[NSRCA-discussion] Foam cutter power supply

[rcmaster199 at aol.com]

Hmmm.



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



What do you think Eddie?



Matt


 



 






-----Original Message-----

From: Ed Alt <ed_alt at hotmail.com>

To: General pattern discussion <nsrca-discussion at lists.nsrca.org>

Sent: Thu, 21 May 2009 5:40 am

Subject: Re: [NSRCA-discussion] Foam cutter power supply



  
                
Paul:

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.
  
?
  
?
  
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.
  
?
  
Ed
      
----- Original Message ----- 
    
From:     Paul LaChance     
    
To: NSRCA Mailing List 
    
Sent: Thursday, May 21, 2009 4:25   AM
    
Subject: [NSRCA-discussion] Foam cutter     power supply
    



    
Hi all,
    
?
    
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?? 
    
?
    
Thanks in advance,
    
?
    
Paul
    
    
      

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