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5 hours ago, Warwick said:

Hello, I am new to  the use of Arduino's and having quite a bit of a headache.  I want to simply control my 00 gauge turntable.  I bought a Nema 17 stepper motor and a Dual H Bridge L298N Stepper Motor Driver Controller.

I used a sketch for a small stepper motor with shield (28BYJ-48 Stepper Motor)  A sketch  worked with this stepper motor but not with the Nena 17.  I have used the example sketch in the IDE sketches but the stepper gets very hot when stopped.

I only want to make the turntable go clockwise and anticlockwise and stop at my track on a turntable.  I haven't found a simple sketch to do this, later I would like to programme stopping points

Can anyone help, I am useless at sketch writing and learning is not coming easily to me.

Have a look at this topic.

It's been done to death.

There's several options from several contributors to the thread.

My latest incarnation uses a Arduino Nano and A4988 driver.

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6 hours ago, Robin2 said:

An L298N is a very poor choice for a stepper motor driver. You should get a specialised stepper motor driver such as a Pololu DRV8825. A specialised driver has the ability to limit the current to protect the motor
 

Not strickly true as L298 is sold as a stepper motor controller and does have the ability to limit the current.

It is intended to be used with a L297 (or similar) which offers full control of the signals:

aKyKm.jpg

 

 

The two sense inputs are used to control the current in the motor coils

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17 hours ago, melmerby said:

Not strickly true as L298 is sold as a stepper motor controller and does have the ability to limit the current.

 

Alas, the marketing guys got their hands on the typewriter :)

 

...R

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  • 2 weeks later...

The L298 is a very dated product . It does not have any instrinic current control . It has over temp protection but only on a short term basis , it provides a sense current oupu5 , but that in itself isn’t current control 

 

there are far better driver chips these days 

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23 hours ago, Junctionmad said:

The L298 is a very dated product . It does not have any instrinic current control . It has over temp protection but only on a short term basis , it provides a sense current oupu5 , but that in itself isn’t current control 

 

there are far better driver chips these days 

For us un-initiated name one or two.  Thks

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As I understand it the Pololu DRV8825. is specifically for a stepper motor.  The L298 on the other hand will drive a servo or, my special interest, a small DC motor.  So is their a better unit than the dated L298?

Thanks

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The L298 is indeeded somewhat dated but IMHO should not be just dismissed offhand.

 

It is the stepper motor driver used in the official (and many unofficial) Arduino stepper motor shields. I have a Velleman one and it works just fine.

 

It is intended however to be used with a driver IC (normally L297 etc.) which controls many aspects of how it drives the coils of the motor including full drive current control.

If used on it's own it is very basic and lacks much of that control more modern all-in devices can give.

 

EDIT

IMHO Starting from new I would buy a more up to date controller chip.

Edited by melmerby
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12 hours ago, Theakerr said:

As I understand it the Pololu DRV8825. is specifically for a stepper motor.  The L298 on the other hand will drive a servo or, my special interest, a small DC motor.  So is their a better unit than the dated L298?

Thanks

The Pololu website has a wide range of DC motor drivers as well as stepper drivers. Equivalent products are also available elsewhere.

 

...R

Edited by Robin2
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On 19/08/2020 at 20:09, Theakerr said:

As I understand it the Pololu DRV8825. is specifically for a stepper motor.  The L298 on the other hand will drive a servo or, my special interest, a small DC motor.  So is their a better unit than the dated L298?

Thanks

What do you mean by “ servo “ , 

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J, should have said RC Servo motor as Simond explained.  The only benifit i can see to using a L298 to drive a servo is you can do other things at the same time and whilst i am not sure I think it would be difficult to drive two servo motors doing different things at the same time.  Back to my challenge, I did do some looking on both the Pololu and HobbyTronics pages and if I am reading the data correctly none will do what I want.  Specifically I want to bring a small DC motor to a programmed gentle stop and a programmed gentle start.  All the units there appear to cut off at about 4 volts, so they will go from 4 to 0 directly.

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13 hours ago, Theakerr said:

 and whilst i am not sure I think it would be difficult to drive two servo motors doing different things at the same time. 

An Arduino Uno can control up to 12 servos at the same time and a Mega can control even more without needing any shield or motor driver.

 

...R

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43 minutes ago, Robin2 said:

An Arduino Uno can control up to 12 servos at the same time and a Mega can control even more without needing any shield or motor driver.

 

...R

Providing the servo power is provided seperately and not from the Arduino itself.

 

 

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14 hours ago, Theakerr said:

J, should have said RC Servo motor as Simond explained.  The only benifit i can see to using a L298 to drive a servo is you can do other things at the same time and whilst i am not sure I think it would be difficult to drive two servo motors doing different things at the same time.  Back to my challenge, I did do some looking on both the Pololu and HobbyTronics pages and if I am reading the data correctly none will do what I want.  Specifically I want to bring a small DC motor to a programmed gentle stop and a programmed gentle start.  All the units there appear to cut off at about 4 volts, so they will go from 4 to 0 directly.

You need 3 connections to a servo; Power, Ground and Signal. The signal determines the position.

A L298 is not really any good for servos but will drive 2 ordinary dc motors.

 

But If you use a Mosfet to drive a motor it can be controlled from an Arduino with a PWM signal

Edited by melmerby
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3 hours ago, Donw said:

If you want a bit more power there is the option of the IBT-2

 

Don

How much more power do you want?:jester:

Handy module though.

 

£9.26 & free postage on AliExpress

https://www.aliexpress.com/item/1900887029.html?algo_pvid=ccd09e71-e5c2-4ecd-8bb2-a265759ee25d&algo_expid=ccd09e71-e5c2-4ecd-8bb2-a265759ee25d-7&btsid=0b0a119a15981259209671537eb5c8&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_

 

Edited by melmerby
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10 hours ago, Donw said:

well it quotes 43A I think . Probably needs a water cooled heatsink :jester:

Certainly could handle 5A or so which is more thn the drivers quoted.

 

Don

If its power Mosfet output transistors it probably doesn't need excessive heatsinking.

Power is only dissipated if there's current flowing through a resistance and power Mosfets have very low ON resistance (possibly 0.01 ohm), control would be PWM so the Mosfet would be either on or off

Even the full 43A (at 100% drive) through 0.01ohm would only dissipate 18.5W (43*43*0.01)

With 5A only 0.25W.

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I have played around using a L298 and the output was of course a PWM signal.  The problem is that at low RPM as in a small DC brushed or can loco motor coming to a stop, i.e going through the 4V to 0V range or any loco that require less than 4V and starting from a stop (if it will start) the motor literally screams and will if not careful (according to what I have read) can burn a motor out.   I have read that changing the PWM frequency can potentially eliminate this problem and I understand that later Arduino have the ability to change the PWM frequecy.  However, I have not found a sketch that does this and i don't have the skill to develop my own.  Background to all this is that I wanted a station stop module but could not find one that met all my criterea of which the biggest was I did not want to make any track cuts.  As a result I have built a station stop module that uses a servo motor directly connected , as in mechanically, to a controller.  It works pretty well but I cannot help but feel there is a better way.

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