# Using Step Up Board to Power 12v DC motor from 3 AAs

Goal:

Power an arduino with 3 AA batteries and use a step up board to also power a 12v DC motor

I basically used the following guide, but I introduced the step up board with goal of a low power battery operation

http://www.instructables.com/id/Automatically-water-your-small-indoor-plant-using-/

I've already set up the following successfully:

1) 9v battery source for both Arduino and motor stepped up to 10v to power the motor using an pn2222 transistor for the switching mechanism

2) 4 AA battery source @ 6v for both Arduino and motor stepped up to 10v to power the motor using an pn2222 transistor for the switching mechanism

3) 3 AA @ 4.5v stepped up to 10v to power the 12v motor directly (no Arduino)*

Unsuccessful:

3 AA battery source @ 4.5v for both Arduino and motor stepped up to 10v to power the motor using an pn2222 transistor for the switching mechanism

Possible cause:

Running the negative line through the pn2222 transistor through the arduino results in less current than is required to start the motor.

Must determine how to ensure enough current when running through the arduino. Important to note that I've successfully powered the motor through the step up with 3 AA batteries without the arduino and the pn2222 transistor. This demonstrates that there should be enough current and voltage to power the motor using the step up board with 3 AA batteries.

See attachments for my current setup.

Doesn't power motor:

Powers motor:

The motor in the instructables is a 12V 1000mA device, the 2n2222 is good for 500 mA. Suggest you use a logic level mosfet instead of the bipolar transistor.

Recognize also that when you step up the voltage, you also multiply the current required from the source - if you have 4v input and want 12v output at 1 amp, you need to supply a minimum of 3 amps from the 4v source (12v/4v gives a multiplier of 3 - and that is assuming 100% efficient (which it is not so you will need even more)) 4a from AA batteries is pretty high - typical alkaline will not handle it although NiMH and NiCd can for a short period (lower internal resistance). You indicate that it does run the motor without the Arduino but not with it - I suspect if you measure the voltage from the batteries when you try and run the motor, you will find the voltage drops way down. For something pulling that much current, you would be better with a 12v supply that can handle the motor then regulate that down for the arduino (and use a MOSFET as the switch as suggested above).

The green wire that goes from the transistor to the GND connection on the top edge of the Nano (top as oriented in the photo) - I think I'd prefer to see that going directly to the ground rail of the breadboard.

I think you might be putting a bit too much current through the Nano's internal ground-ground connections.

Due_unto: Suggest you use a logic level mosfet instead of the bipolar transistor.

Thanks. I just ordered these:

https://www.amazon.com/gp/product/B01I1KAP6Y/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1

Hopefully they do the trick.

gpsmikey: you need to supply a minimum of 3 amps from the 4v source (12v/4v gives a multiplier of 3)

Yikes...I may be going in a complete wrong direction to accomplish my goal then.

gpsmikey: For something pulling that much current, you would be better with a 12v supply that can handle the motor then regulate that down for the arduino (and use a MOSFET as the switch as suggested above).

I will try this next. I was trying to avoid the power regulator since it is my understanding that it consumes a lot a power. Your point regarding the step up board probably eliminates any potential gains. I considered using an external "switching" regulator rather than the onboard "linear." I'd like to avoid needing 8 AA batteries. I have a 6v pump I was unable to get to work on the circuit. Maybe the mofset will solve that issue allowing me to use less batteries.

Should work ok if the parts aren't zapped when you get them. FQP30N06L, Vgs = 5A, ID = 16A, Rds = 25 to 35 milliohm \$15 for 10 pieces and packed in non-static dissipating foam in a plastic box, vs \$1.12 each from Digikey.com, properly shipped in an ESD tube in an ESD bag. Not the way I would have bought them.

GypsumFantastic: The green wire that goes from the transistor to the GND connection on the top edge of the Nano (top as oriented in the photo) - I think I'd prefer to see that going directly to the ground rail of the breadboard.

I think you might be putting a bit too much current through the Nano's internal ground-ground connections.

Thanks. I'll give that a try later.

CrossRoads: Should work ok if the parts aren't zapped when you get them. FQP30N06L, Vgs = 5A, ID = 16A, Rds = 25 to 35 milliohm \$15 for 10 pieces and packed in non-static dissipating foam in a plastic box, vs \$1.12 each from Digikey.com, properly shipped in an ESD tube in an ESD bag. Not the way I would have bought them.

Point noted for the future.

I'm in a rush to get a working prototype and wasn't sure about any other website's shipping speed.

The big distributors, Digikey and Mouser, often ship the same day if ordered by some time deadline. They don't fool around!