Optoisolator selection

[heepofajeep]

Hi, I am search of an optoisolator for a project I am working on. My requirements are just that the optiosolator has a 100% duty cycle, and PIC18 compatible output.



I am looking at this 4N29 Optoisolator, but cannot determine if it has a 100% duty cycle. **broken link removed**



Thank you very much!

 

[Hero999]

I don't think I've ever heard of an opto coupler that can't do 100% duty cycle.

Providing you don't exceed the maximum power dissipation for either the transistor or LED then it'll be fine.

 

[TKS]

duty cycle???

Duty cycle means 1hour working half hour rest (when 50%)..

how can optoisolator has that? if its goal is something you cant know beyond??

Tks

 

[Hero999]

Or it could mean 1:mu:s on and 2:mu:s off.

The idea is that the device cools inbetween cycles. For example you can quickly move your finger through a candle flame without burning it but if you hold it in the flame it will burn.

 

[heepofajeep]

Or it could mean 1:mu:s on and 2:mu:s off.

The idea is that the device cools inbetween cycles. For example you can quickly move your finger through a candle flame without burning it but if you hold it in the flame it will burn.

I am assuming this is what it is. Weird that apparently the majority of them have a 100% duty cycle, because the first 3 or 4 I looked at were <50%. Here is an example: https://www.electro-tech-online.com/custompdfs/2006/12/ps2501.pdf It is 1:mu:s on and 2:mu:s off kind of thing. I believe I found one that will work, however, in this one: https://www.electro-tech-online.com/custompdfs/2006/12/hcpl2630.pdf

Thanks!

 

[Hero999]

Where does it say that?

There is a duty cycle rating for peak emitter current and transistor current but nowherre does it say the maxium duty cycle is <100% at the normal current. I think you're misinterpreting things.

 

[heepofajeep]

I am sorry, I may very well be misinterpreting... I actually picked up the duty cycle from this example schematic from sparkfun, same place I got the datasheet from. https://www.sparkfun.com/datasheets/Components/PS2532-Example.jpg
Another similar scenario here: **broken link removed**

 

[Hero999]

That's just an example.

Look at the first page.

The average current is 20mA for the input diode and 60mA for the detector.

The input diode can work at 40mA if the duty cycle is 50% at 1ms.

 

[heepofajeep]

Perfect. Thank you very much for clearing that up for me!