Logarithmic
See my other post.
Doo-Hickeys
These Doo-Hickeys are designed to be plugged into the receiver of an RC car in place of a regular servo, so if you buy one that advertises itself as for this purpose, then you can send it a srandard servo pulse from your picaxe (or other servo controller).
I did indeed hook up the
I did indeed hook up the original speed controller to the drill and to a 12V 1.5 Amp power supply. It didnt have enough juice to break the friction from the planetary gears in the transmission.
Short Answer…not enough Amps…the battery supplies enough amperage. However the battery is only a 1AmpHr battery…and I need sustained Amperage for up to 30 minutes.
So the hunt is on for a better PWM and a 250W power supply
just move the one
just move the one direction. But I did some calculation and the negative force applied to the wheel, which has a radius of 3 inches is ~5 lbs, so multiply that by the radius and it has to overcome 1.25 ftlbs and with a max RPM of 90
Ρ= ( (90rpm)x(2∏)x(1.25 ft/lb))/33000 = .021 hp
the PK51 motor stalls with 12VDC stalls at 396 oz-in convert that into ft-lbs
396 * .005208333 = 2.0624 ftlbs at stall.
So you can see that either the PK51 or the drill motor are pretty much what I need.
Question is how to power it.
I suppose I could switch to use an AC motor
**An untested circuit **
Here’s a possible driver, if you have a method of generating the PWM Note, this will invert the PWM signal, so 100% will have the motor off, 0% duty will be full on. Probably a bad design issue.
Parts list :
Vishay Schottky Rectifier, 20 A 20TQ045PBF $1.59
http://www.mouser.com/search/ProductDetail.aspx?qs=MYVaeE1wThIt6euH0T6mtQ%3d%3d
IRF N-chan MOSFET 60 v 50 A IRFZ44PBF $1.30
http://www.mouser.com/Search/ProductDetail.aspx?qs=%2fRKvNCQzLu0R%252bpFoqVUQ5w%3d%3d
On Semi GP transitor 75 v 600 mA P2N2222ARLG 0.27
http://www.mouser.com/Search/ProductDetail.aspx?qs=ZXBb0xZ9WeA2JhxpqSlwrw%3d%3d
Vishay Power resistor 39 ohm 3 watt 0.46
http://www.mouser.com/Search/ProductDetail.aspx?qs=LCMWAU1DZcyMDzF6dawmsQ%3d%3d
Xicon resistor 330 ohm 1/4 watt 0.10
http://www.mouser.com/Search/ProductDetail.aspx?qs=toAOiZ7FbseylIZzSFvRvg%3d%3d
Shipping might be more than the parts, and I haven't tried this, I have seen the IRFZ44 in a variable speed drill, and I think this might be an adequate digital interface circuit. Hopefully some folks can check this out, and if you feel comfortable soldering something together, give it a shot. Have a fire extinguisher nearb=, just in case. :)
Confirmed
IRFZ44 already has builtin flyback diode. On principle, though, this circuit WILL work. It’s what we eventually came up with here.
FET Flyback no worky
… unless it’s around the motor, giving a path for the motor coil current to go. That’s why I added the schottky diode around the motor since the diode in the FET won’t help the motor lose it’s stored energy.
I knew that
Of course. My application has a worm drive, so it doesn’t need that type of brake. D’uh.