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Bending Blanket Controller?
http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10102&t=14554		 Page 1 of 1
Author:  Brad Way [ Fri Nov 16, 2007 11:28 am ]
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I am curious what everyone is using to control the temps of their bending blankets? A few months ago I thought someone did a really great job with a temp. controller hooked up to a thermocouple and relay to control the temp. Anyone remember where this post is? (I could not locate it).
Author:  LanceK [ Fri Nov 16, 2007 11:34 am ]
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Hi Brad, I just plug it in and unplug it in intervals. I use a digital Thermometer to monitor the temp.
Author:  Heath Blair [ Fri Nov 16, 2007 11:57 am ]
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i use the router speed controller that john hall of blues creek sends with his heating blanket.


 
Author:  FishtownMike [ Fri Nov 16, 2007 11:57 am ]
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John at Bluescreek guitar sells a controller very cheap i have one for my bender that he made. Works great.
Author:  Heath Blair [ Fri Nov 16, 2007 11:58 am ]
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in fact, here it is at harbor freight. i think its the exact same one.


http://search.harborfreight.com/cpisearch/web/search.do?catP ath=All%2BProducts%252F%252F%252F%252FUserSearch%253Dvariabl e%2Bspeed&currentPage=1&lastPage=10&isNext=true& amp;isPrevious=false&category=&attributeValue=&a ttributeName=&requestedPage=1

Author:  Brad Way [ Fri Nov 16, 2007 2:17 pm ]
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I have router speed control but I am thinking about going to a 2 blanket setup which will push the watts over the capacity of the controller. I guess I could use 2 but was thinking there was a better way.
Author:  Bruce Dickey [ Fri Nov 16, 2007 2:48 pm ]
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You can buy a 1000 Watt 110V. Commercial Dimmer at your local home improv store. The standard ones are just 660 Watts and under-rated.

I wired my single blanket up with a simple male plug. I wired my 1000 Watt dimmer to a duplex receptacle. That allows me to power up full starting out, then power back to about 70 to 80 percent for the balance of the time.

I started like Lance, just plug and unplug, but graduated to a dimmer and found it convenient. Nothing like pulling out a nice set of sides and witnessing you've turned it to toast, hence, control is good.

Also, bend in a breeze-free environment. Ceiling fans and air conditioners are banned during bends at my shop! And good luck bending....
Author:  Bruce Dickey [ Fri Nov 16, 2007 3:02 pm ]
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Brock posted his double bending blanket setup a while back. Here he has a timer, powering up a dimmer, wired to a duplex receptacle, one set for each blanket.

Pretty cool, and the timer gives you that little comfort that you'll not burn your shop down, or house, if you get called away during bending.

Yep, it's happened, but I'm not telling you who it was......
Author:  douglas ingram [ Fri Nov 16, 2007 3:23 pm ]
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Any recommendations for the thermometer?

This is all very timely, my heating blanket arrive today!
Author:  Bruce Dickey [ Fri Nov 16, 2007 3:32 pm ]
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WalMart cooking utensil section. Digital, goes to 400F, costs about 12 bucks.
Author:  tippie53 [ Fri Nov 16, 2007 11:38 pm ]
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    Be careful of the light dimmer. The difference between the router speed control ( VSI ) switch and the light dimmer ( Variable Resistor or Rheostat ).
   VSI works by pulsing voltage. This gives the blanket full voltage but in pulses as though you are turning on and off a switch.
     Variable resistors and Rheostats work with a variation in resistance thus lowering the voltage without lowering the current ( Series circuit ). This can cause early burnout of the heating element.
john hall
Author:  Bruce Dickey [ Sat Nov 17, 2007 8:18 am ]
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Hmmmm, John, never heard this before.

The 1000 Watt Dimmer is rated to handle the blanket (875 watts @ 110 volts) all day long. The dimmer is set into an aluminum heat sink and is safe for residential wiring with the appropriate load.

Actually it's the dimmer that gets warm bleeding off power to the blanket, making it actually last longer. Your comments just kind of caught me by surprise.

Maybe we can have a burn-off one day, your blanket and router speed control against my blanket and 1000 watt rated dimmer!   

Time to get my continuing Ed Hours for my Masters License, 2007 is drawing to a close.....   
Author:  tippie53 [ Sat Nov 17, 2007 2:08 pm ]
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    Your dimmer will work. The difference is the way the current is diverted. lowering voltage still doesn't decrease current ( Ohms Law to a series circuit ) . The dimmer will have a heat sink to dissipate the heat as you are still using the 1000 watts .
    This is more an efficiency issue of the circuit. In a VSI switch the voltage is pulsed and there is a time when no current is flowing thus the circuit is more efficient. The wattage handing on the dimmer can handle the load but over time the blanket will fail from the dimmer.
   I tried many different control systems until I found this set up. I agree if you bend 2-3 sets a year it is pretty much a moot argument. In my case , I bend every day and often I am bending 6 to 10 sets a week.
   I get about 4 years per blanket. I am on my 2nd blanket . My first one was a 32 inch blanket and I donated that one to a needy student 3 years ago. My current blanket is going strong but showing wear. The heating element is fine , the cord is what is degrading at this point as the power cord is out the side and not the end . Cost wise there isn't that much difference.
     Another great use is as a coffee warmer during bending , nothing but the best in my shop LOL
john
Author:  Bruce Dickey [ Sat Nov 17, 2007 3:44 pm ]
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John, you are contradicting yourself.

"Your dimmer will work. (Be careful of the light dimmer.)" Which is it?

The next comment is unsubstantiated, just wondering where you came up with this?

"This can cause early burnout of the heating element."

It's never burned out any of my heating blankets.

Both the blankets and the dimmers are a match electrically and loadwise and must meet UL listing requirements to be sold in the USA.

I suggest that both the speed controller for a router and the light dimmer will work well and meet UL listing requirements. I don't think either will cause premature failure of a device it is intended to operate.






Author:  D.L.Huskey [ Sat Nov 17, 2007 5:17 pm ]
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The older or cheaper dimmer switches used variable resistors to lower the voltage to the load.

The newer switches use an internal circuit to simply chop up the voltage or turn it on and off at a variable rate.

Even at half throttle, the newer dimmer switch output voltage will still be 115 volts, but in pulses at about 120 times a second.

I've never checked one of the Harbor Freight Router speed controllers. Although they are a lot cheaper than a Levitron Dimmer.

Like Bruce I use a 1000 watt dimmer with my blankets, non variable routers and such, and haven't any problems with any of them.
Author:  tippie53 [ Sun Nov 18, 2007 4:20 am ]
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    It seems that if the dimmer you have has the circuit you are using the same thing. The variable resistor type is the one I am concerned about.
     The new design is just what you need. As for where I came up with this , I went to school for electronics in the 70's.
   You are correct as for load requirements. A variable resistor or any resistor just lowers the voltage but current remains the same in a series circuit. The vsi circuit pulses the full voltage and is more efficient and doesn't create excess heat.
   
Author:  JohnAbercrombie [ Sun Nov 18, 2007 8:17 am ]
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Any household-type dimmer you can buy nowadays is the 'pulsed' type- not a simple rheostat. The pulsing radiates RF like crazy and will cause no end of problems if you have radio as one of your hobbies. If you have an old Walkman radio, put it on AM and take a walk around the house. I removed a bunch of dimmers to get the RF noise down.

Whatever you use as your 'dimmer', I second the recommendation for a timer in the circuit- it just makes everything easier and safer.

Cheers
John
Author:  Bruce Dickey [ Sun Nov 18, 2007 9:54 am ]
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John, I was using some timers and they would not shut off. They came from a quality electrical supplier and was a known name brand. I quickly returned both and just want to caution folks to test them properly before depending on the timer for shut-off backup.

Brocks above is how I wired mine except he added a second switch to the timer, a single pole. That is redundancy, but it's cheap redundancy.

The timer shuts off, the single pole switch gets switched off, and you unplug it. Heck, that should do it.
Author:  tippie53 [ Sun Nov 18, 2007 10:57 am ]
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I agree you want to be safe. It is good advice to double check your safety devices on a regular basis. A new controller is cheaper than a new shop.
john
Author:  JohnAbercrombie [ Sun Nov 18, 2007 12:45 pm ]
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[QUOTE=Bruce Dickey] John, I was using some timers and they would not shut off. They came from a quality electrical supplier and was a known name brand. [/QUOTE]

Bruce-
Thanks for the warning- I'm not sure which 'John' you were addressing, but I appreciate it anyway.
Were the bad timers the 'digital' type or the old 'wind-up' style?
I use the 'wind-up' type, and I'm usually around the shop to hear the loud 'click' as it shuts off. I don't think I'd leave a heater unattended- I'm quite paranoid, especially when I look across the shop and see the alcohol, lacquer thinner, etc nearby.

Cheers
John
Author:  Bruce Dickey [ Sun Nov 18, 2007 3:24 pm ]
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Yes, the wind up type timers would run down, but not click off, as you mention. A manufacturing defect for certain. The only reason you need the timer is to shut the circuit off.

I'm with you, when bending, it's not a time to take phone calls or be otherwise distracted.
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