Running Moteino from 2 x AAA cells

[Felix]

Well if you find something good keep us updated
But make sure the booster is very low quiescent current, otherwise it defeats the purpose of low power.

[Saxx]

Yeah, I see the LED now... Well, I have a few Arduino Pro Minis that I use, with a power LED. I have just removed the LED with a small screwdriver, and that works just fine. I'll let you know how these behave when I have tested them.

[ieris]

As already mentioned from Felix, I think the best way would be if you remove the regulator and change the frequency to 8MHz. I have running some Moteinos in this configuration with 2xAA batteries since several months without problems.

I have custom build Moteinos w/o regulator and with 8MHz resonator running on 2xAA batteries very well.
Also I have created a low power Moteino which runs from 1 AA battery

[TomWS]

I have custom build Moteinos w/o regulator and with 8MHz resonator running on 2xAA batteries very well.
Also I have created a low power Moteino which runs from 1 AA battery

I'm curious as to why you have a resonator instead of using the internal 8MHz RC Oscillator?

Tom

[Lensdigital]

I had some good luck with running Moteino (on stock 16Mhz) on single AAA battery for about 6-8 months (transmitting temp/humidity date about every 5 minutes). I did have to buy 3.3V step up booster from Sparkfun for this tho...  Without booster and voltage regulator it can probably last a year. I'm building a custom board similar to Moteino but designed to run of 3V coin (it has jumper to bypass 3.3v voltage reg) cell to see if it works...

[ieris]

I have custom build Moteinos w/o regulator and with 8MHz resonator running on 2xAA batteries very well.
Also I have created a low power Moteino which runs from 1 AA battery

I'm curious as to why you have a resonator instead of using the internal 8MHz RC Oscillator?

Tom

Because of using serial communication.

[TomWS]

Because of using serial communication.

Ah, ok.  Makes sense if you need high speed UART comms on a low power device.   

[ulli]

Hi,

I plan to use a MCP1640 with 1xAA battery to run my Atmega328p with RFM69 and IR-Diode or 2xRelays. Does anybody have experience with the MCP1640?
Would it be sufficient for my application?

I would appreciate to get a feedback.

[ieris]

Hi,

I plan to use a MCP1640 with 1xAA battery to run my Atmega328p with RFM69 and IR-Diode or 2xRelays. Does anybody have experience with the MCP1640?
Would it be sufficient for my application?

I would appreciate to get a feedback.

Must be ok, as I know Ray from opensprinkler using it in AASaver project.
And you can take a look at pololu - http://www.pololu.com/category/132/step-up-voltage-regulators
I'm using LTC3525, as it has less components (was important for my project).

[TomWS]

Hi,

I plan to use a MCP1640 with 1xAA battery to run my Atmega328p with RFM69 and IR-Diode or 2xRelays. Does anybody have experience with the MCP1640?
Would it be sufficient for my application?

I would appreciate to get a feedback.

I've used the MCP1640 in a 2 cell boost configuration (3.0V->5V) and think that it is a fine boost circuit.  Just bear in mind, boosting from 1.5V to 3.3V will almost triple the current drawn on the battery... A AAA battery has about 1200mA Hr, which will translate to about 400mAHr available at the Mote & peripherals... 

Tom

[Felix]

Also mind that the MCP1640 can only deliver 100mA, and probably that's going to be at top efficiency, meaning VIN close to VOUT. Maybe that's why it's $0.68 in QTY of 1.

[ulli]

Hi,
sorry for the very late reply but I lost the thread...

I already built up a moteino clone with RFM69HW and a IR-Diode. I am running it with the LowPower Library to reduce the power consumption as good as possible.
The power supply is solved with the MCP1640 and 1xAA battery. Everything works fine so far. Hopefully it will run several month!
I will definitely will give a feedback!

But just a few questions regarding your comments for my low power application
* Isn't right, that to use a coin cell would not be better than my circuit because the coin cells do not have much capacity
   220mAh for example (http://www.digitalsmarties.net/products/coin-cells)
* Do i really almost triple the current draw with a MCP1640? Is that your experience in such a configuration? The efficiency of the MCP1640 is not bad...
* I also think about reducing the current consumption by increasing the resistances of my pullup resistors..
  Do you know the max resistance which I can use for SPI chip select pin of the RFM69 and the reset pin of the atmega328p and RFM69?

Best regards,
  Ulli

[TomWS]

Hi,
sorry for the very late reply but I lost the thread...

I already built up a moteino clone with RFM69HW and a IR-Diode. I am running it with the LowPower Library to reduce the power consumption as good as possible.
The power supply is solved with the MCP1640 and 1xAA battery. Everything works fine so far. Hopefully it will run several month!
I will definitely will give a feedback!

But just a few questions regarding your comments for my low power application
* Isn't right, that to use a coin cell would not be better than my circuit because the coin cells do not have much capacity
   220mAh for example (http://www.digitalsmarties.net/products/coin-cells)

The issue with coin cells is that they can not supply much in the way of surge power.  In your waking state, even if you are drawing only 10-15 mA you will drain the coin cell rapidly, even if very low duty cycle.

* Do i really almost triple the current draw with a MCP1640? Is that your experience in such a configuration? The efficiency of the MCP1640 is not bad...

If you factor 3.3V output / 1.5V input / 0.8 efficiency, you get 2.75 multiplier on the current drawn from the 1.5V source.  Also, Felix's earlier point about the MCP1640 is valid, you need to take care (either with capacitors or reduced max load) not to exceed 100mA peak.

* I also think about reducing the current consumption by increasing the resistances of my pullup resistors..
  Do you know the max resistance which I can use for SPI chip select pin of the RFM69 and the reset pin of the atmega328p and RFM69?

I'm not sure the pull up resistor values will contribute much loss since they are active so rarely and the leakage current otherwise is nanoscopic... (I just coined that :-)
Further, I think there is already an internal pullup resistor on the reset line.

Tom

[Felix]

I'm actually taking a serious look at MCP1640 which has 100mA listed, but can do up to 4-800mA, see datasheet. I think if it's stable, it could replace the uber expensive LTC3525. Last time I bought a strip of 100xLTC3525 I spent about $340, still hurts.

[TomWS]

I'm actually taking a serious look at MCP1640 which has 100mA listed, but can do up to 4-800mA, see datasheet. I think if it's stable, it could replace the uber expensive LTC3525. Last time I bought a strip of 100xLTC3525 I spent about $340, still hurts.

One thing to watch for, Felix, is that the max current is usually the current into the inductor.  If it's a boost converter, 800 mA can become no more than 100mA into Vout in a hurry!  I think you know this, but with a 5:1 price difference, it's easy to forget 

The one thing I DO like about the LTC3525, and you used this to advantage in the Power Shield, is the fact that Vin can be greater than Vout, something most boost converters can't deal with.

At this point, I've found the best and easiest implementation is running remote battery operated motes at 8MHz internal so I can run directly off 2X cylindrical cells, typically Lithium Iron Disulphide (AKA Eveready 'Utlimate' Lithium).  I've found these to be the most reliable batteries over a wide temperature range with good life and power density.

It's also pretty easy to pull the MCP1703 from the Moteino board so I can drive the 3.3V pin directly.

Tom