Drive heat tape with variable voltage

[jon_mcbee]

I am looking to wrap some copper pipe with heat tape and drive the heat tape by either varying the voltage or current based on a temperature reading taken from the pipe.  I am hoping someone here has done this before and can recommend heat tape that can be driven in this manner, with a programmable power supply driven by LabVIEW.  I have done a little looking but am only finding heat tape that is either on or off, but it seems like what I am looking for shoulod exist.  Any thoughts or suggestions are welcome.

[biozen]

With a variable voltage power supply you could very well implement PID control.

We do something similar in one of our temperature-control products but do on-off PWM for PID control. The tape is switched by an SSR, and depending on the PID calculations the on-off times vary. Duty cycle is about 2 seconds.

Hope this help,

Mohit Mahajan.

www.BioZen.co.in

Starting with LabVIEW

[AnalogKid2DigitalMan]

I have used HTS/Amptek  (www.heatingtapes.com) in applications in conjuction with a manual variable supply from Payne Engineering. The supply basically takes the 120VAC sine wave and chops it (like a light dimmer) akin to PWM. One caution in the tape manual is to use heavy insulated or silicone rubber tapes for applications that involve metal or conductive surfaces.

As mentioned above, use a counter/timer scheme for a variable PWM. If using tapes that run on the AC mains, use an isolated solid state relay to pass power to the tape.

Hope this helps

-AK2DM