[BUILD LOG] - First DIY Build - Numpad Mod

[Bunford]

Check this link out . <url>http://www.instructables.com/id/Hacking-a-USB-Keyboard/</url>

Use "[ ]" instead od "< >" for your links. Just a tip

I'll check it out later after work. Cheers!

[extraclassic]

Typical that I pick myself up a numpad for an absolute beginner mod, and it ends up being a complex numpad!

Nothing complex about that Numberpad. Some have that socket and some don't. Same goes for keyboards.

The sheets of plastic with white dots on them have conductive traces leading back to that socket. When the top sheet is pressed onto the bottom sheet the white dots touch and complete the circuit which types out a character.

So with this in mind you first need to decide which characters you want to use then follow the traces back to the socket on both the top and bottom sheet (Please note that a multimeter with built in Continuity tester will make light work of this process)

As an example say you want to use the number 1 button.
You follow the trace from the white dot on the top sheet and it goes to pin 3 on the socket, then you do the same for the bottom sheet which might lead to pin 7 (these are just examples)

So what does this tell us?
Well now we know that pin 3 and 7 create the number 1 so if you was to solder a wire to each of these pins and then touch them together it would type out the number 1. You will find that some numbers lead back to the same pin like in this image.



This is example from this project.

http://www.djtechtools.com/forum/showthread.php?t=23322

Repeat this process for the other buttons.

As for pushing the wires directly into the socket. That is the first thing I would try, you might get lucky.

[Bunford]

what you could do is precisely copy the circuit on the plastic contact sheets. That way, if there is some sort of matrix being used, it'll still work properly.

the contact sheet circuit is quite easy to see - should be relatively simple to emulate with wires and arcade buttons. The bonus should be that you won't need to do as much soldering

Sorry, complete noob here. But what exactly does this mean?

I'm assuming what you mean is treat the circles on the plastic sheets as the arcade buttons and the straight lines as wires, and kind of daisy chain the arcade buttons as per the mapping on the plastic contact sheet. Am I right in thinking that?

If so, how would I daisy chain the arcade buttons?

[VirtualLogic]

Yer that's what milo means

[MiL0]

that's correct

daisychaining the arcade buttons might mean soldering more than one wire to each terminal on the arcade button... you need to look at the plastic contact sheets and work out what's going on.

if no one else attempts it, I'll try and knock up a wiring diagram in mspaint later tonight.

also, extraclassic is right on the money... you don't need to understand how the matrix works... just that by completing the circuit in different ways causes one of the numpad buttons to be pressed. Have you got a multimeter? If not, time to get one! They're very cheap on eBay (mine was less than £5) and are pretty much essential for this kind of project.

[Bunford]

Will attempt to map the keys later and post my findings to see if they make sense.

Also, woudl this Multimeter do the job: http://cgi.ebay.co.uk/ws/eBayISAPI.d...tchlink:top:en

There are cheaper ones on there, but are from Hong Kong and China and can't be bothered to wait a month for it to be delivered!

[MiL0]

yeah that's the one I got (mine was a few quid cheaper but from China).. it works pretty well except that it doesn't have a buzzer... just a visual alert instead.

I think Maplin are doing a cheap one at the moment too:

http://www.maplin.co.uk/domestic-multimeter-37279

good if you've got a Maplin nearby

[Bunford]

Fab stuff! Got two Maplin stores within a mile and they're opening a third within about three minutes of my flat in a couple of weeks. Will pop in tomorrow to pick up the multimeter you linked to. Cheers Mil0!

[Bunford]

Ok, from the pointers so far. I've tried to work the mapping out on the plastic cointact card. The numbers are the number on the 12 'ZIF' contacts. As far as I understand from looking at the ribbon connector, the first 3 aren't used. Now, I think I've worked it all out, but need someone who understands it to check if possible please.

What I have is:

[kooper1980]

Find this thread fascinating. Good effort on starting this mate.

Now that you know which wires have to connect to generate each number on the numpad whats next? how does this info now help you to the next stage of your mod?