Looks like you should buy a few MOSFETS and make an h-bridge. But driving the lower side of the h-bridge from 5 volt logic level is not super easy.
Either that or just use a 12Volt motor On Wed, Oct 28, 2020 at 1:05 PM Gene Heskett <ghesk...@shentel.net> wrote: > On Wednesday 28 October 2020 14:30:39 Chris Albertson wrote: > > > I bit of information from Polulu's web site. They say.. > > > > "*While VNH3SP30’s over-voltage shutoff doesn’t activate until 36 V, > > in our experience, shoot-through currents make PWM operation > > impractical above 16 V.*" > > Which pretty well explains my problems. > > > This seems reasonable for the intended automotive use case where a > > lead/acid battery is supplying the power. but there may be transient > > up to 3X the nominal battery voltage. > > > > I've never run these using more than the nominal 15.7 volts I get from > > a fully charged LiPo battery and when bench testing I use a 12 volt > > power supply that does about 13.5 volts. Try running your motor on > > 12 volts > > > > I think the way to go is to just buy from Polulu and not try to sav $2 > > on eBay. Polulu actually offers support Here is one that seems to > > actually handle higher volts https://www.pololu.com/product/1457 > > Which reads much like the ones I bought two of, for less that half of > polulu's asking for that board @$60/copy. > > > Or you just buy four MOSFETS and build you own switch > > > > Another one I was not going to recommend because of the cost is really > > excellent and again their support os excellent. I had a problem and > > they offered to replace the unit. They will also talk with you about > > software. But you pay for the support in the product price. > > Obviously. > > > This unit has input from the quadrature encoders and runs the PID loop > > itself. The computer (That would be some HAL component in LCNC) > > sends only the desired position or the desired velocity of one of the > > interfaces. There are a few to choose from, RS232, USB, PWM and > > analog. ThePID has an autotune feature that can get you in the > > ball-park > > > > I use one of these to drive a mobile robot's traction motors. It > > pushes a lot of complexity out of my control computer because this > > controller does the encoder processing and PID control . But these > > are $90 devices and I've switched to using these > > > > https://protosupplies.com/product/vnh2sp30-dual-monster-motor-shield/ > > > > The above is the EXCELLENT tutorial on using the VNH3SP30 chip and the > > dual-chip version attached to an Arduino-like board with zero wires or > > solder. It just plugs in. But I buy the dual-chip boards from China > > for $7 each. Much cheaper than the 90 Roboclaw units. > > > > These dual-chip drivers are widely cloned because the design is Open > > Sourced. The Egle design files are available > > > > So my now-standard motion control setup is one of these: > > ebay.com/itm/Dual-VNH3ASP30-... > > <https://www.ebay.com/itm/Dual-VNH3ASP30-replace-VNH2SP30-Stepper-Driv > >er-Module-30A-Monster-Moto-Shield/291549918162?hash=item43e1bab3d2:g:14 > >wAAOSwVb5d8guN> plugged into one of these you can get for about $14. > > www.st.com/en/evaluation-tools/nucleo-f446re.html > > > > My experience is that I can drive this with a lipo battery for hours > > and the chips are not even warm. That may change as my current > > project is a Kidie car conversion. It is the kind of toy car that > > hold two 6-year old kids and goes up to 6 MPH on the sidewalk. > > Fisher-price sells them > > www.target.com/p/power-wheels-tough-talking-jeep-powered-ride-on-black > >-red > > <https://www.target.com/p/power-wheels-tough-talking-jeep-powered-ride > >-on-black-red/-/A-53016862#lnk=sametab> The car is being adapted to > > autonomous self-drive and will do laps around the block with no > > driver. > > These VNH3SP30 chips (and the nucleo-f446re) will power the rear drive > > wheels. The car's total weight (including a lead/acid marine > > battery) is about 100 pounds. The driver chips really can handle > > maybe 100W per chip or 50W continuous > > Given their admitted NOW maximum voltage, good deal. But 12 volts might > not even start this 24 volt motor. :( > > Thank you for finding that bit of data that is NOT in their docs on the > STM site. But I'll also stand by my comments re the poor internal gate > drivers, way too small to drive a high current device as the gate > capacitance in some of those can be a major piece of a microfarad. It > takes higher powered drivers to charge and discharge that level of gate > capacitance in a timely manner when it is comeing on it is essentially a > miller run-up, the gate capacitance is multiplied by the devices gain > forming a huge negative feedback loop while the drain voltage is > falling. A higher drain=worse effect. And the effect is there again when > its turning off, the rising drainvoltage feed back thru that > capacitance, slowing the off transition by the same feedback mechanism. > Needs about 100x what they actually built in an oxide lined tub on the > same die, to do the job right. Plainly, the chips layout designer > should have been fired, along with the prof that supposedly taught that > coarse. > > Thanks Chris. > > Cheers, Gene Heskett > -- > "There are four boxes to be used in defense of liberty: > soap, ballot, jury, and ammo. Please use in that order." > -Ed Howdershelt (Author) > If we desire respect for the law, we must first make the law respectable. > - Louis D. Brandeis > Genes Web page <http://geneslinuxbox.net:6309/gene> > > > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
