I'm using L293E to drive one motor in two direction.

Output 1 and output 4 are connected to the motor and I alternate Input 1 (1A) and Input 4 (4A) between VCC and GND. (never input1 == input4).

Vs and Vss of the L293E are both connected to VCC = 12V.

Here's my schematic : Schematic

The problem is when I connect Input 1 to VCC = 12 and Input 4 to GND. I measure 10.8V between output1 (1Y) and output4 (4Y), yet when I connect the motor it doesn't turn.

The motor is a small motor. For instance, when I connect it directly to the power supply (12V), it only sucks about 400mA.

Here's the datasheet of L293E

  • \$\begingroup\$ There are likely many things wrong where. Measure the voltage across the motor while it is connected, and you will probably find it is no longer the unloaded value you measured before. \$\endgroup\$ – Chris Stratton Jun 5 '19 at 12:07
  • \$\begingroup\$ @ChrisStratton True. but what does that mean ? \$\endgroup\$ – Yassine Jun 5 '19 at 12:08
  • \$\begingroup\$ It means you need to start debugging the problem. Read the links about why this is a horrible chip, use your meter to see where the unexpected (to you) voltage drop is. \$\endgroup\$ – Chris Stratton Jun 5 '19 at 12:33

when I connect Input 1 to VCC = 12

Here's another problem - the data sheet tells you that the maximum input voltage is 7 volts yet you are using 12 volts. A more detailed study of output weaknesses associated with the L293 is here. It may answer some of your other observations.


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