I build a remote control that connects to a PC with USB. The large remote control lets my toddler select and play videos on an old computer.
This is a relatively simple project. The core component is either a USB keypad or a wireless USB keypad.
Then I figured out which leads on the numpad correspond to which numbers, soldered wires on the circuit board and connect them to the buttons on the remote.
You will also need a PC, a monitor and speakers. Any old PC or Mac will do, as long as it capable of playing video (about 450 mhz and above). Basically any computer that's 8 years old or younger will be able to do this. I used VLC to play the media files, but you can use an media player that allows you to change the shortcut keys.
I finished the whole project in about four hours.
Step 1: Parts Needed
The whole project cost me about $7. Depending on the items you have lying around you will spend more or less.
I went with the wired remote, because anything not bolted down in my house has a tendency to end up somewhere where you wouldn't expect it. Lego blocks in the cup boards, lunch boxes in the bedroom, wooden spoons in the living room etc. If you have a toddler, you know what I mean. Not very practical to have a wireless video player remote in your front yard. I already had the numpad, but you can buy one from newegg.com for $10, or $30 for a wireless one.
Once you have your numpad, it's wise to first connect it to the computer and configure the player and test to see if you can actually control the player with the numpad.
In addition to the numpad I used the following computer parts:
An old Compaq M700 laptop. The laptop has a crappy battery and the lid keeps closing by itself. My wife used it, but she kept complaining that it was too slow.
I salvaged a 17" Philips monitor with build in speakers. When i found it, it was not working. I opened it up and found bulging capacitors. $2.30 in capacitors and 30 minutes later I had a monitor to use for this project.
On the electronics side, you will need some wire, a couple of buttons, solder and a soldering station.
This is where you have to decide how many buttons you want to implement.
I went with 5 buttons, play/pause, next and previous and fast forward and fast backward.
The buttons I used were ordered from Jameco:
315441- 2x Black Buttons
315432 - 3x Red Buttons
Step 2: Configure VLC Media Player
First create a playlist of movies in VLC.
If you want, you can save this playlist, associate it with VLC if this hasn't been done already and put a link to the playlist in your startup, so that the player will automatically start when windows starts up.
Then open Preferences and set VLC to start in full screen.
Next, open the hotkey preferences and change the hotkeys to the numbers on the keypad that you plan to use with the VLC media player. Initially I was unable to set the keys to numbers, but after upgrading to the latest VLC player, I was able to do so.
Now is the time to test your numerical keypad to see if it will work with your configuration.
This was also the point where I connected the laptop, monitor and speakers.
Step 3: Build or Prepare the Project Box
You can use any type of box here. Since it's for a toddler, I suggest something heavy, otherwise they will try to pull it away and throw it in the toilet. If you go for a plastic box, stuff it with some metal or stone ballasts.
I made a box with some MDF I had left over from a previous project.
I decided that 15 x 15 cm x 10 would be a good size and used a hacksaw to saw the boards. After sawing them I used sanding paper to flatten the sides get rid of the sharp edges. Pay extra attention to this. You can be sure the box will be shoved, pulled pushed thrown, kicked, stand on and laid under, sharp edges and corners should be avoided.
Then I measured and drew the locations of the holes and drilled them.
Knowing the dimensions and the locations of the buttons, I used Adobe Photoshop to create a template that I used to spray paint the symbols on them.
I had already decided on the sizes of the symbols based on the size of the box itself and used the grid in Photoshop to make the symbols the size I needed them. Making the symbols is easy. Simply draw a black square and rotate it, then cut it in halve. Since most symbols consists of this halve square, copy and paste it to different layers and resize where needed.
I printed on thick paper and used a box cutter to cut out the symbols.
Then I used photo glue to attach the template to the top and tape to mask the sides (don't skip the photo glue if you spray the symbols on - if you don't you will end up with fuzzy edges on the symbols).
Next I applied a layer of gloss clear coat to prevent all kinds of stains on the box (MDF isn't really toddler proof without it). I then glued the four sides to the top and drilled holes in the bottom so I could screw that in.
Step 4: Modifying the Numerical Keypad
Next I took the keypad apart. Now, depending on the numpad, you will encounter different hardware inside, but all numpads should work according to the same principle.
They have a grid and each horizontal and each vertical line will connect to a pin on the USB chip.
In my case the grid itself was not a circuit board but conductive lines on two plastic sheets with an isolating sheet in between them. Although this is a very elegant design, it meant I couldn't directly solder onto the grid and had to trace the numpad circuit to figure out where to solder the wires.
Since I needed 5 buttons I had to trace the leads of the following buttons:
1, 2, 4, 5, 7 and 8.
Then I numbered the pins on the circuit boards and traced which numbers used which pins (look at the pictures for more clarification) and drew a small schematics for these buttons.
So to type the number 1, contacts 7 and 2 need to make contact, to type a 2, contacts 7 and 4 need to make contact with each other.
Then I soldered wires where the printed circuits was exposed. This was probably the hardest part, since these points were quite small. After soldering the 5 wires, I applied glue with my hot glue gun to prevent the contacts from breaking off the circuit board.
Then I hooked up the circuit board to the computer, opened notepad and verified if the numbers would come up if I connected the correct wires.
Step 5: Insert the Buttons and Connect Them to the Numpad Circuit Board
First I soldered short wires to the buttons, then I inserted the buttons in the holes and glued them from the back. I didn't trust hot glue for this and applied a blob of liquid nails.
I did the same with the numerical keypad, I placed it in a blob of glue in between the buttons.
Then it was simply a matter of following the diagram I made previously to connect the wires that are attached to the circuit board to the buttons. I first twisted all the wires together and did another test with the video player to make sure it did what I wanted and then soldered them together.
And the last step was attaching the bottom with four screws. Glue seemed out of the question, considering that it would make any repairs very hard.
Make sure you secure the USB cable where it comes out of the box. You can be sure it will pulled on savagely.