|Good Keyboard is the Key to Calculator Success !|
Message #11 Posted by Bernhard on 7 July 2005, 8:23 a.m.,
in response to message #10 by Eric Smith
IMHO, Eric's points in the previous post are correct, let me emphasize:
1. Use a mask-ROM off-the-shelf microcontroller instead of ASIC.
If you choose a manufacturer which has a compatible FLASH part,
you can start production with these and lower your risk.
2. There are so many small China based LCD manufacturers looking for
business you will find someone who makes your custom LCD at very low
cost (if ordered at least by the 1,000s). If you agree to pay all
NREs up front it is likely they will even make you a lot of 1000 or
3. Now the keyboard issue (hah !):
Except for HP, no pocket calculator manufacturer EVER has managed to build a good keyboard. The superior HP quality has several factors:
a) double injection molded keys with eternal and virtually indestructible legends that simply won't wear off
b) keys are hinged which gives them a unique feel of precision and quality (and increases operational life of the contact). They don't wobble under the finger. Just compare tactile key feedback of any Classic, Woodstock and Spice HP with a TI of the era (TI keys not hinged)
c) the snap-action contact strips themselves - not too much snap, just right to feel "easy", and not too soft (to feel "mushy").
Casio calculator keys always feel mushy, like poking your fingers
in soft s... (you guess what I mean).
d) the gold-plated counter-contacts on the keyboard pcb for reliable contacts
e) the overall mechanical assembly (with calculator shell) so the keyboard does not twist and bend.
f) plastic membrane under keys to protect contacts from contamination.
So far the factors which made HP calculator keyboards absolutely superior.
One historical anecdote: when the TI scientific calculators came out (and were somewhat cheaper than HP) the purchasing department of a major defense contractor tried to talk their engineers into buying TIs instead of HPs. These however already knew the poor reliability of TI keys (often leading to miscalculations) and responded: with a HP, I need to do my calculations just two times, get two identical answers, and can use the result in full confidence, while with TI, I need to do them five times or even more and then, among the different results, pick the numbers which appear more often, as they seem to be the most likely ones, all just due to keyboard bounce or keys not responding. (It was the 1970s when they made very long calculations such as center of gravity of missiles using these pocket calculators, because PC's and CAD software didn't exist).
Needless to say they got their HPs.
Bottom line: if you want to make a superior calculator for serious quality work, then you ought to have the best keyboard possible.
Before you find an answer how to manufacture such a keyboard (with the legendary HP look and feel and reliabilty) at affordable costs,
your calculator project most likely won't succeed.
-----> Good keyboard is the key to calculator success ! <------
(The only other road is to make cheap throwaway disposables, like other calculator manufacturers do, even today's HP (sigh), but I'd doubt this road leads to sustainable success)
Edited: 7 July 2005, 10:57 a.m. after one or more responses were posted