Led limiting resistor

[HankMcSpank]

Hello,
I have a line where the current varies from 1 to 5 amps.
I would like to insert a resistor which will turn on an optocoupler rated at 1.5 volts , 10 mA
The issue here is that at 5 amps i need a 0.24ohms resistor , and at 1 amp i need a 1.2 ohm resistor.
Assuming that i use the 1.2 ohms resistor, at 5 amps will generate 6 volts and fry my opto.
I need help to solve this issue, which i do not know how to do it
Regards
Ion

iF you place a 450R resistor in series with the opto, that'll ensure the voltage doesn't exceed 1.5V/10mA at the opto for 5A through the element ....of course the opto will only then 'get' 300mV if the element current drops to 1A....but without knowing more about the opto blah blah

[mister_e]

Why not using a Current transformer?

[igeorge]

I think Mister_e solution it is something which i will consider, but i have to solve the conversion of 10 mv ac/60 hz to a decent DC voltage so i can use it with a comparator.
As i said, analog it is a mystery for me.
Regards
Ion

[Demon]

I don't understand why the need for complicated design.

Wouldn't an appropriately rated relay do the job just as well (isolate both sides), be easy to install and be able to withstand a lot more?

[igeorge]

I believe that the relay first will not withstand the 5 amps on the coil.
The second issue is that voltage is chopped by the SSR and heat controller, and the relay will come to a point when it will go crazy ON-OFF-ON , and the signal to CPU will be a pulsating one.
Thank you

[Demon]

I believe that the relay first will not withstand the 5 amps on the coil. ...

I would think that would depend on the rating of the relay.

...The second issue is that voltage is chopped by the SSR and heat controller, and the relay will come to a point when it will go crazy ON-OFF-ON , and the signal to CPU will be a pulsating one.
Thank you

That little detail might be a big problem.

[igeorge]

Thank you Demon,
I am testing now a ACS712 and in the scope it looks like a sine wave - 60 HZ, swinging between +1 volts to + 3.5 volts
I will get tomorrow an LTC1966 from Linear Technology , which is an RMS to DC converter and start working from there
Regards
Ion

[rsocor01]

I believe that the relay first will not withstand the 5 amps on the coil.
The second issue is that voltage is chopped by the SSR and heat controller, and the relay will come to a point when it will go crazy ON-OFF-ON , and the signal to CPU will be a pulsating one.
Thank you

You can rectify the AC signal before feeding it to the relay. Add diodes and a capacitor and you are set. Like demon said, you might be making it more complicated than what it is.