Re: Newbie to design

Colin wrote:
Hi everyone.
I am sure somebody here will have the answer. I am attempting my first (complicated??) design and hope you guys can help.
For the first part, I am considering using a 4x3 matrixed numerical keypad for up to 4 (6, preferably) users to enter their own secret PIN. Once set, each user can input their PIN to activate a logic 1. There needs to be a separate logic 1 output for each user.

I have come up with a design that does part of this. The user's PIN is selected in 4 bit binary by DIP switches (it's ok if the "master" user knows the PIN of the others). When the PIN is entered, logic gates determine if the PIN input matches that set by the DIP switches and allows a logic 1 to be output, otherwise logic 0 is retained. This is fine for just one user, but how do I adapt for multiple users? Or perhaps there is an easier way.

I'd also like to include a LCD to make the system user friendly. In fact, I already have the display module. It's "Reflective LCD display,162D-BA-BC". It can be found on the RS website <http://rswww.com>; stock number 532-6470. A pdf data *** is also available here.
Please bear in mind that I need to utilise the display for other things too such as time of day and also as a countdown timer for each user.

This is just one section of the overall project.
I prefer to keep the component count to a minimum, but also need to use readily available parts.

I am considering the use of PIC chips, but have to admit my knowledge of them is very limited.

If anyone can help, I am happy to answer any questions you may have to the best of my ability.

Regards,
Colin (yes, another one)
The way I'd do this would be to use a PIC with flash, and have it remember the PINs. I'd set up the "master" user with a way to access the thing to enter PINs (and delete them). Basically, if you're spending the $$ on a microprocessor, you want to make it do all the work you can.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

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"Applied Control Theory for Embedded Systems" came out in April.
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