Keypad to display circuit

[RogerB]

I want to use a 4x3 keypad to enter 4 numbers on an LED array or 4 x 7-segment LEDs, one of the non-numeric keys would need to be able to clear the display. What would be the easiest way to achieve this please?

 

[Harald Kapp]

The answer depends on your understanding of 'simple'.

This calls for a small microcontroller that scans the keypad, stores the entries and controls the display.
This is a simple hardware setup which on the other hand will require some programming.

Another method would use a counter to address the digits of the display, a register for each digit of the display to store the number, a decoder to generate the 7-segment code from the binary register output, a few gates to de-bounce the keys, a clock oscillator to ontrol the timing and possibly a few flip-flops and gates for controlling the proper sequencing.
No programing required.

I leave it to you to judge what is 'simple' in your opinion.

 

[RogerB]

It would appear from your reply that the micro controller is the simpler way. Is there a recognised circuit that I could copy please?

 

[ArmRules]

Can you write code and have the tools needed to program the microcontroller? The circuit is only 1 factor. Code also needs to be written to drive the display and read the keypad

 

[Minder]

There is a Micro example on Nigel Goodwin's Tutorial site in assembly also the code is available in C if preferred, on the internet with search.
M.

 

[RogerB]

I have limited experience of assembler from the 1980's and some in Coral 66 whilst in the RAF, but no PIC experience. I don't have any equipment to do such programming, but would be prepared to consider getting some.

 

[ArmRules]

Given your level of experience and If you have no micro preference, then an AVR is probably the lowest development cost option. I would get an arduino uno, a display board (maybe one based on the MAX7219 which will reduce the amount of pins you need to breadboard and ease your programming somewhat), a keyboard, a breadboard and some jumper wires
I would first do all my firmware development using this option as it will give you know good hardware. In many cases the cost of these development boards is lower than what you can build from scratch so unless you have an enclosure/space constraint just packaging up this solution will work for your final implementation..

 

[RogerB]

Many thanks for your response, I will look at your suggestions and move forward from there.