I’m having a couple of expansion boards made with some small variations based on emontx4/expansion_boards/CTExt at main · openenergymonitor/emontx4 · GitHub
Looking at the first jack socket the resistors R1 and R2 don’t show their values in the schematics and the values aren’t shown on any of the other corresponding resistors e.g. R7 & R8.
Can someone please advise what resistors should be used for these?
They should be exactly the same as the corresponding resistors on the emonTx4 itself, which, when you understand a voltage-output current transformer does not require a burden, means the value of the two in parallel is ∞.
What you’re actually looking at are place-holders for a SMT and a wire-ended burden, should either be needed.
It’s exactly the same in the emonTx V3 and emonPi, which use the SMT burden but not the wire-ended resistor - but if you require a special value, you remove the SMT resistor and solder in a wire-ended one.