Power Consumption for Battery use (sleep at 33µA

Hi,

Not sure if this should be here or in "programming" but I'll start here.

Like many I'm trying to reduce power for battery operation.

My setup:

Pro Mini Clone with 3.3v regulator in circuit. Power LED disconnected. No I/Os connected to anything. I changed the fuses so the Brownout function is disabled.

Using Nick Gammon's Sketch J on the Pro mini with nothing connected the current is ~ 30 - 33 µA. Nick's website states the current should be in the 1µA area. Now looking at a typical low dropout regulator it seems the quiescent current is in the 50µA area so I think I'm doing pretty well.

Question: Has anyone had similar results? Would like to know if I was really missing something.

Thanks

John

Remove the regulator. Most of that 33 uA is probably the quiescent current.

There is no need for a regulator, unless some peripheral requires 3.3V.

The need for 3.3 volts for my RFN69 radion requires me to keep the regulator.

You should try to use 3.3V 8MHz version of ProMini and avoid regulator.

Hi,

I guess the regulator is the limiting factor in this case. I cannot however remove it because the RFM69 is limited to 3.3 volts.

Then don't use that radio. The NRF24L01+ runs on as little as 1.9V.

See this solar powered/supercap remote sensor project.

JohnRob:
I cannot however remove it because the RFM69 is limited to 3.3 volts.

So why does the datasheet say it will run on 1.8v ?

The voltage limitation for the RFM69 is not the low end but the high end. If I start with a battery voltage of 4.5 or so I must regulate it down to be below the max RFM69. Hence the regulator.

If you power your project using 2xAA batteries (NiMH or alkaline), you don't need a regulator at all.

Another possibility is to use a lithium battery, with a series diode to drop the voltage below 3.6V.

Or, you can do much better than the regulator you have. The MCP1700 Low Quiescent Current LDO 3.3V reg has a quiescent current of 1.6 uA.

JohnRob:
If I start with a battery voltage of 4.5 or so I must regulate it down to be below the max RFM69.

So don't start with 4.5v ..........................