Aruino + L293D + external supply issue

Hi,

I use an external 5v supply to power L293D and a small bipolar stepper motor (5v) plugged on arduino Fio (3.3v).
It work fine as i expected with “stepper one revolution” sketch exemple. So the problem is, when i disconnect the external power supply, the motor continues to rotate powered by the arduino board and i noticed that the L293D is heating fastly.

Any suggestions please.

Image link to my wiring circuit:

http://www.hostingpics.net/viewer.php?id=544645L293Dsteppermotor.jpg

Thanks

Up!!!! :)

Please, why if i disconnect the external motor power supply, the motor continue to cycle through the code?

Thanks

If you disconnect power from pin8 on the L293, the motor should stop turning and cool down. You may have a wiring error.

Check the voltage on pin8 with the motor power 'disconnected'.

Thanks for your response.
However i followed the L293D wiring used.
I made a drawing of my wiring… may be i skipped something.
Can you tell me if my wiring is ok ?

http://img15.hostingpics.net/pics/844159L293DFioWiring.jpg

L293D pins 4, 5, 12, 13 and external motor supply negative have common ground (hooked to arduino GND pin).

L293D pin 1, 9, 16 have common positive to 3.3V arduino pin.

L293D pin 8 is hooked to external motor supply positive (+)

Even if i disconnect the external motor supply, the motor continues to rotate ???
Where is my mistake?
Thanks

Check the voltage on pin8 with motor power disconnected. If the motor runs a 0v then you have have a magic motor that requires no power :)

Try another L293 chip.

[quote author=joe mcd link=topic=180224.msg1337569#msg1337569 date=1375308948]

Check the voltage on pin8 with motor power disconnected. If the motor runs a 0v then you have have a magic motor that requires no power :)

Try another L293 chip. [/quote]

Magic motor :D Ok i disconnect the external motor supply on the L293D. Only the FIO board is powered with a 3.7 lipo battery. The motor is always rotating. I checked with a multimeter connected to L293D pin 8 (Multimeter on DCV position 20 ..... red wire of multimeter on pin 8 and black wire on common ground). Multimeter display 4.2 V.. (it increases gradually until it reaches 4.2V)

What's wrong?

I changed the l293D component, but the problem persists. The motor still run when external power is disconnected. :( It is necesseraly a wiring problem. Do i have to connect together the Enable 1 (pin1), Enable 2 (pin9) and Vss (pin16) to the 3.3V arduino Fio pin when using an external 5V power supply for the motor ???

Reminder: I use a small 4 wires bipolar stepper motor + L293D + Arduino Fio powered by a 3.7v lipo + 5v External power supply to the motor (connected to pin 8 of L293D). I'm using "stepper one revolution" sketch exemple.

Maybe i need to see the side of Enables Pins (pin 1 and 9 of the L293D), by hooking them on digital pin of the arduino board and not to the 3.3v ? What do you think ?

Harduino: Hi,

I use an external 5v supply to power L293D and a small bipolar stepper motor (5v) plugged on arduino Fio (3.3v). It work fine as i expected with "stepper one revolution" sketch exemple. So the problem is, when i disconnect the external power supply, the motor continues to rotate powered by the arduino board and i noticed that the L293D is heating fastly.

Any suggestions please.

Image link to my wiring circuit:

http://www.hostingpics.net/viewer.php?id=544645L293Dsteppermotor.jpg

Thanks

For the L293 the external motor supply should be at least as high as the logic supply (see recommended operating conditions in the datasheet).

As a consequence you may have damaged the chip. You cannot operate the chip safely this way as far as I know because the motor current is being routed via some on-chip diode or transistor not designed for that current (I think).

A workaround is to sense the expernal supply voltage via a voltage divider and disable motor drive when it is too low / not present.

MarkT:

Harduino: Hi,

I use an external 5v supply to power L293D and a small bipolar stepper motor (5v) plugged on arduino Fio (3.3v). It work fine as i expected with "stepper one revolution" sketch exemple. So the problem is, when i disconnect the external power supply, the motor continues to rotate powered by the arduino board and i noticed that the L293D is heating fastly.

Any suggestions please.

Image link to my wiring circuit:

http://www.hostingpics.net/viewer.php?id=544645L293Dsteppermotor.jpg

Thanks

For the L293 the external motor supply should be at least as high as the logic supply (see recommended operating conditions in the datasheet).

As a consequence you may have damaged the chip. You cannot operate the chip safely this way as far as I know because the motor current is being routed via some on-chip diode or transistor not designed for that current (I think).

A workaround is to sense the expernal supply voltage via a voltage divider and disable motor drive when it is too low / not present.

Thank you for your reply... The 5v external motor supply is higher than the 3.3v logic supply or sorry i don't understand what you mean by "the L293 the external motor supply should be at least as high as the logic supply". Here is the datasheet of the L293D i use : http://pdf.datasheetcatalog.net/datasheet/stmicroelectronics/1330.pdf

Harduino:
For the L293 the external motor supply should be at least as high as the logic supply (see
recommended operating conditions in the datasheet).

As a consequence you may have damaged the chip. You cannot operate the chip safely this way
as far as I know because the motor current is being routed via some on-chip diode or transistor
not designed for that current (I think).

A workaround is to sense the expernal supply voltage via a voltage divider and disable motor
drive when it is too low / not present.

Thank you for your reply…
The 5v external motor supply is higher than the 3.3v logic supply or sorry i don’t understand what you mean by “the L293 the external motor supply should be at least as high as the logic supply”.
Here is the datasheet of the L293D i use :
http://pdf.datasheetcatalog.net/datasheet/stmicroelectronics/1330.pdf

This means that you need to provide +5V or higher to 8 and 16 pins. L293 can work with low or no supply on 8 (Vs, bridge supply), but work unstable with voltage under 5V on 16 pin (Vss, logic supply). It have been tested with 3 different L293D.