hooking up the A3959SB

[raitl]

So the chip is this one: **broken link removed**
and I've included my circuit.

I'm going to use these chips to run 2 18V cordless drill motors on my bot with PIC. The motors draw about 1.4-1.5Amps continous, spikes as high as 3.4Amps. So these chips would be perfect. I do not want to use the on-board PWM, but stick with my 16F867A to handle the speeds. So as much as I can understand, I do not need to use the osc pin (can pull it to ground) but what do I do with BLANK, PFD1, PFD2 pins?

I've tested the circuit on breadboard, but all I got was some hissing noise from the motor. What am I doing wrong?

Oh, I used 2.2 Ohm resistor for Rs and Vref was 18V. Tried with Vref 5V aswell, no difference.

**broken link removed**

 

[Nigel Goodwin]

I'm going to use these chips to run 2 18V cordless drill motors on my bot with PIC. The motors draw about 1.4-1.5Amps continous, spikes as high as 3.4Amps.

No idea on those chips, never heard of them - but I suspect you are EXTREMELY low in your ideas of what current the motors might take!. I would expect stall and heavy load currents in the tens of amps?, you need to either limit the current, or make sure your controllers will handles high currents.

 

[raitl]

I don't think the current is not going to get that high even when braking. Because I'm going to stick with the original reduction which has such a high ratio, that I can't turn the wheel even when not braking the motor. So it would be logical to assume, that I won't even have need for the braking action. Right?

My other choices are:

MC33886DH

5A max

and

SN754410NE

1A max


So does anyone have any experiance with these IC's?

 

[Nigel Goodwin]

I don't think the current is not going to get that high even when braking?

I strongly suggest you try measuring it! - stall currents from DC motors are HUGE! - even if it's too powerful to stall, it will take a high current under high loading!,

 

[raitl]

5.5Amps when I grabbed the motor and held it.