5V Source for SN754410 "ENABLE" Pins

4jaba6

New Member
I am using this chip for a motor control project.

Pins 1 and 9 need to be enabled with +5V on this chip for the motors to run.

+ 5v source goes to a 10K Resistor and then splits to the 2 pins.

In past, have used a Separate +5V source ( or used +5V from VCC1 CHIP Logic Power (pin 16 ).

I am asking for opinions on which of the two +5v source to use.
I believe the approved solution is the VCC1.
Am trying to determine the pros & cons.
It seems that using a separate +5V source's only downside is extra parts and extra space.
What are con's of using VCC! ?

TIA,

John
 

inglewoodpete

Senior Member
Some people had experienced problems using the SN754410, as discussed here. I've only ever used the larger L298, which was used because I was driving larger motors, so can't comment personally on the SN754410.

When driving a motor off the same supply as the microcontroller, ensure that each has it's own power wiring all the way back to the power source (Ie no motor current shares a wire with the microcontroller).

Logic Earth2.jpg
 

westaust55

Moderator
There is no problem in using the +5 V d.c. powering the SN754410 Vcc1 to also pull the two enable pins high - using a 10 kOhm pull up resistor as you suggest.

Remember also to ensure that the 0 Volt line to the SN754410 is also connected to the 0 Volt line for the microcontroller.

like IWP I have never used the SN754410 myself - always the L293D in the past (recently have been using a DMOS H-bridge driver with much lower internal volt drop - but only available as a SMS package).
 

inglewoodpete

Senior Member
Remember also to ensure that the 0 Volt line to the SN754410 is also connected to the 0 Volt line for the microcontroller.
As tempting as it might be to connect the two device 0v points directly, the 0v line between should be routed via the power source. That will all but eliminate current surges and back-EMF from the reactive load affecting the relative voltage on the 0v pin of the PIC.
 

4jaba6

New Member
There is no problem in using the +5 V d.c. powering the SN754410 Vcc1 to also pull the two enable pins high - using a 10 kOhm pull up resistor as you suggest.

Remember also to ensure that the 0 Volt line to the SN754410 is also connected to the 0 Volt line for the microcontroller.

like IWP I have never used the SN754410 myself - always the L293D in the past (recently have been using a DMOS H-bridge driver with much lower internal volt drop - but only available as a SMS package).

westtaust55,

Thanks to you and Inglewoodpete for your replys.
By "0 volt line", I believe you are referring to ground ( 4 pins on SN754410 ).
Please correct me if wrong assumption.

I have used this chip in past with success controlling small motors.
The motors were driven by 5v.
If using larger motors, I would use the L298.


John
 

westaust55

Moderator
By "0 volt line", I believe you are referring to ground ( 4 pins on SN754410 ).
Please correct me if wrong assumption.
Yes, 0 volt is what is often referred to as “ground”.
But if battery powered or through many power supplied The 0 volt connection is not connected to ground (and thus is not earthed/grounded as is the metalwork on a mains powered device).
 
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