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Joystick design
Gday All
Need some low level electronics help.
I am repurposing a bulky old joystick into an EQMod controller that i can hold in one hand.
I have bought a new small ( thumb operated ) joystick assy and have started designing how to fit it to the old controller.
The old joystick used a CY7C63000A-PC chip, and as such, it has to manually read the pots by timing the charge time of an RC filter.
The specs say that a std joystick uses a 100k pot
which feeds a 2.2k resistor and then a 1500pf capacitor to ground.
ie +5V - pot - 2.2k - tapping - 1500pf - gnd
The tapping between the resistor and capacitor then directly feeds the pin on the controller, which does the time calcs.
My new joystick uses 10k pots, so i know i need to redesign the values of the RC filter to get equivalent time constants, but whereas "the book" states that you go directly to the controller pin, my old joystick used a 1n4487 diode here. Notwithstanding this will give a forward voltage drop that will affect the trip points, a 1n4487 is an 82V zener????
It is fitted forward biased, so is operating as std diode,
but why the hell would it even be fitted????????
Why pick such an oddball size?????
Andrew
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