motor speed controller for kids' electric car

"Tom is Biasically Wrong"

** Last 5 seconds - if he were lucky.

... Phil

"DJ Delorie"

** None of the relevant to the OP's query.

..... Phil

"David Eather"

** Absolutely correct. ** The item on eBay is junk.

The OP has no idea what specs he really needs.

..... Phil

"DJ Delorie"

** No DC motor benefits from high frequency PWM.

The practical range is from a few hundred Hz to a few kHz ONLY.

.... Phil

"DJ Delorie"

** Don't you ever get sick of posting BS ?

.. Phil

"Tom is Biasically Wrong"

** Like 50 to 100 amps.

..... Phil

How do you know phil? Did you test one?

Tom

Many of the golfcart / electric vehicle motor controls run between 15Khz and 20 Khz. I think that is to keep the audio from the motor low. Mike

Don't get him started. Anyway, he's right. The thing is only rated for 15 amps. Also, there's a question at the bottom of that item from somebody that wants to use the controller on an electric bike. Seller says no, can't use it for that.

"Tom is Biasically Wrong"

** Cos I have lots of actual experience with such devices and YOU have none.

FUCKWIT

..... Phil

Don't get him started. Anyway, he's right. The thing is only rated for 15 amps. Also, there's a question at the bottom of that item from somebody that wants to use the controller on an electric bike. Seller says no, can't use it for that.

The OP said he needed 10-15 amps. I didn't suggest he buy it, I just said before you build, look here. There has to be at least $20.00 worth of parts in it.

Tom

"Tom is Biasically Wrong"

** The OP is a clueless jerk.

** Same thing - FUCKWIT !! ** One 15amp MOSFET, one 555, a cheap pot and a box.

Will self destruct in milliseconds with a stalled motor.

..... Phil

How do you know how much eperience I have Phil? Tom

"Tom is Biasically Wrong"

** Easy to tell YOU have NONE.

You spew STUPID and WRONG advice all the time.

BTW

You have "eperience " all right.

Everything you spew is stolen from the " enet " .

..... Phil

Sorry for my typo Phil, good night.

I tried to post this under my usenet account but it didn't work, so I'll have to use google:

I read through most of the posts. I'll endorse those who made statements to the effect that the drive frequency for a motor is so low that a

555 will do just fine. You can run it around 1kHz, ballpark, but anything from 100Hz to 10kHz would probably work. I'd choose 400 Hz myself. Don't forget the freewheel diode. A power Schottky is a good choice for this. You can get the gearshift effect with a switch that has multiple taps connected to a resistor network. That ought to be really fun. Use 12 volts, but have the top speed something less than 100%. Experiment to find the best "governor" frequency. The usual way of hooking up a 555 astable gives duty cycles only between 50% and 100%, nothing less than 50%. You can give it a full range of duty cycle by putting a diode across pins 6 and 7 with the cathode at pin 6. Then it will get down to zero, or almost. If you want continuously variable with a pot, tie one end of the pot to pin 6, the wiper to pin 7. Just a reminder, you still want a little signal diode like a 1N4148 as I mentioned across 6 and 7. The other end gets connected to a resistor, and the other end of that resistor gets connected to pin 8. The reason you don't tie the pot directly to pin 8 is because if you turn the pot all the way to the end then it will short Vcc to ground when pin 7 discharges. The 1k resistor prevents that. The pot should be an order of magnitude or greater than the protection resistor, so you're looking at a 10k or 100k pot. Do your frequency calculations and choose the timing cap accordingly. Don't forget basics like a 0.1 bypass cap on the pins of the 555, especially if you use the bipolar version. I don't have a mosfet on the tip of my typing fingers to suggest, but you can use digikey's parametric search. click on site map--part search-- discretes--mosfets. Get N channel with I guess 100 or 150 volts Vds. No need for a logic level device if you are using 12 volts, just get a standard mosfet. Choose Rds by figuring out how much power it will dissipate at 15 amps. Actually, if your kids stall it and keep the throttle down it could draw a lot more than that for a good ten seconds. Stuff happens. So build in a big safety margin. Make sure either that the heatsink is electrically insulated, or the mosfet is insulated from the heatsink.

n a t

To clarify my ambiguous wording

"Just a reminder, you still want a little signal diode like a

1N4148 as I mentioned across 6 and 7. The other end gets connected to a resistor, and the other end of that resistor gets connected to pin 8."

The protection resistor gets connected to the end of the pot opposite pin 6. The protection resistor does not get connected to the diode.

"gearhead"

I read through most of the posts. I'll endorse those who made statements to the effect that the drive frequency for a motor is so low that a 555 will do just fine. You can run it around 1kHz, ballpark, but anything from 100Hz to 10kHz would probably work. I'd choose 400 Hz myself. Don't forget the freewheel diode. A power Schottky is a good choice for this. You can get the gearshift effect with a switch that has multiple taps connected to a resistor network. That ought to be really fun. Use

12 volts, but have the top speed something less than 100%. Experiment to find the best "governor" frequency. The usual way of hooking up a 555 astable gives duty cycles only between 50% and 100%, nothing less than 50%. You can give it a full range of duty cycle by putting a diode across pins 6 and 7 with the cathode at pin 6.

** The best arrangement is the one shown here.

C1 could be changed to 0.022 with advantage.

The OP will need about 4 x BUZ11s in parallel to be safe and use a 15 or 20 amp thermal breaker in the battery line

..... Phil

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Ohh don't do that, My wife got two at a garage sale for $10 each. The batteries in each were gone. But you can buy replacement gel cels (I think I got them from Digi-key) for $10 each... two per vehicle.. Total cost about $30 per car. (Oh I hade to replace one of the foot toggle switches that turns on the power.) (Plus of course a bit of my time... but heck then I'm a hero to both my wife and kids.)

George H.