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alternating relay circuit

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New Member
we have two h2o pumps that are controlled by an alternating relay to share their run time. Problem is that if we are away and one of the motors goes out on overload the relay will latch onto that pump and not cycle to the other pump. Any ideas on how to draw a circuit that will sense the load, so that the relay knows that the pump it cycled to ok to go??? Ihave looked for a "smart relay" that can sense if there is a load but no luck .Thanks


Active Member
Put a small resistor in series with the pumps (with small i mean low resistance, 0.1 ohm or lower .. depending on how much current these pumps use; but it must be a powerfull resistor capable of dissipating the power).

When a pump is activated, the current it draws will create a small voltage drop over the resistor, this can be measured and used as a feedback to the control part...

When no voltage drops over the resistor you know there is no load
When too much voltage drops over the resistor you know there is an overload...

Of course; if those pumps are really powerfull (talking industrial over here) the resistors you must use will cost quite a lot, an take up quite some space
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