I'm a newbie, hacking a circuit.. switches

I got my Arduino last week and have had my first opportunity to have a play around with it. I have a Duemilanove board connected up to USB for power/control.

I have had some fun running though the blinking tutorial etc and would like to move onto my first project.

I have a circuit board that I have pulled out of a home easy 307 switch

I have two questions

The circuit is powered by a 3.3v CR2032 battery, Will it be okay to run from the 3.3v from the Arduino?

The circuit has two banks of switches, one bank turns on/off one device the other bank turns the other device on/off.
I would like to hijack the switches on the circuit with my Arduino then program it to imitate the switches.... the problem being that the buttons on the circuit currently are normally closed.
How can I get the Arduino to control these switches?? I assumed they would be normally open and then use a pin to pull it high.

I did very limited electronics in school many years ago :-[



Will it be okay to run from the 3.3v from the Arduino?

Probably not the arduino can only provide about 50mA from it's 3v3 supply.

How can I get the Arduino to control these switches?

Well post the link now you have your first post and let's see. It all depends on how much current and voltage they switch.

thanks for the intrest…

The device is a transmitter, it sends a command to a remote device via a wireless signal. The remote device switches a mains socket on/off




I have a volt meter and will be testing the amp’s that the circuit pulls shortly. I have tested the buttons and they have no resistance in there normal state, when pressed it breaks the connection.


If I understand what you are trying to do you could replace the mechanical switches with MOSFETs. You will have to size them correctly for your amperage and tie your grounds together.

The usual Arduino example about a MOSFET is with a N-MOSFET which sinks current. That means that you can complete a circuit, replacing a switch with N-MOSFET if switch closes a path for the current to ground.

In essence, yes. I want to replace the push button switches on the circuit with the Arduino.

I will read up about MOSFET's.

Thanks for the point in the general direction.



a fet is a bit of overkill for a remote control powered by a coin battery

It is simpler to use an opto isolator. The output from the arduino is treated just like driving an LED. The output is then a transistor that will conduct when the LED is on.

That's a coincidence. I'm looking at doing something very similar here, where I have a remote I'm hacking. Instead of trying to reverse engineer the transmitter and making a clone of it, I'm just going to bend the board so I use optoisolator channels in place of physical buttons. There are eight buttons (4 on, 4 off) which makes quad optoisolators seem like a really good idea.

Much easier to bend something that works than to build it from scratch. Then, I "just" add an arduino ethernet shield, and I have a network controllable set of mains sockets :smiley: