Hello everybody,
my name is Ioanna, and i m currently playing with different monitoring circuits. I made the simplest one which works fine, and i have also done the accuracy tests suggested for the emonTx ( i will post the whole comparison datasheet at the end of the project)
Right now, i want to build this one and though the voltage measurement seems almost perfect, i have some trouble with the ct. First of all i am not sure how it should be connected since my understanding of the circuit is super poor. Should i connect it like the image below? (it does not need a burden resistor it has one built-in)
With this connection, It seems to have a bias of 0.03 which is super frustrating, though stable, because even the simpler version was more accurate.
Can you please tell me what i m doing wrong, or whether its supposed to be this way?
thanks a lot in advance
ps: also if you have other circuits to suggest, it would be more than welcome! I am also planning to build the power box!
Re: op amp circuit problem with the ct
I think you need to read this again. Where to connect the c.t in the words on that page. The other end of the c.t. of course goes to the Arduino input.
Re: op amp circuit problem with the ct
Thanks Robert for the reply!
I put one end at the "mid-point" and now it got even crazier. I get 0.40 Amps for no load.. I think i should really understand how this thing works..
Re: op amp circuit problem with the ct
It is possible that the op.amp is unstable and is generating a signal of its own. Try a small capacitor - say 100 nF, from output to ground.
Re: op amp circuit problem with the ct
yes that was it!
thanks so much!