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We are talking about 250-300W of resistive load here so standard
dimmer should do just fine.<br>
<br>
Roman<br>
<br>
<div class="moz-cite-prefix">On 7/8/2013 11:10 AM, Richard Sloan
wrote:<br>
</div>
<blockquote
cite="mid:CADh_Q82PdsUdbNNX_x7pxz2ap0zMQ5GafwLGUOTAbFwxqw2tPQ@mail.gmail.com"
type="cite">
<div dir="ltr">
<div>Just need a high power dimmer as the cheap dimmers are
300-500W<br>
<br>
</div>
Richard.<br>
<br>
</div>
<div class="gmail_extra"><br>
<br>
<div class="gmail_quote">On Sun, Jul 7, 2013 at 3:33 PM, Roman
Gargulak <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:roman@cncwings.com" target="_blank">roman@cncwings.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div text="#000000" bgcolor="#FFFFFF"> Henri,<br>
<br>
The dimmer switch is a crude idea for this kind of
regulation, but it may work, you will need to try it. It
worked for me when I needed to cut 6ft long wing halves on
my cutter.<br>
I would strongly advise against using dimmer switch
directly, without isolation transformer as you will be
dealing with mains voltage and can electrocute yourself.<br>
Your 5V transformer will not work unfortunately with 8ft
of wire, it will not provide not enough voltage to push
required current through.<br>
<br>
1000°C sounds rather high, I think nichrome wire should
not be used above 800°C-900°C. If it is that hot (1000°C)
it may break easily.<br>
You will need close to 50V (that's dangerous level
already), I have a 1:2 step down transformer with a dimmer
switch that you can borrow if you want.<br>
Also, I have plenty of 0.009" stainless steel wire, but I
am not sure if it can sustain that high temperature
without breaking, on top of it, it's resistance is higher
than nichrome (about 10ohms/ft) so you will need really
high voltage to heat up 8 feet of it.<br>
<br>
In my opinion, your best bet is a guitar string (G), maybe
run two in parallel to reduce resistance.<span
class="HOEnZb"><font color="#888888"><br>
<br>
Roman</font></span>
<div>
<div class="h5"><br>
<br>
<br>
<div>On 7/7/2013 12:52 PM, Henri Kuschkowitz wrote:<br>
</div>
<blockquote type="cite"> Hey guys,
<div><br>
</div>
<div>It might be good to clarify what I want/need.
After some more research I think I also have a
better understanding in general of my
requirements. I (will) have various cuts of
acrylic, max 7' long, 1/8" thick that I need to
bend at a straight angle. As such I require evenly
distributed temperature. I similar idea to Roman's
foam cutter is probably to closest example. Just
to be sure, I am trying to have a setup with a max
1000deg C heat wire. The video I posted earlier
seems to do the trick easily if i use 22 gauge
Nichrome wire across 8ft and just a dimmer switch
for 110V and 15Amps (12Amps). I do have access to
a 5V 60Amp transformer, but with my limited skill
set I am worried about breaking it. Could someone
give me some pointers how I would calculate if I
can reach the temperature I am looking for?</div>
<div><br>
</div>
<div>I have used the formula on <a
moz-do-not-send="true"
href="http://www.heatersplus.com/nichrome.html"
target="_blank">this</a> page to get some
details about what I would need for my setup and
am currently looking through some more. I am
trying to see if I can use the "G" string idea
Roman pointed out since Nichrome wire is nowhere
to be found in the area and shipping will take a
bit too long for my taste.</div>
<div><br>
</div>
<div><br>
</div>
<div>Cheers all,</div>
<div>Henri</div>
<div><br>
</div>
<div><br>
</div>
<div><br>
<div>
<div>On 2013-07-04, at 10:36 PM, Roman Gargulak
<<a moz-do-not-send="true"
href="mailto:roman@cncwings.com"
target="_blank">roman@cncwings.com</a>>
wrote:</div>
<br>
<blockquote type="cite">
<div text="#000000" bgcolor="#FFFFFF"> I do
not think that particular PID controller
will work with this application as it is not
meant for fast switching, it is meant for
relatively slow processes.<br>
The wire itself has very little mass so slow
switching will not work as wire will cool
off quickly.<br>
You really do not need closed loop with
feedback for this, the variac is good
solution but maybe a bit overkill, if your
heated wire is only 3-4 feet long.<br>
<br>
On my CNC foam cutter I use 0.009" wire
which has quite high resistance and I need
only about 18-20V to heat it up.<br>
With 20AWG wire (which has over 0.030"
diameter) you will need lower voltage and
higher amperage, which variac will provide,
just be cautious and treat it as mains as
someone wisely pointed out already.<br>
<br>
If you can not find wire, you can always use
steel guitar strings, "e" string is 0.009",
"G" string is 0.016" (talking about guitar G
string here, just to be clear ;-) )<br>
If you can not find variac, you can always
try to use regular step down transformer and
dimmer switch on the primary side.<br>
Or since you will need low voltage, you can
try just regular bench top power supply.<br>
<br>
Roman<br>
<br>
<br>
<br>
<br>
<div>On 7/4/2013 4:25 PM, Michael Grant
wrote:<br>
</div>
<blockquote type="cite">That power supply is
also known as an autotransformer.<br>
<a moz-do-not-send="true"
href="https://en.wikipedia.org/wiki/Autotransformer"
target="_blank">https://en.wikipedia.org/wiki/Autotransformer</a><br>
<br>
Care should be taken with an
autotransformer, while the voltage can be
set low, there is no, none, zero galvanic
isolation.<br>
Meaning the full current of the service is
available (20amps). Treat the output as
you would treat 120VAC direct from a
receptacle...<br>
<br>
I've never seen one in the lab, but they
do have a variable DC supply that is
maybe 3amps and 30v max.<br>
Depending on the load, the heating
element, you might be able to use one of
those twisty things for lights...<br>
Alternatively, an AC thermostat for bang
bang control with hysteria should also
work if you keep the thermal loop tight.<br>
<br>
The last and best option would be a ~$14
PID controller from ebay, that would give
the best thermal regulation. <br>
Sometimes they come in a kit with an SSR
(solid state relay) and a thermocouple for
a little more dough...<br>
Here's one kit for $24...<br>
<a moz-do-not-send="true"
href="http://www.ebay.ca/itm/100-240V-Digital-PID-Temperature-Controller-max-40A-SSR-K-Thermocouple-Probe-/290825156892?pt=LH_DefaultDomain_0&hash=item43b687b91c"
target="_blank">http://www.ebay.ca/itm/100-240V-Digital-PID-Temperature-Controller-max-40A-SSR-K-Thermocouple-Probe-/290825156892?pt=LH_DefaultDomain_0&hash=item43b687b91c</a><br>
<br>
<br>
Michael<br>
--<br>
<a moz-do-not-send="true"
href="http://krazatchu.ca/"
target="_blank">http://krazatchu.ca/</a><br>
<br>
<br>
<div class="gmail_quote">On Thu, Jul 4,
2013 at 4:07 PM, Henri Kuschkowitz <span
dir="ltr"><<a
moz-do-not-send="true"
href="mailto:henri.kuschkowitz@gmail.com"
target="_blank">henri.kuschkowitz@gmail.com</a>></span>
wrote:<br>
<blockquote class="gmail_quote"
style="margin:0 0 0
.8ex;border-left:1px #ccc
solid;padding-left:1ex">
<div style="word-wrap:break-word">So,
I am still getting some more costs
tomorrow, but I think I might go
with this quick/dirty setup: <a
moz-do-not-send="true"
href="http://www.youtube.com/watch?v=wVEf7PfuKxo"
target="_blank">http://www.youtube.com/watch?v=wVEf7PfuKxo</a>
<div> <br>
</div>
<div>What do you guys think? This
leads me to my next question,
would anybody know if the lab has
an item similar to this:
<div>
<div><a moz-do-not-send="true"
href="http://www.temcoindustrialpower.com/products/Variable_Transformers/TVT001.html?utm_source=temcotransformer.com&utm_medium=Banner+Ad&utm_campaign=Variac+TVT001"
target="_blank">http://www.temcoindustrialpower.com/products/Variable_Transformers/TVT001.html?utm_source=temcotransformer.com&utm_medium=Banner%2BAd&utm_campaign=Variac%2BTVT001</a></div>
<div> </div>
<div><br>
</div>
<div>Cheers all,</div>
<div>Henri</div>
<div><br>
</div>
<div>
<div>
<div>On 2013-07-04, at 7:54
AM, Alex <<a
moz-do-not-send="true"
href="mailto:alexbarbour@bell.net"
target="_blank">alexbarbour@bell.net</a>>
wrote:</div>
<br>
<blockquote type="cite">
<div dir="auto"
bgcolor="#ffffff">
<div><font face="Arial">Henri</font></div>
<div> </div>
<div><font face="Arial">Angle
iron is a common
name applied to
steel angles. some
are extruded in the
heavier sections and
have a sharp outside
corner.</font></div>
<div> </div>
<div><font face="Arial">Some
are bent from flat
stock and have a
radiused corner.</font></div>
<div><font face="Arial">These
are better for use
as formers for
plastics.</font></div>
<div> </div>
<div><font face="Arial">Home
depot. Hardware
dept.</font></div>
<div><font face="Arial">CTC
ect.</font></div>
<blockquote
style="BORDER-LEFT:#000000
2px
solid;PADDING-LEFT:5px;PADDING-RIGHT:0px;MARGIN-LEFT:5px;MARGIN-RIGHT:0px"
dir="ltr">
<div style="FONT:10pt
arial">-----
Original Message
----- </div>
<div style="FONT:10pt
arial;BACKGROUND:#e4e4e4"><b>From:</b> <a moz-do-not-send="true"
title="henri.kuschkowitz@gmail.com"
href="mailto:henri.kuschkowitz@gmail.com" target="_blank">Henri
Kuschkowitz</a> </div>
<div style="FONT:10pt
arial"><b>To:</b> <a
moz-do-not-send="true" title="alexbarbour@bell.net"
href="mailto:alexbarbour@bell.net"
target="_blank">Alex</a>
</div>
<div style="FONT:10pt
arial"><b>Sent:</b>
Wednesday, July 03,
2013 9:12 AM</div>
<div style="FONT:10pt
arial"><b>Subject:</b>
Re: [Lab] Plastic
Bending Strips</div>
<div><br>
</div>
<div>Hey Alex,</div>
<div><br>
</div>
<div>I have a very
particular type of
acrylic we are going
to be using that I
doubt comes
'bendable'. Angle
iron? I haven't seen
those before. Got a
reference or
suggestion?</div>
<div><br>
</div>
<div>Cheers,<br>
Henri</div>
<div><br>
On 2013-07-03, at
8:03, Alex <<a
moz-do-not-send="true"
href="mailto:alexbarbour@bell.net" target="_blank">alexbarbour@bell.net</a>>
wrote:<br>
<br>
</div>
<blockquote
type="cite">
<div>
<div><font
face="Arial">On
the other hand
they do
produce an
acrylic sheet
that can be
bent cold .</font></div>
<div><font
face="Arial">Have
done small
pieces by
hand. For
larger OR
thicker ( say
1/8 inch +
)one needs a
former for the
edge. Angle
iron with a
round egde
serves well.</font></div>
<div><font
face="Arial">Alex
B</font></div>
<blockquote
style="BORDER-LEFT:#000000
2px
solid;PADDING-LEFT:5px;PADDING-RIGHT:0px;MARGIN-LEFT:5px;MARGIN-RIGHT:0px">
<div>
<div>
<div
style="FONT:10pt
arial">-----
Original
Message -----
</div>
<div
style="FONT:10pt
arial;BACKGROUND:#e4e4e4"><b>From:</b> <a moz-do-not-send="true"
title="henri.kuschkowitz@gmail.com"
href="mailto:henri.kuschkowitz@gmail.com" target="_blank">Henri
Kuschkowitz</a>
</div>
<div
style="FONT:10pt
arial"><b>To:</b>
<a
moz-do-not-send="true"
title="lab@artengine.ca" href="mailto:lab@artengine.ca" target="_blank">lab</a>
</div>
<div
style="FONT:10pt
arial"><b>Sent:</b>
Tuesday, July
02, 2013 3:09
PM</div>
<div
style="FONT:10pt
arial"><b>Subject:</b>
[Lab] Plastic
Bending Strips</div>
<div><br>
</div>
Hey guys,
<div><br>
</div>
<div>I figured
it's a good
time to start
asking the
collective for
some feedback.
We are planing
on bending
larger sheets
of acrylic
(they will
definitely not
fit into the
laser cutter)
and I am
looking at <a
moz-do-not-send="true"
href="http://www.briskheat.com/p-152-rh-plastic-bending-strip-heater.aspx"
target="_blank">bending strip heaters</a> to build a custom heating
element for
our purposes.
Before I go
ahead ordering
the pieces I
was wondering
if anyone had
ever used such
a thing and/or
knows of a
good local
source? For
saving some
money, I
wonder if
reusing a
baseboard
heater could
do the trick
:P</div>
<div><br>
</div>
<div>Cheers
all,</div>
<div>Henri<span
style="white-space:pre-wrap"> </span></div>
<div><br>
</div>
</div>
</div>
<hr>
<div>
<div><br>
</div>
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