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I have a RF remote control for the garage that I would like to control via Arduino.

With a multimeter, I detected around 3v across the button.

I have soldered two wired on either side of one of the buttons, and connected one side to digital pin 12 and the other to ground.

While this worked fine, I did notice that the remote depleted of all battery in a day.

Trying to marry theory with practice, did this occur because I did not use a pull-up / pull-down resistor?

Update RF Board with Arduino As recommended by Cornelius, I removed the battery and connected the 3.3V and Ground directly to the battery terminals.

As Andy Aka predicted, I measured the voltage from ground to the positive terminal of the button, and it is ~5V, which will end up damaging the board.

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  • \$\begingroup\$ In the remote, is the button connected to the ground with one pin? \$\endgroup\$ – Cornelius Apr 29 '14 at 17:56
  • \$\begingroup\$ It appears so Cornelius. There is only one pin on either side of the button. I can add photos if it will assist. \$\endgroup\$ – Ari Apr 29 '14 at 18:22
  • \$\begingroup\$ Why don't you use Arduino's power supply to power the remote too? You can use a 3.3 regulator for this. \$\endgroup\$ – Cornelius Apr 29 '14 at 18:37
  • \$\begingroup\$ I thought of this as a solution too. I was concerned that I had made a highly inefficient circuit, as the button cell battery would usually last a long time sans Arduino. \$\endgroup\$ – Ari Apr 29 '14 at 18:47
  • \$\begingroup\$ Picture would definitely help, along with a schematic of what you have done so far. \$\endgroup\$ – Justin Trzeciak Apr 29 '14 at 18:57
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Connecting arduino ground and an IO pin across the button is probably really not recommended. For a start you might find that your arduino ground and IO pin are now forcing the transmitter to have maybe up to 6V across it: -

schematic

simulate this circuit – Schematic created using CircuitLab

I'm not saying the wiring is like this BUT neither are you - you are guessing and you might do some damage so tread carefully. Ideally you need to connect the arduino ground pin to ground on the radio (see the symbol I've drawn) and the GPIO line to where the transmit circuit of the switch is.

I can also see why your battery became drained because, when you shut your arduino down it in effect shorted the switch and probably transmitted a constant carrier wave all day!!

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  • \$\begingroup\$ You were right to assume those things, it explains why the battery drained quickly and why it didn't worked as I expected. \$\endgroup\$ – Ari Apr 29 '14 at 20:15
  • \$\begingroup\$ I believe I have improved the circuitry of my design by connecting both the positive terminals of the battery and the positive side of the button to the Arduino's 3.3V header, and connecting the ground side of the button to the digital pin 12. As far as I can tell it is working as it should. The only issue that I can tell, is the digital pin HIGH has a value of 5V. I have looked up a solution and a voltage divider is recommended. \$\endgroup\$ – Ari Apr 29 '14 at 20:34
  • \$\begingroup\$ @fanuch - you can draw a diagram like I did in your question - circuitlab is there for all to use as far as I know? I'm suggesting this because it still sounds dubious what you are proposing. \$\endgroup\$ – Andy aka Apr 29 '14 at 21:30
  • \$\begingroup\$ Unfortunately, it didn't work. Not sure if there is insufficient current or something, but the digital pin acting on the button turns on the LED, but does not open the garage. When I apply 3.3V directly on the negative terminal of the button, the garage does open. This is the schematic I am about to try using an NPN transistor. ![circuit][2] [2]: i.stack.imgur.com/EOfXY.jpg \$\endgroup\$ – Ari Apr 29 '14 at 22:03
  • \$\begingroup\$ you need a pnp transistor with emitter to 3 3v and pull the base down via a 1 kohm resistor to activate it. \$\endgroup\$ – Andy aka Apr 29 '14 at 22:20
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Just use a relay to simulate the button press. Then there is no risk to the Arduino board. Just wire up the Arduino to control the relay.

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