heating element: the correct voltage and how to set it up

sir.orange · Post by **sir.orange** » Tue Jun 14, 2011 8:10 am

hello,
I ve been in electronic forums for several months with this topic , unfortunately without much progress. i m looking for the right configuration of my heating element.
At first the components used. the PID controller is from www.pohltechnic.com has a temperature ramp function with 32 presets and on / off function. The controller has two outputs for two mats. operating voltage of the regulator is 230V AC, but it can be wired that the heat elements work low voltage (eg 50v)
the heat mat is a fabric made of glass and carbon filaments each with 7 strings carbon. ordered here: http://www.gerster-techtex.com/content.php?page_id=736 product number 15 043 (. see pdf) price is about 9euros per meter.

following electrical data are given for the heating mat:

Length.U......I........R...............Temp.......P
100cm 45V 3.8A 11.85 Ohm 75 °C 171W

200cm 45V 1.9A 23.7 Ohm 37.5 °C 85W

the voltage was 45v to try with this one. The voltage can be chosen lower or higher.
Analogy from the manufacturer table:
1 ° C = 2.28 W
=> 230W correspond to about 105 ° C (assuming 5°C ambient temperature)

info: 230V Connected directly provides more than 600W -> ca 280°C the weaving filament (polyester) melts ...

a normal busbar in Germany is 230V AC and a fuse against 16A. With these facts, I want to achieve 105 ° C.
to sum up my caculation:
I have 2x 230Watt (is about 100°C) for secure circuit (the pid controller), makes 460 watts power per load circuit, I have 2 load circuits, makes the sum 920Watt total power of both heating tracks.

The whole should be low-voltage operation, optimal would be 74V, since electric current is 3.12 A (6.2 A power per load circuit, a total of 12.4 A -> less than 16A main fuse) and I achieve 230Watt power per mat.

big question:
Which transformer/voltage converter provides me 920W and 74V ??

Or are there other ways the 100 - 105 ° C to reach, with max. 16A ??

and im looking for a material to prevent my cassettes and press being undervoltage during the curing...!?

i d be really happy if someone could help me to finish this. thats annoying me since weeks, as i have just basic knowledge of electronics.

thx for any new ideas

the knit webs soldered to a cu-plate

inside of the controller, with 2 outputs for the electrical load. each one can be loaded with a maximum of 6,3A

OAC · Post by **OAC** » Tue Jun 14, 2011 11:00 am

Good links!
Gerster says that max temp is 180°C, can't you just adjust the voltage to the mat until you reach your temp? I remember "chrismp" had a link to a "high watt" regulator....
But better, write to Gerster and ask....

I will laborate with this later this year...

Good luck!

chrismp · Post by **chrismp** » Tue Jun 14, 2011 11:03 am

don't try to regulate the voltage. transformers are way too expensive! just use a large dimmer instead to regulate the amperage at 230v and limit the maximum wattage that way.

two of these and a watt-meter will do the trick: http://www.shop-electronic.com/product_ ... 600VA.html

OAC · Post by **OAC** » Tue Jun 14, 2011 12:08 pm

There you go! Chris knows this stuff!

sir.orange · Post by **sir.orange** » Tue Jun 14, 2011 12:54 pm

chrismp wrote:don't try to regulate the voltage. transformers are way too expensive! just use a large dimmer instead to regulate the amperage at 230v and limit the maximum wattage that way.

two of these and a watt-meter will do the trick: http://www.shop-electronic.com/product_ ... 600VA.html

chris, seems you re versed in this electronic stuff. so i have to bother you further more.
Could you specify me this? what exactly does the power controller from your link? I have here a link of a power controller too, did you mean this with "watt-meter". do i have to combine these two modules.
http://tinyurl.com/5rqqyub

chrismp · Post by **chrismp** » Tue Jun 14, 2011 1:12 pm

well, instead of trying to regulate the voltage which takes some pretty expensive equipment, you just regulate the ampere. The formula for power output is Watts = Volts x Ampere. So if you're able to lower the ampere with a controller then you lower the power output in watts.
The one conrad is pretty much the same thing as the one i posted. The watt meter (or ampere meter...doesn't matter) is just so you know what wattage you're currently running. for example: http://www.conrad.de/ce/de/product/1253 ... Detail=005

for the power controller you'll need a heatsink (and preferably a small fan) as well.

sir.orange · Post by **sir.orange** » Tue Jun 14, 2011 1:21 pm

ah ok. thanks so far!
so i m going to connect that with an electrician or someone who is more familiar with electricity than me.

any ideas on how to isolate? 230v could really bang... i want to place the mats directly under the aluminum cassettes....

found this company: http://www.heatmanagement.com/de/produk ... silikon,15 but as i received the offer i quit plans.. 4x0,5m would be something like 800euros...

chrismp · Post by **chrismp** » Thu Jun 16, 2011 11:01 am

you could impregnate the heat strips with silicone resin...here's the stuff i used for my heat blankets: http://www.amazon.de/Silikon-Kautschuk- ... B002R5R55Y
takes about 1kg for one blanket.

other possible way would be using heat resistant foil like this vacuum foil: http://www.timeout.de/index.php?page=sh ... =1&lang=en
we used this for our first set of heat blankets, but it's quite delicate.

btw, if you want to communicate in german, just send me a pm

Jibber · Post by **Jibber** » Thu Jun 16, 2011 11:48 am

Is there a minimum order value for this heating mat? Sounds interesting :-)

chrismp wrote:btw, if you want to communicate in german, just send me a pm

Please keep us updated

Cheers, Christoph

chrismp · Post by **chrismp** » Thu Jun 16, 2011 12:41 pm

for the price this is an interesting solution indeed! insulation is crucial though...the tiniest rip could cause a fire (i've had this happen to our first set of heat blankets!). and you're better off not touching your press when you have the blankets plugged in. grounding the cassettes helps too.
still, all diy ventures with high current are risky and you better know what you're doing.

Jibber · Post by **Jibber** » Thu Jun 16, 2011 10:21 pm

I think Plywood posted this once: http://www.swiss-composite.ch/pdf/i-heizformen.pdf Could be interesting at least for the german speaking shapers.

Cheers, Christoph

sir.orange · Post by **sir.orange** » Sat Jun 18, 2011 3:00 am

chrismp wrote:you could impregnate the heat strips with silicone resin...here's the stuff i used for my heat blankets: http://www.amazon.de/Silikon-Kautschuk- ... B002R5R55Y
takes about 1kg for one blanket.
http://www.timeout.de/index.php?page=sh ... =1&lang=en
we used this for our first set of heat blankets, but it's quite delicate.

i think i ll take one of these methods! persoanlly i m for the rtv silicon, it s more resistent especially to be handled near the metal cassettes, sharp edges eg. but im afraid that it could insulate not only electricity but also heat? what are your experiences, how much heat (%) do you have "to sent", and what temperature do you have near the laminate?

chrismp/Jibber wrote:btw, if you want to communicate in german, just send me a pm

... great! sometimes it s really hard to explain in english whats even hard in your mother tonge

Jibber wrote:Is there a minimum order value for this heating mat?

don t think so, i bought 8 meteres, not a very industrial quantity...

chrismp · Post by **chrismp** » Sat Jun 18, 2011 9:24 am

i'd recommend using silicone resin as well. i don't know how much it actually influences the heat transfer, but with the blankets i built with regular resistance wire it produces more than enough heat at 700w per blanket.
the only problem i see with your construction is to make sure that all the carbon strands are covered in silicone when you press it (which i recommend doing for smoothness of the blankets). in my build the resistance wire is sandwiched between to mats of fiberglass that are then covered in silicone resin (you could sandwich your heaters too).

sir.orange · Post by **sir.orange** » Sun Jun 19, 2011 4:04 am

chrismp wrote: the only problem i see with your construction is to make sure that all the carbon strands are covered in silicone when you press it

...that would have been my next question!

i want to keep things as thin as possible.what do you think about my idea:
i ll make two thin layers of silicon, let them cure and sandwich the heating mats "dry". so i can produce a thin layer of silicone (if the curing surface is really flat...) and dont mess up my carbon heating with silicone; can be sperated, deconnected and repaired if necessary

kniklas · Post by **kniklas** » Sun Jul 17, 2011 11:33 pm

Hi,
2 comments regarding the the first post in this thread.

1. It is not possible to link power to a specific temperature. The data from the supplier is only valid for a specific test condition (ambient temp, thermal conduction & convection etc). It is possible to overheat the heating blanket at a very low power setting if the thermal conduction is very low.
2. Regarding power: P=U*I. If you use 230VAC from the mains I think you need to divide Upeak=230VAC with the square root of 2 to get Urms (root mean square)= 162,63V. If using a 2m blanket with a resistance of 23,7Ohm the power will be 1116W and the current I=6,86A.
If you should use 2 blankets in the set up (above and below the ski) you can connect them in series and get a total resistance of 23,7*2Ohm which leads to half the power and current P=558W, I=3,43A.

If you plan to use this info please verify with an electrical engineer...I don't want to cause any accidents.....

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heating element: the correct voltage and how to set it up

heating element: the correct voltage and how to set it up