Switching of a running ULN2003 Stepper Motor Driver IC

Thread Starter

Doceave

Joined Nov 16, 2019
26
I have an ATTiny24 IC cycling its output pins in order to drive a number of stepper motors at a specific speed. A single ATTiny24 drives drives 6 ULN2003's which in turn drive a 28BYJ stepper motor each. The ATTiny's only job is cycling its outputs to drive the ULN2003's.

Another programmable IC, and ESP32, needs the ability to turn each of these of the stepper motors on/off.

This image describes the ATTiny24--UNL2003--Stepper combination:
1573901329703.png
I request advice regarding how the ESP32, using one GPIO pin could turn one stepper motor on/off without interrupting the ATTiny24 or other motors.

Everything runs from the same 5V source.

A simple schematic would be greatly appreciated.
 

Thread Starter

Doceave

Joined Nov 16, 2019
26
Ideally I would like to make use of N-channel MOSFET's or NPN transistors to do the job. Just not sure where in the above circuit to begin doing the switching...
 

Thread Starter

Doceave

Joined Nov 16, 2019
26
I don't understand what you are asking for.

Just set all the IO lines to 0 and the motor is off.
The IO lines cannot be switched off for just one motor. There are many such ULN2003s running off the IO lines. I need to switch off just the motors individually
 

Thread Starter

Doceave

Joined Nov 16, 2019
26
You could use a P-channel MOSFET or a PNP transistor to switch off the +5V supply to the motor under control of the ESP32.
Thanks AlbertHall --- would you kindly help me with a schematic of a PNP transistor switching the 5v supply? I have some BC539's lying around.

The motor should draw no more than 100mA.
 

AlbertHall

Joined Jun 4, 2014
8,543
It would look like this:
My apologies---- BC559 (a general purpose PNP transistor)
The BC559 maximum rated current is 100mA so you would be pushing your luck using this for a 100mA motor. The 2N2907A (600mA) would be better. The circuit would look like this:
1573908789070.png
 

Thread Starter

Doceave

Joined Nov 16, 2019
26
This is precisely what I was hoping for! Thanks so so much!

Would you show me also perhaps how this could be achieved with a NPN-PNP arrangement where the motor is powered from a 12v source? (I tried this and couldn't get it working)

It would look like this:

The BC559 maximum rated current is 100mA so you would be pushing your luck using this for a 100mA motor. The 2N2907A (600mA) would be better. The circuit would look like this:
View attachment 191581
 

BobaMosfet

Joined Jul 1, 2009
839
I have an ATTiny24 IC cycling its output pins in order to drive a number of stepper motors at a specific speed. A single ATTiny24 drives drives 6 ULN2003's which in turn drive a 28BYJ stepper motor each. The ATTiny's only job is cycling its outputs to drive the ULN2003's.

Another programmable IC, and ESP32, needs the ability to turn each of these of the stepper motors on/off.

This image describes the ATTiny24--UNL2003--Stepper combination:
View attachment 191568
I request advice regarding how the ESP32, using one GPIO pin could turn one stepper motor on/off without interrupting the ATTiny24 or other motors.

Everything runs from the same 5V source.

A simple schematic would be greatly appreciated.
The ULN2003A is a transistor array, open collector. A positive input results in the output being grounded. So if you want to turn a motor off, simply put a high voltage signal on all 4 inputs and disconnect your RED common power.


1573910371699.png
 

AlbertHall

Joined Jun 4, 2014
8,543
Actually you don't the NPN transistor. You can use one of unused sections of the ULN2083A providing you aren't driving another motor with it.
1573914732577.png
 

AlbertHall

Joined Jun 4, 2014
8,543
You missed the Rbe for Q1 when the ESP32 is Low.
It is being driven low by the micro so I don't think a base emitter resistor will make any difference.
[EDIT] sorry thinking about the wrong transistor But I don't think some itsby bitsy leakage will affect the stepper motor.
 

ScottWang

Joined Aug 23, 2012
6,834
It is being driven low by the micro so I don't think a base emitter resistor will make any difference.
[EDIT] sorry thinking about the wrong transistor But I don't think some itsby bitsy leakage will affect the stepper motor.
The circuit in #12 also had the same problem, I just mentioned that don't let a base at a floating status.
 
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