Hello! I am doing a school project and I'm having a lot of trouble figuring out the logistics. I am making a device that uses an arduino and two stepper motors to rotate and arm and have it collapse to a certain position. However, it is required that the project is powered by a standard 120VAC wall outlet. I'm using a nema 8 and nema 17, both 4 wire bipolar. How should I go about utilizing that power for the project? Surely 120Vac is too much for the motors and the nano is not able to take AC voltages. Any help is appreciated!
If your steppers are 5V steppers (I have no knowledge about steppers), you can use a cellphone charger of sufficient capacity. Can you post the specs of the steppers.
I think a good starting point would be a schematic or block diagram that shows ALL the components of your project.
I suspect you haven’t included a driver for your steppers, hat will have a significant impact on your choice of power source.
The nema 8 is rated at about 5V and the 17 is rated at 12-24V. They also are rated at 0.6A and 2A respectively.
I was thinking of the A4988 driver but I'm worried since it has a max input current of 1A, I may not get the torque I need from the motor.
Go to any thrift shop and in the electronics section, you should be able to find old wall warts (AC to DC regulators) such as the ones we use for cell phones. Find any old one, doesn't have to be from a phone (most of modern electronics run on DC, not AC anyway, that's what all those power bricks/wall warts whatever you call them do - take mains voltage and convert it to what devices use).
On the wall wart will be printed something like "INPUT 120VAC OUTPUT 12VDC 500mA" so in this case, it's changing mains voltage AC into 12 volts DC to a maximum draw of 500 milliamps. This 9VDC wart would be suitable for your Nano alone, but at only 500mA, likely couldn't handle the current requirement of the Nano and the two motors.
So always find the one at the voltage you need with the highest milliamps/amps rating. remember, voltage is delivered, ie it's always the pressure on the circuit from the power source. Amperage isn't delivered per se, it's demanded by the devices you're using. So you can't have too high an amperage rating on the wall wart but you can certainly have too low. Add up the current needed by all the devices and select a wall power adapter that's a rated for more, a little more or a lot more, whatever they have but more.
Then take your wall wart, cut off the end and split the two wires, positive and negative and insert them into a screw terminal block or such to the length you require (so at least three - for each device). DO THIS ALL UNPLUGGED OBVIOUSLY and I'll stop with the annoying caps lock now. That's your 12V line. Then feed the outputs of the motors into two separate buck converters, each dialed into the voltages you need for your motors. Feed the last open 12V line into the Nano VIN pin, ground to circuit ground it can handle up to 12 V in (needs 7 V to operate reliably when powered from the VIN pin, according to the tech specs), and I think Robert should be your mother's brother if i haven't missed anything.
EDIT tie all your grounds to one place which tie into the negative of the wall wart.
EDIT EDIT don't use the 5V pin on the Nano to power a motor. It's better to deliver power to devices using external, regulated power, in general (I use buck converters as previously mentioned)
The driver is not the solution to the problem converting AC 120V to DC 12-24v
Please show datasheets of your motors. To select a suitable driver and PSU you need the electrical values of the motor coils. At least the values for the Nema17 are shurely not the coil values, but the supposed values for a currentcontrolling driver.
You can use a DRV8825 instead of the A4988, but 2A is still a lot even for the DRV8825. You need good cooling. But you can operate the stepper at a lower amp if you don't need the full torque. A TB6600 may be a better choice.
N.B. NEMA17(NEMA8 tells nothing about electrical values of a stepper. It only defines the dimensions of the mounting plate.