Hi,
First I wanted to express my gratitude to the picaxe group. I've been working with these chips for ~2 years and searching the forum has saved me from a lot of headaches and user blunders.
OK, here's the problem. I use the 28X1 with the 28X project board (AXE 020) to control a battery powered field instrument. The 28X1 is powered by 3 AAs while a separate battery drives some solenoids. These instruments are deployed for up to a year in freezing conditions and are in low power sleep for 99% of the time so ultra low power sleep is essential.
I run a simple test program just to check the power draw during sleep for each 28X1 chip. Chips are inserted into the same 28X project board which is pre-assembled with inputs tied to ground . After program is downloaded and serial comms cable is removed.
(http://www.rev-ed.co.uk/docs/axe020.pdf)
' 28X1 low power test program
' fresh AA batteries
' 28X project board#2, no modifications or added circuits to project board
' no solenoids connected, darlington driver in socket but not used.
' program editor 5.2.5
' runs at 4MHz which is resonator on 28X project board
Main:
disablebod ' turns off brownout detect, lowest power sleep
sleep 3
enablebod ' turns on BOD, bumps current draw to ~200 uA
sleep 3
goto Main
The first 28X1 chips I received were great, I had sleep currents of 1.6-1.9 uA The most recent chips I received all have much higher current draw during sleep. These results use the same 28X1 project board so the only difference is the 28X1 chip.
chips#1-3: 1.6-1.9 uA, firmware= A.2, processor batch# 07012QC
chips#4: 103 uA, firmware= A.2, processor batch# 07012QC
chips#5-10: 125-129 uA, firmware= A.3, processor batch# 08103MD
At first I thought it was a firmware issue since the older chips were A.2 but I have an A.2 chip that draws 103 uA during sleep. Then I thought it was the processor batch# but I have a 07012QC chip that draws over 100 uA. All the newer chips have the A.3 firmware and batch# 08103MD and higher current draw of around 125 uA. I also have some new 28X2 chips, both 5V and 3.3V and they draw <3 uA with the same test procedures (slightly different program).
Anyone encounter this before? Have any ideas why the more recent 28X1 chips have higher power draw and any potential fixes? 125 uA may not sound like a lot of power draw for some people but it’s lethal for my application. Adding more battery capacity is not a viable option.
Thanks very much,
Thomas
First I wanted to express my gratitude to the picaxe group. I've been working with these chips for ~2 years and searching the forum has saved me from a lot of headaches and user blunders.
OK, here's the problem. I use the 28X1 with the 28X project board (AXE 020) to control a battery powered field instrument. The 28X1 is powered by 3 AAs while a separate battery drives some solenoids. These instruments are deployed for up to a year in freezing conditions and are in low power sleep for 99% of the time so ultra low power sleep is essential.
I run a simple test program just to check the power draw during sleep for each 28X1 chip. Chips are inserted into the same 28X project board which is pre-assembled with inputs tied to ground . After program is downloaded and serial comms cable is removed.
(http://www.rev-ed.co.uk/docs/axe020.pdf)
' 28X1 low power test program
' fresh AA batteries
' 28X project board#2, no modifications or added circuits to project board
' no solenoids connected, darlington driver in socket but not used.
' program editor 5.2.5
' runs at 4MHz which is resonator on 28X project board
Main:
disablebod ' turns off brownout detect, lowest power sleep
sleep 3
enablebod ' turns on BOD, bumps current draw to ~200 uA
sleep 3
goto Main
The first 28X1 chips I received were great, I had sleep currents of 1.6-1.9 uA The most recent chips I received all have much higher current draw during sleep. These results use the same 28X1 project board so the only difference is the 28X1 chip.
chips#1-3: 1.6-1.9 uA, firmware= A.2, processor batch# 07012QC
chips#4: 103 uA, firmware= A.2, processor batch# 07012QC
chips#5-10: 125-129 uA, firmware= A.3, processor batch# 08103MD
At first I thought it was a firmware issue since the older chips were A.2 but I have an A.2 chip that draws 103 uA during sleep. Then I thought it was the processor batch# but I have a 07012QC chip that draws over 100 uA. All the newer chips have the A.3 firmware and batch# 08103MD and higher current draw of around 125 uA. I also have some new 28X2 chips, both 5V and 3.3V and they draw <3 uA with the same test procedures (slightly different program).
Anyone encounter this before? Have any ideas why the more recent 28X1 chips have higher power draw and any potential fixes? 125 uA may not sound like a lot of power draw for some people but it’s lethal for my application. Adding more battery capacity is not a viable option.
Thanks very much,
Thomas