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Running a STM32F405 with a single NiMH AAA


#1

Place your bets…

So how long will a 550mAh AAA NiMH run a STM32F405 (Cerb processor) which constantly reads a MPU9150 using I2C and sends the current time over UART using a RF Pipe with sucks a constant 17ma as it has a 100% duty cycle in receive mode…

Secs…mins…???


#2

7.5 hour


#3

If only…


#4

That was reflecting my wish:)


#5

@ 7.5hrs the RFPipe would use 127.5mAh just sitting there


#6

8.2 hours.


#7

Won’t even start…


#8

at 1.2v no…

I forgot to mention it’s using a boost reg to get 3v3 which I think is running at 85% efficiency at best…


#9

AA’s easy… not with AAA’s…


#10

Here are the test bits…

Single 1.2v NiMH 550mAh AAA running at 168mhz = 3 hours runtime
Single 1.2v NiMH 550mAh AAA running at 84mhz = 4 hours runtime

Two 1.2v NiMH 2000mAh AA running at 168mhz > 24 hours runtime

Points to note
RF module has a 100% receive duty cycle so uses 17ma constantly.
TX is 14ma when sending data each second.
Mini Juice is not overly efficient using 1.2v > 3.3v …

Will be interesting to see how Microbe.Net fairs with a single AAA :slight_smile:


#11

How many power cycles have those batteries been through? 550mAh might be the wishful thinking.


#12

@ Duke Nukem - they are new so only 5 cycles. They were the smallest capacity AAA’s Maplins had…