DC motor drive problem

agfa · 2006-12-09 02:44

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Post Edited (agfa) : 2/13/2007 2:13:09 PM GMT

bennettdan · 2006-12-09 05:37

Can we see the code their might be a better way, like the PWM command. I have a few Motor curcuits I can share that might be better for you but require a little more hardware but frees up alot of process time and you wont have to use PWM.

TechnoRobbo · 2006-12-09 18:11

supply the motors from 4 AA batteries. The amps drawn by the stall torque can fry out your stamp or make it act goofy. Make sure you tie the grounds together.

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Have Fun

TR

bennettdan · 2006-12-09 23:57

agfa

···· You can use Express PCB they have some free schematic software and PCB layout software that is easy to learn and you can convert the schematics to Bitmaps that anyone can see.

·The PWM command is nice but you cant do much else with the stamp if you use it so hardware PWM is the next step or a better Micro..

I have attached a simple hardware motor controller that you can make have more Amps by just parralleling the Mosfets.

You can read about the Digital Pot in the Whats a Microcontroller Text...the 4n25 is just an optoisolator to protect the stamp.

Hope this helps let me know if I can help...

TechnoRobbo · 2006-12-10 04:21

Prior to adding optocouplers to a robot project and using switching transistors, everytime it hit an obstruction. stalled it would hang up the processor. And I was using a seperete supply. Any type of weight load requires the motor to start with very high amps and your circuit feel the heat.

I now use 4N35's for all dc switching circuits (motors, relays whatever) cause at 30 cents each they're much cheaper to replace. And you don't have to tie the grounds together so you have full galvanic isolation.

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Have Fun

TR

Post Edited (TechnoRobbo) : 12/10/2006 2:29:47 PM GMT

bennettdan · 2006-12-10 04:23

Yes this schematic uses 4n25 optos but you can use 4n35 in the same spot..optos are just plan cheap protection..

Mike Green · 2006-12-10 04:29

You are not likely to damage the Stamp or any other regulator by trying to overload it. They all have thermal and shortcircuit protection. What may be happening is that the load of the motor at times is causing the regulator to shut down briefly, thereby resetting the Stamp.

bennettdan · 2006-12-10 05:24

Yes I agree with you Mike I use the 4n25 for mainly switching 10v or more to either a mosfet or a IGBT. But I also use the optos to up the stamps output current sometimes..

TechnoRobbo · 2006-12-10 14:59

That make sense Mike. One other experience was that the rc controlled circuit I was using also powered through the Vin stopped working - robbed of power , I assumed, cause I sunk all my amps through the stalled motors (2 of then).

I guess the point I'm making is watch out for those cheap motors. If your using them as a drive, test your design on a slight incline the load is considerably more. One way of avoiding this is to use geared motors. They are not as cheap as the 3-6v nor are they as fast but they have reasonable starting torque and they break better, ungeared motors free spin and generate voltage from their momentum, especially down hill.

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Have Fun

TR

PJAllen · 2006-12-10 15:26

agfa said...
Also does anyone know of a cheep or freebee software I can use to·create schematics so they can be posted.

Am I the only guy with a flatbed scanner on the Forum?
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Rory Storm · 2006-12-10 19:33

afag,

saw your little rant on Chris the other day.

http://forums.parallax.com/showthread.php?p=619644

You are the little terror.··

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bennettdan · 2006-12-11 00:25

agfa

You will like hardware PWM because it frees up alot of procces time in the stamp to do other things..

DC motor drive problem

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