Bending a home security control panel to your will

Does your home have a security system but you don’t subscribe to the monitoring service to make it work? Rip that baby off of the wall and do something with it, or just build your own system around it. If you have a DSC PC1500RK control panel [CaitSith2] shows us how easy it is to control the buttons, LEDs, and buzzer. If you’ve got a different model this is still a good jumping off point to start your own reverse engineering.

There are only four connections that need to be made. [CaitSith2] is using an Arduino for the demonstration. He connected the red wire to voltage, the black wire to ground, the yellow wire (clock) to digital pin 3 and the green wire (data) to digital pin 2. A communication cycle starts by setting the data line high, then clocking out eight bits to capture keypresses. 16-bits are then clocked in to set the LEDs and drive the buzzer. This is shown in the video after the break as well as documented in his sample code. We’ve embedded the sketch after the break to preserve it in case the pastebin code goes missing in the future.

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One wire reads the keypad from the APRS radio mic

[Shane Burrell] decided to spend some time learning how the keypad on the his Kenwood TM-710A APRS radio mic works. It uses a different technique than you might think. Normally a grid of buttons is scanned as a matrix to detect keypresses, but this hardware actually counts pulses on a serial wire to take each reading.

The stock radio sends a steady digital pulse to the handset and with each pulse the mic pulls the line low. It then uses a 4017 decade counter to see what comes back. If the edge count matches it means nothing is pressed, but a change in the number of pulses returning to the base unit can be used to extrapolate which button has been pressed.

[Shane] went on to implement this control technique using an AVR chip in place of the  radio base unit. He used the data gained from measuring the pulse behavior using an oscilloscope to write the firmware for the project. He filmed a bit of a demo after the break which shows his findings.

We’re not quite sure how this would translate into your own home-brew projects, but the thought of scanning a keypad with two pins of a uC is quite desirable. Sure there is the 555-timer frequency technique, but we’re always down with new ideas.

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Buzzer project for classroom team games

Want to host a Jeopardy tournament with your friends? Looking to add a bit more fairness to your school’s knowledge bowl? Perhaps you should build some buzz-in hardware of your own.

Here you can see [Matt Hanson's] take on this idea. He used one Arduino to gather not just buzzer info, but also keypad data from four satellite controllers. Each has an RJ45 jack, allowing it to connect tot he base unit with an Ethernet patch cable. We like the color coding that [Matt] chose, which matches the color of the arcade button to the keystone jack on the base. And of course the fantastic look of the water-jet cut cases isn’t lost on us either.

You may wonder why he included a key pad on each controller? It looks like he and a few others worked together to develop a team-based math game for use in school.

Full featured security lock demonstration

[Arshad Pathan] let us know about his latest project, a modular code lock that can be adapted to many different situations.

The user interface is made up of a character LCD screen and a 3×4 keypad. For this example [Arshad] is using a stepper motor as the locking mechanism. When the board is first powered up it runs the stepper in one direction until receiving input from a limiting switch. In this way, the microcontroller calibrates itself to ensure the lock is in a known position. From there it waits for user input. An unlocked door can be locked at any time by pressing the * key. Unlocking requires entry of the correct password. And a password can be changed by entering 9999 (followed by the old password when prompted).

In the video after the break [Arshad] does a great job of demonstrating the various modes which he has programmed. This stands on its own, but we always love to have more details so we’ve asked if [Arshad] is willing to share a schematic and the source code. We’ll update this post if we hear back from him.

Update: [Arshad] sent in a couple of schematics which can be found after the break.

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Adding keypad security to your automobile’s ignition system

[BadWolf] managed to make some free time to get back to his own electronic projects. This time around he’s created a security system for his car. It’s patched into the ignition, preventing the engine from starting when the key is turned. A driver must first insert the key, then type the combination on a keypad in the center console before the car will fire up.

While he was working on the project he also decided to add a start button to the dash-board (we think it does make it look like a later model vehicle). The keypad is driven by an Arduino Nano which has the start code stored in it. Power for the system is provided by a USB hub hidden behind the dash which he thinks will also come in handy with future hacks.

When the proper code is entered, you’ll hear a rendition of the Super Mario Bros. theme. The speaker also lends a pleasant beep with each keypress. See the demo clip after the break to hear it for yourself.

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Repaired microwave keypad looks as good as new


Instructables user [Rohit] had an out-of-warranty microwave with a broken membrane keypad. Much like our friend [Alexandre] from Brazil, he found the cost of replacement parts beyond reasonable, so he had to find a way to repair it instead.

He disassembled the front cover of his microwave to get at the main controller board. Once it was detached, he removed the keypad’s cover to get a closer look at the matrix underneath. While taking notes on how the matrix was wired, he found that some keypad traces connected to other traces rather than buttons. He says that they are likely used by the microwave to detect that the keypad is present, so he made sure to short those traces out on the controller board when he wired everything back together.

He replaced the aging keypad with microswitches, but rather than mount them on the front panel of the microwave, he drilled holes for each switch so that he could mount them inside the face plate. Once everything was wired and glued in place, he re-mounted the keypad’s cover. Now the microwave looks stock but has firm, reliable, user-serviceable buttons that are sure to last quite a while.

Keypad uses a PIC’s built in capacitance functionality

[Giorgos Lazaridis'] most recent project was to build a capacitive touch pad. Since he’s using a PIC 16F1937 it will be relatively easy. That’s because it has a 16 channel capacitance sensing module built right in. But there are still some design considerations that make the development a bit touching.

This isn’t the first time he’s worked with capacitance sensing. Through past experience he has found that it is very important to position the microcontroller as close to the button pads as possible. Because of this, the chip is soldered on the back of the PCB used for the keypad itself. Because he’s hand soldering vias, he also used some foam tape to raise the button pads just a bit. This way they will be flush with the acrylic overlay, which cannot sit flat on the board due the via solder joints.

Check out the video after the break to hear [Giorgos] walk us through the project.

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