This is for low power rectification
Well, there you go. One man's low power could be another man's low signal. I guess we will just have to leave it at that.
@(*steve*) I was attending an Arduino class last night at the Dayton Amateur Radio Association club house when I noticed someone driving a slide with a small Superior Electric stepping motor. His motor was the same physical size as the M061-FD08 motor I plan on using to move a pair of homemade trombone-style tuning capacitors (used in lieu of a vacuum variable capacitor which I don't have yet) mounted on my loop antenna for the 80m (3.0 to 4.0 MHz) ham band.
I asked what he was using to drive the stepper from his Arduino Uno R3, and he said there were four Darlington power transistors between the motor windings and a computer power supply of nominally 12 volts (or more!). His motor was rated at 10 VDC. "Hmmm," says I to myself. To make a long story short(er) I realized he was NOT using PWM to modulate the four-phase drive pulses applied to the stepper. The motor was quite warm to the touch, although the Darlingtons were pretty much at room temperature. These are 200 step per revolution motors, or 400 steps per revolution with the four-phase half-step drive he was using. That might not be enough resolution to tune my loop antenna accurately with direct drive to a 1/4-20 lead screw.
So I went online to see what I could find to drive my stepper in microstep mode. Lo and behold, Digi-Key was featuring CREE N-channel enhancement mode silicon carbide power MOSFETs, along with silicon carbide Schottky diodes. Woo woo! The CREE MOSFETS are all rated for 1200 V at various currents starting at 4.9 A for $5.25 each in small quantities. If I can figure out how program my Arduino to microstep in PWM mode at fifty kilohertz or so, the CREE MOSFETs just might be up to job. My stepper is rated at 1.25 VDC at 3.8 A for 53 oz.-in. of holding torque. I am tentatively planning to drive a stainless steel all-thread 1/4-20 rod on a brass nut, but the ham at the DARA club house was using a plastic toothed-belt drive, which moved the carriage quite fast but, IMO, with not much accuracy or precision.
Some experimentation is required, but I will probably stick with the lead-screw approach instead of the belt drive. When I get this working, I will post in the project section of this forum.
73
de AC8NS
Hop
