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Secrets of the Kill-A-Watt - Self test mode and more (Read 14810 times)
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Posts: 342
Re: Secrets of the Kill-A-Watt - Self test mode and more
Reply #1 - Aug 10th, 2011 at 8:56pm
This guy posted a really good schematic of the KAW:

And made a simple KAW to serial interface that is opto-isolated for safety. It uses a PIC micro to do the serial and source code is included.

And of course, the famous "Tweet-A-Watt" project, which uses a XBee RF transmitter to send the information via wireless. There is also information on sending data to a Google App Engine backend and making graphs with it. The data is serial so you can do almost anything with it.
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« Last Edit: Aug 10th, 2011 at 9:05pm by electron »  

kaw-schematic1.pdf (38 KB | 788 )
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Posts: 342
Secrets of the Kill-A-Watt - Self test mode and more
Aug 10th, 2011 at 6:43pm
I was looking for a reset mode for the KWH reading, like hold down the KWH button for 5 or 10 seconds and it resets the time and KWH readings. Would be better than having to unplug it all the time.

WARNING! Do not try this, I have no idea what these things do and am just guessing. You may "brick" your KAW and make it worthless. You have been warned!

I found this for my model P4400 (the standard one): Hold down the "Volt", "Amp" and "KWH" keys for 3 seconds.

"SEL" appears. (actually a upside down "F" but it means "SELF" for self test mode)

Pressing "Amps" is like menu up, "Watts" is like menu down.
"Hz" is like "set" or "Enter" on a keyboard.
"Volts" exits the mode and lets you try any settings you changed till you power it off again.

The rest here is me guessing what the menu things do, in order....

rAGE - ???
oPEn - ???
V 110 - Volts for the unit is 110V
V 220 - Volts for the unit is 220V
10 1   - ???
1 10   - ???
Blinking every display pixel test
oFF - press "Hz" and you can now use "Amps", "Watts" to make a offset value go up or down. Probably due to part variances in manufacturing, possibly a ADC calibration value for amps or volts.
SAVE - DON'T DO IT!!! It's pretty obvious what this does.

I changed some stuff (on my extra KAW) and after pressing "Volts" it started reading 220V readings for a 110V plug. Interesting. As soon as I powered it down everything was normal again so I think you have to use the "SAVE" feature to make it permanent. BUT DON'T DO IT!

Well, that's it for now. Still no reset mode darn it.

Another little secret is that the KAW senses AC Amps on the Neutral side of the AC. So if you were going to try to sense something using only the hot wire you would have to rig something up so the KAW's input terminals are switched in reverse.

It also means if you have some sort of screwed up ground that is also connected to Neutral from some other place, or Neutral connected to another Neutral from some other place, the KAW will read wrong.

Pictures of some of the test screens are attached.
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kaw-self-test1.jpg (36 KB | 892 )
kaw-self-test2.jpg (32 KB | 867 )
kaw-self-test3.jpg (35 KB | 846 )
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