I am new to the forums, but not new to Arduino. I am trying to build a system where I use an SCT013 20A sensor to determine how often a sump pump is turning on. I followed this tutorial:
(Youtube - Measuring AC Current with Arduino)
I do not care about the current it's drawing - I simply need to know how long it runs and how much time there is between cycles. The pump uses about 6 to 8 Amps when it's on.
After a lot of troubleshooting, I think there is something wrong with my SCT013 sensor itself and not with my Arduino circuit or code. I've read and researched and Googled and searched the forums, and basically I'm just trying to determine if I got a "bad" SCT013 sensor. So, taking the Arduino out of the picture entirely, I decided to try testing JUST the SCT013 sensor. Based on everything I've read, this should be fairly simple. Take the SCT013 and snap it onto the power cord for an appliance that draws a lot of current, then use a multimeter to test the AC output from the sensor pins.
For testing purposes, I put the blue transformer loop of the SCT013 around the AC power cable of a 1500W household space heater. I test the Volts AC across the output pins of the SCT013 with my trusty Sperry Multimeter (AC voltage resolution 0.005V). With the heater OFF, I read 0.000V AC on the output pins. With the heater ON and blasting at maximum output, I still read 0.000V AC on the output pins. I have tried comparing each of the 3 output pins of the 3.5mm "headphone jack" connector to each other individually in every possible order. I read 0.000V AC regardless the pins tested. I thought, maybe the output is DC volts? Nope. Still 0.000V regardless the pins tested and whether the heater is on or off.
I thought perhaps I had one of the current-output SCT013 models rather than the voltage-output SCT013 model sensors. Doing a current test with the multimeter also results in a 0.000 A current detected, regardless the pins in contact with the meter, and regardless if the heater is on or off.
Do I have a defective SCT013 sensor, or am I doing something wrong testing it? I thought testing it would be as simple as connecting a voltmeter to the two pins, switching the meter to Volts AC detection mode, and putting the transformer loop onto a cord drawing a lot of current. What am I missing? Thank you in advance for your help.
The split core needs to go around just one wire going to your AC heater. If it goes around both the hot and neutral, the current going each direction will cancel out.
They sell line splitters to separate one side from the other:
I just tested with some spare Romex cable and the space heater (for about 10 seconds) and it reads 0.65V AC across the output pins on the multimeter when the blue clip is only around the hot wire and the heater is on (neutral kept separate). It reads 0.000V AC in the same position with the heater off, so it is detecting current properly and putting out an appropriate proportional voltage.
Since you have a 20A CT and your pump uses 6-8A, you could convert this to operate as a 10A CT and double the output voltage just by using 2 loops (turns) through the hole. Just count the loops through the hole, not around outside of the CT.
Good idea! I'm using a cord that is too short to double the wire through it - it's an 8 inch long extension cord that I stripped the insulation off. If I go with a longer cord in the future, I'll double loop it. I may step down to the 10A sensor.
I live in a very wet area. The spring thaw causes my sump pump to run every 2-3 minutes for about 6 weeks straight. Now the current draw from the sump pump is being detected properly, and the code stores the 200 most recent times between pump operation in a matrix. It then cycles through displaying the most recent cycle time, the average of the most recent 10 times, 50 times, 100 times, and 200 times on an LCD1602 display, followed by a status display. It gives me an idea of whether the pump is operating more or less frequently. I have a small Wyze camera pointed at it and at a transparent sump pump check valve, so I can see everything remotely. All connected to a UPS. I'll post pictures when I have them.
Thank you for all of your help. I hope to solder all of this to a project board soon since it is still on a breadboard with finicky wires and connections held together with alligator clips.
Correct, just the outer insulation sheath of the extension cord, that encloses the white, black, and green-sheathed wires, has been removed - and only about two inches of the sheath - enough to get the clamp around the black (hot) wire. No bare copper exposed. All live 120V wires are still fully insulated.
