Need a simple circuit design for heater and power indication....
Need a simple circuit design for heater and power indication....
(OP)
Hi All,
Can someone help me with this?
We need to design a 120VAC circuit to power a 50 deg C PTC disc heater and have two power indicating lamps - one that shows power is ON and the other to show if the heater has failed. I realize power on could just be a neon lamp in parallel across the heater, but how can I indicate when the heater has failed?
Thanks,
Glenn
Can someone help me with this?
We need to design a 120VAC circuit to power a 50 deg C PTC disc heater and have two power indicating lamps - one that shows power is ON and the other to show if the heater has failed. I realize power on could just be a neon lamp in parallel across the heater, but how can I indicate when the heater has failed?
Thanks,
Glenn





RE: Need a simple circuit design for heater and power indication....
RE: Need a simple circuit design for heater and power indication....
I should have explained it better.
We don't need a lamp on with no power - just two lamps: one to show when 120VAC is present and one to show if the PTC heater has failed (and power is still on). When power is off both lamps will be unlit. If heater has failed, the power lamp will be lit and the heater lamp will be off.
Glenn
RE: Need a simple circuit design for heater and power indication....
RE: Need a simple circuit design for heater and power indication....
RE: Need a simple circuit design for heater and power indication....
As opposed to a custom design effort to engineer a PTC failure detection system.
RE: Need a simple circuit design for heater and power indication....
RE: Need a simple circuit design for heater and power indication....
Yes, it's a 120 VAC line.
A digital readout is not desired - client wants just a cheap visual indicator for power on and heater working / passing current. Do PTC heaters usually fail open or shorted? I assumed open.
OperaHouse,
The PTC has 40 ohms @ 25C (360W). Can you steer me to the current transformer with built-in LED's?
RE: Need a simple circuit design for heater and power indication....
Lower currents can be handled by additional turns.
RE: Need a simple circuit design for heater and power indication....
If the OP needs help with this, post details of the PTC heater (e.g. PN, link to data sheet).
RE: Need a simple circuit design for heater and power indication....
RE: Need a simple circuit design for heater and power indication....
RE: Need a simple circuit design for heater and power indication....
It's still an open question what the Imax/Imin ratio is for your heater. I'd call the "application engineer" at Spectrum and ask for this info. He/she might even have some other good ideas.
RE: Need a simple circuit design for heater and power indication....
Hard to tell without any actual indication of failure mode or even typical current curve for normal operating conditions.
Undercurrent / Overcurrent should be all you need. Not the cheapest option by a long shot though.
RE: Need a simple circuit design for heater and power indication....
RE: Need a simple circuit design for heater and power indication....