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How to check if circuit is powered?

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ggv

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Hi,
I need to know whether some circuit is activated (drawing power). I.e. I have a water pump out there in the field and I need visual evidence in my house to see when it is on. Of course I can use DPST relay using one pair of terminals to connect an LED, another - to power the pump 220V circuit. But is there a more simple solution to get the LED on using the same 220V circuit?
 
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optoisolator to feedback voltage Vsat?
 
A current transformer (CT), diode, resistor and LED circuit. A ct like this: **broken link removed**

What HP is the pump? Or, what is the current (I) listed on the motor? That will determine the proper CT to use.

I'll post an example schematic shortly.
220VAC CT.JPG
 
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Thanks cowboybob. Is transformer really necessary? Can the schematics be just connected in parallel to the pump's circuit?
 
Thanks cowboybob. Is transformer really necessary? Can the schematics be just connected in parallel to the pump's circuit?
Yes. But I wouldn't recommend it. All that tells you is that the pump is powered, not the the pump to actually pumping, i.e., drawing current.
 
This ckt will do as you ask, i.e., transformerless (although only indicating power to pump is ON).

The circuit posted previously did not work. My apologies - I got it off another site and when simmed, it failed. See below.
But, again, dangerous voltage levels are present with the circuit.
 
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OK, thanks. What would be the value of the resistor? According to my basic understanding of Ohm's law is it 1.1 kom given that LED current is 20 mA ?
 
BTW, Welcomw to ETO, ggv!

I removed the first schematic. See above.

New circuit (this simmed just fine):
upload_2015-3-1_17-8-48.png

NOTE: R1 & R2 should be 1W resistors.
In this circuit, LED current is about 5.7mA. R3 and R4 can be adjusted to suit the needs of the LED you choose to use.

And I repeat: This circuit poses a severe electrical shock hazard!! Take all appropriate safety measures.
 
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View attachment 91107
NOTE: R1 & R2 should be 1W resistors.
In this circuit, LED current is about 5.7mA. R3 and R4 can be adjusted to suit the needs of the LED you choose to use.

........................
R3 and R4 are in series and can be replaced by one resistor.
 
From the same company that Bob mentioned earlier. I used these for heating elements and they work great for heating elements, pumps and just about anything drawing between 3/4 amp and up. Non intrusive, no problem and they cost about $11.50 USD each.

https://www.crmagnetics.com/Products/CR2550-P13.aspx

There is also this variation:

https://www.crmagnetics.com/Products/CR45-P76.aspx

While none of this stuff will tell you is a pump is running dry or not pumping water they will tell you if the pump is drawing current. CR Magnetics is just an example of a single company, there are others likely making the same thing.**broken link removed**.

Ron
 
The simplest, easiest, cheapest method of lighting a LED when 240Vac is present in a circuit I have found is to buy one of these at the local thrift shop:

41ZLGarB%2BkL._SY300_.jpg


I can buy all I could ever use at my local Habitat for Humanity store for $0.25 ea... They have boxes with hundreds of them. You may even have one in the junk box left over from some old cell phone.

I like the ones that make 4 to 6Vdc. Cut off the plug, and wire it to a LED and resistor...

The input side of these will take 100V to 250V, 50 or 60Hz. The output side is isolated from the input side by the internal transformer.
 
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The simplest, easiest, cheapest method of lighting a LED when 240Vac is present in a circuit I have found is to buy one of these at the local thrift shop:
OK, but how do I connect this to the motor circuit? Through a relay?
 
OK, but how do I connect this to the motor circuit? Through a relay?
You connect it in parallel with the power going to the motor.
 
Hi,
I need to know whether some circuit is activated (drawing power). I.e. I have a water pump out there in the field and I need visual evidence in my house to see when it is on. Of course I can use DPST relay using one pair of terminals to connect an LED, another - to power the pump 220V circuit. But is there a more simple solution to get the LED on using the same 220V circuit?

You need to be a little more specific about what you are trying to achieve here, otherwise it's all guesswork. Do you need to know if the pump is actually pumping or just has power going to it, or are your requirements something else altogether?

If you need to know if the pump is actually pumping, a small pressure switch on the output of the pump that triggers a short duration timer type arrangement would probably be effective. In the case of just knowing if power is going to the pump, why not just fit a simple and effective Neon Indicator to the supply going to it. For the something else altogether, I'll need my crystal ball ;)
 
I needed a remote low-voltage LED indicator to let me know when my 240V 2HP well-pump is running. I wired the cell phone charger in post #13 across the 240V line going down the well (inside the pump control box). I used two 1A fuses between each prong of the charger and L1 and L2.

If the pump quits working, I will know that soon enough because my water pressure drops. I am more interested in remotely monitoring the pump run times. For example, I can tell that my irrigation system is watering...

The isolated 5V side of the charger goes to ~500 feet of low-voltage twisted pair to the remote LED. I put 220Ω in series with both the +5V and 0V output of the cell phone charger. That way, the current to the LED is limited, and if a short where to develop in the 500ft cable, the cell phone charger is isolated from the short by the two resistors.
 
Is rectifier bridge really necessary? Do you think LED will flicker if it takes every second AC pulse ?
The bridge is used to isolate, as much as possible, the 220VAC from the LED side of the circuit. A single diode does not isolate the 220VAC at all.

However, I found this device (https://www.automationdirect.com/ad...nge_AC_Current_Operated_Switches/ACSN100-AE-F) (USD$28.00).

A simple switching device that detects the current flow (as little as 500mA) of any one wire feeding the pump (the wire would be routed through the hole in the device). Connect the device's two output wires in series with a battery/resistor/LED circuit and you'll have proof-positive that the pump motor is operating. And the circuit would completely isolated from the motor's 220VAC (look at an example at the bottom of page 4 of the link: https://www.automationdirect.com/static/specs/acuampacsn100.pdf).
 
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