This is a project I did for the Make:NYC Labs. We don't have a power supply for everyone to test their completed projects, so I took 20 minutes and about $6 in parts and made a snake.
This snake uses 8 alligator clips, 2 banana plugs, and a reasonable length of CAT-5 cable.
What? You don't keep a stash of shrink tube around? Bah. Use tape.
First we strip out about 4 inches of wire and separate the striped and solid ones to create positive and negative busses. We attach the appropriate banana plug to each group.
Then we strip away about 1/3 of the wire covering from the other side of the cable. Shrink tube the junction where the covering ends to prevent fraying. We shrink tube each pair of wires together to keep them from coming apart then attach alligator clips to their respective wires.
Make:NYC is having a name badge contest and I needed a badge to demonstrate at the first meeting.
I had some CrystalFontz Serial LCDs (Model CFA-632 $37) laying around and these neat little modules have a boot EEPROM that you can program to load text and graphics when power is applied to the module without serial data input.
I attached a voltage regulator for the power supply (battery eventually). I also connected the serial cable for programming. I then glued an "attractive" foam bezel to the front of the LCD.
This is the CrystalFontz boot programmer.
The finished product with lavish nylon string neck loop and 9v battery power source!
I should be able to cook up a halfway decent badge for the next meeting.
Now don't tell the co-op board, but I crafted a plan to ditch my Mul-T-Lock key for good. My apartment building, of course, uses an intercom system to remotely unlock the front door for guests, deliveries, etc. This keychain upgrade gets me in the front door... keylessly.
The mechanism is simple enough, just a momentary button on the panel in my apartment, but the mess of wires in the wall is a little unsettling. I took some meter readings of the terminals and sorted out the door button wiring. You can see where the door button is soldered through the PCB, which made it easier to identify the proper terminals. This panel has a "Door", "Talk" and "Listen" button. The "Door" button is normally-open and the circuit is about 22V. In the following steps we're going to effectively bypass the button with our own circuit.
I purchased a relatively cheap RF relay kit from Carl's Electronics. The HD2Combo 2-channel RF relay kit. These things are fun and just $30, get one even if you don't think you'll ever use it. Don't forget a 12V supply for the board. This is a rolling code transmitter, so no -- not just anyone with a remote can activate the relay.
Okay so, kit and intercom meet. I connected one of the normally-open relay circuits on the RF board in parallel to the "Door" button with wires marked "To Relay" and "From Door" in the photos above. This configuration allows either the relay or the button to operate the door. If your particular application uses a normally-closed circuit to open the door, wire the button in series and connect it to the normally-closed circuit on your relay.
Also show in the above photo are the 12v DC supply wires (black) and the antenna wire (also black).
My apartment is actually directly over the building entry, so range on the transmitter fob is not nearly an issue. I can activate the relay from my bedroom or from in front of the building. It's not the most impressive hack, but it sure makes my life easier.
And there you go. A keyless entry. So what's the second button do? Nothing. At least, not yet.
TODO: Hide the receiver and wire.
This is one of those things where I might caution that you not try at home unless you're very snuggly with your landlord.
The USB cable on my RetroPad is cumbersome in the car. So, I got rid of the wire! I bought a cheapy Targus wireless keypad and popped it open along with an original NES controller I had.
I cut out the controller IC and cable. I trimmed the PCB and glued a AAA battery holder in. I'll be replacing the keypad's original AA battery with a NiMH AAA.
Here's the tricky part. The NES controller uses 8 inputs and one ground for it's switch state input. The keypad uses a 4x5 matrix decoder. So I split the ground trace on the control pad into 2 parts (you can see this cut in the second image below) and gave each ground to a column on the keypad. Then I jumpered pairs of buttons on the control pad and connected each pair to one of four rows on the keypad, effectively giving me / 8 2 0 for A B Sel Start and * 9 3 . for Up Rt Lf Dn.
That's it! I connected the battery, moved a few components around to allow the back to close and we have a working wireless joypad from an original NES controller. Now I just map the keys the joypad generates in our emulator to the proper buttons and I'm playing Dr. Mario in the car.
There are a couple issues. First, this is a cheap RF keypad. It has an effective range of 3-4 ft, but fine for the car or desk. Also, this keypad doesn't like it when you use more than one key at once. So, when playing Super Mario Brothers, while running and you jump, you stop going forward. I think both of these issues can be resolved up upgrading to a more expensive keypad. Cost: $27 (not including the controller) Time: 2 hours
