Hello,
I bought two Stepper Motor HAT for Raspberry Pi Bonnet. I am stacking those to control 3 stepper motors, each rated for 12v/1.5A and the phase resistance is around 25 ohm. And I am powering the HATs with one adapter which supplies 12v-1.5A current.
All the motors are connected to belt and pullies to move minimal loads. I was able to rotate all three motors with the adafruit library in Raspberry Pi.
But I am facing problems while-
1. I am trying to rotate a single motor for a longer period like a full 360 degree, it is stopping intermittently-like the power is dropping sometime.
2. When I connected all three motors at the same time, and tried to rotate one by one, the drivers were cut-off from the adapter power completely in the middle of rotation.
Could you please help on the issues?
Power Interruption in the middle of stepper rotation
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- zaidur
- Posts: 3
- Joined: Mon Nov 22, 2021 1:50 pm
- adafruit_support_bill
- Posts: 88145
- Joined: Sat Feb 07, 2009 10:11 am
Re: Power Interruption in the middle of stepper rotation
You probably need a higher capacity power supply.
Stepper motors are not at all like DC motors. When using a simple driver such as the HAT, the motor will draw maximum current when not moving (holding current) and decreasing current as the step rate increases.
12v into 25 ohms works out to 0.48A per phase. Since there are two phases active most of the time, that will be 0.96A per motor when stopped.
Multiple motors would definitely overload your power supply. It is no surprise that they lost power.
When running a single motor, there are a few possible reasons for intermittent stepping behavior:
1) a bad connection or marginal solder joint somewhere
2) a faulty power supply
3) Your Pi is busy with other things. Since the Linux is a multitasking operating system, your program will be sharing the CPU with other tasks. If it doesn't get a slice of the processor time at the exact time it needs to take a step, there can be some visible hesitation in the stepping.
Stepper motors are not at all like DC motors. When using a simple driver such as the HAT, the motor will draw maximum current when not moving (holding current) and decreasing current as the step rate increases.
12v into 25 ohms works out to 0.48A per phase. Since there are two phases active most of the time, that will be 0.96A per motor when stopped.
Multiple motors would definitely overload your power supply. It is no surprise that they lost power.
When running a single motor, there are a few possible reasons for intermittent stepping behavior:
1) a bad connection or marginal solder joint somewhere
2) a faulty power supply
3) Your Pi is busy with other things. Since the Linux is a multitasking operating system, your program will be sharing the CPU with other tasks. If it doesn't get a slice of the processor time at the exact time it needs to take a step, there can be some visible hesitation in the stepping.
- zaidur
- Posts: 3
- Joined: Mon Nov 22, 2021 1:50 pm
Re: Power Interruption in the middle of stepper rotation
Hi, thanks for the reply.
I am not totally sure what did you mean by "High Capacity" power supply. Does this mean more Ampere or Voltage? And what is your suggestion on power supply rating based on the resistance and voltage of motors given?
I am not totally sure what did you mean by "High Capacity" power supply. Does this mean more Ampere or Voltage? And what is your suggestion on power supply rating based on the resistance and voltage of motors given?
- adafruit_support_bill
- Posts: 88145
- Joined: Sat Feb 07, 2009 10:11 am
Re: Power Interruption in the middle of stepper rotation
Current is measured in Amps and you need more amps to run more of those motors.
As calculated above, you will need at least 0.96A per motor at 12V. So to run 3 of those motors at 12V, you should look for a power supply capable of delivering 3A or more.
https://www.adafruit.com/product/352
As calculated above, you will need at least 0.96A per motor at 12V. So to run 3 of those motors at 12V, you should look for a power supply capable of delivering 3A or more.
https://www.adafruit.com/product/352
- zaidur
- Posts: 3
- Joined: Mon Nov 22, 2021 1:50 pm
Re: Power Interruption in the middle of stepper rotation
Thanks. I will try with something more than 3 amps.
Please be positive and constructive with your questions and comments.