Mycroft2152
Senior Member
I've been interested in using the PICAXE in solar powered circuits. I received a new batch of PICAXE 08M's that were firmware Rev 9.2 with the BOD (Brown Out Detector) command, as was discussed previously.
I ran a series of tests comparing the current usage PAUSE and NAP commands with the BOD enabled and disable. NAP puts the PICAXE in the low power mode.
<code><pre><font size=2 face='Courier'>
BOD Enabled BOD Disabled
Clock Pause Nap Pause Nap
4 MHz 0.74ma 0.09ma 0.66ma <0.01ma
</font></pre></code>
Rechecking the BOD enabled/disabled current with a more acccurate meter gave 0.093 vs 0.0018 milliamps.
All the tests were run with a 5 volt regulated power supply and the current measured during the PAUSE or NAP command.
Also, all pins were set to outputs, to avoid floating inputs and the programming connector disconnected.
At the same time, I also underclocked the PICAXE to see the effect on power usage, by poking to the $8F location. Hoping to further reduce the power usage.
All values are in milliamps
<code><pre><font size=2 face='Courier'>
BOD Enabled BOD Disabled
Clock Pause Nap Pause Nap
8 MHz 1.28 0.09 1.16 <0.01
4 MHz 0.74 0.09 0.66 <0.01
2 MHz 0.52 0.09 0.45 <0.01
1 MHz 0.40 0.09 0.32 <0.01
500 kHz 0.34 0.09 0.26 <0.01
250 kHz 0.32 0.09 0.23 <0.01
125 kHz 0.30 0.09 0.22 <0.01
31 kHz 0.12 0.09 0.03 <0.01
</font></pre></code>
Looking at the data, it would seem that underclocking could reduce the power requirements. Except there is the trade off in speed. At 4 MHZ, the PICAXE runs at approximately 2000 steps per second, while at 31 kHz it will run at approximately 16 steps per second, 128 times slower but only at 1/25th the current While the current requirements are less, the longer step time seems to offset any overall power savings. This would have to be confirmed in a real world situtation where actual calculations are performed.
TANSTAAFL!
Myc
Edited by - Admin on 16/07/2006 00:54:38
I ran a series of tests comparing the current usage PAUSE and NAP commands with the BOD enabled and disable. NAP puts the PICAXE in the low power mode.
<code><pre><font size=2 face='Courier'>
BOD Enabled BOD Disabled
Clock Pause Nap Pause Nap
4 MHz 0.74ma 0.09ma 0.66ma <0.01ma
</font></pre></code>
Rechecking the BOD enabled/disabled current with a more acccurate meter gave 0.093 vs 0.0018 milliamps.
All the tests were run with a 5 volt regulated power supply and the current measured during the PAUSE or NAP command.
Also, all pins were set to outputs, to avoid floating inputs and the programming connector disconnected.
At the same time, I also underclocked the PICAXE to see the effect on power usage, by poking to the $8F location. Hoping to further reduce the power usage.
All values are in milliamps
<code><pre><font size=2 face='Courier'>
BOD Enabled BOD Disabled
Clock Pause Nap Pause Nap
8 MHz 1.28 0.09 1.16 <0.01
4 MHz 0.74 0.09 0.66 <0.01
2 MHz 0.52 0.09 0.45 <0.01
1 MHz 0.40 0.09 0.32 <0.01
500 kHz 0.34 0.09 0.26 <0.01
250 kHz 0.32 0.09 0.23 <0.01
125 kHz 0.30 0.09 0.22 <0.01
31 kHz 0.12 0.09 0.03 <0.01
</font></pre></code>
Looking at the data, it would seem that underclocking could reduce the power requirements. Except there is the trade off in speed. At 4 MHZ, the PICAXE runs at approximately 2000 steps per second, while at 31 kHz it will run at approximately 16 steps per second, 128 times slower but only at 1/25th the current While the current requirements are less, the longer step time seems to offset any overall power savings. This would have to be confirmed in a real world situtation where actual calculations are performed.
TANSTAAFL!
Myc
Edited by - Admin on 16/07/2006 00:54:38