DC Motor Drive L293D

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kanni1303

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I used L293D to run Stepper motor and i did it with Bipolar Stepper Motor successfully... Then i came to know that is Dual H-Bridge Ic that can run DC motor in both directions... then i connected as like the diagram... logic input of 5V and motor supply of 12V with 7805 and 7812 regualtor respectively from 12V 5Ah battery... but the problem is the IC heating very hot within secods... I am using 12v 300mA DC Geadred Motor... but L293D can drive upto 600mA per channel and peak of 1.2A... but dont know what is the mistak i did... pls help me with this.. and also the motor runs only on Low input not on high and even when enable pin is not High... pls check my diagram and make me where i made mistake...

**broken link removed**

150RPM 12V DC motors with Gearbox
6mm shaft diameter with internal hole
125gm weight
Same size motor available in various rpm
2kgcm torque
No-load current = 60 mA(Max), Load current = 300 mA(Max
 

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It's normal for a motor driver IC to get very hot. What you need to do is put a heat sink on it, which should stop it from getting overly hot. Alternatively, as very question suggested, you could try using an H-bridge IC with a higher power rating (which would run cooler). If you decide to change ICs, you could use the 754410; it is pin-compatible with the L293D but has a higher current rating.

-Nate
 
but the for the problem...??? without enable pin how it could run....??? and at low input it is running but not on high.... the truth table given in datasheet fails when i connect like this... i dont know where the problem comes....
 

i am having 16pin IC with 4 gnd... and what could be the reason for the problem... is the truthtable wrong or my connection wrong... i searched for many times... wheni give DC motor driver usign L293D all uses the same circuit diagram... but what should be the problem... IC is in good condition... because i am having two IC and tried with stepper motor it runs perfectly... that too stepper motor rated current is 600mA but the dc motor rated current is 300mA... pls help me correctly wher should be the problem...
 

what is the difference between the two circuits i did in the attached file... pls help... i think i am missing in giving logic to the driver IC
 

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Have you checked the Vih maximum volatage for these devices. For logic supplies more than 7V it specifies the logic input level should not exceed 7V. In your schematic it looks like you are feeding it 12V.

Brian.
 

no all are 5v only.... when i give supply to motor the problem occurs....
 

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I suspect your problem is that the enable and control inputs are floating when the switches are opened. Try connecting a pull-down resistor (10K?) between each input and ground. This will ensure the output stage is turned off when the input isn't driven.

Brian.
 
Yes i completely forgot about this resitor... it is must to show that low must be less than .8V and high should be atleast 2V... i missed that one... thanks for correcting... i didnt think on this point... and also pls tell me that i can use L293D for the motor i specified....?????
thnx a lot...


- - - Updated - - -

Yes i completely forgot about this resitor... it is must to show that low must be less than .8V and high should be atleast 2V... i missed that one... thanks for correcting... i didnt think on this point... and also pls tell me that i can use L293D for the motor i specified....?????
thnx a lot...

 

Hello!

you can use L298 instead of L293
Click to expand...

1. That's not the point. He's asking why the L293 gets so hot although it is used within its
characteristics, well below its maximum ratings.

2. If you advice for another chip, you should also tell why. I guess there are thousands
of other drivelers, and possibly dozens / hundreds within the voltage and current range he
wants. Why L298 rather than another one?

Dora.
 

This is the motor I use **broken link removed** and as per datasheet of L293D says it can be operated at 600mA but my motor is 300mA(MAX) as specified in the motor features... now i want is L293d can be used for driving this motor.... but it gets heated up very often... before that i used Bipolar Stepper motor of 24V and 600mA but it worked fine so that only i selected this.... but now it begins to problem... is the datas given me are wrong or it is on my side the mistake... if so what i should do... it is annoying me when i see the circuits for L293D Dc Motor Drive while it works for this much peoples.... pls check with attached..
 

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Connect your motor to 12 V 2 A power supply and also connect an ammeter in series with the motor and see what max current it draws. Then if your motors current rating is more then you can use a 4 amps TIP IC between L293D and motor. What is the extra voltages you are giving to the motor (+ and - pins across motor in Proteus) ?? The motor will be powered by L293D with 12 V. Connect the motor as shown in the image but you have to give 5V to Vss and 12V to Vs.
 

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Last edited:

I've just used a 754410 in a new design which is very similar to yours and it runs almost cold. There are a few points I would make that might help, I do not use ISIS so I can't simulate for you or even be sure the simulation would be accurate.

1. you show two 7805 5V regulators, both with 5V at their input pins. This will not work, they need around 3V more on their inputs than outputs to regulate properly. The one on the right should have a capacitor across it's input and ground pins and output and ground pins

2. By using two regulators, you run the risk of supplying the logic inputs before the supply on pin 16 is present. This can cause 'latch up' in the input stages and damage the IC.

3. Tie the unused inputs of the L293D to ground. if left floating there is a risk of it randomly switching or even oscillating which would increase the current it draws.

4. Make R1, R2 and R3 higher values, I would suggest 1K otherwise you waste current through them, particularly in R3.

5. Make sure you are using the "D" version of the L293 (L293D not L293). If you are using the non-D version you must add fast diodes between the motor outputs, ground and supply as detailed in the data sheet.

6. Ensure all the ground pins are connected. It is normal for these devices to run hot under continuous load so it's essential that you conduct the heat away through the pins as well as is possible. Sometimes, it's necessary to add an additional heat sink as well. Construction on prototyping boards is not advised.

7. Check the motor specification and make sure the 300mA max is the current under load and not the idling current. It's possible you are actually drawing considerably more than 300mA if the motor is driving something.

Brian.
 

1--- i properly used in real time hardware... i used 9V battery and in simulation i was urge to show by replication i was like that...
2--- for logic i must use 5V supply only... so in my setup i get from 12V regulator output that i use for the motor power...
3--- i am going to use four motors so there wont be unused inputs... for heating what can i do...???
4--- okay i changed to 1K
5--- I am using L293D NE Package...
6--- Ye i made that... there are totally four gnd points...
7--- Idle is 60mA and load is 300mA(max)...

i know about 754410 but after trying in stepper motor only i selected L293D.... i need to run 4 motors... I need where is the problem...



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I dont have 2A supply.. but i am having 12v 5Ah battery can i use that... what should i do if so i am using that battery i mentioned... thnx for Your concern... and what is meant by TIP IC...
 

5Ah battery means it can give 5 amperes continuously for one hour. Are you using 7805 to give 5V to MCU from your 12V battery? If yes, you can use battery like that. What is your 7805 regulator current rating? You say that you will drive 4 motors and each motor draws 300 mA max. If all the motors run at the same time then total current of the circuit will be 300 mA * 4 + current for MCU board which will be say around 1500 mA = 1.5A. Your motor driver should br run at 50% of it max ratings to avoid heating. L293D datasheet says that it can supply 600 mA per channel. So, you are using at 50% of max rating. Post your actual hardware circuit. Maybe your L293D is defective and so it is heating up. Try with another L293D.

TIP series are high power darlington transistors.
 

7805 regulator can supply upto 1A...
and i am going to use two 7805 for motor alone and another 7805 for microcontroller unit and other devices... and i should check ampere rating now...
if my amp rating are high and if i want to use L293D then what can i do with TIP...

 

You said that your motor is 12 V 300 mA then why do you want to use 7805 for motors? You do't need any regulator for motor. If yo want then you have to use 7812. If you want to use TIP transistor then I think TIP 50 or TIP 100 will do. https://www.futurlec.com/TransPowerTIP.shtml You have to connect two transistors for each motor. L293 is enough for you but if it is heating even after replacing the device then put a good heatsink and see. Try using ULN2803A between l293D and motor. It has 8 inputs and 8 outputs and each channel is 500 mA max.
 

No!

The 2803 can only sink current so it won't work in a H-Bridge configuration. It also has lower current capability than the L293. Although each output of the 2803 can sink 500mA, the total package can't handle 4 Amps!

My comment on using two 7805s for the logic supply was meant to warn of the danger of the one providing the control signals powering up before the one providing the VCC logic supply. Feeding both from the same 7805 prevents that happening.

Brian.
 

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