[Gasification] Gasification Digest, Vol 17, Issue 8

[Michael Redler]

"Do you want a servo motor driver or a stepper driver?"

(FWIW) I've often saved myself the time and cost of building a stepper 
driver by using a permanent magnet, DC gear motor, driven by a PWM (555 
timer circuit and a SSR, for example).

I know it's a lot less sophisticated than a stepper but, in some 
applications it works fine. Of course, if you wanted better control over 
a wide ranger of speeds, I'd stick to plan "A". David summed that up nicely.

...my $.02

Mike

David G. LeVine wrote:
> At 10:08 AM 11/13/2007, you wrote:
>   
>> Targeting 80 millivolts with manual controls distracts the driver 
>>     
> >from the task at hand. If an air-valve could be positioned by logic, 
>   
>> a biomass-fueled vehicle could be operated much more safely.
>>     
>
> The logic is not difficult.  Do you want a servo motor driver or a 
> stepper driver?  How big a motor?
>
> The best way is a buffer amplifier, an integrator (yes, those are 
> necessary to smooth things out) and a micro (like a PIC16F family 
> with an A/D built in) to make decisions.  You are talking no more 
> than $100.00 for the logic, but finding a coder may be rough.  For a 
> stepper, the controller can be as simple as 4 resistors, 4 FETs or 
> BPTs and 8 diodes.  For a DC motor, it isn't much worse.
>
> Remember, you are looking for a fairly coarse and slow (for a micro) 
> system.  A time constant of 1 second is incredibly fast for a human 
> and slow for a micro with a simple program.
>
>
> David G. LeVine
> Nashua, NH  03060
>
>
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