Message #1 Posted by DaveJ on 14 Nov 2009, 6:19 p.m.
I thought I'd start a new thread on this design. So those who don't want to talk about credit card calc design, please ignore.
Two basic design options are presenting themselves:
1) Less powerful design (say PIC18) with high contrast 8 digit 14 segment LCD display window 45mm x 8mm. Thickness can be no less than 4mm.
2) More powerful design (say PIC24 or PIC32) with lower contrast 35mm x 9mm 128x32 dot matrix display window. This would allow 4 lines of 16 characters with an 8x8 font. Bigger fronts are of course possible to compensate for the lower contrast. This is the same display as for the uWatch MK2. Thickness can be no less than 3mm. More expensive by at least $10 in parts cost.
Both designs would be standard credit card dimensions, entirely solar powered (need to get samples and test, but looks possible), possibly have super cap power backup, a standard ICSP programming header on the edge, and a Micro SD card is also possible. And other edge mounted stuff is also possible, like a rocker switch, IR LED etc.
Micro USB connector is only possible on the 4mm 14sgement LCD design.
I see backlight as being pointless on both.
Either design could of course have a powerful processor and Micro SD card etc, but I think all that power is kinda pointless on the limited 8 digit 14segment display design.
Either design can have either a membrane overlay or capacitive touch sense keypad. As many keys as can fit.
The membrane option adds some thickness due to the material and the domes (say 0.5mm minimum), but is possibly much cheaper once NRE is taken out, and people could in theory design their own own to have whatever key overlay they like (it just sticks on the panel).
The cap touch sense is the thinnest option, and no NRE for the overlay. But it does use more power (likely not an issue), and would not have any tactile or key "feel". A flat stick-on adhesive graphic overlay would be an option, allowing users to add their own stick-on custom overlay.
So, a few questions:
1) Who would buy such a thing? (cost say $60-70 approx)
2) What display/thickness option and why?
My initial thought is that thickness should be the main criteria, as much as I love high contrast 7 segment displays. So the more expensive 128x32 dot matrix and cap touch panel seems the best option.
Case is entirely resin fibreglass with a choice of funky colours top/bottom.
I've got all the parts bar the solar cell and am getting rather excited! :->
Edited: 14 Nov 2009, 6:31 p.m.