The L293B issue

Question

Hi, im trying to use the L29 with only one (PWM) digital pin.

normaly Pin 2 and Pin 7 go to digital pins on the arduino and they determine the spin direction.

The code is aways one high and one low - meaning that pin2 gets 5 volts and pin7 gets 0 volts or vice versa.

Now i dont need to change directions of the rotation, Can i just hook up pin 2 to 5 volts and leave pin 7 free (or should i connect it to ground)

I have tried whats shown in the picture above, but it doesnt work.

Also I am only running one motor, the other side of the chip doent need to be connected to anything right?

Where could be the problem?

Thanks in advance

billabott · Accepted Answer

Nice Diagram.

Q: Should pin 7 should be connected to ground?

A: It depends. Yes, if you use a four diode bridge. No, if you are using a single diode to protect pin 3 from back EMF(or counter EMF). Then pins 6 and 7 can be NC (not connected).

Just thinking about what you said normally "Pin 2 and Pin 7 go to digital pins" to set the direction; these pins are not floating, they are either at +5 volts or ground potential.

Additionally,it appears that the data sheet indicates that you must supply the bridge diodes to make the motor run in both directions with this device.

I can see that if you only need the motor to turn in one direction then you may use either pin 3 OR pin 6 and a single diode. The direction of rotation will be determined by your choice of pins and your choice of potential (0 or +5 volts) on the other side of the motor. Two of the four combinations will result in no rotation - so choose wisely. Also you must install the diode with the proper polarity. See the Data Sheet.

Don't forget that pin 9 pin 16 also needs +5 volts.

Pin 8 Vs is Supply Voltage

Pin 16 Vss is Logic Supply Voltage

It is pin 16 that needs the positive voltage to drive the IC's logic gates and amplifiers.

Good luck with your project.

The L293B issue

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