I would use a digital pot, and a TDA2005 (10W x 2) or similar. All DC coupled. You could use two devices to increase output. Used as simple, linear output, voltage amplifier, it will sink or source power. Connect the motor to the speaker terminals. No caps!
One amp will be biased to mid-rail, and the other will swing gnd-Vcc according to the pot value. Depending on the digital pot , you could drive it with I2C, up/down or SPI. Start off with a normal pot to play around with. The output of the device is output protected. Use a good heatsink. Regards Roland 2008/12/22 Javid Butler <javidbut...@cox.net> > > > > It's absolutely a cost issue, and the servo drives are way to exotic for > this project. I only need a small motor that just drives or brakes > according > to the rate that the computer sent. I had an idea of letting a thyristor > shopping up the frequency, but it would be much easier to run a DC motor > and > then decrease the power in a classic DC-motor-rpm controller way (cut the > DC > into a square wave). > If the value given is under 0, switch to a heat sink and let the motor act > as a generator. If the value is above 0, switch to power and turn the > square > code on. I still think it's not more than a 12 V ~30 W motor we speak about > - maybe not even that. > > > I think you are on the right track, but there are a lot of questions to > work out. It sounds like the motor will only ever turn in one direction, > whether it is driving or passively braking. This is fairly simple to > accomplish, although you will need some way to switch from the drive element > to the heat sink at 0 drive value. At the power level you are working with > there are plenty of devices that will work-bipolar transistors, FETs, and > IGBTs. It all depends on your PWM switching frequency and how simple you > want the drive circuit to be. > > If the motor needs to run both CW and CCW then you will have to use an > H-bridge drive, and that gets more complicated. > > Javid > > ------------------------------------------------------------------------------ > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
