I need a help designing Motor Driver Circuit

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Discussion Overview

The discussion revolves around designing a motor driver circuit for a 12V DC motor, specifically a power window motor, using the L293D motor driver chip. Participants explore issues related to overheating of the chip, current requirements of the motor, and potential solutions for driving the motor effectively.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant reports that the L293D chip overheats after a few seconds of operation, despite using a 9V battery and claims that connections are correct.
  • Another participant questions whether the inputs to the motor driver are static or switching, suggesting that switching inputs could affect performance.
  • Concerns are raised about the power supply, with one participant suggesting that a 9V battery may be underpowered for the application.
  • It is noted that the L293D can handle up to 1A, and if the motor consumes more than this, it could lead to overheating.
  • One participant mentions that the motor's specifications indicate it can draw 3A at no load and up to 7A at full load, suggesting the need for a driver that can handle higher current.
  • Suggestions are made to either use a different driver capable of supporting higher current or to design a custom driver using larger transistors.
  • Another participant provides a brief explanation of how an H-bridge configuration works for driving DC motors and emphasizes the importance of selecting appropriate transistors for the required current.
  • Concerns about battery life are raised, noting that a 9V battery rated at about 0.5Ahr would last only a few minutes under a 7A load.

Areas of Agreement / Disagreement

Participants generally agree that the current requirements of the motor exceed the capabilities of the L293D chip, but there is no consensus on the best solution, with multiple competing views on how to proceed.

Contextual Notes

Participants mention specific current ratings and limitations of the components involved, but there are unresolved questions about the exact current draw during operation and the suitability of the proposed solutions.

Who May Find This Useful

This discussion may be useful for individuals designing motor driver circuits, particularly those working with DC motors and seeking to understand the implications of current ratings and driver capabilities.

medosoft
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I'm designing a driver circuit for a 12V DC motor (Power Window). I'm using an L293D motor driver chip.
According to the http://www.zartronic.fr/doc/Z1/L293D_ST.pdf the chip can withstand a supply voltage Vs up to 36V. I'm only using a 9V battery.
The circuit and the motor are working well. However, after a few seconds the L293D chip would overheat. If I stop it, it will not work again until it cools down, and if I leave it I'm afraid the chip would be burned
I'm sure there is nothing wrong with my connections because I've redone them many times.
Do you know the reason or the solution to the problem?!

You can get the proper chip connection from http://www.aishack.in/2010/08/simple-motor-driver-circuit/
 
Last edited by a moderator:
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Are your inputs static or are they switching at some frequency?
 
I'm only using a 9V battery.

as in little NEDA1604? for a car window motor?

http://www.electronicsnmore.com/images/9v-pana.gif

You're way underpowered i think.

Did you heed the heatsink instructions on pages 10, 11 & 12 of datasheet?
http://www.ti.com/lit/ds/symlink/l293d.pdf
 
Last edited by a moderator:
The driver IC that you are using can handle up to 1A, if the IC is over heating so it may be due to that the motor is consuming higher current.

Try to measure the current, and if it was greater than 1A and if your connection are all correct, use smaller motor.

Regards,
Hisham
 
the_emi_guy said:
Are your inputs static or are they switching at some frequency?

No, they depend on the end user pressing a push button
 
jim hardy said:
as in little NEDA1604? for a car window motor?

http://www.electronicsnmore.com/images/9v-pana.gif

You're way underpowered i think.

Did you heed the heatsink instructions on pages 10, 11 & 12 of datasheet?
http://www.ti.com/lit/ds/symlink/l293d.pdf

No .. Power Window is the model of the motor
You can view it from here
http://www.cytron.com.my/viewProduct.php?pcode=MO-PW-R&name=Power Window Motor (Wira) - Right

And you're probably right about the current .. unfortunately, I have to use this motor because a smaller motor will not perform the function required
 
Last edited by a moderator:
And you're probably right about the current .. unfortunately, I have to use this motor because a smaller motor will not perform the function required
As it is shown from the data sheet of the motor, at no load 3A, and at full load 7A.
So you have to use another driver which can support higher current, or you can make your own driver with transistors that can handle higher current.
 
hisham.i said:
So you have to use another driver which can support higher current, or you can make your own driver with transistors that can handle higher current.

Can you explain more about how to use this transistor?
 
  • #10
  • #11
Dc motors drivers consist of transistors that are connected in H-bridge configuration.
See the attached picture to have a look on how H-bridge looks like.

When transistors T1 and T3 are on and transistors T2 and T4 are off, current will flow from VCC2 through T1, to T3 then to ground, and the motor will rotate on some direction let's say to the anti clock wise.

When transistors T2 and T4 are on and transistors T1 and T3 are off, current will flow from VCC2 through T2, to T4 then to ground, and the motor will rotate on the opposite direction.

So you can drive your motor using this configuration but you have to choose the correct transistor that can handle the current that is required by the motor in your case 7A.

Google for H-bridge Dc motor controller, you will find a lot of schematics, and you can share your design for any information needed.

Or try to find a supplier where you can buy H-bridge that can handle this current.

Hope this helps,

Hisham
 

Attachments

  • H bridge.png
    H bridge.png
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  • #12
A quick google search revealed that a 9V battery is rated at about .5Ahr. This means that it will last about 4 min on a 7A load.

Hope you have a good supply of them. Your best bet is to find a 12V lead acid battery.
 

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