Help for overheating L293D

[ozgur84]

Hello,

I made a project yesterday. I control a stepper motor with L293D and arduino uno.

Basicaly, I connect the 4 digital pins of arduino to the input pins of L293D (6 pins with two enable pins), I supply the circuit with 5V of arduino both for logic supply and motor supply and I ground back to the arduino. It works great.

However, my problem is when I want to supply the motor with an 12V source externally with a power supply (max 1.2amp). L293D heats itself like crazy (luckily it has a in-built thermal shutdown). I should also say that I use a common ground connection for both arduino and adaptor.

Does anyone have an idea about what the problem could be? should I also add a resisstor to the motor supply input for limiting the current?

Regards

 

[crutschow]

That device will get very hot without a heatsink. Heatsink mounting is shown on pages 10 and 11 of the data sheet.

Also the continuous output current rating is 1A for the device so you should keep it below that. Even then each output that is on will cause a dissipation of over 2.6W in the chip.

You might want to consider a driver that uses MOSFETs to lower the dissipation.

 

[ozgur84]

That device will get very hot without a heatsink. Heatsink mounting is shown on pages 10 and 11 of the data sheet.

Also the continuous output current rating is 1A for the device so you should keep it below that. Even then each output that is on will cause a dissipation of over 2.6W in the chip.

You might want to consider a driver that uses MOSFETs to lower the dissipation.

Hello and thanks for the reply. I checked the datasheet and I will consider the heatsink idea. But I still have two questions

1. how can I lower the current? if I connect a 20ohm resistor to the motor supply of the L293 for 12V supply voltage, would it work? It should lower the current to 0.6amp, right?

2. I have 4 TIP 3055 at home, can I connect them to each output of L293D and supply the 12V over them? So that I can only use the same 5V of logic supply for the motor supply input of L293D and it will only send the output signal to the gate of TIP 3055s. so, all the current will flow over the MOSFETs ??

 

[unclejed613]

you should also include snubber diodes, as inductive kickback at the very least will cause the chip to heat up, at the worst damage the output devices in the chip.

 

[ozgur84]

you should also include snubber diodes, as inductive kickback at the very least will cause the chip to heat up, at the worst damage the output devices in the chip.

I added the dioeds before like the project below. even though, L293D heated itself. Now I do not use them because it makes the breadbord connections quite complicated...

 

[alec_t]

Now I do not use them because it makes the breadbord connections quite complicated...

Better a complex breadboard layout than fried components

 

[ozgur84]

Better a complex breadboard layout than fried components

I have just completed a pcb which contains the diods and connection ports there is a short circuit an a forgotten connection on pcb, I will correct them tomorrow and I will try the circuit. And hopefully I will have more space on the breadbord

do you have any ideas about my quiestions at post#3 ? it would be a great help

 

[ozgur84]

This post is stil unsolved guys! come on and tell your ideas about the mosfets please

 

[audioguru]

A 20 ohm resistor will limit the current into a DEAD SHORT to 0.6A from the 12V supply.
Your motor is not a dead short so the current with a series 20 ohm resistor will be less than 0.6A.
We do not know how much current the motor uses so guessing about a resistor is useless.

A TIP3055 is a power transistor, not a Mosfet. It needs a base current much higher than your arduino can supply.
If you use "logic-level" Mosfets then they turn on so well when driven by the arduino that they do not get warm.

EDIT: Your title and text talk about a weak little L293 but your schematic shows a powerful L298 that can be bolted to a heatsink.
Which do you have??

 

[ozgur84]

This is the motor
https://www.electro-tech-online.com/custompdfs/2013/03/motor_m42sp_6nk_e.pdf

And the datasheet says max peek current/phase is 400mA. does it means 1.2Amps in total?

A TIP3055 is a power transistor, not a Mosfet. It needs a base current much higher than your arduino can supply.
If you use "logic-level" Mosfets then they turn on so well when driven by the arduino that they do not get warm.

Could you give some examples for a logic level mosfet for this purpose?
how does this look like for example?
https://www.sparkfun.com/products/10213

EDIT: Your title and text talk about a weak little L293 but your schematic shows a powerful L298 that can be bolted to a heatsink.
Which do you have??

I have the L293D

 

[alec_t]

The FETs in that Sparkfun link look fine for your project.

 

[audioguru]

The Sparkfun Mosfets are only N-channel. You also need P-channel to get the forward and reverse running.

The L293 is not designed to use a heatsink.

Your motor's datasheet does not make sense.
It shows a 12V and a 24V supply but the maximum current is the same at 400mA.
400mA in the 5 ohm winding is a driving voltage of only 2V, not 12V and not 24V.

The datasheet for the L293D says to use high-speed diodes but you used extremely slow rectifiers.

 

[ozgur84]

The Sparkfun Mosfets are only N-channel. You also need P-channel to get the forward and reverse running.

The L293 is not designed to use a heatsink.

I have seen something like this when I search for piggyback. I cannot help laughing to its name but there is a heatsink application even though it does not have a metal heatsink mount. don't you think that it might help?

https://www.acroname.com/robotics/info/ideas/stacking/stacking.html

Your motor's datasheet does not make sense.
It shows a 12V and a 24V supply but the maximum current is the same at 400mA.
400mA in the 5 ohm winding is a driving voltage of only 2V, not 12V and not 24V.

this must be a shame for a company like mitsumi

The datasheet for the L293D says to use high-speed diodes but you used extremely slow rectifiers.

do you mean the mosfet examples? what would you offer to use as a fast rectifier?

 

[audioguru]

I think the L293D is cooled through its 4 ground pins so piggybacking and adding the Mickey-Mouse metal heatsink will not work.
Use an L298 that can be bolted to a real heatsink.

A 1N5817 is an extremely fast 1A/20V Schottky diode.

 

[ozgur84]

I think the L293D is cooled through its 4 ground pins so piggybacking and adding the Mickey-Mouse metal heatsink will not work.
Use an L298 that can be bolted to a real heatsink.

Micky mause heat sink... hahahahahhah that was a good one. It seems that I will eventualy switch back to a L298 as you said...My little poor L293D should wait for another project. Because the project is on a breadboard, it has not have somewhere to dissipate the heat. I am not sure whether a copper plate through the ground pins will also works when I build the pcb...

A 1N5817 is an extremely fast 1A/20V Schottky diode.

Thanks for the advice. I will also buy them and keep them in stock.