Optimizing Propeller Circuit To Run Off 2x AA Batteries... Is This Possible?
Mahonroy
Posts: 175
in Propeller 1
Hey guys,
I am wanting to build a simple circuit that runs off 2x AA batteries... if this is even possible. If not, what would you recommend? Different battery or something different all together?
Anyways, its just a circuit containing the propeller, a NRS24L01+ module, and it will take sensor readings and periodically transmit them, that is it.
What is the best way to configure the propeller so that it uses as little battery power as possible? I heard that generally the less Mhz you run, the less power... can this run without an external oscillator at a lower Mhz?
Can I run the propeller off 2x AA batteries in series? This will only be 3.0 volts, and will go down from there... will this be a problem?
Should I use a step up converter to convert this power up to a 3.3 volts?
I am wanting to build a simple circuit that runs off 2x AA batteries... if this is even possible. If not, what would you recommend? Different battery or something different all together?
Anyways, its just a circuit containing the propeller, a NRS24L01+ module, and it will take sensor readings and periodically transmit them, that is it.
What is the best way to configure the propeller so that it uses as little battery power as possible? I heard that generally the less Mhz you run, the less power... can this run without an external oscillator at a lower Mhz?
Can I run the propeller off 2x AA batteries in series? This will only be 3.0 volts, and will go down from there... will this be a problem?
Should I use a step up converter to convert this power up to a 3.3 volts?
Comments
P1: 2V should be ok at rcfast speeds, switch to rcslow when you're waiting for something for longer than a minute.
And all cogs should be using waitcnt or waitpin while sleeping and not some polling loop.
So you don't need a crystal but actual hz will not be precise as rc's are often off by 10% , so don't use it to count actual seconds etc
brownout detector disabled.
I called Analog Devices and talked to them about how to best accomplish power for three rails: the Prop+Nordic(3.3V), another power rail at 7.25V, and another at 5v. This is what they gave me based on my requirements. It is a programmable step up. With 2 AA batteries running all 3 step up regulators, I get about a day out of it. I timed it once but forgot what it ended up at exactly, but I was happy with it for the project.
With LUA / NodeMCU very easy to program.
and direct upload to ThingSpeak possible as well.
I do this with my cistern water level data.
It runs in RCslow mode while waiting and in XTAL1 mode for precise timing when activated. It works for around one year now without changing batteries.
And how long are you hoping to run the device on fresh batteries?
Incidentally, you may want to look at picking up one of Parallax's new badges (https://www.parallax.com/product/20000) for prototyping. It has a 3.7V lithium-ion battery and a small prototyping area to connect the NRF24L01+ breakout board.
Thanks for showing that chip, that does look interesting. Do these chips work by bringing up the voltage regardless of what the input is? e.g. 3.0v, 2.7v, 1.5v all get brought up to the 3.3v (or whatever you have it set at)? I have not used one before so I am curious, I will definitely research some more. That would solve the problem of the propeller browning out at like 2.7v and would get longer life out of the aa batteries.
Curious what you were powering that needed the 7.25 volts? Was this the part that drained the most current from your circuit?
The ESP8266 was an option, but after researching it, it looked like it had a huge current draw. This was the main reason why I decided on the nRF24L01+ for this part.
It looks like the mAh for those batteries are generally around 1500 or so, while the mAh of AA batteries is closer to 2000. If 2x batteries were connected in series, it would still be 2000 mAh I believe (just at 3v now). So this is similar to your 123 cell, at a much smaller size, so this might be a good option. Are those batteries available at most stores or do you have to order them?
I just thought 2x AA batteries would be good since they are so readily available and have decent mAh ratings. The plastic enclosure is pretty small (approx. 4" x 3" x 1") so even 2x aa batteries will be tight.
I was hoping for the device to run for at least 1 year. My friend has this indoor digital thermometer that has an external sensor that uses RF that goes outside and it runs off 2x aa batteries, and it has been running for over 2 years. I was hoping to get comparable performance.
Thanks again for all of the info so far!
If you stay with AA batteries - and your cost/performance requirements allow - then you may wish to include a scheme to boost and regulate output. That way, you can keep supplying 3.3V even when the battery cell voltage becomes too low. There are many options on the market ... This is just one example that came up from cranking "AA to 3.3V" through a search engine.
The device I linked has a min and max input, and a programmable output that you set with resisters very easily to the voltage you want anywhere from 3V to 20V, 2 amp. I needed 3 dedicated rails, and used 3 of the devices on the same board. You can see the board in my gadget photos posted earlier.
Enjoy!
Mike
The ESP has a deep sleep mode.
So if you just need to report a sensor value every hour this is an option.
If you need to measure and report every second it will not last long.