How to "sense" 1.5 Amp's of current?

A current transformer works very well with AC like that.

The thing to remember is that it is a CURRENT transformer not a voltage transformer, so you must not leave it open circuit. The output current is set by the input current and the turns ratio. There is a maximum output voltage that you can take. The transformer specification should say that.

It is quite easy to wire the output to a bridge rectifier, then a capacitor and a resistor.

You get much less power in the resistor for the same voltage drop, and it is much safer.

@Khristie: How would I do that? I have never used current sensing before.

Her is a nice little Current sense. They work just like a transformer.
https://www.electro-tech-online.com/custompdfs/2008/07/P524.pdf

I think Digikey has some as well.

Mike that looks interesting, how could I use it?

Well, you have your AC line, which is primary and essentially 1turn going through the xformer which is the secondary say the secondary is 50 turns. So if 1 amp is running through the primary 1/50 current will run through secondary. Have a resistor load on secondary and using ohms law Vsense = Isense x Rload (E=IR). For given voltage across Rload you know what I primary is. Check out this link on transformer equations. May help explain.
Transformer Formulas

Keep in mind the voltage would still be AC.

I'll try and reply before this thread gets locked.

Krumlink said:

@Khristie: How would I do that? I have never used current sensing before.

Click to expand...

This datasheet shows how it is basically done at the bottom:
https://www.electro-tech-online.com/custompdfs/2008/07/3110.pdf
The I is the one wire of the AC lamp cord you pass through the core. It is also the amperage though that wire. They include a formula for you. So, if you put a 1K resistor on the output of the current transformer, you would get apx 0.48 volts RMS AC across the resistor for a current of 1.5Amps which agrees with the chart they provide you:
1.5A x 1000hm: / 3100 = 0.48V
You could amplify this voltage with an OpAmp (Or try a 10K resistor) and then rectify it to detect the 1.5A threshold.

The tiny transformer is made for high frequency SMPS and might not work at the mains frequency.

audioguru said:

The tiny transformer is made for high frequency SMPS and might not work at the mains frequency.

Click to expand...

No, its made for 50 / 60 Hz (look at the data sheet at https://www.electro-tech-online.com/custompdfs/2008/07/3110-1.pdf

Its a CURRENT TRANSFORMER. It needs a resistor in parallel with the secondary (or else an ammeter) so it doesn't develop a high secondary voltage.

I think he was speaking about the one I suggested and I think he might be right. I should have looked more closely at the data sheet.