control of 90-volt, 2.4-amp DC motor

Moto has some high voltage / high power (1000V, 10A) MOSFET's with 5V gate inputs. Real handy! (Free samples, too. 800.441.2447) TTYL, Brian. spam_OUTbbolesTakeThisOuTmicrochip.com ______________________________ Forward Header __________________________________ Subject: PWM control of 90-volt, 2.4-amp DC motor Author: "BOWDEN; ANDREW V JR" <.....ABOWDENKILLspam@spam@SCANA.COM> at Internet_Exchange Date: 6/16/95 11:25 AM Hi, all. I'm interested in controlling a 90-volt, 2.4 amp DC motor with a PIC using PWM. This is not a servo application, just simple but precise speed control in one direction with braking. Unfortunately, all of the books I have seen on power supplies seem to assume that any application over about 24 volts only requires current in the milliamps range. Can anyone suggest a good AC to DC conversion circuit, preferably without a transformer? Second, can anyone suggest a proper interface circuit that will allow the PIC to perform PWM. In other words, perhaps control of a MOSFET that does the switching with proper protection for the PIC. Any assistance would be eagerly and gratefully received. BTW, I have the capability to handle attached graphics files if anyone wants to include a schematic. :) Andrew

> in the milliamps range. Can anyone suggest a good AC to DC conversion > circuit, preferably without a transformer? > Sorry ? Could you plese explain what for (Input/Output parameters) ? At least I didn't understand the connection of that problem with a DC motor control (unless it's related to getting the 90 Volts DC from a 115/230 V AC net). > Second, can anyone suggest a proper interface circuit that will allow > the PIC to perform PWM. In other words, perhaps control of a MOSFET > that does the switching with proper protection for the PIC. If you want to do breaking, you'll need some possibility of electronically short-circuiting the motor. With a full bridge it's easy, but that requires 4 power transistor vs. 1 for a simple speed control. For the power part: at that current/voltage I'd use a bipolar transistor. High voltage mosfets tend to be more difficult to organize. Anyway, the power part of this circuit (without breaking) could be: optocoupler for PIC protection, pull-up resistor and a pnp (perhaps darlington) between motor and positive supply. Should work, but try it beforehand. > > Any assistance would be eagerly and gratefully received. BTW, I have > the capability to handle attached graphics files if anyone wants to > include a schematic. :) If you need one, drop me a line - I don't think we should handle schematics on the list, but in case I talk complete gibberish, the other people here are bound to provide some corrective feedback. Bye Markus