Let's Make Robots!

H-Bridge IC making DC motors run slow (TA7267)

I'm using a TA7267 (H-Bridge) to drive a small Mabuchi DC motor. I'm suplying the IC with a reference voltage of 3V, and the operational voltage is 5V. The terminals of the DC motor are connected directly to the OUT1 and OUT2 pins. However, the motors are working pretty slow.

I've been checking the datasheet and they suggest you can add a resistance in parallel to the motor, but I don't know what value it should be, and if it would make a difference. Any idea why this would happen? 

Battery voltage going down every second

Hello,

What could be the reason that makes the voltage of a 9V battery drop every second? Im trying to build a line-follower robot, and I'm doing the circuit in a general purpose PCB (the one with holes). I'm using a MCU (PIC16F877A) and in the beginning I had only the DC motors connected and it was all good, but after I connected the CNY70 the problems started. The circuit I'm using is:

foo_0.png

Controlling a DC Motor (Mabuchi FA-130)

Hello,

I'm trying to run a Mabuchi FA-130 (#18100) DC Motor, it uses 3V and 2.1A when stalled. However, I did some measures and when I forced the motor to stall it consumed nearly 4A, but I think this was some sort of coincidence since It has never happened again.

I'm using a circuit similar to this one posted by Simon Z in his post:

simple_dc_motor_sch.jpg

(By Simon Z and taken from http://letsmakerobots.com/node/7990)