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PeterJ
PeterJ
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I'd give this answer above a +1 but I'm too new here. Current limiting/regulating diodes are great. I know that this is old, but I tackled a similar problem a while ago and would have found this thread useful so I thought I would share my findings:

I used a rectifier into several current limiting diodes in series to control an opto-isolator. The Semitec E-202 passes 0.5-2 mA across a voltage range of 0.5 to 100V. Six E-202s in series into a Vishay SFH618 Opto should pass 0.5 mA fairly easily (assuming something like 3.3V or 5V available for opto supply). 

There isn't a ton of wiggle room and your output signal will be fairly small, but you'll have very good isolation and reliable sensing of presence/absence of voltage between about 4.5V and 600V (remember 480 Vrms gives you 580Vdc out of the rectifier).

I'd give this answer above a +1 but I'm too new here. Current limiting/regulating diodes are great. I know that this is old, but I tackled a similar problem a while ago and would have found this thread useful so I thought I would share my findings:

I used a rectifier into several current limiting diodes in series to control an opto-isolator. The Semitec E-202 passes 0.5-2 mA across a voltage range of 0.5 to 100V. Six E-202s in series into a Vishay SFH618 Opto should pass 0.5 mA fairly easily (assuming something like 3.3V or 5V available for opto supply). There isn't a ton of wiggle room and your output signal will be fairly small, but you'll have very good isolation and reliable sensing of presence/absence of voltage between about 4.5V and 600V (remember 480 Vrms gives you 580Vdc out of the rectifier).

Current limiting/regulating diodes are great, I tackled a similar problem a while ago so thought I would share my findings:

I used a rectifier into several current limiting diodes in series to control an opto-isolator. The Semitec E-202 passes 0.5-2 mA across a voltage range of 0.5 to 100V. Six E-202s in series into a Vishay SFH618 Opto should pass 0.5 mA fairly easily (assuming something like 3.3V or 5V available for opto supply). 

There isn't a ton of wiggle room and your output signal will be fairly small, but you'll have very good isolation and reliable sensing of presence/absence of voltage between about 4.5V and 600V (remember 480 Vrms gives you 580Vdc out of the rectifier).

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user43687
user43687
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I'd give this answer above a +1 but I'm too new here. Current limiting/regulating diodes are great. I know that this is old, but I tackled a similar problem a while ago and would have found this thread useful so I thought I would share my findings:

I used a rectifier into several current limiting diodes in series to control an opto-isolator. The Semitec E-202 passes 0.5-2 mA across a voltage range of 0.5 to 100V. Six E-202s in series into a Vishay SFH618 Opto should pass 0.5 mA fairly easily (assuming something like 3.3V or 5V available for opto supply). There isn't a ton of wiggle room and your output signal will be fairly small, but you'll have very good isolation and reliable sensing of presence/absence of voltage between about 4.5V and 600V (remember 480 Vrms gives you 580Vdc out of the rectifier).