Kilowatt/hour Meter

<body topmargin=0 leftmargin=0 marginheight=0 marginwidth=0> <table cellpadding=0 cellspacing=0 border=0><tr> <td valign="top" height=90 BGCOLOR="#006699" TEXT="#080000" background="1fcfd5a3.jpg"> <div> <FONT SIZE="5" COLOR="#000000" FACE="Arial" ><B>BIT Company</B></FONT><B>    </B><B> |     </B><A HREF="index.htm" TARGET="_top" TITLE="BIT Company"><U><B>home</B></U></A></div> <div> </div> </td> </tr><tr> <td valign="top" height=390 BGCOLOR="#FFFFCC" TEXT="#080000"> <div> <I>Kilowatt/hour Meter</I></div> <bR> <div> <IMG SRC="202e0080.gif" border=0 width="480" height="8" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"></div> <bR> <div> <B>Unfortunately my camera has gone to the digital dump so there won't be photos for a while.</B></div> <bR> <div> <B>This device was originally designed to provide metering for a separate residence here rather than incurring the minimum $18/month meter reading fee charged by the local power company. Since it is so economical to build, it's also handy to evaluate how much energy is used by appliances, water well pumps (easy way to see how much water is being used), water heaters, computers, televisions, lots of applications.</B></div> <bR> <div> <B>You will need to open the </B><FONT SIZE="3" COLOR="#0000FF" FACE="Arial" ><A HREF="id74.htm" TARGET="_top" TITLE="KWH Processor schematic"><U><B><U>schematic</U></B></U></A></FONT><A HREF="id74.htm" TARGET="_top" TITLE="KWH Processor schematic"><U><B> </B></U></A><B>on a separate screen or print it out for the circuit description.</B></div> <bR> <div> <B>T1 and T2 are the current-sense transformers. If you are only monitoring a 120 volt circuit, you only need one. As the cheapest commercial units ran $30 each, it behooved me to find a substitute. In order to not have to disturb house wiring, a clip-on core was desirable and poking around for something cheap and available, I purchased a pair of Radio Shack 273-104 s</B><B>nap-together toroid</B><FONT SIZE="3" COLOR="#000000" FACE="Arial" > </FONT><B>c</B><B>hoke cores. A little experimentation (no useful data supplied) indicated they would be adequate for the job and at $7.99/pair retail, hard to beat. </B></div> <bR> <div> <B>U1a (upper op-amp) performs as a precision rectifier summing the voltages which are </B><B>proportional</B></div> <div> <B>to the current running through the primaries of T1 and T2. U1b serves as a buffer from the control voltage (upper limit) terminal of multivibrator U2 and provides a virtual ground for U1a.</B></div> <bR> <div> <B>U2 converts the voltage generated by the precision rectifier (100 mV/KW) into a pulse train (4.55 Hz/KW) which is divided by the 14 stage ripple counter U3. The output of U3 drives U4, a one-shot, which advances the good, old-fashioned (and cheap!) Veeder-Root mechanical counter.</B></div> <bR> <div> <B><IMG SRC="27618e00.jpg" border=0 width="280" height="224" ALIGN="BOTTOM" HSPACE="0" VSPACE="0"> </B></div> <div> <B>I get them for 3 bucks apiece plus shipping and they never forget! The counter can be remoted as far from the </B><FONT SIZE="3" COLOR="#0000FF" FACE="Arial" ><A HREF="id75.htm" TARGET="_top" TITLE="KWH Processor layout"><U><B><U>circuit card</U></B></U></A></FONT><B> as you like. Obviously, with the 100mV/KW analog output available, one could include one of the many under $10 digital volt/panel meters as a real-time indicator of consumption. </B></div> <bR> <div> <B>As usual, you must </B><FONT SIZE="3" COLOR="#0000FF" FACE="Arial" ><A HREF="id17.htm" TARGET="_top" TITLE="Contact Us"><U><B><U>e-mail</U></B></U></A></FONT><B> me to get the parts list. Specify what you want, I'm not taking time to automate this. When I used to publish the complete package, within a painfully short time, I would find what I was offering </B><FONT SIZE="3" COLOR="#FF0000" FACE="Arial" ><B>free</B></FONT><B> was being peddled on the web. I promise not to sell your addy to more than 30 overseas spammers!</B></div> <bR> </td> </tr></table></body>