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

microwave_keypad_repair

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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Repairing a broken microwave keypad

microwave_keypad_fix

[Alexandre Souza] needed a microwave pretty badly, but he didn’t have a lot of cash on hand. He located one for a great price, but once he got home he found that things weren’t working quite like they should be (Google translation).

After some investigation, he narrowed the problem down to a bad keypad membrane. Unfortunately for him, this model of microwave was never sold in Brazil (who knows how it got there) and the only membrane he could track down had to be shipped in from the US at a cost of $80.

Rather than pay such a high price for a simple membrane, he opted to fix the microwave himself. He dismantled the control panel and thoroughly traced the keypad matrix to get an understanding of which pins toggled which functions. With a piece of protoboard and almost two dozen push buttons in hand, he built his own keypad and wired it directly into the microwave’s control board.

With labels written in marker it might not be the nicest looking thing you have ever seen, but it works a treat and is a great money-saving hack.

Keypad input scanning by a 555 timer

[R-B] designed a 555 timer circuit to scan a keypad. Keypads are common interfaces for small projects and require row and column scanning by a microcontroller. [R-B’s] setup allows you to reduce the number of pins used on the microcontroller to just two. One is an interrupt that is triggered when any of the buttons are pushed, the other reads the frequency from the 555 chip. Each button has its own resistance which alters the frequency of the 555. The microcontroller reads the frequency for 100ms using a timer. The number of timer overflows that occur during that period directly correspond to the button press (five overflows for the numeral 5, zero overflows for the numeral zero).

We usually debounce our button presses for 40 ms, this is more than twice that amount of time but still not a staggering difference. It does make us wonder if you will miss quick button presses? The only really way to know is to try this out yourself. Check out the video after the break and don’t forget to leave a comment with your own experiences in working with the circuit.

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Building a security access panel

It turns out that hacking together a security keypad is remarkably simple if you know what you’re doing. [Don] needed to add a keypad with an RFID reader on it. He had previously built a USB RFID reader and thought he could integrate those concepts into the new unit.

He once again started with a serial to USB converter and removed the voltage converter IC for later use since he doesn’t need TTL levels for this project. The keypad is a USB product and it turns out there’s a hub inside. With plenty of space inside for the serial converter PCB and a blank spot at the top where he mounted the RFID reader, he adding a few passive components to wire it up and connect it to the hub. The only connection is the original USB cord but the PC will detect both the keypad and the converter.