One element, two controls?

[drksky]

Would it be possible to build a controller that has both a PID and a dial-type controller for a heating element and be able to use both without switching outlets?

For example, a 2-vessel system like a BrewEasy where I would want to control the mash with a PID and control the boil with something like Auber's new digital boil controller. Yes, I'm aware that PIDs can be switched to manual mode so maybe this is just a hypothetical.

Could you use two SSRs and a 3-way switch to select which SSR to use but energize the same outlet?

Would you want to?

 

[Bobby_M]

You could use a 2PDT switch to select which SSR is supplying the element, but that's not even necessary. You can run the element line in series through both SSRs. In effect, the boil controller would still set the element's effective wattage while the PID is still doing its thing to reach set temp. When you want to use the system as a boil controller only, all you have to do is set the PID set temp to something like 250F and that SSR would stay on full time. If that PID selected has a manual mode, you could just set it to 100%. While this type of setup is a little more expensive than a PID w/manual + one SSR, you do get much more finite power control and that control can be layered on the PID function as well.

The one application where this is useful is in the case of a RIMS where you want to use a 5500 watt element. Let's say you want to be able to use it to heat your strike water and even provide on demand sparge water. You'd run that in PID mode with power at 100% on the digital boil controller. When it's time to RIMS your mash, you'd set the boil controller to 20% for a gentle, surge free operation.

 

[drksky]

So what I'm thinking about trying first is a "kettle RIMs" similar to a BrewEasy or Brutus and I'm thinking this might be a useful way to do this This way I could, as Bobby says control the output of the BK element (3750w boil coil) so that it doesn't keep over shooting.

I'm really not sure if this is even an issue in a system like this since there's a lot more volume in the kettle than there would be in a RIMs tube, and I haven't really seen much so far on anyone's experiences with a BrewEasy which is really closer to what I'm planning on doing.

 

[Bill_in_VA]

You could even make it simpler than Bobby suggested. One SSR, tie the commons of your PID and PWM on the signal side and use a SPDT to switch which hot on the signal side is triggering the SSR.

 

[Bobby_M]

I thought of that too but I don't know enough about the circuitry in the devices to know if it's OK to apply 5 volts externally on the SSR control outputs.

 

[Deece]

You could even make it simpler than Bobby suggested. One SSR, tie the commons of your PID and PWM on the signal side and use a SPDT to switch which hot on the signal side is triggering the SSR.

I plan on doing this soon. I'm going to use Auber's new boil control rather than PWM. just got the last of the bits and pieces ordered this week.


Sent from my iPhone using Home Brew

 

[drksky]

Going back to Bobby's original answer, to wire two SSRs in series just connect the out of the boil SSR to the in of the PID SSR, right? That way, even if I'm using the PID, the boil controller could control the available power going to the PID SSR and therefore the element.

I like the idea of being able to have the PID control the temperature but being able to adjust the amount of power the PID SSR is getting on the fly.

 

[Brumateur]

Yes two SSRs in series will work. But be aware - they will generate twice more heat. So you will need a bigger heatsink.

 

[drksky]

Yes two SSRs in series will work. But be aware - they will generate twice more heat. So you will need a bigger heatsink.

I'm looking at the Auber 12 X 10 enclosure with the 60A heat sink. Should be enough.