Project Battery Drains Quickly

My automated blind project works exactly as it is intended to, however my 9v battery drains within about one day of use. Idealistically, I'd like to have to change the batteries every 6 months to a year. Currently my project is powered by an 9v battery with a 5v regulator in front of it. It is powering the ATMEGA328p drawing 5v, nRF24l01 module drawing 3.3 (I used two diodes in series to drop the voltage to about 3.1 actual volts being used by the module), and an H-bridge module to drive a micro gear motor.

Any ideas?

What does the project do?
Without knowing what the power demands are , its impossible to determine how big a battery you will need to last 6 months without recharging.

If by 9 volt battery you mean one of the small rectangular PP3 ones then you have no chance. Not only don't they have a lot of power you are immediately burning some of it off with the voltage regulator. And then you are running a motor off it?

Rechargeable single cell (AA, B, C, D) batteries are 1.2 volts, so four of them will give you 4.8 volts. You could also consider one of the 'buck' converters to step the voltage up or down to 5 volts. I've not used one so can't offer any advice on that front.

mauried:
What does the project do?

"9v battery with a 5v regulator in front of it. It is powering the ATMEGA328p drawing 5v, nRF24l01 module drawing 3.3 (I used two diodes in series to drop the voltage to about 3.1 actual volts being used by the module)"

HarringtonG1000:
My automated blind project works exactly as it is intended to, however my 9v battery drains within about one day of use.

That sounds about right.

Have you bothered to measure the current draw with a multimeter?

9V batteries have about 500mAH of capacity. If it lasts 24 hours that means you're drawing about 20mA.

HarringtonG1000:
Idealistically, I'd like to have to change the batteries every 6 months to a year.

The secret to this is:
a) Use power components that don't constantly burn power (eg. 5V regulators, diodes for voltage drops...)
b) Put the chip(s) to sleep for as much time as possible.

There's tons of info on the web for both of those things.

I'd power the nRF24l01 from a pin on the Mega328 so you can switch it on/off on demand. The nRF24l01 only needs about 15mA, that's well with the capabilities of a Mega328 pin.

I'd also power the whole thing from three AA batteries. They'll have four times the capacity of a 9V PP3 and you're not throwing away half your electrons with a 5V regulator.

By doing both those things and putting the chip to sleep as much as possible ... it should run for years (depending on how much you use the motor).

AA NiMH's with 2Ah or so aren't too hard to find.

mauried:
What does the project do?

HarringtonG1000:
My automated blind project works exactly as it is intended to

Except ... it doesn't. :frowning:

HarringtonG1000:
however my 9v battery drains within about one day of use. Idealistically, I'd like to have to change the batteries every 6 months to a year.

Currently my project is powered by an 9v battery with a 5v regulator in front of it.
...
Any ideas?

Dead simple.

Use a "Plug pack" (USA: "Wall wart").

Problem solved easily, completely and uniquely.

MarkT:
AA NiMH's with 2Ah or so aren't too hard to find.

So it could last 4 days...? :astonished:

Thanks for the replies! Unfortunately the motor won't run on 3.3v. It's actually meant to run on a minimum of 6v, so I'm already pushing it with 5. What if I used a 3.3v regulator to power the project? I do have one pin left on the chip that can be used to power the RF module and I can hook up the h-bridge directly to 4 AAA batteries (size is of concern, otherwise I would do 4 AA). I'm thinking that would be my best course of action, no?

HarringtonG1000:
What if I used a 3.3v regulator to power the project?

Won't make any difference.

The current (amps) passing through the regulator will be almost the same at 3.3V as 5V. The only difference is that the 3.3V regulator will turn an extra 1.7V into heat (it will get hotter than the 5V regulator).

Call me a noob, but how can I step the voltage down to 3.3v to power the chip? I need at least 4 batteries (for around 6v) to power the motor. Perhaps if I power the arduino with 3 batteries and put a zener diode between the 3rd and 4th battery and connect the vcc of my h-bridge module to the 4th battery? Does that make sense or is there an easier way?

Nick Gammon wrote a tutorial on how to reduce the power of Arduino microprocessors: Gammon Forum : Electronics : Microprocessors : Power saving techniques for microprocessors

Obviously your big draw is the motors for the blinds, so you need to make sure these are powered off when not in use.

You can get various power regulators to boost or reduce power as needed by your design. Pololu.com sells various regulators with different characteristics: Pololu - Regulators and Power Supplies

I would echo the others, do you really need blinds to be battery operated? I would think about using a power adapter that provides the power you need, and you can get some that have multiple power outlets with different voltages.

MichaelMeissner:
Pololu.com sells various regulators with different characteristics: Pololu - Regulators and Power Supplies

Yes, but they consume a couple of milliamps when idle. You can't go into a low-power sleep with one of those.

HarringtonG1000:
Call me a noob, but how can I step the voltage down to 3.3v to power the chip? I need at least 4 batteries (for around 6v) to power the motor. Perhaps if I power the arduino with 3 batteries and put a zener diode between the 3rd and 4th battery and connect the vcc of my h-bridge module to the 4th battery? Does that make sense or is there an easier way?

4 batteries only gives you about 5V in practice (they only give 1.5V when brand new).

Yes, you can connect the Arduino across the first three batteries. They will drain slightly faster. I don't think you need a zener for that, but I haven't seen your circuit.

Dear,
If you must run your circuit off battery... You should try using 6V 4A Lead Acid Maintenance free rechargable battery.
I have not seen your circuit, but it should last very long .
Further if you want to run it for real long time like months together.. You shoud use same kind of battery suggested above.. but of 12V 7A rating.
You can also use Build/use a solar battery charger which would keep those batteries always topped up.

Amarinf:
If you must run your circuit off battery... You should try using 6V 4A Lead Acid Maintenance free rechargable battery.
I have not seen your circuit, but it should last very long .

Nope.

Making the battery run for two (or even three) days instead of one doesn't solve the basic problem.

To solve the problem you need to reduce the power consumption. I mentioned how to do it but so far the OP doesn't seem to have done anything in this regard.

Amarinf:
If you must run your circuit off battery... You should try using 6V 4A Lead Acid Maintenance free rechargable battery.

As long as you have it continuously connected to a suitable mains-powered "float" charger.

(SLA batteries do not tolerate being left in a discharged condition for any significant duration.)

Amarinf:
You can also use Build/use a solar battery charger which would keep those batteries always topped up.

Not a bad idea. Does of course require more complex installation (mounting the solar cell out in the sun) and significantly more expense than just plugging a "plug pack" into a wall socket though. And you still need a charge regulator.

You'd like your PP3 9V battery to last for 6 months (4392 hours) ?
Well, let me see ... 400mAh battery and 4400 hours, so that needs to get the current below 0.09mA.

Unplug your arduino.
Unplug your 3.3V device.
Unplug anything else which draws 0.1mA or more.

Now your battery should last for the six months.