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  1. #1
    I have a setup that uses 2 x 18650 3.7V 4000Mah batteries in series ( producing 7.8Vdc. Im trying to control a 6-9V dc miniature motor with 2 buttons 1 button to CW and the other to CCW
    Ive been told that a L293d will work but ive blown up 5 so far
    I think the problem is im imputing too high a current into the Vcc1 (pin 16) which calls for 5V (max 7) attached is a diagram i found with basic setup I would appreciate someone confirming the setup IF I REDUCE INPUT TO 5VDC
    Also if i connected something to the end of the + 7.8v feed to reduce the current to 5V .
    Im not electronics savvy so appreciate any help
    Thanks Richard
    Attached Files Attached Files

  2. You will need to put the 7.8V onto pin 8 (VCC2) and all your switching and VCC1 have to be 5V. So you need a LM7805 voltage regulator to derive that 5V.

  3. #3
    Quote Originally Posted by cropwell View Post
    You will need to put the 7.8V onto pin 8 (VCC2) and all your switching and VCC1 have to be 5V. So you need a LM7805 voltage regulator to derive that 5V.
    Hi thanks assume the lm7805 can just come off the end of the main feed ( going to vcc2pin 8) so betweem 8 and 16 or does it need dedicated feed?
    thanks

  4. No, you don't need a separate input, you can connect the 7.8V from the two batteries to VCC2 and the input of the LM7805 (pin1). Pin2 connects to GND and connect the out put (pin3) to VCC1 and all control inputs through the switches.
    Last edited by cropwell; 03-08-2020 at 02:11 AM.

  5. #5
    Hi so as drawn now OR does the feed go straight to 8 and no feed to 9 ? if so does the common power for switches come off pin 9 or am i wrong again. appreciate the help
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

Name:	L293 wiring diagram for 2 push buttons rev A.jpg 
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  6. 5V output of the lm7805 goes to switches.

    Click image for larger version. 

Name:	L239d.jpg 
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  7. #7
    Thanks very much so im actually switching 5 v thru the switch but the output to motor 11 14 is the 7.8V ?
    think ive got it now

  8. It's worth reading section 10 of the attached data sheet re. heatsinking - if you're drawing high currents:-

    https://www.ti.com/lit/ds/symlink/l293.pdf

  9. #9
    Hi
    thanks Doddy
    the motor is rated
    mA: 120
    Stall mA: 200
    so dont think is very high so im not worrying about heatsink ( am i correct?

  10. To be honest I almost deleted my post, reviewing the link that I provided - it didn't feel like my concerns were going to be realised. Proof of pudding is a wet finger on top of the device when rapidly changing direction, but it looks like the device is adequate without heatsink. If you burn your finger, however...

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