I found this nema 11 stepper motor on amazon that says its rated voltage is 3.8v. Can I use this stepper motor with 5v. Thanks.
Stepper motors have a rated voltage and current. Yours have a rated voltage of 3.8 Volts and a rated current of 0.8 Amperes which basically says that if you hook it up to 3.8V it will draw 0.8 A.
If you were to provide a higher voltage, your stepperit will draw more current and get very hot. That’s not good in general.
Usually you would not hook it up straight to a voltage source but you would use a Stepper motor driver to regulate the current and prevent this to happen.
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I have one more question, will a nema 17 stepper motor that has a rated voltage of 12v for example, just have less torque if i provide it with 5v?
Nema 17 is the size of the mounting plate (1.7 inch).
It has nothing to do with the motor specs.
You should use a 12volt (or 24volt) supply for your 3.8volt/0.8A stepper.
And a current controlled stepper driver.
The driver reduces the current to a safe value (that YOU have set it to).
A higher supply voltage (and a stepper driver) means torque won't drop off at higher speeds.
Leo..
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Some reading
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This is irrelevant, steppers are current driven. They have a rated current, resistance and inductance.
Stepper drivers act as current drivers.
Normally the supply voltage is chosen to be high enough to overcome the back EMF from the motor (both inductive and rotational back EMF), and the driver is supplied with this voltage. The faster you want the motor to spin, the higher the voltage.
The current is normally fixed at the nominal level for that motor (to get the best torque/performance from it).
Common stepper drivers for small motors are A4988 and DRV8825.
Common voltages used with steppers are 12V, 24V, 36V, 48V, 60V, 80V or even higher, the higher values being used in high performance CNC machines typically, where fast "rapids" are important. Many uses only 12V or 24V is enough. Note that the supply voltage must be at least several volts higher than the product of motor current and resistance, otherwise the driver chip won't be able to function properly.
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I don’t see How what you say - which is correct - makes what I shared irrelevant. It was answering the question.
There's a lot of confusion about bipolar steppers out there, most motor vendors even don't know bipolar low impedance steppers are current driven and give specifications as if they were DC motors.
I pounce on this misunderstanding as it catches many beginners out. Your post #2 just perpetuated the problem I'm afraid.
Such motors don't have a rated voltage (other than insulation breakdown), they have current, resistance, inductance, and its the inductance that really affects the ultimate performance - the resistance just sets the thermal limit (max continuous current).
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The rated voltage is just the voltage that produces the rated current into the winding in steady state.
I thought I clarified this stating higher voltage were fine and drivers would regulate the current. Increasing the available voltage to the driver decreases the time it takes to reach steady state, increasing the motor’s maximum possible operating speed, operating torque and mechanical power output.
But with increased current comes an increase winding power loss, which increases the temperature of the motor. The motor is also stiffer between steps which can create (audible) vibrations. That can obviously damage the motor. So a trade off needs to be found.
Where do you see an increased current? The driver regulates the current, so it will not exceed the rated current ( if you set it correctly in the driver ) - even with higher voltages.
Well that’s the crux.
The original question was not mentioning a driver at all. So powering with 5V would lead to the increased current
Obviously because the poster didn't know about current drivers ( and that his stepper needs one ).
Hence the second part of my supposedly irrelevant answer
Anyway. I think we agree on the technical part.
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Surely 
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