Small PID regulator for temperature control
Small PID regulator for temperature control
(OP)
I am trying to put together a compact temperature control instrument to be placed inside a small chamber. For this I would like to buy a PID regulator, preferably with a sensor (Pt100) input and a relay output to switch a battery on/off. The difficult part is that I only have a volume of about one cubic inch (15 cubic centimeters) available. I would prefer to buy something as complete as possible so I can get going as fast as possible.
Does anyone know where I can buy compact PID regulators for temperature control?
Does anyone know where I can buy compact PID regulators for temperature control?





RE: Small PID regulator for temperature control
Felix
RE: Small PID regulator for temperature control
it may not be enough for the power stage.
Can you give some specs?
<nbucska@pcperipherals DOT com> subj: eng-tips
read FAQ240-1032
RE: Small PID regulator for temperature control
Best Regards,
John Solar
RE: Small PID regulator for temperature control
Can't you just put the thermocouple in the controlled environment - "chamber"? What are you controlling? As mentioned, PID might not be for you.
RE: Small PID regulator for temperature control
RE: Small PID regulator for temperature control
RE: Small PID regulator for temperature control
RE: Small PID regulator for temperature control
You have a box.. A heater run thru a PTC that is residing in the box..
You throw the switch.
The box heats up.
The "PTC fuse" trips eventually at say 90C. It stays tripped down to 20C??
Kinda too much hysteresis maybe?
Not that special PTC couldn't do the job. Raychem makes heater ribbon that is PTC material in a matrix. The ribbon heats up to it's design temp and no more since the matrix expands and the resistance climbs.
You could probably put this stuff in an insulated inclosure that would then stay at some fixed delta from the outside environment.
RE: Small PID regulator for temperature control
RE: Small PID regulator for temperature control
www.eetasia.com/ARTICLES/ 2005MAR/B/2005MAR01_CTRLD_TA01.pdf
RE: Small PID regulator for temperature control
RE: Small PID regulator for temperature control
I have used PTCs many times... They're in at least four products I've designed. Generally they are a major pain in the butt to use. They are so sensitive to ambient that half the time your product will fry b4 they trip and at low temps the PTC will trip prematurely!!
I hunted down the specific pdf you mentioned which catagoriclly stated that "the power must be removed" to reset them.
I have included the relavent passages below;
"When the fault is cleared {(and power is removed)}, the system begins normal operation with no service or part replacement necessary."
"{Once the power is removed} and the fault is cleared, the
temperature of the PolySwitch device drops below its trip
temperature, allowing it to reset to its low resistance state which enables the circuit to operate normally."
But all this a-side, these suckers aren't temperature specified! They are CURRENT specified at some ambient. This means you'd have to jam specific amounts of current thru the PTC to get it to trip *near* some specific ambient.
Furthermore PTCs drift *A LOT* 5% in 1000Hrs. So your temp setting would change over time. Rather quickly!
If you don't really care about the temperature as in water pipe anti-freezing heat tracing, where the pipe must remain above 32F, then poly type temp control will work fine as no one cares about drifting from 40F down to 38F.
This all a mute point anyway as this poster was an obvious *PAR* {Post And Run}
RE: Small PID regulator for temperature control