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Topic: Can't run DC motors with L293D shield with external power (Read 3857 times) previous topic - next topic

aarian4u

I have supplied 12v to the 2 L293D shield for accommodating 4 DC gear motor (12V, on no load approx 50mA current drawn by each) and controlled it by Arduino Mega.
The problem is when I powered the mega through computer usb it drive the motors very well but when supplied through external power of 9v (tried  9v battery as well as DC adapter of 1A supply, also tried adapter for supply through usb (5V,1A)) it can not run the motors.
What is the problem I can't understand??

AWOL

9V batteries are great for running smoke alarms, but terrible for running anything that requires much current.
AA cells are much better.

aarian4u

But I know the current required by the motors are supposed to supply by the L293D supply.

MarkT

The grounds should be commoned.  Also have you _measured_ the voltages of each
supply to check they are correct?  A multimeter is you eyes and ears :)
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

JimboZA

I'm confused: you start by saying you provided 12V....

I think we need to see the circuit. What voltage, from what source, have you provided to pin 8 of the L293? (That's the pin that supplies power to the motors, not to be confused with pin 16 which is 5V to run the chip itself.)

(L293 drops about 2V internally by the way.)
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Dr Perry Cox: "Help me to help you, help me to help you...."
Your answer may already be here: https://forum.arduino.cc/index.php?topic=384198.0

aarian4u

@MarkT I have measured all the voltages, as I said earlier to the arduino mega give 9.07V, and to the L293D give 12.48V.


aarian4u

@JimboZA
At first also i am confused by the circuit board of L293D (picture is given in the attachment), when I worked with different voltage from 5V to 12V it actually worked with single voltage.

But now when i powered the arduino through computer usb it run the motors and when through external power it can't run.   :smiley-confuse: 

JimboZA

You need to look at the circuit of that board....
Johannesburg hams call me: ZS6JMB on Highveld rep 145.7875 (-600 & 88.5 tone)
Dr Perry Cox: "Help me to help you, help me to help you...."
Your answer may already be here: https://forum.arduino.cc/index.php?topic=384198.0

aarian4u

Is the problem for the L293D Driver or for the arduino? If it is for the driver then how computer usb supply can run all things smoothly?

aarian4u

When I am increasing the load to the motor, voltage across it drops to 0v and the current through it increasing to a max value of 110mA and then drops to 0mA so the motor goes stop. It is happening when I powered the arduino through external DC adaptor of 12V.

But when powered through computer USB current goes to a max value of 180mA and here fixed.

In each process L293D given to 12V,1A through DC adapter.

So what is the problem with it? I have to run it with external power and the problem is i cannot give any load to the motor as it is stopped. Please help anyone  :smiley-sad:

JimboZA

You need to look at the circuit of that board....
That's still true....

Is that a jumper towards the top right side, just above the "E" in "EN2"? Perhaps that has something to do with using external power?

Where's the datasheet?
Johannesburg hams call me: ZS6JMB on Highveld rep 145.7875 (-600 & 88.5 tone)
Dr Perry Cox: "Help me to help you, help me to help you...."
Your answer may already be here: https://forum.arduino.cc/index.php?topic=384198.0

aarian4u

Yes these EN1 and EN2 are enable pins connected by jumper.
Datasheet was not given to me but you can see the attachment below.

JimboZA

I think you should provide circuit diagrams of your setup, both the working and not working ones.

In both the working / not working cases, what voltage do you find on the L293's pin 8?

MarkT mentioned the grounds need to be wired together: I don't think you mentioned them yet... are they?
Johannesburg hams call me: ZS6JMB on Highveld rep 145.7875 (-600 & 88.5 tone)
Dr Perry Cox: "Help me to help you, help me to help you...."
Your answer may already be here: https://forum.arduino.cc/index.php?topic=384198.0

aarian4u

Ok I will give the circuit diagram but first i have to draw it. I will upload it soon. Thank you.

Tonoloek

I have the same problem, I checked the voltajes of the motors, and it's about 1.5 - 2V, it's to small to run the motors. I have a 12V and 4Ah baterry, and the motors only produces a small sound.

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