Step #2: The Timer Circuit
- The circuit used in this project is based around the 555 timer IC. Power for this circuit is supplied by the 5V line from the computer that also powers the mouse. This is connected to pins 4 and 8 of the IC. The output of this circuit is a series of pulses that alternate between HIGH (5 volts) to LOW (0 volts). This is what will activate and deactivate the click function of the mouse. A small diode is added to the output to prevent the circuit from shorting out if the rapid fire button and the left mouse button where ever pressed at the same time. This circuit is connected to the mouse through a small momentary switch that acts as the rapid fire button.
- The frequency of these pulses is determined by the value of the capacitor that is connected to pins 1 and 2 and the value of the resistor that is connected to pins 2 and 3. I used a 10 µF capacitor and a 4.7 kohm resistor. This produces a frequency of about 15 Hz (about 900 pulses per minute). By decreasing the value of the resistor and or the capacitor, it will increase the output frequency. By increasing these values, it will reduce the output frequency. If you would like to calculate the exact frequency you can use the following formula.
Frequency = 0.72 / (R x C)
"R" is in units of ohms and "C" is in units of Farads.
- I first prototyped this circuit on a breadboard for testing and then I soldered it together onto a small printed circuit board.
Step #3: Prototype and Test the Timer Circuit on a Breadboard
First I prototyped the circuit on a breadboard to test it. I powered it with a 5 volt USB power supply. I also used a variety of meters to monitor the output. Once you are satisfied that the timer circuit is working properly, you can connect it to the mouse.
Step #10: Modify the Design to Work With Console Controllers
This circuit can easily be modified to work with a console video game controller. The only thing that you need to do is reverse the orientation of the diode. The buttons on a mouse normally connect to the positive supply voltage (5V) to activate each function. However a console controller typically connects to ground when the buttons are pressed. The output of the timer circuit is already a series of pulses that alternate between 5V and ground. So all you have to do is reverse the diode and the output of the timer circuit will connect the controller to ground.