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+---
+title: "Zeus Hammer"
+date: 2018-05-03T11:59:37+02:00
+---
+
+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.
+
+.. FIXME: add demo video
+
+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.
+
+.. image:: /images/zeus_hammer_schematic.jpg
+
+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.
+
+.. image:: /images/zeus_hammer_breadboard.jpg
+
+The completed system looks like this.
+
+.. FIXME: add image of completed system
+
+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.
+
+.. FIXME: add video w/ tune/detune
+
+.. _`PS/2`: https://en.wikipedia.org/wiki/PS/2_port
+