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### Topic: Is this possible without relays (Read 1 time)previous topic - next topic

#### mjdano

##### Oct 19, 2012, 09:03 pm
Ok first I would like to state that I'm very new to the Arduino and everything it can do. My background is in computer networking and physical security equipment so i'm just starting to learn much of this. So here is my idea , I'm not sure if the Arduino and the different shields I've seen are capable of this or not.

I have access control panels all over the place in our complex of buildings. In some locations I wire a simple push button to the input on this panel to unlock the electric strikes on the door and another one to lock the doors again. My problem is I need to run wires everywhere to make these buttons work. I want to know if it is possible to use an Adruino + Network shield + Relay shield at the panel side and an Arduino + Network shield on the office side to do the same thing over the network. I have found devices that would do this but they usually come with a good size price tag.

From my research and experimentation it looks like this should be easy. My main unknown at this point is do i really need a relay shield to simulate the pushing of a button. I've tried to measure if there is any voltage on the input of the panel since I would guess that is how it is sensing if the button is pushed (opened or closed contact). I didn't get any real voltage readings from the meter it was so low. The relay shields I've found are mostly for higher voltage ratings but I just need a way to close the contact for a second.

#### johnwasser

#1
##### Oct 19, 2012, 09:32 pm

I've tried to measure if there is any voltage on the input of the panel since I would guess that is how it is sensing if the button is pushed (opened or closed contact). I didn't get any real voltage readings from the meter it was so low.

Sounds like you need a new meter.  It is unlikely the voltage across the button would be much less than 1V in both the open and closed states.
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#### rayshobby

#2
##### Oct 21, 2012, 03:30 am
You can use a transistor, a mosfet, or opto-isolator to simulate button press. But I agree that no voltage reading between the two wires is strange.
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#### retrolefty

#3
##### Oct 21, 2012, 03:37 am
Might those panels and switches be using AC voltages rather then DC voltages, did you measure for both types of voltage? If you don't have detailed electrical drawing to assist you then your kind of on your own to analyze how the existing circuits work and at what voltage type, amount and current flows. It's not a good or easy task for someone that doesn't have a lot of electronics hardware knowledge and experience.

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