220vAc to 3v/5vDc low current ic for indication only

Thread Starter

barg

Joined Dec 23, 2015
78
Hi,

I need an IC (preferred single one) that has the ability to convert directly from 220vAC to 3v/5vDc - only for indication - if there is an Ac power in the Ac wires line and to indicate that feedback to a micro controller (no need for high current, up to 200mA is enough).

Also, if there is a simple circuit that is a very RELIABLE for a self building?
Appreciate your assistance
 

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ronsimpson

Joined Oct 7, 2019
2,004
preferer it to be in an Ic (so-8 such..)
That IC is inside the "black box" from post #2.
The IC needs other parts and they all add up.

Please tell more about what the 5Vdc powers. Maybe if we understood everything.

Would it be OK if L or N were tied to "-"? So there are really only three legs. This leaves your " for indication " thing sitting on the power line.
1638022742909.png
 

Thread Starter

barg

Joined Dec 23, 2015
78
Hi,

I would like to activate a motor with two options, manual switch and also a Relay by the mcu, both from the same power source(ac).

I would like to avoid a case that the relay will activate the motor in the same time as the manual switch is pushed on. for that, i need to sense the voltage ( if the voltage after the manual switch >0Vdc, the relay should be Disabled).

issue is, the relay gets the power source to the motor from the same wire..

Appreciate your suggestions.
 

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ronsimpson

Joined Oct 7, 2019
2,004
I think you are not trying to power the micro but to just see if 110Vac (220vac) is there or not. Is that right?
This could be really simple.
 

Thread Starter

barg

Joined Dec 23, 2015
78
yes, of course, the mcu and the relay (5v control the relay, 220v is for the motor) are from different 5v source. just to see if the mechanical switch is on.
 

ronsimpson

Joined Oct 7, 2019
2,004
This opto isolator is for AC input while most are for DC input. The 220K 1W resistor will drop the voltage and limit the current. You could use two 110k 1/2 watt resistors or tour 1/4 watt resistors.

On the computer it needs ground, supply (5V or 3.3V) and a digital input to the computer.
1638033830160.png
There is good isolation so the power line and the computer are completely not connected.

If you only have DC type isolators we can change the circuit to make them work.
 

Thread Starter

barg

Joined Dec 23, 2015
78
Opto isolator is a good idea, can you please explain how to find in the data sheet the ac relevant info? for example i use 220vac and looked it up in the TLCT1600 data sheet and didn't found ac info max rating, though it is written in the introduction ac input...
 

ronsimpson

Joined Oct 7, 2019
2,004
Link to data sheet
In the LED side (input) they often run 10mA through the part. It does not care which direction in this case. It has two LEDs in parallel. One for + and one for -. I would size the resistor so about 5 to 10mA passes. That will light one of the LED well. On the output side the photo transistor can pass a couple of mA.
 

Thread Starter

barg

Joined Dec 23, 2015
78
Got it Thanks.

As for the current calculation, could you please advice how you got to 220k?

i=v/r: 220vac/0.01A= 22k and you got 220k... i must be missing something here.
 

ronsimpson

Joined Oct 7, 2019
2,004
LOL I just copied some ones circuit, with out thinking. Sorry for the math mix-up.
10mA and 220V = 2.2 watts, 1mA and 220V = 0.22 watts.
So pick current in that range. Watch the wattage on the resistor(s). And know small resistors can not with stand 220V.

This graph is for the Current Transfer Ratio (saturation)
It is best at about 10mA. CTR is the input current compared to the output current.
At 1.0 you put in 10mA and the transistor can switch almost 10mA. (you should use it at less than 10mA to get it to turn on hard)
At 1mA it has a ratio of more like 0.5. So the transistor can only handle 0.5mA or less.
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