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<DIV><FONT size=2 face=Arial>Matt:</FONT></DIV>
<DIV><FONT size=2 face=Arial>That might work, although I don't know if you would
be getting much out of the light bulb at the current levels that would heat a
nichrome wire. It might be easier to just start with one turned up about
half way (the fine tune dimmer) and the course control turned all the
way down, then gradually turn up the course control dimmer until the wire is hot
enough to melt some foam. Mark that setting, then try the fine adjust to
see if it gives the needed span of control. If not, bump the course
control up a little and repeat the initial calibration. Never tried it
myself, but that ought to work. Another way is to get a step down
transformer and place that on the output of just one dimmer control. The
secondary winding is then at a lower and safer voltage and you can do the fine
tuning with just one control. I have a setup that works this way that I have
used for small stuff, but it could be done with larger setups too.</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial>Ed</FONT></DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV><FONT size=2 face=Arial></FONT> </DIV>
<DIV>----- Original Message ----- </DIV>
<BLOCKQUOTE
style="BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px">
<DIV
style="FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: black"><B>From:</B>
<A title=rcmaster199@aol.com
href="mailto:rcmaster199@aol.com">rcmaster199@aol.com</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-discussion@lists.nsrca.org</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Thursday, May 21, 2009 11:22
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: [NSRCA-discussion] Foam
cutter power supply</DIV>
<DIV><BR></DIV>Hmmm.<BR><BR>It may work really well if the light (low watts)
was in series with the NiCr wire. He might get a visual cue as to where to
turn the dimmer<BR><BR>What do you think Eddie?<BR><BR>Matt<BR>
<DIV><BR></DIV>
<DIV><BR></DIV>
<DIV><BR></DIV>-----Original Message-----<BR>From: Ed Alt <<A
href="mailto:ed_alt@hotmail.com">ed_alt@hotmail.com</A>><BR>To: General
pattern discussion <<A
href="mailto:nsrca-discussion@lists.nsrca.org">nsrca-discussion@lists.nsrca.org</A>><BR>Sent:
Thu, 21 May 2009 5:40 am<BR>Subject: Re: [NSRCA-discussion] Foam cutter power
supply<BR><BR>
<DIV id=AOLMsgPart_3_415f6040-1a37-4132-9287-2d74e5a30e12>
<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>
<BLOCKQUOTE
style="BORDER-LEFT: rgb(0,0,0) 2px solid; PADDING-LEFT: 5px; PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px">
<DIV
style="FONT: 10pt arial; font-size-adjust: none; font-stretch: normal; -x-system-font: none">-----
Original Message ----- </DIV>
<DIV
style="FONT: 10pt arial; BACKGROUND: rgb(228,228,228); font-size-adjust: none; font-stretch: normal; -x-system-font: none; -moz-background-clip: -moz-initial; -moz-background-origin: -moz-initial; -moz-background-inline-policy: -moz-initial"><B>From:</B>
<A title=plachance@cox.net href="mailto:plachance@cox.net">Paul LaChance</A>
</DIV>
<DIV
style="FONT: 10pt arial; font-size-adjust: none; font-stretch: normal; -x-system-font: none"><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; font-size-adjust: none; font-stretch: normal; -x-system-font: none"><B>Sent:</B>
Thursday, May 21, 2009 4:25 AM</DIV>
<DIV
style="FONT: 10pt arial; font-size-adjust: none; font-stretch: normal; -x-system-font: none"><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>
<DIV></DIV>
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