Barrel Jack Vs Vin for battery power??

First of all I am very new to all of this so my knowledge is extremely limited.

I want to power my Arduino Uno and a 6v motor with as little number and smallest batterie or batteries I can. I tried using a energizer 12 a23 battery and it has plenty of power to run my motor. I have programmed the motor to run through a digital output pin when certain conditions are met by using a transistor and plugging it into the computer. It runs fine when I do that. However, when I pull the usb out and try running it off of the battery through the Vin the motor is much much weaker. Would it work better to hook the battery up through the barrel jack? I am not sure what else I can do to get enough power to the motor. I am very confined by space (no wider than a aaa battery and not enough room to run a whole bunch on top of each other). The size of this little 12v battery is perfect and it is strong enough to run the motor it seems only when the motor is hooked up directly to it. Anyone know what might be causing this and what I could do to fix this.

Thanks

I don't think that would help When it's only powering your motor it works perfectly, am I right? But now it has to power you motor AND your arduino, which can also take up quite a bit of power...

You need to provide separate power for the motor without any transistor (which is effectively reducing the voltage and hence current available). I don't mean do away with a transistor between your Arduino and the motor, no no!

You could use a MOSFET which has a very low 'on' resistance.

You could use a RELAY (ideally totally isolated from the UNO via an opto-isolator) which would have no voltage drop across it at all.

What are you using (or going to use when you have finished developing and remove that USB plug) to actually power the Arduino?

Motors require quite a bit of current and will flatten a battery quite quickly. Without knowing more details we are all a bit in the dark.

Post back a schematic of what your design looks like and we can help further :)

This sounds crazy (or not) but I don't really know how to draw a schematic. Basically i have a sensor wired to my arduino and when the temperature warms up it sends voltage to a digital output to turn on the motor. I started by turning on an LED light with no problem and i was able to get the motor to work by adding in a transistor. But, with the battery alone again it easily turns on the light but barely runs the motor when i replace the light with the motor (obviously bc the motor requires more power).

As for what I wii use when finished developing that is precisely what I am trying to determine. Whatever it is it needs to be small as the space is only approx 20mm in diameter. The size of the 12 v a23 was perfect but i am guessing it doesn't have enough current. I could actually actually stack quite a few aaa or aa batteries inside but it would get quite long so would prefer not to.

Hi, What is the application, the battery you are using is not designed for the type of load you have. The battery is for the intermittent use of key remotes and low current usage devices. http://data.energizer.com/PDFs/A23.pdf In fact the performance graph is shown at 0.48mA load current. So it is not going to hold up with your motor and keep a decent voltage output for stable arduino operation.

Tom... :) Do you have a DMM to measure your voltages?

My guess is that when you have this battery and USB both connected to your arduino and engage motor, battery voltage drops below required voltage for arduino so it switches to USB. You thought that the battery was powering your arduino but it's not. Measure battery voltage with a multimeter when the motor is turning.

Yes I am aware that the battery does not provide a strong enough current because I tested it with the usb unplugged and that is when it is not strong enough. I am wondering if anyone has a recommendation for a proper battery that would be small enough. I do have room if absolutely necessary to string together some AAA or AA batteries but would prefer not too. For now I am just trying to determine if I can get a small enough battery or batteries with enough current supply. Eventually, I would like to be able to plug it into a wall to recharge the batteries as well.

Any suggestions on a battery that is quite small (<20mm wide) that provides enough voltage to run arduino and 4.5-6v small toy motor that requires 0.5-0.62 A?

Thanks

Hi,

As for what I wii use when finished developing that is precisely what I am trying to determine. Whatever it is it needs to be small as the space is only approx 20mm in diameter.

Sorry, you don’t know what you will use it for, but it has to be that small! ! ! ! ! !
What requirement of your undetermined application needs it to be 20mm?

Tom… :slight_smile:

liudr: My guess is that when you have this battery and USB both connected to your arduino and engage motor, battery voltage drops below required voltage for arduino so it switches to USB. You thought that the battery was powering your arduino but it's not. Measure battery voltage with a multimeter when the motor is turning.

+1

That is the size of the hole it has to fit in so I can make it portable. It is like a long narrow tube so I do have room to stack aa or aaa batteries if absolutely necessary but would prefer not too. Ideally it would be no longer than around 12" which also has to include an arduino trinket (hopefully), a small motor and a switch.

Try using a low Rds, N-channel MOSFET to connect the motor- to the battery-.
Part like AOI510 or AOI514, Arduino can drive the gate thru a 150ohm resistor. Put a small diode in parallel with the motor, anode to the transistor and cathode to the supply.
10K resistor from gate to Gnd keeps the motor off when the arduino is in reset state (say during sketch startup).
MOSFET-MOTOR.jpg

will that allow me to use that small A23 battery?

An A23?! You want to power a motor off one of those dinky little things?! Hell no!

Why are you powering a 6v motor off a 12v battery? (Oh, it's because the voltage is plummeting to <6v under load because it's a battery designed for smoke detectors and doorbells)

Use AA's, or some LiPo rechargibles. LiPo's also are better at fast discharge than those awful A23 ones.

Do you know how those A23 batteries are built?! It's 8 watch batteries stacked up inside. Would you try to power a motor off something with the current handling capacity of a watch battery? And you thought 9v rectangular crap batteries sucked (with their six sub-AAA cells)!

Ya I learned the a23 battery sucked for that. I also need enough battery power to run the arduino as well, not just the motor. As I mentioned before, the amount of space I have to work with is an issue so would prefer not stacking 4 or 5 AA batteries.

Yeah, that's why I suggested a couple of LiPo cells. There have got to be some available in a good size + shape for you, they make them in rectangular and cylindrical forms. Energy density is higher - and power density is much higher - and voltage is 3.7v per cell, and they're rechargeable.

Sounds like 2 of those stacked is just what I need. Do they come in different sizes too? Like aa, aaa ...etc?

Yes, two lipo batteries in series will probably do. Be careful with charging circuitry though. I never design charging circuits in any of my projects. Just don't want to see things blow up in case I make a mistake.