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Topic: Question: Is it possible to connect 2 L239D in series? (Read 2609 times) previous topic - next topic

ben10

I just read this from adafruit about their motor shield

"Need more power? Buy another set of L293D drivers and solder them right on top of the ones on the
board (piggyback). Voila, double the current capability!"


BrIDo

This wouldn't be series, it would be parallel.

In theory, it would allow your motor to draw double the current, as is the nature of circuits in parallel.

Not sure how it would work in practice though.

If you haven't bought anything yet, there are motor drivers available that can handle a higher current draw in one unit...

RuggedCircuits

Even worse, if you need "more power" then you are probably getting the L293 pretty hot. Putting another one right on top of it is not going to help it stay cool!

I agree, it's better to look at higher power motor drivers than to "stack chips".

--
The Gadget Shield: accelerometer, RGB LED, IR transmit/receive, speaker, microphone, light sensor, potentiometer, pushbuttons

Grumpy_Mike

The problem is that the L293 is made from transistors not FETs and therefore they don't share nicely. Sounds like a marketing ploy with little technical knowledge.

borref


The problem is that the L293 is made from transistors not FETs and therefore they don't share nicely.

The H-bridges are in effect individually controlled switch mode current regulators so load sharing may be ok, but piggy-backing is no solution especially when it comes to heat.

ben10 - you mentioned in another thread that you have a bipolar stepper that needs 1.2A per coil and even with two L293D's there is no way they will sustain this load. I would look for a new controller (or perhaps it is your stepper that should be replaced).

Grumpy_Mike

Quote
The H-bridges are in effect individually controlled switch mode current regulators

No they are not.
Read the data sheet, there is no switching or current control going on in an L293. The output is simply transistors and there is no current sensing input.

If the poster actually means an L239 then these are quad differential comparators and not motor drivers at all.

ben10

Yup it's parallel my bad. Just curious though it could be possible since some are diving into this solution I wonder how did they manage the heating issue specially by piggy backing them. Also it's not mentioned anywhere from the datasheet that this can be done so my guess that this is not advisable, possible but risk is high.

@BenF yeah I will go for 7297 + 7298 since I still need to drive these fat motors, it's a pricey route but it's a sure thing.

RuggedCircuits

I think you mean L297+L298 :)

Our Rugged Motor Driver will handle 1.2A per coil (while an L298 probably will not depending on how it's heatsinked).

--
The Arduino Drum Machine: MIDI development system with 14-track MIDI drum machine sequencer / groove-box software



borref


Quote
The output is simply transistors and there is no current sensing input.

You're right. I thought I knew this datasheet by heart (the L298 has sense/enable terminals), but obviously not. In that case load sharing is not trivial.

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