EmonTx Shield + SCT013-030

Hardware
1

I bought the emontx-shield and soldered as needed (very hard for beginner I found). Using with SCT013-030
According to GitHub - openenergymonitor/emontx-shield: emonTx Arduino Shield I should remove the 33ohm resister for ct1, I could not remove it. Would soldering a path between 33ohm pins be enough to sidestep it and work?
Or using piece of wire soldered onto the holes on either side of the 33ohm resister, would that work?

2

With it I’m trying to use this code:

Changing the voltage calib to:
ct1.voltage(0, 268.97, 1.7);
Seems to be getting me the right voltage

I cannot however get correct current (testing with 1800w kettle) using calib:
ct1.current(1, 30.0);
My multimeter shows 8A current, but the ct Irms reading gives me below:
0.18
0.19
0.15
0.17
0.18
0.19

Any tips or advice appreciated

3

No, both these things would have the effect of making the reading zero under all circumstances.

You will need a medium-sized soldering iron so that you can heat up both ends of the resistor at the same time. When the solder melts, use the iron to wipe the resistor off its pads.

And don’t be afraid to let the iron get really hot before you try. Generally, you will do more damage to the circuit board and the components when the soldering iron is not hot enough - because you apply the heat for a much longer time.

1 Like
4

thank you. So I have to remove the 33ohm and then use any normal wire to bridge the ends where the resistor sat?

5

What you’ve done by not removing the 33 Ω burden is to give the c.t. two burdens, one internal and the 33 Ω. The effect will be to reduce the sensitivity significantly.

6

Okay let me get that soldering iron out again. As a solder beginner, I struggled a lot to solder the shield together. But let me get that 33ohm out now that I know it cannot be sidestepped. Thanks a lot.

7

No, remove the 33 Ω. The c.t. already has a burden inside it, you don’t need a second one. As I wrote above, a link will ensure you always read nothing - always zero.

8

Noted, after removing the 33ohm resistor, do I need to bridge the points on the shield were the resister once sat, to ensure the path is connected with no resister (any plain wire?)

9

Go back and read what I’ve written all the way down this thread. Also, look at the ‘Learn’ section to see how the c.t and burden are connected in relation to the input to the ADC.

1 Like
10

You were spot on. I got the 33ohm off, and now the Irms values look great! Hovers around 0.2A no load, then 8.8A when the kettle comes on. When the kettle switched off, back to 0.2A

Thank you so much!