Maybe it would be wise to determinate the exact voltage where the
motor starts moving with the load and that would be the value where
the PWM should start. We use that fine tuning DCC controlled model
locomotievs that are using a H-Bridge and DC motor.
 
Harry
> -----Oorspronkelijk bericht-----
> Van: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] 
> Namens Jinx
> Verzonden: woensdag 5 augustus 2009 14:39
> Aan: Microcontroller discussion list - Public.
> Onderwerp: Re: [PIC] Lowside PWM motor controller for go-cart
> 
> > How many FETs are you planning to use?  Bear in mind that 
> whilst the 
> > full load current of the motor is only ~21Amps, the stall 
> current will 
> > be much, much higher
> 
> Some time ago I helped a friend out repairing golf carts 
> (trolleys, not cars) of various makes. All had at least 3 
> FETs, the better ones had 4 or 6. Although none of them used 
> a micro and had less-than- optimum power bands. If it were me 
> I might use a look-up table to set the PWM. For example, 
> maybe the first 10% of the pot makes very little difference 
> in terms of getting the motor going against the load, so 
> linearly converting pot position to PWM duty is not the best 
> way. And monitoring motor demand, even simply comparing 
> factors such as current drawn versus revs versus PWM (eg 
> going up or down inclines), can help minimise the need for 
> constant manual speed controlling
> 
> 
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