Building an Automatic Left Mouse Clicker

For reasons too complex to go into, I had a need for a gizmo that automatically clicked the left (or right, it didn’t matter) button on a mouse at a pre-set interval. It needed to be able to do this automatically, and be able to do it for hours. I also needed visual confirmation it was doing it, and be able to turn it on and off easily whenever I needed to actually use the mouse.

The machine the mouse was plugged into had a funny setup and wouldn’t accept a second mouse device, so a fully emulated mouse solution wasn’t really an option, so I went with a simple timer circuit based around a 555 timer IC, a relay and a 12v power supply. This timer circuit would be physically patched into the left button microswitch inside a spare mouse to automate the clicking, and the host machine would (hopefully) be none-the-wiser.

Whereas I could have broken out my spare bits of veroboard and my bucket of bits and built the circuit from scratch, I opted to buy this kit from Maplin. Doing so meant I knew I had all the components I needed, and I could just get on with building the unit.

Soldering up the kit was very easy – it’s only got a few components. I opted to relocate the supplied LED onto a fly cable as I knew I was going to place the unit inside a project box once it was done, and I wanted to be able to see it working. I also cut a trace on the main 12v line and patched in an on/off button so that I could easily disable the unit when it wasn’t needed.

(The built kit, with on/off button and trigger LED)

The kit has two potentiometers; the left one controls the gap between ‘clicks’ and can be adjusted between 1 second and 1 minute. The right one controls the length of the click, from 0.5 seconds to 5 seconds. I needed a gap of 1 minute, and a duration of about 0.8 seconds (based on manually measuring my own clicking of a mouse button with my finger) so I adjusted the pots accordingly. Then I stripped down the mouse, and soldered the two ends of the white wire onto the solder pads either side of the left mouse button microswitch (no picture sorry – Google is your friend here).  When the timer relay fires, it closes the circuit on the white wire which in turn shorts the mouse button microswitch and the mouse circuitry sends a ‘left click’ to the host machine.

(The timer switch wired into the donor mouse)

With the kit built and working, I tested it with a small app I created to ensure that the clicks were always registered, and the gap and duration were correct:

(Good Enough!)

I’ve uploaded a short YouTube Video showing the circuit and the app in use. If you want to download the MouseClicker app, you can get it here.

Finally, I added a power LED (and resistor) across the 12v/Gnd lines, and squeezed the whole thing into a small project box. Now, casing up projects is one of my worst skills, so I’m never very good at this bit (I get too impatient). After doing this one, I’m now seriously considering a 3D printer, because designing something in Sketchup and printing it out has to be better than badly cutting little holes in boxes…

(Boxes… and cutting… Ugh)

Finally the case was cut and built. I added some little rubber feet that I had lying around (they came with a Raspberry Pi case originally) so it wouldn’t slide around when I pressed the button, and this is the result:


(All done. Doesn’t it look nice?)

To use, I press the red button, and the green LED lights to show the unit is active. Whilst it’s active, the relay triggers every minute and ‘clicks’ the left mouse button. The red LED flashes every time the trigger fires. To disable and use the mouse normally, I just press the red button again to switch the unit off.  It works perfectly.

Feel free to contact me if you have any questions.