24v Motors, run on 12v?

[sanddrag]

Originally Posted by team222badbrad

We also needed to find 24 volt speed controls. So we looked to Innovation FIRST's other company http://www.ifirobotics.com/ and we used their Battle Bot speed controls!

Or you could save 50 bucks and go with something like this http://www.robotcombat.com/marketplace_robowars.html

[Kevin A]

You could try something like this - http://www.solorb.com/elect/solarcirc/pwm1/
I believe that that steps up the voltage using capicitors charged in parallel and drained in series.

Best of luck!
Kevin

[Jacob Morgan]

I've never tried this, and not extremely informed on circuits and such tho i plan to learn..

why couldnt' you just get a potentiometer and modify so you can hook a servo, or small motor to it to turn it on command.

Then hook it to the motor..

would that not satisfy as a cheap speed control?


or am I just waayyyy out in left field here..

[sanddrag]

You would need a circuit to convert the potentiometer signals to pwm and you would also need some transistors to actually handle the power. And some sort of chip to run it all.

[Jacob Morgan]

ooo I see, I always thought the potentiometer was always just essentially a dimmer switch like you use in your house for lights, that it would go in between the motor and the battery and by turning it you would increase the motor speed, vice versa..


Guess not :-p..

Im also now looking at some wiper motors if these wheel chair motors fall through, The first one I built I used power window motors and they worked great but I can't remember what model car they were from, and cant' find any that look like them:-/

[sanddrag]

I don't believe a household dimmer switch will work either because those are for AC and your project (I assume) is DC.

[Jacob Morgan]

I didnt' figure it would, I was just using it for comparison. found that out on another project I had (DDR pad for siblings)


on these..

http://cgi.ebay.com/ws/eBayISAPI.dll...tegory=11 769

the shaft shoes to be 3/8" thread, if i read it correctly. The wheels I have have a 3/4" hole. Has anyone done something similiar to this....

Im thinkin about getting some circular stock (3/4"Diameter) and then putting a piece in the wheel, welding it in place(weld on wheel) then tap the stock for a 3/8" hole and just thread it onto the end of the wiper motor? I was going to make the stock a few inches long since the shaft on the motor is so short...

Anyone do something similiar?

I will either get 2 of those motors, or the wheelchair motors.

[sanddrag]

Originally Posted by Jacob Morgan

http://cgi.ebay.com/ws/eBayISAPI.dll...tegory=11 769.

You can get those exact motors a bit cheaper here As for your wheel, you can do that but you need something to make sure it doesn't unscrew itself when you go the other way.

[Jacob Morgan]

wow thanx !

I alreayd thought about that.. I figured I could try loctite, if that didnt woork drill a hole in the shafts and put a cotter pin thru?

just all in theory..

Only concern, how strong would it be? say I had a 2" shaft and only prolly a 1" or so will be screwed onto the motor.. would it want to give?

just thinkin of all scenarios i can.. thanx..

[Andy A.]

Originally Posted by Jacob Morgan

ooo I see, I always thought the potentiometer was always just essentially a dimmer switch like you use in your house for lights, that it would go in between the motor and the battery and by turning it you would increase the motor speed, vice versa..


Guess not :-p..

A pot will act just like a resistor if you put in line with the motor. The more resistence it is set for, the more voltage it will convert to heat and the less voltage your motor will see. The less voltage to the motor, the slower it will turn. You can prove it to your self with a small motor, pot and battery.

This means that a pot will act as a very crude speed control. The problems are big though. One, unlike PWM, the motor is not running at its normal voltage- it will turn slower but with far less power, just as if your battery were dying. Secondly, all that power your dropping across the pot is becoming heat. If your pot is not designed to dissapate enough power, it will burn up. Thirdly, you may not be able to find a pot that has the range and correct number of turns.

Rember that when the pot/speed controller has the motor 'stopped', it will be making its self into a neat little space heater. This is a sure way to let out magic smoke.

All in all, pots make poor speed controllers.

-Andy A.

[sanddrag]

Originally Posted by Jacob Morgan

I alreayd thought about that.. I figured I could try loctite, if that didnt woork drill a hole in the shafts and put a cotter pin thru?

That would work except a cotter pin would bend and/or break. A roll pin might work, but a large dowel pin would be your best bet.

[Jacob Morgan]

between the two motors i've posted, what would you guys recomend?

The wheels I have are 10" diameter, with a 3/4" hole in in them.

if I use the wheelchair, i'll moist likely have to use them on a 12v circuit, atlesat for a while..

If I use the wiper motors(12v), i'm going to buy some round steel (3/4" D) and tap a 3/8" hole in it and then weld it to my tire, then thread it on the motor.. I'll try loctite, and if that doesn't work drill a hole and put a pin of sometype in it.


What do you guys think?


edit..

http://www.realityslap.com/~dante/robot/

has the design for the frame i've built (its done) and the wheel adapter that i stated above that i'll need to make for the power window motor..

any comments? I know my drafting etiquette is prolly rusty.. if u see anything big wrong iwth it let me know and i'll fix it.