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LDmicro Forum - 220vac input voltage

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220vac input voltage (by Alex)
hello, for my application i had to use a limit switch located 30 meters far from my microcontroller, due to the far distance i was not able to use 5vdc, can´t affort for a 24vdc power supply, i only have 220vac avaliable and so 5vdc, i have been searching information about ac voltage for MCU inputs and i found that it is possible using a diode bridge and optocoupler.


have not tested yet, i need to calculate values for the input circuit diagram given, has some one ever used AC voltage for input to MCU?
Thu Apr 11 2019, 21:57:15, download attachment plc 220vac input circuit diagram.jpg
(no subject) (by Ziggy)
I have used similar approach in line loss sensing application for 3 phase power.

You do not need the zener diode.

Choose an AC input optocoupler - this is an optocoupler with internal inverse parallel LEDs.
calculate a series resistor to limit the current to say 20mA peak...( peak value of 220vAC. Design done. No need for a bridge rectifier.
Fri Apr 12 2019, 00:45:03
(no subject) (by Alex)
thanks for your reply, what about PC814, see image please, but I doubt that at 60 Hz (in my case) my input will be toggling every 20 ms. How can I avoid this toggling and by using mimimum components to get continuous signal until power is present on input of PC814
Fri Apr 12 2019, 01:15:04, download attachment pc814 input 220v_corregido.jpg
(no subject) (by Ziggy)
Well asked.

On the output side use a bit of capacitive filtering.
I do not know the state of input pin ( Pullup/pulldown and what are these resistance values)?

!0K may be a bit too high. I might go with 4k7.
20mS only happens for 50Hz supply, at 60Hz it would be 16 odd mS in fact 8 odd mS since the pulses will occur on 120Hz peak values
Fri Apr 12 2019, 02:03:55
Voltaje de entrada 220vac (por Alex) (by Calubert)
Estos son capsulados la entrada es 220v salida 3,5 etc,se fabrican en varias tensiones de salida

Fri Apr 12 2019, 06:38:11
(no subject) (by Alex)
to Ziggy:

i ill use pull down resitor (resistor value = 10k ohm),then change it to 4k7 for 5vdc? could you tell me what value you consider the best option for capacitive filtering?

to Calubert:

si usara eso el tiempo que tardan en encender y en apagar suele ser no despreciable; una fuente conmutada suele tardar como medio segundo en encenderse y en apagarse depende de la resistencia que use para descargar su condensador de salida, yo usaré un limit switch, eso significa que en ese limite la operación que realice mi microcontrolador deberá detenerse, pero no lo hará hasta que el condensador se descargue, me comprendes?
Fri Apr 12 2019, 08:40:47
(no subject) (by Ziggy)
A simple RC filter would suffice.
At 4k7 and say 8ms time repetition rate of the pulse train i would thinkfilter time constant should be approximately five times the pulse repetition rate.
Try 1uF tantalumcap in parallel with4k7 resistor
Fri Apr 12 2019, 09:18:16
(no subject) (by Calubert)
Si (usa entrada analoga ya que funciona hasta 5v y calcula la caída de la longitud. yo tenia un problema con la radiación que emitía una alarmas inalambrica y lo solucione con una entrada analógica, la distancia hera 50 metros de cable pero se utilizo cable ampantallado y diámetro 2,5mm
Fri Apr 12 2019, 11:12:50
por Alex (by Calubert)
Hola alex te he echo un programa para que no hagas nada externo a tu comentario del pulsador que colocas a 30 metros ya que este programa funciona con tu caída de voltaje ya que la calculas y modificas la comparación.
si tienes alguna duda puedes consultarme y si quieres que te lo ponga en tu programa en el LDMicro puedes colocarlo aquí en el foro o a [email protected]
saludos Paulino
Sat Apr 13 2019, 08:58:12, download attachment ales.ld
(no subject) (by Alex)
gracias Calubert lo probaré también
Sat Apr 13 2019, 11:09:30
(no subject) (by Tom J.)
Alex, a couple years ago I made an inductive pickup to show secondary ignition traces. With what I learned I'd think it relatively easy to take a sensitive transistor like a 2222 and a coil of wire and maybe a smallish capacitor to make a simple sensor for what you need to do.
Sun Apr 14 2019, 00:09:48
(no subject) (by Alex)
thanks for your reply Tom J. another great idea :)
Sun Apr 14 2019, 02:29:34
(no subject) (by bfwolf)
Combined circuit for 230VAC (60..230VAC) oder 24VDC (4..60VDC/AC) digital inputs - CSI8

There was once a kit published by the german ELV-journal magazine called CSI8.

It offers digital-inputs for 2 voltage-ranges and uses capacitors as AC-resistors and so minimises enegrgy-waste.

Sun Apr 14 2019, 05:36:41, download attachment CNY17_UC.pdf
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