high current PWM Circuit
kbash
Posts: 117
Does anyone have a relatively cheap circuit for controlling "Reasonable amounts" of voltage and current? say: 12 - 60 volts... 5-20 amps using Prop PWM?
I did a simple PWM with a TIP121 on the ground leg of a voice-coil actuator. I had to do a LOT of fine tuning to get a reasonable sine wave. The PWM gave me virtually NO output until I got up into the 85% duty cycle range. I had to create separate look-up tables for both the up and the down sides of the wave for some reason. I didn't really do any other optimization and I got it to work for MY purpose, but I know there are better transistors to use and a few of the ongoing threads could benefit from a solid, standard, circuit.
( Notably, Pedward's micro-stepping and Macrobeak's motor test function. )
The PWM object works great if you need voltage only or a tiny amount of current, but many of the motors, actuators, heaters, etc. we need for "Real world control" need large amounts of power. A higher voltage version of the HB-25 might be nice. However... for micro-stepping... you'd still need 4 of them. Anyone got something better that they might share with the community?
The photo below is the wave I finally managed to get with the attached code. Not perfect, but good enough for what I needed.
I did a simple PWM with a TIP121 on the ground leg of a voice-coil actuator. I had to do a LOT of fine tuning to get a reasonable sine wave. The PWM gave me virtually NO output until I got up into the 85% duty cycle range. I had to create separate look-up tables for both the up and the down sides of the wave for some reason. I didn't really do any other optimization and I got it to work for MY purpose, but I know there are better transistors to use and a few of the ongoing threads could benefit from a solid, standard, circuit.
( Notably, Pedward's micro-stepping and Macrobeak's motor test function. )
The PWM object works great if you need voltage only or a tiny amount of current, but many of the motors, actuators, heaters, etc. we need for "Real world control" need large amounts of power. A higher voltage version of the HB-25 might be nice. However... for micro-stepping... you'd still need 4 of them. Anyone got something better that they might share with the community?
The photo below is the wave I finally managed to get with the attached code. Not perfect, but good enough for what I needed.
Comments
Second, I'd switch to making lookup tables as a DAT block. far less typing to setup, and only a little harder to use. (I.e. Long[@sine1][idx] instead of sine1[idx] )
Lawson
http://search.digikey.com/us/en/products/IRF3708PBF/IRF3708PBF-ND/811850
However, I don't know about your specific application.
Of course, any system dynamics depends a lot on what load you're driving, especially if there are large inductances or capacitances involved.
http://search.digikey.com/us/en/cat/integrated-circuits-ics/pmic-mosfet-bridge-drivers-external-switch/2556427?stock=1
Those are mosfet bridge drivers, so they drive two N-channel mosfets from a logic input to make a half-bridge. I don't know how many channels you need, or I'd pick one out for you. Most of the datasheets have application circuits with good explanations of how to use them. Reply with details on your app, and I'll try to help you more.