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Topic: Can L293D really be put in parallel? (Read 6470 times) previous topic - next topic

electricviolin

Jul 28, 2015, 03:46 pm Last Edit: Jul 28, 2015, 03:46 pm by electricviolin
I know people "piggyback" the two ICs, but that didn't work for me (well, I just wired them in parallel on a breadboard). Both chips got warm, but one got significantly hotter than the other. After some research, I found this post, which led me to this datasheet, which said this:

Quote
PARALLELING OUTPUTS
Higher output currents can be obtained by paralleling
the outputs of both bridges. For example, the
outputs of an L298N can be connected in parallel to
make a single 3.5 A bridge. To ensure that the current
is fairly divided between the bridges they must
be connected as shown in figure 2. In other words,
channel one should be paralleled with channel four
and channel two paralleled with channel three.
Apart from this rule the connection is very straightforward
- the inputs, enables, outputs and emitters
are simply connected together.
The outputs of an L293 or L293E can also be paralleled
- in this case too channel 1 must be paralleled
with channel 4 and channel 2 with channel 3.
But if two bridges are needed this is not a good idea
because an L298N may be used. However, if only
Figure 2 : For higher currents outputs can be paralleled.
Take care to parallel channel 1
with channel 4 and channel 2 with channel
3.
This says I have to flip around some of the connections, but it also doesn't mention the l293D, only the l293. Would I use this method for the l293D as well (I am not sure if the extra diode does anything to affect this).
"To invent, you need a good imagination and a pile of junk" -Thomas Edison

raschemmel

If you look at page 2 of the datasheet you will see that normally a dual motor setup  for bidirectional robot motors would be done like this

(illustration to the right of the title "TRUTH TABLE")

The quote you cited is saying that instead of inputs 1 & 7 for motor 1 which is connected to output pins 3 & 6, (with the second motor inputs 15 & 10 for motor 2 on output pins
14 & 11), they are saying that all 4 of the L293  drivers should be configured as a single motor /dual driver setup using input pin 1 jumpered to input pin 15, and input pin 7 jumpered to input pin 10, and the single motor connected across output pins 3-14 jumpered together and 6-11 jumpered together .

Inputs
1,15 (jumpered)
7,10 (jumpered

outputs
3,14 (jumpered)
6,11 (jumpered)

Why ?
I have no idea, but that's what they are saying.
One chip should be used for one motor with twice the current.
If a second motor is needed a  second chip is required, configured the same way.

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electricviolin

I am only using one motor, but it is a stepper motor, so would it follow the same principle? (I don't fully understand if that is possible)
"To invent, you need a good imagination and a pile of junk" -Thomas Edison

MAS3

You are getting confused because you found something similar, but not equal to what your were looking for.
What you have found, is suggested to use when you are using a single bidirectional motor.
They are suggesting that setup, so the heat generated, will be more spread across the chip, and can be better dissipated.
Otherwise the heat would be concentrated to a single side of the chip.
But this isn't at all what you're looking for.
You need to know the the 4 center pins aren't just there to offer some connection point for GND level.
They also are there (and at that location) to help heat be dissipated.
You absolutely need to facilitate that, and it looks like that's what you forgot and why the units got (too) hot.

You can stack multiple 293's to each other and connect each pin.
But be sure the center pins 4, 5, 13 and 12 are well connected to a larger copper surface.
Or even connect some kind of heat sink to each of these 8 pins (or whatever number of chips you use times 4).
Have a look at "blink without delay".
Did you connect the grounds ?
Je kunt hier ook in het Nederlands terecht: http://arduino.cc/forum/index.php/board,77.0.html

electricviolin

So trying to do this in a breadboard is not possible? I don't mind soldering them together, but I am assuming I would need thermal paste etc. to keep their temp the same so the transistors inside all work the same amount.
"To invent, you need a good imagination and a pile of junk" -Thomas Edison

MAS3

A breadboard is a bad idea if you need heat dissipation in this way.
Using thermal grease sounds like a good idea, and it won't harm if it doesn't actually help.
Try to create a nice large copper surface to be connected to the GND pins.
Have a look at "blink without delay".
Did you connect the grounds ?
Je kunt hier ook in het Nederlands terecht: http://arduino.cc/forum/index.php/board,77.0.html

jremington

Why not just buy a modern stepper motor driver and save yourself the trouble?

raschemmel

#7
Jul 28, 2015, 06:13 pm Last Edit: Jul 28, 2015, 06:14 pm by raschemmel
Quote
I am only using one motor, but it is a stepper motor, so would it follow the same principle? (I don't fully understand if that is possible)
Well, if you look at the schematic of a stepper motor how many windings do you see ?
Maybe the fact that you only have one motor shaft has got you confused. Two windings
is the same as two motors for all practical purposes when discussing the topic of your original post (paralleling L293s).

Quote
So trying to do this in a breadboard is not possible?  
Yes, it is possible, but as I said before, you need two chips, not one, and each needs to be wired as I said (one chip per winding).

If you pay attention to what MAS3 said about the heat dissipation and heat-sinking the GND pins in the center of the chip, MAYBE you can think of a way to do that if you stacked them but your original post suggests that combining sections 1 & 4, 2 & 3, is a better idea than stacking them. The difference is that you can no longer drive two motors from the same chip. You must dedicate one chip to each motor. You should still try to find a way to provide some heatsinking but it should still work on a breadboard without melting it if your motor doesn't draw too much current.

Using an L298 is a smarter way to go because those modules come heatsinked.
Be aware there are 15 different flavors of L298 modules. Look at the photos VERY CAREFULLY and see if you can figure out the difference.
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

electricviolin

So, let me just check if I got this right:

I can treat the stepper as 2 different motors, and use 1 chip per "motor" (so essentially two chips for one stepper). I would wire it by connecting pins 1-4 and 2-3 to allow the chip to spread heat along the whole chip rather than one side of it.

Is this correct?
"To invent, you need a good imagination and a pile of junk" -Thomas Edison

MAS3

It is one motor, but likely two coils.
If so, then yes.
Have a look at "blink without delay".
Did you connect the grounds ?
Je kunt hier ook in het Nederlands terecht: http://arduino.cc/forum/index.php/board,77.0.html

DrAzzy

#10
Jul 28, 2015, 07:16 pm Last Edit: Jul 28, 2015, 07:17 pm by DrAzzy
I would wire it by connecting pins 1-4 and 2-3
Not pins 1 and 4 - you're paralleling channel 1 and channel 4, so you're connecting input 1 and input 4, output 1 and output 4 (not physical pins 1 and 4). Likewise with 2 and 3. You also tie the enable pins together.
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electricviolin

Right, okay I see. I am assuming it is two coils, but I will have to check to make sure. If it is 4 wires, it has to be 2 coils, right? 2 coils (2 wires each). Is this for certain or should I check this somehow?
"To invent, you need a good imagination and a pile of junk" -Thomas Edison

raschemmel

#12
Jul 28, 2015, 07:36 pm Last Edit: Jul 28, 2015, 07:44 pm by raschemmel
Like I said, reread my post. All the wiring details are there. You need to pay closer attention to what you're reading and stop "skimming".
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

electricviolin

You said in a previous post that pins 1 and 15 had to be connected, but I believe it should be pins 2 and 15
"To invent, you need a good imagination and a pile of junk" -Thomas Edison

raschemmel

Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

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