hi all
here is description of what I wanna do :
I have a device with an input providing at 12 VAC.
This device is activated if the 12 VAC is shorted to the ground.
I am looking to activate this device with arduino.
I tried to use ULN2803AN to do that but does not seem to work.
I can do that with a relay activated by arduino but I am looking for another solution rather then a relay,
any suggestions are welcome
thank you

 

Opto isolator 4N35 etc.?
Max.

 

Opto isolator 4N35 etc.?
Max.

thanks a lot
any integrated circuit including a a number of opto isolators ?
for exemple including 8 optoisolator in a single circuit
thank you

 

A schematic or drawing of what you intend would help.
Max.

 

it would also help if you posted the actual device name and a link to the datasheet.

 

actually that is a traffic light cabinet,
the input to call a ped phase are 12 VAC
if we short them to the ground of the cabinet it makes a ped call,
I am looking to do this short by using an arduino

 

Use a relay.

 

While you are reluctant to use a relay it is likely the most logical choice. Another option might be a Triac circuit or as a package a low voltage SCR with a low voltage control (5 V control). Much of this will depend on the current when you shunt the 12 VAC to Ground. Crydom is one leading manufacturer maybe something like this:CX240D5-B they make plenty from big to small . They can also be driven in several optical coupled ways.
Keep in mind "Dry Contact" implies a switch or relay contact. A SCR or Triac may work.

Ron

 

Opto isolator 4N35 etc.?
Max.

I've done that before for 5V devices, but I've also successfully used a couple of resistors configured as a voltage divider (470 and 330 ohms), and added a couple of Schottky diodes to protect the MCU's pins from transients. The arrangement has proven to be very robust and reliable. I've done things this way because using an ordinary button to manage a 5V signal eventually leads to failure due to natural oxidation at the button's contacts. Using a 12V signal through the voltage divider creates a current of 15 mA. Which is enough to produce a small spark in the contacts when these are activated, thus removing any accumulated grease or oxidation on them.

https://www.digikey.com/en/articles/techzone/2012/apr/protecting-inputs-in-digital-electronics​