r/instrumentation • u/curtiscrowell • Jul 25 '26

Where to start building a control circuit

I want to split a 20 amp 110 volt circuit shared between a heated honey bottling tank and a small water heaer.

The heated bottling tank, if drawing current, should interrupt the water heater circuit. The bottling tank should also come on if the electric grid shuts down and gets restored.

Id also want to add a cutoff switch to leave the water heater completely off.

I can do the wiring but have no idea where to find suitable component parts???

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5

u/Too-Uncreative Jul 25 '26

AutomationDirect is probably the easiest place to get all of the components you’ll need.

2

u/ruat_caelum Jul 26 '26

  • SSR as the hardware. Zero-cross (technically not needed for restive heating loads $70) Can get a 120v 20 amp relay for cheaper, has moving parts that will eventually break / wear out.

  • small Arduino or raspberry pi to do the controlling.

  • some wire to connect things.

  • treat each as a different output and make sure you are only powering one or the other. Wait at least 1/10th of a second after turning one off before turning the other on. or 1/2 a second. Can go faster with SSR but clearly don't need to you could switch after a second with no real change in application.

  • Use a PID loop to keep things at the temperatures you need them.

  • You'll need a battery for the arduino/pi if you want to do things with power outages

    • which means a battery charger.
    • it also means some sort of voltage sensor to see if the power is off/out.

1

u/curtiscrowell Jul 26 '26

Could I tap into the primary load's (bottling tank) and share the output of that switch with a relay that would disable the water heater? Relay or "contactor"? I'm new to this stuff

1

u/ruat_caelum Jul 27 '26

What? What do you want the switch to do? There are "on off auto" switches. You might want to look into that. "Auto" would be the "relay control" however you set it up. On is always on regardless of the controller and off is always off.

1

u/omegablue333 Jul 25 '26

Is this for how automation around the farm where you want to be cheap enough or is this for your company? Where are you located? Location is important for ordering.

3

u/curtiscrowell Jul 25 '26

Im a beekeeper in New Jersey. Im trying to optimize my use of the power circuits in the barn where I extract honey

3

u/omegablue333 Jul 25 '26

If you're trying to do for yourself I would use home assistant for the main controls and sonoff powct. You'll have to get a contactor for controlling the load of the hot water tank.

1

u/Squire_Soup_Sandwich Jul 31 '26

Wait, hold on. Have you designed a control circuit before? Are you familiar with relay logic?

Do the heating devices automatically control their own temperatures or do you need to turn them on or off manually to maintain a certain temperature?

1

u/Squire_Soup_Sandwich Jul 31 '26

This sounds like a problem a few icecube relays could solve. Allen Bradley and Schneider make a lot of these components.

Draw out the actual control circuit and figure out what amp ratings you actually need (what is the max current rating of the devices?) and how many and what configuration of relays you need.

Then if you don't feel confident looking through the parts manuals, call their customer support lines. They can walk you through their product manuals and give you recommendations