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<DIV><FONT size=2 face=Arial>Paul:<BR>The way a light dimmer works is to chop a
variable percentage of the AC voltage waveform off, so the brighter the light
is, the more full and complete the 60 hz sine wave is that represents the
voltage applied to the load (the bulb). As you reduce the output, it chops off
more and more of the output. It has to work this way, otherwise the dimmer
would be the size of a toaster oven to have enough mass and surface area to
dissipate the heat that would build up in it if all it did was to drop a portion
of the voltage across it. In other words, it is either all the way off for
a period of time (no power dissipated in it at that time), or all the way on
like it was a piece of copper wire (no appreciable power disspated at that
time). Anyway, what you are apparently reading is the what the meter still
"thinks" is the RMS (root mean square) voltage of the sine wave. It
probably is reducing the meter reading somewhat, but not nearly as much as you
might expect.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>The reason this works for heating the nichrome wire
at the right temperature is for the same reason the light bulb would get
dimmer. You are changing the average power delivered to the resistive load
(the nichrome wire), so even though there are still some high voltage peaks, the
average power is managed effectively. I hope this helps.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Ed</FONT></DIV>
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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: black"><B>From:</B>
<A title=plachance@cox.net href="mailto:plachance@cox.net">Paul LaChance</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A
title=nsrca-discussion@lists.nsrca.org
href="mailto:nsrca-discussion@lists.nsrca.org">NSRCA Mailing List</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Thursday, May 21, 2009 4:25
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> [NSRCA-discussion] Foam cutter
power supply</DIV>
<DIV><BR></DIV>
<DIV><FONT size=2 face=Arial>Hi all,</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>I was told about a way to make a power supply for
a foam cutter using 2 dimmer switches. I was also told to measure the
final voltage to get an approximate starting point of 15 volts. I am not
getting a voltage change with the dimmers. I have tested to see that
there is a difference by using a drill to see that it is reducing the
speed. Does anyone know how I can measure to get a starting point or is
it going to be trial and error? </FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Thanks in advance,</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Paul</FONT></DIV>
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