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General => General Technical Chat => Topic started by: vlad777 on February 20, 2015, 02:38:42 pm

Title: Antiparallel opto?
Post by: vlad777 on February 20, 2015, 02:38:42 pm

Can someone suggest an optocoupler with LEDs in antiparallel ?
It should be able to handle inrush current so I can limit current with a capacitor.
I'll be running it from mains.

Many thanks.

Title: Re: Antiparallel opto?
Post by: ConKbot on February 20, 2015, 09:12:12 pm

This sounds like a case that needs more information of the end goal instead of an answer to an intermediate task...   

A bridge rectifier after your dropper cap, and a series resistor to help limit the inrush current should function the same as 2 LEDs in antiparallel inside the opto. 

Title: Re: Antiparallel opto?
Post by: dannyf on February 20, 2015, 09:14:21 pm

Take two optos, anti-parallel their led sides and parallel their phototransistor sides.

Title: Re: Antiparallel opto?
Post by: vlad777 on February 21, 2015, 09:41:25 am

 @ConKbot
     Just want to detect presence of mains voltage. (when switch is flipped by some mechanics)
     Don't want to use resistor because of wasting energy.

 @dannyf
     Good thinking , thanks!
     Can you provide a part number for opto that can handle large inrush currents.

Title: Re: Antiparallel opto?
Post by: Zero999 on February 21, 2015, 10:07:12 am

Quote from: vlad777 on February 21, 2015, 09:41:25 am

     Can you provide a part number for opto that can handle large inrush currents.

Most are fine for 100mA or so of inrush.

Use a series resistor in addition to the capacitor. If the capacitor is selected so the continuous current is 10mA and the resistor so the surge is 100mA then the resistor will hardly get warm.

Title: Re: Antiparallel opto?
Post by: miceuz on February 22, 2015, 09:28:53 am

LTV-814 has LEDs in anti-parallel.