Hi Dave,
I will "measure the voltage across the motors under load" and
see what I get.

Thanks,
Kevin

>Hi Kevin,
>
>It looks like you are losing several volts in the bridge.  Page four of
>the datasheet http://www-s.ti.com/sc/ds/sn754410.pdf  (High level output
>voltage and Low level output voltage) indicates you will lose between 2
>and 4 volts (depending upon load and temperature).  You could try
>measuring the voltage across the motor terminals under load to verify
>this.
>
>Best regards,
>
>Dave
>
>"Kevin A. Benedict" wrote:
>>
>> Hi,
>> I posted this under EE, but then found a big discussion from
>> 12/2000 about the tamiya twin motor drives.  I still have the same
>> question, the FA-130 motors are rated 3v@800ma stalled.
>> So why can't I drive the twin motor gear box a pic and
>> a sn754410 chip with 4AA batteries ?
>> One note I did have it set to 58:1 ratio, I am going
>> to try 203:1 next.
>>
>> Thanks in advance,
>> Kevin
>>
>> >>Hi,
>> >>I am driving two small DC hobby motors in a gear box assembly,
>> >>that drives two tank tracks. I wanted to power the F628,
>> >>SN754410 and two motors all from the same 4AA batteries.
>> >>If I drive the two motors right off the 4 AA batteries,
>> >>the tank tracks are powerful and can drive over a thick
>> >>book.  However, when I power the pic/SN754410/2 motors,
>> >>the motors are barely able to turn the tracks ?
>> >>
>> >>In the F628, I have port A set as digital, and set ra1, and
>> >>ra0 high and low to turn on motor a, and follow the same for
>> >>ra2 and ra3, for motor b (through the SN754410 of course.)
>> >>The SN7554410 is just a 1 amp version of the L293D.
>> >>port b is set as output and all pins low.
>> >>
>> >>I quess I'm just looking for a sanity check, I can't believe
>> >>the F628 and H bridge chip are using up so much current
>> >>that the motors can't even turn the tank tracks ?
>> >>I have both enable pins on the h-bridge chip tied to the +5v
>> >>supply through a 10k resistor.
>> >>Any one familiar with these chips ?
>> >>Any thoughs on what's happening ?
>>
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>
>

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