Current Sensor SCT013 overload

[Tobi993]

Good morning!

I have a SCT013 15A sensor with a build it 53Ohm resistor to check the power of my heat pump.
Sometimes the Current through the clamp goes over 15A.
Could the CT be damaged? It which value? Some experience?

Thank you!
Tobi

[TD-er]

This SCT013 sensor looks like a clamp sensor. So there will be no big currents through the sensor itself.
It is working on induction.
According to this link, the current through the sensor itself is 0.05A when the current through the measured line = 100A.

However, it looks like a AC sensor, so make sure your pump is running on AC, not DC. DC currents can probably not be measured with such a sensor. That would require something with a Hall-effect sensor or a shunt in series with the load.

[papperone]

There are different version of SCT-013 clamp sensor as per below table:


Only tha 100A version output in current, the others (like the 15A mentioned here) output in voltage (range is 0-1V = 0-maxA).
Not sure what will happens with more current (I doubt sensor can be damaged) but you need to have a proper circuit to have proper reading and not just attach it to the ADC pin of ESP8266!!

[TD-er]

Do these sensors output a DC voltage? Or is it AC? (looks AC to me)
If AC, then it will be quite hard to measure directly from a ESP chip.
I guess you would need some external circuit to sample the AC voltage, determine Vrms and let the ESP then read that value from there.

Also a 0..1V signal in AC will probably reach higher levels than 1Vpp.

[Shardan]

These sensors give AC voltage so direct connection to the ESP is not a good idea.

Worse, it is ac voltage - so direct rectifying with a diode won't work properly.
Even schottky diodes have a voltage loss.

You can make it work with a rectifying amplifier (Operational amplifier with diodes)
See wikipedia: https://en.wikipedia.org/wiki/Precision_rectifier

Some filtering behind the rectifier will be necessary.

Regards,
Shardan

[TD-er]

These sensors give AC voltage so direct connection to the ESP is not a good idea.

Worse, it is ac voltage - so direct rectifying with a diode won't work properly.
Even schottky diodes have a voltage loss.

You can make it work with a rectifying amplifier (Operational amplifier with diodes)
See wikipedia: https://en.wikipedia.org/wiki/Precision_rectifier

Some filtering behind the rectifier will be necessary.

Perhaps even better is it to add a capacitor like in the "peak detector" section of that Wikipedia page and a transistor to reset the value.
Then you can perform a measurement.

Only thing is that the measured peak value may not be a good indicator of the actual power used by the device monitored.
Especially with an inductive device like a pump, the peak may be a lot higher.

[papperone]

OpenEnergyMonitor uses those sensors with Arduino --> https://openenergymonitor.org/forum-arc ... e/156.html
Of course you need sampling as Voltage is AC, as well if you plan to use the 100A version is even more tricky as it outputs is current...

[Shardan]

OpenEnergyMonitor uses those sensors with Arduino --> https://openenergymonitor.org/forum-arc ... e/156.html
Of course you need sampling as Voltage is AC, as well if you plan to use the 100A version is even more tricky as it outputs is current...

I've done such a circuit - if it is current it is easier. As it is current the diodes voltage drop is far less important.
I found this circuit a while agon in the net:
.

Stromwandler_Verstaerker.png (3.72 KiB) Viewed 23298 times

.
I ommited the OpAmp and connected the filtered voltage from C2 to a ADS1115.

The voltage depends on the load resistor (R1) and the current the converter coil generates.
Usually you will find the value for R1 in the data sheet of the converter coils.

Regards
Shardan

[Tobi993]

Folks, the current measurement is still running!

Take a look here:

http://www.homautomation.org/2013/09/17 ... d-arduino/
Than I forward the measurement data from Arduino to the ESP by I2C and than via MQTT to my Homeautomation visualisation "iobroker".
It works fine, maybe +/-5% precise, but that is enough for me.

The only question I have is, if an over current could damage the CT. At the moment I have just this 15A version, and I measured already 4500W (at230V)!
30A and 100A pieces are ordered...

Thank you!

[grovkillen]

I found this blog post interesting on this particular topic: https://www.alanpullen.uk/projects/pi-w ... nsor-node/

[Tobi993]

Similar, but I take the EasyESP PME devive to transmit it over MQTT

...and it says nothing about over current.

[Domosapiens]

Could be a little late,
but these give a DC output

Bought here:
https://nl.aliexpress.com/item/YHDC-SCT ... 263.rkS8cu

[papperone]

Nice findings those new "digital" version which outputs 0-5VDC
I guess I will order one for testing...

[grovkillen]

"built in overload protection" thumbs up!

This one is rated for 50A:
https://www.aliexpress.com/item/Free-sh ... f831&tpp=1

[papperone]

yep!
just placed order for 5A, 25A and 50A models

[Domosapiens]

@papperone:
50 Amp? What do you do with that?

[papperone]

@papperone:
50 Amp? What do you do with that?

At home my power meter is abel to provide up to 6.6kW, which divided by 230VAC brings to almost 30A (28.8A) thus the 25A could potentially get saturated...
(yes we have a very big house and in summer time with all airco pumps on we consume a lot of energy

[Domosapiens]

with all airco pumps on we consume a lot of energy

.
Wow! If you need airco, then it is time for some solar panels!

This is how I use the clamp.
A short extension wire, where Lead (brown) is separated from Null and Earth:

20171110_150020_small.jpg (522.82 KiB) Viewed 23516 times

With this cord I have the plan to define the state of my gas heating system (CV in Dutch):
Standby/Pump running/Heating gives 10/70/90Watt.

[TD-er]

@Domosapiens.
Just make sure you don't "reken jezelf rijk" (Dutch for over-estimating things)
The power consumption of a pump is quite hard to measure, since its cos-phi is almost never equal to 1.
In other words, when measuring with a clamp, you have to take the Voltage into account or else you will miss the phase shift and then your estimate will be too high.

[Domosapiens]

@TD-er
Yes I know about cos-phi.
But my application is to define the state of the CV (boiler/heater).
No need for precise Watt reading.

Btw:
Seen your nick-name: are you (former) RNLN?

[TD-er]

@TD-er
[....]
Btw:
Seen your nick-name: are you (former) RNLN?

Nope, had nothing to do with RNLN.
I'm active with the same nick on Tweakers.net

[parbar]

Hi,

I jump in to this thread, hope its ok. I'm also interested of the SCTD 010T as it sounds easy to connect to an arduino as it has 0-5 v output. My goal is to measure the mains to the house, both for fun and also to check distribution of the loads (3-phase system). Then of course some kind of warning when current is high and risk of blowing a fuse.

I have not seen the SCTD 010T until this thread and there are limit info on the internet. Already been playing with the sct 013 (emoncms) but the SCTD 010T seems easier just to plug into an adc port.

Have you guys recived your SCTD 010T (thinking of papperone and Domosapiens) and can give some hands on feedback?

Thanks,
Pär

[Domosapiens]

As you can see in the previous picture, I have the SCTD 010T-5Amp.
It's under test.
I use it to measure the type of activity of my central heating.
Central heating using between 10-100 Watt.
SCTD 010T-5Amp results between 8 and 60mV on the breadbord.
For me there is no need to re-calculate it to Volt*Ampere (VA).
(calculation to "Watt" is not possible, because you don't know the phase relationship between Volt and Ampere)
From the 8-60mV, I can define the state of the central heating (off - pump - burning).
Currently experimenting with a "running average" filter for the 10 second samples: (Vt + Vt-1 + Vt-2)/3 to smooth out some inductive start-peaks

[parbar]

Thanks fro the reply. I think I will make an order soon for the 50 A version. I notice that they have in 5 packs on aliexpress.To bad its not 6 pack then I would have for 2 three phase setups.

[Domosapiens]

You can ask !
Put 5+1 in the shopping card.
Go to payment.
Select other method and stop.
Message the seller and ask to adjust the price of your card.
It did work for me a few times with other shops.

[tchi59]

Hi
I am a little bit lost in that SCT clamp
If i am right there are 2 kinds of SCT
1/ SCT-013-000 Primary AC current: 100A => With current output
2/ SCT-013-005/010/020 Primary AC current: 5A => With voltage output

Let 's explain my project.
I want to use an ESP32 to read AC consumption at home (230V)

questions:

1/ What is the best solution in term of CT Clamp (current or voltage) ?

2/ How to interface CT Clamp with ESP32 micro controller ? do i need a dedicated card ?

3/ What library to use in arduino ide?

Thx in advance
Best Regards

[TD-er]

These are just simple convertors from AC current to DC voltage.
So there's nothing really needed as ESPEasy has support for lots of ADCs.

But why not use something like the PZEM-004Tv30 ?
See: https://espeasy.readthedocs.io/en/lates ... #p102-page