I recently created a circuit where a 7.4v servo is activated when a motion senor is triggered. I have attached my schematic. As the servo is 7.4v I am using a DC-DC power convertor feeding 12v 2a in and drawing 7.4v for the servo.
To power the Arduino I cut the cable from the 12v power supply and wired it into the convertor and then with the remaining cut wire, with the barrel, I plugged it into the Arduino.
I’m now looking to add a stepper motor to the project, so when the motion senor is triggered, it activates the servo and a stepper motor.
Is it sensible to use another 12v 2a power supply to directly supply the stepper motor shield rather than using the existing power supply?
I have read that the motor shield can get hot. Would it be a good idea to put a heat sink onto it?
As I’m still a beginner, is there anything else I should be considering when building this circuit?
I know the stepper motor shield sits on top of the Arduino board. From research the shield uses pins 2 through 9 on the arduino. Which means that the pins 10, 11, 12 and 13 are free. I will need to change the pin my servo is currently using to one of the free pins.
As your motor is only drawing 0.33 amps I don't think you will need a heat sink. But be sure to adjust the current limits on the stepper driver to match your motor.
My guess is that your existing 12v power supply will be adequate. However if you want the stepper motors to work at high speeds a higher voltage power supply would be better and that shield seems to have a max of 12v. A Pololu A4988 stepper driver can work with up to 30v IIRC.
The stepper motor I linked to runs at 12v and the motor shield takes a maximum of 12v, should I be supplying more voltage to the shield than what a motor requires? So, always running a shield with a higher voltage input than the motor requires?
In that case would it make sense to use a stepper motor that’s running on a lower voltage? Like this one: Account Suspended
FL42STH25-0404A
Voltage: 9.6V
Current (phase): 0.4A
Inductance (Phase): 36mH
Holding Torque: 166mNm
Shaft version: Single shaft
I’m still trying to figure out the best way to set up the circuit, and currently thinking it might make sense to run two stepper motors rather than a servo and stepper motor. In this instance do you think it would be efficient to run two stepper motors from one shield?
The nominal voltage for a stepper motor is largely irrelevant. What matters is the current. You won't be able to drive a motor effectively with a voltage below the nominal voltage but most stepper motors are powered with higher voltages for better performance. Just make sure to adjust the maximum current on the stepper driver to protect the motor.
The maximum voltage will be set by the stepper driver's capability. Yours seems to be limited to 12v. If you need to use that driver then a motor with a lower nominal voltage would probably perform better. But make sure it has enough torque for your project.
I spent some time reading through the notes, thank you they are very helpful, I will use two stepper motors that each have a torque of 3.4kg (this should be enough for my project). They run at 3v and 1.7a: 3V 1.7A 68oz-in Stepper Motor - RobotShop
Rather than use a dual shield I will use two TB660’s connected to 1 uno board as I would like to have independent control of each motor and the TB660’s supply up to 4A, it looked like many of the other drivers supplied 2A and that might be pushing it a bit with the demands of the motors. I have attached the data sheet for the driver.
It looks like quite a straightforward set up, other than as I’m connecting 2 drivers to one Uno board and each driver requires 3 pins supplied with 5v, do you think I can supply all 6 pins with 5v from the 5V on the Uno board? If not, what might be the best solution to powering all 6 pins 5V?
Photo-Tom:
Rather than use a dual shield I will use two TB660’s connected to 1 uno board as I would like to have independent control of each motor and the TB660’s supply up to 4A, it looked like many of the other drivers supplied 2A and that might be pushing it a bit with the demands of the motors.
That seems wise.
It looks like quite a straightforward set up, other than as I’m connecting 2 drivers to one Uno board and each driver requires 3 pins supplied with 5v, do you think I can supply all 6 pins with 5v from the 5V on the Uno board?
That will be no problem. There is very little current required for the signals.
I am intending to activate the stepper motors using a PIR motion sensor.
It runs on a variable voltage between 3v-6v. It says its source current up to 12 mA @ 3 V, 23 mA @ 5 V. Do you think it will still be ok to supply power to the pir and the 6 pins on both motor drivers? I have attached the datasheet for the sensor.
I have read that when using many stepper motor drivers, one should use a capacitor close to the driver on the motor power supply to help with any spikes. I can’t work out if its best to do this when using the TB6600?
One final thing, I’m planning on wiring the arudino board and driver in close proximity, but would like to have the stepper motors around 3metres away from the arduino board and driver. Do you think I might encounter any problems wiring the stepper motors 3metres away from the drivers?
Photo-Tom:
It runs on a variable voltage between 3v-6v. It says its source current up to 12 mA @ 3 V, 23 mA @ 5 V. Do you think it will still be ok to supply power to the pir and the 6 pins on both motor drivers?
That should be no problem.
I have read that when using many stepper motor drivers, one should use a capacitor close to the driver on the motor power supply to help with any spikes. I can’t work out if its best to do this when using the TB6600?
You need to study the datasheet for the driver. Some of them include capacitors. I suspect an extra capacitor or two won't do any harm.
Do you think I might encounter any problems wiring the stepper motors 3metres away from the drivers?
I don't know. I would use heavier cable to minimize the voltage drop. But there is also inductance and capacitance to consider as the power level will be changing rapidly and frequently and those considerations are beyond my pay grade.
Both supply more amps than the stepper motor requires, but the 12v supply delivers a greater amount of amps than is necessary, which isn't a bad thing. Would it be better to supply more V or more A?
If you have two motors that are specified as 3v and 1.7A then that is about 5 watts per motor which would be about 10 watts total. I would add at least 50% for a margin, so call it 15 watts (or maybe even 20).
A 24v 2.1A power supply provides 50 watts and 12v 3A provides 36 watts. Either should be fine. However steppers perform better at higher speeds with higher voltages so my choice would be the 24v power supply.
