Zeus Hammer

- - -

In case you were having an inferiority complex because your friends' IBM Model M keyboards are so much louder than the -shitty rubber dome freebie you got with your pc... Here's the solution: Zeus Hammer, a simple typing cadence enhancer -for PS/2 keyboards.

- -

The connects to the keyboard's PS/2 clock line and briefly actuates a large solenoid on each key press. An interesting -fact about PS/2 is that the clock line is only active as long as either the host computer or the input device actually -want to send data. In case of a keyboard that's the case when a key is pressed or when the host changes the keyboard's -LED state, otherwise the clock line is silent. We ignore the LED activity for now as it's generally coupled to key -presses. By just triggering an NE555 configured as astable flipflop we can stretch each train of clock pulses to a -pulse a few tens of milliseconds long that is enough to actuate the solenoid.

Since PS/2 sends each key press and key release separately this circuit will pulse twice per keystroke. It would be -possible to ignore one of them but I figure the added noise just adds to the experience.

Built on a breadboard, the circuit looks like this.

The completed system looks like this.

- -

Since my solenoid did not have a tensioning spring I used a rubber band and some vinyl tape to make an adjustable -tensioner. The small orange USB hub serves as an end-stop because I had nothing else of the right shape. The sound and -resonance of the thing can be adjusted to taste by moving the end stop, adjusting the tensioning rubber and tuning the -excitation duration using the potentiometer. My particular solenoid was a bit slow so I added some pieces of circuit -board as shims between the plunger and the case to limit the plunger's travel inside the solenoid core. Here is another -video of the thing in action in which I tune and de-tune the mechanical resonance using the potentiometer.

- -

2018/05/03