For a school quiz team, I have to make a 5 button pad with letters A-E for the multiple choice answers. I would need it to just use USB with no software on the computer. What would be the best way of doing this? I was thinking of gutting a keyboard, and finding the contacts for the a - e keys and have those just on a row in a project box along with the keyboard mainboard. Would I need the arduino for this? Thanks!
Most keyboards... unless they are VERY old, do not actually have "switches" where you can grab contacts. Most switches now are made from conductive in on very "melty" mylar or cheap plastic membrane.
The only hope you have of using the ARDUINO is if you use a TERMINAL PROGRAM on your PC. IF you want to make a USB style 5 button keyboard that emulates a USB HID device... the arduino can do it... but it's a serious "hack".
You want to look at this project. Learning About Arduino and AVR-USB - LearningAboutArduinoAVRUSB I personally do not consider this solution to be "trivial" or easy.
You have better luck with a Keyboard chip, like Atmel AT43USB326.
Yes you are right that most newer/cheap keyboards use plastic film that would be impossible to connect to.
They need to connect to the interface chip inside the keyboard though - so that maybe a point you can connect wires to.
The older the keyboard, the more likely there will be big pads you could solder to.
Typically the connector will have two sets of pins/connection points - often refered to as "columns" and "rows", although they usually don't follow the physical rows/columns of the keyboard.
If I was you I'd pull open the keyboard, and take out the bit that connects to the keys. Plug the keyboard in and open up a word processor. Then I'd get a bit of wire, and start connecting one pin from the rows section and one from the columns. this shoud send a single keypress tot he computer. When you find the combination of row and column that matches the key you want, write it down. When you've found all the keyss, solder wires to the relevant pins and new pushbottons to the other end of the wire. When you push the switch, it will complete the loop between the columns and rows, and simulate a keystroke.
No arduino required, total cost = cost of the 5 new switches.
The arduino AVR HID solution would be more robust, but way more expensive and way more difficult.
A keyboard I took apart had a plastic sheet with little rubber domes to make connections. It's like bubble wrap except it doesn't wear out! Brilliant idea: take one of these plastic things and use an arduino to sense if a button is pressed, then get the arduino to play one of various popping noises! A bubble wrap simulator!
I got off onto a bit of a tangent there, but now I'll go back to the original topic. Anyway, this plastic sheet fit into a little slot in the circuit board with a little ribbon connector. The keyboard is just a big matrix, so connecting the appropriate rows and columns will do the trick.
Sorry if I basically repeated anything someone else said.
Edit: oops, looks like I did.