two PIDs one probe

[mrlard]

does anyone know if this is possible?

i got a few PIDs lying around and fancy using them to control heating and cooling of my conical however i only really want one probe in the conical.

Thing is when i wire them up with one probe the readings go off the scale. obviously because i am messing up the resistance.

any ideas? and no i don't wnat to use an stc1000

 

[miker7301]

does anyone know if this is possible?

i got a few PIDs lying around and fancy using them to control heating and cooling of my conical however i only really want one probe in the conical.

Thing is when i wire them up with one probe the readings go off the scale. obviously because i am messing up the resistance.

any ideas? and no i don't wnat to use an stc1000

Yeah, your wiring 2 PID's to one probe will introduce another resistance to the circuit, I assume your wiring it in parallel, so the 2 wires from the probe go to both PID's (not that it makes a difference, wiring them in series or parallel will not work)

An STC-1000 is the best way of doing this, or as you don't want to use one, then your better off sticking a thermometer in the FV, and applying a heating belt manually.

Sorry, PID's can work, you can set the mode on some to heat things up, and others to cool things down, but each will need it's own probe. or you could use an STC-1000, Mine was £8 from ebay, delivered in under 10 days from HK.

 

[mrlard]

i got STC1000 on everything else - its just i got these PIDs lying around so would like to put them to use.

I been thinking about trying to get one PID to do everything. Maybe se it up to heat and then set the alarm output on the PID to control the other function or visa versa :wha:

the brains not working properly today! THINK!!

 

[miker7301]

Maybe se it up to heat and then set the alarm output on the PID to control the other function or visa versa :wha:

the brains not working properly today! THINK!!

Good luck with the thinking bit! I think I know where your going with your train of thought, but I don't know if it's possible, I can forsee an eventuality whereby you'll have both the heating, and cooling elements on at the same time, which is obviously not what your aiming for.

Perhaps selling one of your unused PID's would be the way forward. Surely someone on here would be interested!

 

[mrlard]

Right i been looking into this and i am pretty sure i can run a single relay PID i have successfully to do both jobs.

The plan is to put the cooling curcuit on the normally closed contact and the heating on the normally open contact. then set it to heating

chuck a 2% dead band in and see what happens


the cooling will be done via a python pump on a maxi chiller and the heating via a trace wire around the conical. hopefully i will be able to put it through auto tune to balance it out a bit.

I will report back

any thoughts anyone?

 

[EskiBrew]

Ensure that you can set the off time for the cooling circuit to something that will not cause the compressor motor problems - they do not liked to be switched on and off frequently. Many controllers have an adjustable minimum interval to prevent this potential damage.

 

[ScottM]

Won't that mean it'll be either heating or cooling constantly with no "off"? Or is there a power relay before the PID relay?

 

[EskiBrew]

Won't that mean it'll be either heating or cooling constantly with no "off"? Or is there a power relay before the PID relay?

Good point - does your PID relay have a both off condition?

 

[mrlard]

Sorry yes it does and I don't need to worry about the compressor as I will only be switching the python pump.

I got it going at the mo works a treat - also down to 1 degree on 60litres with a maxi 110 and a bit of insulation so looks bob on for lagering

 

[EskiBrew]

Ah thanks for clarifying - sounds good then :thumb: