230 detection - circuit question

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Thread Starter

tudstudent

Joined Jun 6, 2009
20
HI all,

I am currently busy with creating an extension for a to be defined interface (arduino, RPI, atmega...).
Initially I just focused on RPI so I wanted to use GPIO, but since at the moment my breakout will use a lot of them an alternative communications method might be better (rs485).

So in short at the moment I am focusing on detecting a light switch turning ON/OFF. At the beginning I used a transformer based power transformer to go to 5V. However I did not like it to have a bulky transformer on my print so I looked further. Since I am on 50Hz 203VAC I needed to have something which was able to phase correct and "stabilize".

I found the following 2 links and created based on those the circuit attached:
https://electrosome.com/transformerless-low-cost-power-supply/
http://www.electroschematics.com/5678/capacitor-power-supply/

My Schematic:
230V_extension.png

BOM List:
230V_BOM.PNG

The 2 main questions I have are:
1. Does this work for my purpose (no delay "off" because of the capacitor, OFF will immediately shut the optoled)
2. Are the parts I selected correct.

Thank you in advance.
 

Reloadron

Joined Jan 15, 2015
7,501
Why not just use a simple AC type opto coupler. You want to detect the presence of 230 VAC On/Off correct? I would just use a selected opto coupler since you don't want to go the transformer route.

Ron
 

Thread Starter

tudstudent

Joined Jun 6, 2009
20
He Ron,

Never heard of, so did a quick google and came accross this great explanation:
http://www.renesas.eu/products/opto/technology/ac/index.jsp

So broadend my search for a good circuit (why develope something new if it already exists):
http://electronics.stackexchange.com/a/33428

The only question open here is:
If you have the 50Hz 230VAC the opto will show light bulbs like figure 3 on this link:
http://www.renesas.eu/products/opto/technology/ac/index.jsp
They advise to use a C. Do I need somthing in parallel to R3 (or another place and if so what type/value would you advise).
 

Dodgydave

Joined Jun 22, 2012
11,284
I would strongly recommend using a transformer to feed your detection circuit,as opposed to a Live circuit on the mains...

then feed it into your opto.
 

Thread Starter

tudstudent

Joined Jun 6, 2009
20
Could you please elaborate a little more on that?
I am no expert in this area and I have thought of a lot of different solutions. My current solution was based on a transformer...
 
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