21 Mar
2007
21 Mar
'07
3:35 p.m.
On 3/21/07, Doug Jackson <doug at stillhq.com> wrote:
On the subject of Blinken lights and toggle switches,
I have had
difficulties finding decent mechanical keyswitches to use for projects.
Essentially, I need to make a hex keypad, with a couple of extra
function keys. I know that now we would simply get a membrane rubber
thing made up, but once upon a time, I would purchase 20 mechanical
switches, and solder them to veroboard.
The last time I needed an odd keyboard, it was for a 5x5 matrix to
test my MatrixOrbital serially-attached 20x4 text VFD input circuit.
I took a bit of bare protoboard and populated it with bare pushbutton
switches I'd harvested out of clock radios and broken TV sets. The
buttons aren't expensive in and of themselves, but I wasn't able to
receive shipments for several more months and didn't want to wait for
the next mail plane. I think it took me a couple of hours to wire it
all together and up to a 10-pin molex header to cable over to the
display. I would rather have used veroboard - it would have taken
much less than an hour.
Fortunately, I had about 30 switches on hand.
More recently, I picked up some IBM leased-line modem front-panels
specifically because they had a hex keypad with double-shot keytops
with the hex digits in them. One place I'd use them is with an 1802
and a 74C923 matrix scanner.
Dunno where you'd find them as components these days, though. I've
been looking for hex keypads at hamfests for years and only recently
spotted these.
-ethan