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4x4 matrix keypad — Parallax Forums

4x4 matrix keypad

qdoggmetsqdoggmets Posts: 14
edited 2009-11-23 23:58 in Learn with BlocklyProp
hi,

i have started to build a wireless remote control. i have the basic stamp 2 revision D and picked up a keypad from grayhill.com for testing/coding/learning purposes. the spec sheet for the keypad is located here: http://lgrws01.grayhill.com/web1/images/ProductImages/Keypads_84BL.pdf

it is a 4x4 matrix keypad

my understanding is that the current of 205ma·will not natively work with the basic stamp module but have been told it·CAN work. how would i go about wiring this correctly?

i believe that the 8 data pins can just be connected to the basic stamp.

id also like to get an understanding of the truth table. i assume that if you pressed a button after wiring everything up correctly...say button 1 then 2 data pins would show being pushed and verifying which 2 are pressed will calculate which button was pressed.

thanks,
kevin

Post Edited By Moderator (Joshua Donelson (Parallax)) : 12/1/2009 9:20:52 PM GMT

Comments

  • Mike GreenMike Green Posts: 23,101
    edited 2009-11-23 23:43
    There are some Nuts and Volts Columns on the use of a 4x4 keypad with a Stamp. Go to the main Parallax webpage and click on the Resources tab. You'll get a page with a link to the Nuts and Volts Columns index. Browse that for articles on keypads.
  • qdoggmetsqdoggmets Posts: 14
    edited 2009-11-23 23:58
    hi,

    i was able to resolve my issues by calling gray hill and talking to an engineer but thanks for your comment.

    first the 84bln back light series from grayhill has the built in 43 ohm restistor. so you can hook a 5v power supply directly to it and not blow the voltage max on the keypad.

    secondly some basic stamp boards(newer models) have a voltage regulator on it. this is a three pronged device near pin 14 and pin 15. the max amperage draw on the basic stamp unit without a regulator is 180 milliamps which is under what i needed to run the keypad with the backlight. luckily mine has it. the voltage regulator allows me to pull roughly one amp.

    thirdly the matrix is how i thought. when you proess the button 2 data pins will show as being pressed. you have to use that combination of pin values to determine which key was pressed.

    additionally as a side note....the x pin in the data sheet is the anode and the y pin is the cathode.

    thanks,
    kevin
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