08M2 power consumption

MartinM57

Moderator
Bit out of practice with PICAXE :(

Trying for minimum power consumption in a small 08M2 project, but not getting what I wanted, so reduced to a minimum...
3.1v supply - 3x fairly flat AA cells
Leg 1 - V+
Leg 2 - Earth
Leg 3 - Earth
Leg 4 - Earth
Leg 5 - Earth
Leg 6 - Earth
Leg 7 - open circuit
Leg 8 - Earth

Program
Code:
#picaxe 08m2

setfreq m32

disablebod

do
loop
Power consumption 15.5mA - was hoping/expecting for something far less than 1mA :(

Ideas?

Edit: setfreq k31 makes no discernible difference
 
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hippy

Technical Support
Staff member
15mA seems rather high. Running an AXE091 board at 3.1V with three PICAXE and various other chips connected is drawing less than that.

On that board, with this loaded into an 18M2, nothing connected to the 18M2 except power and download interface, at 3.1V I am seeing current alternate between 12mA and 14mA ...

Code:
#Picaxe 18M2
Do
  SetFreq M4  : Pause  2000
  SetFreq M32 : Pause 16000
Loop
 
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AllyCat

Senior Member
Hi,

was hoping/expecting for something far less than 1mA :(
Certainly not at m32 ! The basic consumption at 4 MHz is about 600 uA; it will probably increase about 5-fold at 32 MHz. So there's probably something wrong with your 15 mA measurement.

Unless you actually SLEEP or NAP the processor, there's a fair "static" drain, so at 32 kHz it will/should probably consume about 100 uA. But the execution speed will be so S..L..O..W at 32 kHz, that you're almost certainly better running at (say) 4 MHz and taking short NAPs between instructions. Note that the figures in the PIC data sheet are also for the "LP" version, but AFAIK the PICAXEs all use the "standard" version.

Cheers, Alan.
 

MartinM57

Moderator
Code:
#picaxe 08m2

setfreq k31

low 0
low 1
low 2
low 4

disablebod

do
loop
Battery voltage 3.113v (Fluke 73 III)
Current 13.46 mA (Fluke 87 V)

..not even close to expectations :(
 

AllyCat

Senior Member
Hi,

What if you SLEEP the chip for a few seconds, or even pull it out of its socket? Have you tried unplugging the programming cable/adapter?

What is your hardware - you DO have a decoupling capacitor between Legs 1 and 8 don't you (and nothing that could be draining current like a regulator) ?

Cheers, Alan.
 

MartinM57

Moderator
Pull out of socket - current = 0ma
Programmed off board - no programming cable attached during measurements - serin tied low directly
100nf and 47uF between pins 1 and 8
Direct battery feed - only components are 08M2+, battery pack, 2x capacitors, breadboard, jumper wires, 2x Fluke DMMs

HOWEVER...went to my bag of Picaxes and found my last new 08M2+

Same code...
setfreq k31 - 0.03mA
setfreq m4 - 0.59mA
setfreq m32 - 2.21mA
setfreq k31 - 0.03mA (just to check again - make sure it's not a one way street)

Put project code back in, and 08M2+ into project circuit, and all is back on track - and now I've got a 08M2+ with a blob of correcting fluid on it, in a bag by itself, with a note "Suspect low power consumption". Not sure what the failure mode can be though?

Thanks for your time, Martin
 

Goeytex

Senior Member
Probably has a duff internal peripheral, shorted gate, etc. I once received a batch of five 20M2s and 2 of them consumed about 25ma with nothing connected except Vdd and Gnd. All of the I/O pins worked ok. The only symptom i could find other than the high current was that the serial timing was way off.
 
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