Serial port for Kill A Watt - Tweet A Watt compatible
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Re: Serial port for Kill A Watt - Tweet A Watt compatible

by kshyamchandar on Tue Aug 10, 2010 6:28 pm

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Re: Serial port for Kill A Watt - Tweet A Watt compatible

by oPossum on Wed Aug 11, 2010 9:04 pm

ADC conversion time is 2 microseconds.

There are two samples (voltage and current) taken every 984 microseconds.

Timer2 is configured to increment every 8 microseconds, and the Timer2 preset is 123.
So, the Timer2 interrupt flag will be set every 8 * 123 = 984 microseconds.
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Re: Serial port for Kill A Watt - Tweet A Watt compatible

by kshyamchandar on Wed Aug 11, 2010 10:15 pm

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Re: Serial port for Kill A Watt - Tweet A Watt compatible

by kshyamchandar on Mon Sep 06, 2010 2:04 pm

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Re: Serial port for Kill A Watt - Tweet A Watt compatible

by oPossum on Mon Sep 06, 2010 2:11 pm

It is logic level serial, so a USB to logic level (3.3V or 5V) serial cable like this is required. Do not use a USB to RS-232 cable.
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Re: Serial port for Kill A Watt - Tweet A Watt compatible

by wukongnyc on Mon Jul 30, 2012 9:47 am

I am trying to make Xbee based Tweek A Watt and brought all the components needed. I have the same issue that Kill A Watt device that I brought recently (2012) has different board than the original instruction, it seems event different than the one in this thread, but it seems that originator of this thread suggest using optisolator that will make the solution independent of varieties of board. I am new to electronic components/circuits. My questions are:

1) what is optisolator? what are the key functions of it?
2) where I can get one to build the solution as suggested here? are there different types of optisolator?
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Re: Serial port for Kill A Watt - Tweet A Watt compatible

by adafruit_support_rick on Mon Jul 30, 2012 11:22 am

An optoisolator essentially uses LEDs to transmit signals from one electrical circuit to another, such that the two electrical circuits are isolated from each other.

The OP was using this optoisolator device:
http://www.fairchildsemi.com/ds/6N/6N138.pdf

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Re: Serial port for Kill A Watt - Tweet A Watt compatible

by satu1991 on Tue Oct 16, 2012 3:04 pm

For the serial cable, do we have to connect Tx to serial data & Gnd to Ground.
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