I have an old cello side bending iron, which is heated by a 660 watt ceramic cone heating element. It is essentially, a vertical aluminum tube with the heater inside, mounted to a metal base. The base is about 12" X 6" x 1.75 inches high. After lots of google searching I haven't been able to find a replacement temp controller that would fit within the base. Any ideas of an safe appropriate way to control the heat? The current controller looks something like an open relay, having a movable middle metal piece with one metal piece on each side. Turning the shaft going out to the front panel, moves the middle piece to the front or rear metal pieces. Any thoughts? Tom

 

Super cheap and simple- use a AC lamp dimmer rated for more than 660 Watts

 

Do you need simply to be able to adjust the heat, or else to maintain the temperature at a constant (adjustable) value?

 

There is the Picmicro version of the mechanical/thermal oven control in AN958.
Max.

 

It's called a bimetal thermostat, should be easy to replace.

 

Thank you. I googled those and also saw recommendations for woodworking router speed controllers. A beer brewing site discussed cotrolling heaters with a KYOTTO AC Solid State Relay SSR KR2040AX 280VAC 40A and a 500KΩ B type potentiometer. One thing that I did not mention, is I'd like it to keep a steady temperature. The other issue is whether such a control would be able to withstand the heat, directly below the heating element. Typically, the heat needed to bend hardwoods is 350° to 400°.

 

Do you need simply to be able to adjust the heat, or else to maintain the temperature at a constant (adjustable) value?

Yes - thanks - I forgot to mention that fact.

 

if you really need good heat control, a PID controller is your best bet.

And you wouldn't place the controller under the heating element (unless you use the simple thermostat) you place only the sensor there.

 

It's called a bimetal thermostat, should be easy to replace.

That is it - thank you. Here is the underside of the bender - with the control. The second picture shows flat-head screws going into the bender. They hold a metal bar that extends below the bender. You can see that the control is attached to it. So, maybe it senses the temperature.

If I could ask another question, there is also a panel light, which can be seen on the second picture. I've had this bender for over 30 years. When I replaced the ceramic base for the heater, I did not hook up the light. The main reason was the wire was not in good shape. I cannot recall how it was wired. Would the light be in series with the thermostat? Thanks for any assistance you might be able to give.

View attachment 144586

 

if you really need good heat control, a PID controller is your best bet.

And you wouldn't place the controller under the heating element (unless you use the simple thermostat) you place only the sensor there.

Thanks - I'll google that. One thing in favor of a single box without wires going in and out, other than the ac line, is that the sides are wet when they are being bent.

 

That looks like obsolete Asbestos insulation and a little 'ratty'.
There are modern silicone etc insulation for appliance wiring now.
That appears to have the mechanical thermostat as the previous mentioned App note replaces.
It does not need to be near the element.
Max.

 

The lamp can be wired across the contacts of the thermostat to indicate temp has been reached. (lights when they open) or wired in parallel with the element to indicate power is applied.

But no, not in series.

 

The lamp can be wired across the contacts of the thermostat to indicate temp has been reached. (lights when they open) or wired in parallel with the element to indicate power is applied.

But no, not in series.

Thank you, that is helpful. Tom

 

That looks like obsolete Asbestos insulation and a little 'ratty'.
There are modern silicone etc insulation for appliance wiring now.
That appears to have the mechanical thermostat as the previous mentioned App note replaces.
It does not need to be near the element.
Max.

Thanks - yes I plan on all new wire, except for the base which is pretty new. Tom