Forums

Motor Control

Started by tieutaydoc November 18, 2005
Hi, I'm having a weird problem trying to get the bx-24 to control
motors. I'm using a bx24 along with the SN754410 H-Bridge. The weird
thing is that I can control the enabler pin just fine. So I can turn
the motor on/off with the bx-24 but i can't seem to reverse the motor.
I think my problem is that sending the signal putpin to 0 is not the
samething as grounding the pin. I've discover that when I use an
inverter and a switch i can reverse the motor back and forth but not
with the bx-24. I don't understand why i can send the enabler pin with
the signal 0/1 but not the reverse. If anyone have any insight on this
please let me know. Thanks.
Jimmy



When I started reading your message, I thought that the problem was
that you were driving only 1 of the 2 necessary pins on the H-bridge.

1,0 = forward
0,1 = reverse
0,0 = coast to stop
1,1 = brake to stop.

But when you said that you used an inverter and got a good reverse,
then I am not sure what is wrong.

What support circuitry are you using to drive the h-bridge. If you
are only using 1 pin, then you already have an inverter 2 of the
pins on the h-bridge, plus a straight thru signal to 2 others....

I suppose it is possible to damage a pin on the BX so it can source
current but not sink....

I had no trouble with my setup, but I used 2 pins for direction,
plus enable for PWM speed.

Others here will have have good ideas too (better ideas)

-Tony


You wrote:
> I think my problem is that sending the signal putpin to 0 is not the
> samething as grounding the pin.

It should be the same, but it also may be that the pin is not being pulled
up to a 1, so it always looks like it's a 0. To you have a pull-up resistor
on the pin?

Sloan


My problem was that I didn't use the bx-24 ground but a seperate power
supply. That's why I couldn't get it to reverse with the chip. Thanks
Tony for your help.


You can do two power supplies if you use optical isolators.

I use a heavy current 10Amp 12 - 15 volt DC power for motors and a lowly
1Amp 9 - 12Vdc for controller. I can optionally drive it all with the
heavy power supply.

Don Lewis --- In basicx@basi..., "tieutaydoc" <tieutaydoc@y...> wrote:
>
> My problem was that I didn't use the bx-24 ground but a seperate power
> supply. That's why I couldn't get it to reverse with the chip. Thanks
> Tony for your help.
>