Recommended battery power source for NEMA 17 bipolar stepper?

Hi. Can someone recommend a power supply to use for my stepper motor? I tried to test it with a 9V battery and I was told that was foolish. I would like to run it off several AA or C batteries, or a rechargeable lithium ion pack.

I am using a NEMA17 Bipolar Stepper Motor, it's rated voltage is 2V-36V, it's rated current is 1.2A My driver is the DRV8834 Low-Voltage Stepper Motor Driver Carrier which operates at 2.5–10.8 V and can deliver up to approximately 1.5 A per phase continuously without a heat sink or forced air flow (up to 2 A peak).

Ultimately I want to power this motor for 12-24+ hours on one charge or set of batteries, but it will only be doing one step every 1-15 minutes, so it won't be running at full speed the whole time. Right now I'd just like to get it running so I can start writing my program and testing it though.

Get a wallwart for now. http://www.mpja.com/5-Volt-DC-Plug-Power-Supply-4A-Regulated/productinfo/18520%20PS/ Replace with a 2-cell (7.4V) high amp-hour LiPo later on when you've determined your actual needs.

CrossRoads: Get a wallwart for now. http://www.mpja.com/5-Volt-DC-Plug-Power-Supply-4A-Regulated/productinfo/18520%20PS/ Replace with a 2-cell (7.4V) high amp-hour LiPo later on when you've determined your actual needs.

So I need to hook the wallwart up to a 2A resistor to use it? I don't want to fry my driver...

Also, I should mention I don't want to spend $200 on the battery haha

Google LiPo batteries, they are common & inexpensive, many radio control car places carry them.

You said the motor and driver are both rated for >7.4V; no resistor needed.

CrossRoads: Google LiPo batteries, they are common & inexpensive, many radio control car places carry them.

You said the motor and driver are both rated for >7.4V; no resistor needed.

The wallwart says it provides 7.4V at 5 amps though, the driver is rated for 2A, do I need to protect it? I don't want to fry my driver board

A stepper motor draws full current all the time even when stationary. If it has to be battery powered I suggest a large lead-acid battery - perhaps a used car starter battery if you can use 12volts.

That stepper driver can only take up to 10.8 volts and that will limit the performance of the motor. If you could get a driver that can take up to 30volts you could use a 12v or 24v battery.

So I need to hook the wallwart up to a 2A resistor to use it?

I have no idea where you got this concept from. I suggest some study of the difference between amps and volts.

You can only fry something if you have too many volts AND there is a big enough supply of current. If the voltage is correct it doesn't matter whether there are thousands of Amps available, the device will just take what it needs. If you have the correct voltage and not enough amps you may damage the power supply. The best option is the correct voltage and a surplus of amps.

...R

The motor will only draw the current when the controller lets it have & low outputs acros a coil - and the current will be limited by all the parts in series: the source voltage, the motor impedance, and the voltage drop across the driver. Say the motor coil was connected to 5V on one side and the driver connected the other side to Gnd and had a 1.1V drop on its transistors doing that. Then the current would be (5V - 1.1V)/motor winding resistance = amps if left on long term. Steppers work by getting pulses of current thru them, so they have an AC component of resistance called impedance. So the current will be different if you could measure it during pulses than if you use a multimeter and measure the coil winding statically (unpowered) and calculate as above.

So: no resistor.

CrossRoads: Get a wallwart for now. http://www.mpja.com/5-Volt-DC-Plug-Power-Supply-4A-Regulated/productinfo/18520%20PS/ Replace with a 2-cell (7.4V) high amp-hour LiPo later on when you've determined your actual needs.

Can you recommend somewhere I can buy the female part that I can use to plug that power supply into my protyping board? I don't know what to look for

Also if you could recommend a part that I could plug that battery into that I can put on my protyping board that would be great.

I just ordered this part here: http://www.allelectronics.com/make-a-store/item/dcj-1/2.1mm-dc-power-jack/1.html?extra=a%3A2%3A{i%3A0%3Bs%3A40%3A"03823345592a403b2f4a37a59384e7ab28f02be1"%3Bi%3A1%3BN%3B}

Hopefully it’s the right one?

Also, could you suggest a similar plug that I could use to link the battery you mentioned to my breadboard?

Drill a hole, screw this onto your board - or onto your enclosure wall. http://www.mpja.com/55mm-OD21mm-ID-Chassis-Power-Connector/productinfo/18549%20PL

Theoretically if I run the 1.2A stepper at 5v that’s 6 watts,

which means this battery: http://www.ebay.com/itm/NEW-Duratrax-Onyx-LiPo-2S-7-4V-2000mAh-25C-Traxxas-DTXC1837-NIB-/390785819028?_trksid=p2054897.l4275

Would give me at least 2.5 hours of run time, correct?

I need to find a battery that can give me 25 hours, or at least 12… that’s also cheap… $25 is ideal. Anything over $50 I probably cannot consider.

The stepper will be moving full speed the whole time? Then yes, 1.2A * 25 hrs = 30AH battery = 30,000mAH Maybe this? http://www.batts.com/duracell-mn918-6v-30ah-alkaline-lantern-battery.html Puts you into big battery league. Are you sure you need that much power?

duncan916: I need to find a battery that can give me 25 hours, or at least 12... that's also cheap... $25 is ideal. Anything over $50 I probably cannot consider.

Cheapest solution (which I suggested earlier) is to get a stepper driver board that can use a higher voltage and then get a used 12v car battery - probably free or cheap.

Always assume that the amp-hour rating written on battery stickers is 2 times higher than the real usable value.

...R

The DRV8834 has an "enable" option. If whatever you're moving with the stepper motor doesn't require that the motor stay energized (you're not performing a vertical lift or such) then you can sleep it and save a lot of power. A stepper normally stays energized - power flowing - to maintain torque.

If you are performing vertical lifting or such then you might want to consider a gear-head stepper so that the intrinsic gearing losses provide more holding force when the motor is de-energized. There's also the opportunity to use a spring-loaded solenoid or an RC servo to lock the position so you can de-energize the stepper; you haven't provided details on what you're building but I'm willing to bet you'd still come out way ahead on power usage in either respect.

Robin2:

duncan916: I need to find a battery that can give me 25 hours, or at least 12... that's also cheap... $25 is ideal. Anything over $50 I probably cannot consider.

Cheapest solution (which I suggested earlier) is to get a stepper driver board that can use a higher voltage and then get a used 12v car battery - probably free or cheap.

Always assume that the amp-hour rating written on battery stickers is 2 times higher than the real usable value.

...R

Thanks, but a car battery is too big for what I want to use it for

CrossRoads: The stepper will be moving full speed the whole time? Then yes, 1.2A * 25 hrs = 30AH battery = 30,000mAH Maybe this? http://www.batts.com/duracell-mn918-6v-30ah-alkaline-lantern-battery.html Puts you into big battery league. Are you sure you need that much power?

Luckily the stepper will not be moving anywhere close to full speed during that time. At most maybe one step every 10 seconds to a minute. I think I will get this battery and do some endurance tests: http://www.ebay.com/itm/NEW-Duratrax-Onyx-LiPo-2S-7-4V-2000mAh-25C-Traxxas-DTXC1837-NIB-/390785819028?_trksid=p2054897.l4275

I'll probably get 25 hours out of it running it the way I will be. Can you recommend a good way to hook the battery up to my breadboard so I can easily attach, detach it?

Perhaps if you know what those connector plugs it uses are called and I can search for those with wires on one end? Thanks for your help...

duncan916: At most maybe one step every 10 seconds to a minute.

Remember a stepper draws full current even when stationary unless your application allows you to use the enable pin to switch it off without losing position.

I realize a car battery is big and heavy. But smaller alternatives with enough capacity will be expensive.

...R

Robin2:

duncan916: At most maybe one step every 10 seconds to a minute.

Remember a stepper draws full current even when stationary unless your application allows you to use the enable pin to switch it off without losing position.

I realize a car battery is big and heavy. But smaller alternatives with enough capacity will be expensive.

...R

I'm considering using a worm gear to driver the plate I am going to be rotating so I might be able to switch it off between steps, but I'm not sure.