This programmable power supply is the perfect addition to your bench tools. [Debraj Deb], who previously built a whole house power monitor, designed this build around a PIC 18F4520 microcontroller. The desired voltage is set with an attached keypad, resulting in a digital output on the 8-bits of port D. The port connects to another protoboard with an R-2R digital-to-analog converter resulting in the target voltage. A set of transistors amplifies the current and a power transistor then takes care of the final output. After the break you’ll find two videos, the first walks us through the hardware and the second demonstrates the device in action, along with measurements of its performance. This certainly provides a lot more functionality than an ATX power-supply conversion.
Update: A big thanks to [Debraj] who sent us a code package as well as the schematic (PDF) used during testing. We’re having trouble getting the code package up for download right now. Check back later, hopefully we’ll have it up soon.
Continue reading “PIC programmable power supply”
[Dan McGrath] tipped us off about a solution for a problem that most people don’t have. He built a web-based entry system for his garden gate. This isn’t quite as original as that chain and sprocket dorm room system, but it does use a keypad for entry. [Dan’s] already got a web server and home automation box that is always running. He coded a webpage that presents a virtual keypad for code entry. If the right code is input the system unlocks the electronic strike on the other side of this gate. Since the interface is a web page you can load if from any web browser (an iPhone is used for demonstration purposes after the break). But if you don’t have internet access you’re in trouble; there’s no physical keypad. But we guess you could always just jump the fence. Continue reading “Automated entry for a garden gate”
It’s that time of the year again. The leaves are changing colors, it’s getting colder outside, and all the littler hackers are off to college. Which means we get to see an influx of dorm room locks and openers.
[Adam] is back at it again with a new keypad dorm room lock. Last year he had an exceptional setup using a car keyfob, so we’re a little curious as to why he would revert to such a low level system as a keypad that isn’t even color coded.
Perhaps its in his “new” way of presenting the hack. Rather than a blog or write up, he documents the entire most of the process in a little less than 20 YouTube videos. Watch him testing out the system after the jump.
Continue reading “Keypad door lock, better than last years keyfob?”
Our friend [Sprite_TM] took a look at the security of a code-protected hard disk. The iStorage diskGenie is an encrypted USB hard drive that has a keypad for passcode entry. After cracking it open he found that the chip handling the keypad is a PIC 16F883 microcontroller. He poked and prodded at the internals and found some interesting stuff. Like the fact that there is an onboard LED that blinks differently based on the code entered; one way for the right code, another for the wrong code of the right number of digits, and a third for a wrong code with the wrong number of digits. This signal could be patched into for a brute force attacking but there’s a faster way. The microcontroller checks for the correct code one digit at a time. So by measuring the response time of the chip an attacker can determine when the leading digit is correct, and reduce the time needed to crack the code. There is brute force protection that watches for multiple incorrect passwords but [Sprite_TM] even found a way around that. He attached an AVR chip to monitor the PIC response time. If it was taking longer than it should for a correct password the AVR resets the PIC before it can write incorrect attempt data to its EEPROM. This can be a slow process, but he concluded it should work. We had fun watching the Flash_Destroyer hammer away and we’d like to see a setup working to acquire the the code from this device.
Here’s two input devices you can easily build with materials you already have on hand.
To the left, [John] built a 3×3 keypad matrix from paper and tinfoil. The rows and columns are made up of strips of tin foil on the front and back layers of paper. The layers are separated by spongy double-stick tape. A ‘keypress’ results when the gap between the conductors is compressed with your finger.
In much the same way, [Dave Fletcher] built a touch potentiometer. He made two resistance plates by scribbling pencil lead on sheets of paper. When the two plates face each other, separated by the same type of foam tape as before, they can be pressed together to form a circuit with a variable resistance. This results in a crude version of the SparkFun softpot.
If you watched the video before reading the article (like we did) and started shaking in your boots at a voice controlled lock system, prepare to be disappointed. His spoken commands are actually to his son to press the appropriate keys on a keypad off screen, the lock is not actually voice controlled.
But still, [Michael Krumpus’] door lock is pretty astounding. By using a torn apart CD drive he easily attains a nice fast and smooth linear motion to bolt and unbolt his door. It wont open his door like some locks we’ve seen, but it will probably be added sometime in the future…right alongside voice commands.
[Colin Merkel] had a little problem: he was continually forgetting his electronic key card, locking himself out of his own dorm room. Like any normal Hack a Day reader, rather than getting in the habit of always carrying his card, the natural impulse of course is to build this elaborate rig of electronics and duct tape. Right?
The result is an additional keypad that can be used to gain access…not by altering the existing electronic lock, but with a secondary mechanism that operates the inside door handle. An 8-bit PIC microcontroller scans the outside keypad (connected by a thin ribbon cable), and when a correct access code is entered, engages a 12 volt DC motor to turn the handle. It’s a great little writeup that includes a parts list, source code, and explains the process of keypad scanning.
It’s similar to the RFID-based dorm hack we previously posted. By physically operating the handle, most any approach could be used: facial recognition, other biometrics, DDR pad, or whatever inspired lunacy you can dream up.