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Topic: Help for overheating L293D (STILL UNSOLVED) (Read 5497 times) previous topic - next topic

ozgur84

Mar 08, 2013, 05:38 pm Last Edit: Mar 09, 2013, 02:57 pm by ozgur84 Reason: 1
Hello,

I made a project yesterday. I control a stepper motor with L293D and arduino uno. I finished programming yesterday and posted under this topic.
http://arduino.cc/forum/index.php?topic=152747.new;topicseen#new

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 and adaptor, 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

robtillaart

do you have a link with tech info about this L293D ?
Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

Grumpy_Mike

It gets hot because it is passing too much current. So try and calculate how much current this is to see if the L239 is up to the job.
You could add a heatsink if it is. Otherwise get another driver that is up to the job. Or lower the voltage, only as a last resort add a resistor to each coil.

Erdin

The L293D is a older component. It has a 2 or 3V voltage drop. So is produces a lot of heat.
Newer motor drivers use mosfets, they have very little voltage drop.

The magic word is "piggyback".
The L293D allows to have more than one parallel. So you can solder 1 or 2 or 3 extra L293Ds on top of the first one.
Be sure to make good solder connections for all pins.

ozgur84


do you have a link with tech info about this L293D ?


here is the datasheet of L293D from texas instruments, I have the one from ST (second link)
http://docs-europe.electrocomponents.com/webdocs/0b76/0900766b80b7662c.pdf
http://docs-europe.electrocomponents.com/webdocs/0e77/0900766b80e779ea.pdf

ozgur84


It gets hot because it is passing too much current. So try and calculate how much current this is to see if the L239 is up to the job.
You could add a heatsink if it is. Otherwise get another driver that is up to the job. Or lower the voltage, only as a last resort add a resistor to each coil.


if I connect a 20ohm resistance to the motor supply pin of L293D for 12V supply voltage, should it work for lowering the current? I reckon, It should lower the current to 0.6amp ?? 

ozgur84

#6
Mar 08, 2013, 09:22 pm Last Edit: Mar 08, 2013, 09:27 pm by ozgur84 Reason: 1

The L293D is a older component. It has a 2 or 3V voltage drop. So is produces a lot of heat.
Newer motor drivers use mosfets, they have very little voltage drop.

The magic word is "piggyback".
The L293D allows to have more than one parallel. So you can solder 1 or 2 or 3 extra L293Ds on top of the first one.
Be sure to make good solder connections for all pins.


what are the alternatives as a new mosfet based component for L293D? L298? I first bought L293D and that's why I wanted to build my project with it.
piggyback is a cool name and nice idea though :)

I have two ideas which I want to ask you too

1. if I connect a 20ohm resistor to the motor supply pin of L293D for 12V supply voltage, would it work for lowering the current? I reckon, It should lower the current to 0.6amp ??

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 signals to the gate of TIP 3055s. so, all the current will flow over the MOSFETs ??

jtw11

Take a look at the range of automotive h-bridges from ST.... Pololu sell premade boards if you don't wish to do your own http://www.pololu.com/catalog/product/708

As far as I'm aware, they have the lowest total on resistance of any integrated h-bridge solution currently available, orders of magnitude less than what you're using now!

ozgur84


Take a look at the range of automotive h-bridges from ST.... Pololu sell premade boards if you don't wish to do your own http://www.pololu.com/catalog/product/708

As far as I'm aware, they have the lowest total on resistance of any integrated h-bridge solution currently available, orders of magnitude less than what you're using now!


Thanks, but I want to do this as my own project :)

jtw11

Quote
Thanks, but I want to do this as my own project


I was referring more to the IC itself - I'm using the VNH2SP30 as my h-bridge IC in a design I'm working on as one chip amongst ~40 ICs...

Grumpy_Mike

Quote
if I connect a 20ohm resistance to the motor supply pin of L293D for 12V supply voltage, should it work for lowering the current? I reckon, It should lower the current to 0.6amp ?? 

Just about the worst thing you can do. If you must use resistors have one in each coil. It will lower the current to much less, what is the resistance of your coils?

ozgur84


Quote
if I connect a 20ohm resistance to the motor supply pin of L293D for 12V supply voltage, should it work for lowering the current? I reckon, It should lower the current to 0.6amp ?? 

Just about the worst thing you can do. If you must use resistors have one in each coil. It will lower the current to much less, what is the resistance of your coils?


the coil resistance for each coil is 5ohms.

could you also comment to my second idea at reply# 6 above? is there a chance that it works?


ozgur84

#12
Mar 09, 2013, 03:21 pm Last Edit: Mar 09, 2013, 03:28 pm by ozgur84 Reason: 1
Update: I learned that the TIP3055 is a power transistor so the new idea is using n-chanel mosfet like IRFZ44N. But my question is still valid :)

Grumpy_Mike

Quote
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 signals to the gate of TIP 3055s. so, all the current will flow over the MOSFETs ??

No that won't work. You need a H-bridge circuit for a bipolar motor and you won't get one like that.

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