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| BreakingOhmsLaw:
Hi everybody and a happy new year. I'm currently designing a controller for my two drainage pumps that keep my basement turning into an unwanted swimming pool. Both pumps are on their own circuit breaker, and I want to detect if that breaker has triggered. So, I need to detect whether AC is present. Now, there is the classic way of taking a big resistor, or capacitive dropper, and triggering an optocoupler. But that will constantly piss away a couple of mA. Something rubs me the wrong way to waste a couple of kWh per year just to detect if voltage is present. There must be a better way. I do have a current sensor in place that monitors the power consumption of the pumps and checks them against spec to detect a failing or blocked pump. But that only is useful if the pump is running, and that's not always the case. It runs 2-3 times per hour for a couple of minutes at most. So, what's a better and efficient way that doesn't use more than a couple of mW? |
| BreakingOhmsLaw:
Putting something across the breaker probably violates a hundred rules. You can buy breakers with a mechanical interface to a reporting switch like the ABB S2C-H11L, but rebuilding the switchboard is not an option. I have three phases (breaker on each) going into my controller. L1 feeds the controller, L2 feeds Pump 1, L3 feeds pump 2. |
| ajb:
How low is low enough power for you? I think it will be tricky to get much better than a sensitive optocoupler. Maybe use a relay to only enable the ac-referenced measurement circuitry periodically to check if AC is present? Or do similar with a PV-output optocoupler to power some low power/high sensitivity detection circuitry on the AC-referenced side? |
| Benta:
Current transformer. No loss (except a bit in the burden resistor). But what you have on the secondary side is up to you. |
| BreakingOhmsLaw:
--- Quote from: ajb on January 03, 2025, 08:08:31 pm ---Maybe use a relay to only enable the ac-referenced measurement circuitry periodically to check if AC is present? --- End quote --- Not a bad idea actually. Will take that into consideration. |
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