liamando
Posts: 1
Joined: Tue Jul 31, 2018 10:04 am

Questions considering l239D IC

Tue Jul 31, 2018 10:27 am

Hi,
Background:

I am designing a brush mechanism. It requires two step motors to operate in sequence with each other. They are both connected to belt driven linear actuator, link (http://ooznest.co.uk/3D-Printer-CNC-Kit ... tuator-Kit) this is the x-axis.
The stepper motor used is the NEMA17 2.00A.

And this the y-axis, link (http://ooznest.co.uk/3D-Printer-CNC-Kit ... tuator-Kit). The motor used is the NEMA17 1.40A.

The brush goes along the axis stops, the y-axis raises it, the brush returns to the start of the x-axis then the y-axis lowers it again. To provide mono directional brushing.

I am running both motors using l293D IC chips wired like this link, (https://learn.adafruit.com/adafruits-ra ... s/overview). Each motor has its own l293D chip.

There is an external power supply unit attached, link (http://ooznest.co.uk/3D-Printer-Electro ... wer-Supply)

Issue:

The motors are struggling a bit. The x-axis motor is going a bit slower than I would like, decreasing step size causes belt slippage and vibration.

The y-axis motor is incapable of raising the gantry plate vertically, can do downwards direction. Can travel both directions when held horizontal, so suggests lack of pulling power.

Possible Solution?:
Is it that the l293D chips cant operate such high amp motors?

Thanks for any and all advice.
I also used the code on this site, modified to give both motors unique variables, link (https://learn.adafruit.com/adafruits-ra ... s/overview)

Photos:
https://www.flickr.com/photos/134499184 ... 7572162741

Sorry new to asking for help so don't know what photos to take

Thanks

pcmanbob
Posts: 6671
Joined: Fri May 31, 2013 9:28 pm
Location: Mansfield UK

Re: Questions considering l239D IC

Tue Jul 31, 2018 8:12 pm

Hi.

I presume that the 2.00A and 1.40A are the current rating for the motors you are using.

The L293D has a current output of 0.6A and a peak current of 1.2A per channel, so I would say the L293D is some what under rated for driving your motors.
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OutoftheBOTS
Posts: 711
Joined: Tue Aug 01, 2017 10:06 am

Re: Questions considering l239D IC

Tue Jul 31, 2018 10:15 pm

To drive a stepper motor it is easier to use a driver that is designed for stepper motors so that you don't have to create the stepping pattern but rather operate a direction pin and a step pin, these drivers also quite often have micro stepping to get smoother operation and also these drivers are usually a chopper driver to give better torque. The most common used little stepper driver is the DRV8825 used by most 3Dprinters ans small CNC machines it can drive up to 2amp at 24v.

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