I would like to control the motor direction using an LM324(as a window comparator) & an L293D. the two output pins of my LM324 go to the Logic input pins of the L293D. The output voltage of the LM324 is 10.58V. According to the datasheet of the L293D the maximum input voltage to the logic pins should be less than equal to 7V. I cannot seem to understand the current requirements of the L293D using the datasheet. I wish to find the correct value of resistance wish is to be connected between the LM324 output pins to the input pins of the L293D.


closed as unclear what you're asking by Olin Lathrop, Voltage Spike, Daniel Grillo, Dave Tweed Nov 24 '16 at 15:28

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  • \$\begingroup\$ Find an open collector comparator like the LM339 and pull the output up to your 5V rail. Done. Op amps make garbage comparators anyway. \$\endgroup\$ – Matt Young Oct 22 '16 at 3:37
  • \$\begingroup\$ My PCB is already built around the LM324. But I can still add resistors to it. \$\endgroup\$ – Jonathan Pereira Oct 22 '16 at 3:39
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    \$\begingroup\$ if you dont know how to interface logic, you certainly dont know how to interface and control a motor. Define the overall interface specs first \$\endgroup\$ – Sunnyskyguy EE75 Oct 22 '16 at 3:50
  • \$\begingroup\$ Regardless, don't use an antiquated, lossy L293D. See the "Related" column to the right which is literally chock full of explanations why. \$\endgroup\$ – Chris Stratton Oct 22 '16 at 4:17
  • \$\begingroup\$ The L293D & LM324 have already been added to the PCB. There is still scope to add resistors between them. \$\endgroup\$ – Jonathan Pereira Oct 22 '16 at 4:21

(too long for a comment)

As I stated in a comment with your previous question, the input current requirements are in the datasheet section 6.5 part I inserted there (Iih and Iil):

enter image description here

What is it that you don't understand?


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