Power issues with new Kill-a-watt and related material

XBee projects like the adapter, xBee tutorials, tweetawatt/wattcher, etc. from Adafruit

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mabarnett0
 
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Power issues with new Kill-a-watt and related material

Post by mabarnett0 »

It looks like this has been brought up a few times but I was unaware of the issue when I bought my kit. Might I suggest someone put a notice on the Tweet-a-watt product page or in the instructions?

So the issue with the new Kill-a-watt models is that the board will not supply enough current to charge the capacitor to the needed level and when the XBee tries to boot, there is not enough of a charge to power the integrated microcontroller through boot and in to sleep mode so it gets stuck in a reboot loop. As far as I can tell, the newer models are not packaged any differently. My solution was jumping the board off with a 9v battery hooked up to a 5v regulator but it was mentioned that unplugging the XBee for a minute or two will allow the capacitor to charge enough for it to boot. Hopefully you guys can use some of the following info to let customers identify the boards.


Here's a shot of the product label in case anyone would like to compare against a known good model number or serial.
Image


You can see some slight differences between the newer model with the smaller 2902 IC mentioned in the instructions and the non-working model I have. Mainly, missing test points, different through hole component placement and some component orientation. The image from the instructions is first for comparison, mine is second followed by my back of board.
ImageImageImage


The problem stems from the component labeled U5 in the last image. It's a 5v regulator(WS78L05) that maxes out at a whopping 100mA, who knows how much of which is used by the 2902, custom IC and LCD.
Image


Last, just to be thorough, pictures of components on the second board.
ImageImage

adafruit
 
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Re: Power issues with new Kill-a-watt and related material

Post by adafruit »

Some customers have tried extending the sleep period to 5 or 10 seconds with success.

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