4x3 Button Matrix - Page 1
Forum section: electronics / projects

author: Brown
author_rank: Contributor
timestamp: December 17, 2013, 12:30:53 pm
content: PLEASE tell me this is designed correctlyhttp://imgur.com/a/s1rMV

author: tszaboo
author_rank: Super Contributor
timestamp: December 17, 2013, 12:38:10 pm
content: No. Everything is shorted.

author: kxenos
author_rank: Frequent Contributor
timestamp: December 17, 2013, 12:41:49 pm
content: No, it's not designed correctly!. Except the fact that whoever designed the schematic doesn't know how to draw schematics, whoever designed the PCB should be beaten by the one who designed the schematic because he mixed the buttons. He also should be beaten by half the eevblog forum members because he hasn't followed any rule of pcb design and his board is just a mess! I can't describe it any better, sorry! It's just so ugly!!!

author: Brown
author_rank: Contributor
timestamp: December 17, 2013, 12:49:51 pm
content: I designed it I though it was wrong and I don't know how to use Eagle. Can you guys make me a proper one if you have time? Thanks

author: mariush
author_rank: Super Contributor
timestamp: December 17, 2013, 12:50:28 pm
content: Please see Microchip's Tips'n'Tricks documents that show you various tricks and the circuits:TIP #2: Input/Output Multiplexing............................ 1-2TIP #3: Read Three States From One Pin............... 1-3TIP #4: Reading DIP Switches................................. 1-3TIP #5: Scanning Many Keys With One Input......... 1-4TIP #6: Scanning Many Keys and Wake-upFrom Sleep.................................................. 1-4TIP #7: 8x8 Keyboard with 1 Input........................... 1-5TIP #8: One Pin Power/Data................................... 1-5TIP #9: Decode Keys and ID Settings..................... 1-6http://ww1.microchip.com/downloads/en/DeviceDoc/01146B.pdfTIP #2 Input/Output Multiplexing.............................. 3TIP #3 Read Three States From One Pin................ 4TIP #4 Reading DIP Switches.................................. 5TIP #5 Scanning Many Keys With One Input........... 6TIP #6 Scanning Many Keys andWake-up From Sleep................................... 8TIP #7 4x4 Keyboard with 1 Input...........................10TIP #8 One Pin Power/Data....................................11TIP #9 Decode Keys and ID Settings .....................12http://ww1.microchip.com/downloads/en/DeviceDoc/40040c.pdf

author: kxenos
author_rank: Frequent Contributor
timestamp: December 17, 2013, 01:02:10 pm
content: Quote from: Brown on December 17, 2013, 12:49:51 pmWell I guess we have to beat you then!I don't have time to draw it for you but I have time to tell you some things you could do to improve your design. Plus I don't use eagle anyway.Well, one important thing is that in the schematics, you try to avoid passing wires through components. So, you have to place the wires near the switches like in this picture and not underneath them.

author: kxenos
author_rank: Frequent Contributor
timestamp: December 17, 2013, 01:11:41 pm
content: And then, for the PCB, check this layoutYou see what he did? He used the internal connections of the switch pins to continue the line to the next switch horizontally and so he could run the vertical signals underneath the switches.Also, having component labels visible on your PCB helps.

author: amyk
author_rank: Super Contributor
timestamp: December 17, 2013, 01:17:31 pm
content: Googling "keyboard PCB" also returns a bunch of useful images. A keyboard matrix is a very regular structure, so your PCB layout should also be regular. Having the traces run in random directions everywhere doesn't work so well.

author: Brown
author_rank: Contributor
timestamp: December 17, 2013, 06:00:31 pm
content: Kxenos, I used the first image and made thisis it correct?

author: kxenos
author_rank: Frequent Contributor
timestamp: December 17, 2013, 06:19:15 pm
content: Quote from: Brown on December 17, 2013, 06:00:31 pmMuch, much better!What about the PCB??

author: free_electron
author_rank: Super Contributor
timestamp: December 17, 2013, 07:36:54 pm
content: here is a trick : when using thos e4 pin tact switches : use opposite corners. that way it doesnt matter how you install the swirtch. it will work

author: amyk
author_rank: Super Contributor
timestamp: December 18, 2013, 06:04:00 am
content: Is there a reason why you're deliberately placing the pads in different places? Your layout still looks very irregular for a standard matrix keyboard.