Let’s rollback the hobby electronics calendar a few decades with [myvideoisonutube’s] alarm activation control circuit using a matrix style phone keypad. The circuit is quite old using CMOS 4081 with 4 ‘AND’ gates to hardwire the access code. [myvideoisonutube] references [Ron’s] “Enhanced 5-Digit Alarm Keypad” schematic for this build changing the recommend keypad with a more common matrix style keypad found in touch pad phones. These types of matrix keypads wouldn’t work outright for the input so he cut some traces and added hookup wires to transform it into a keypad with common terminals and separately connected keys. We love seeing such hacked donor hardware even when it requires extensive modifications. [Ron’s] source circuit included a simple enough to build tactical button keypad if you can’t find a suitable donor phone.
Learning how to use mostly discrete components instead of a microcontroller would be the core objective to build this circuit outside of needing a key-code access point or other secure 12 V relay activated device. Such a device would be quite secure requiring a 4 digit “on” code and 5 digits for “off”. You couldn’t just pull off the keypad and hotwire or short something to gain access either. The 4 digit on “feature” does knock the security down quite a lot. However, all keys not in the access code are connected to the same point so you could increase your security by using a pad with more keys.
On [Ron’s] site you will find a detailed construction guide including top and bottom view for placement of all the components on veroboard. Join us after the break to watch [myvideoisonutube] demo his version.
Continue reading “5 Digit Security Code Activated Relay Using Mostly Discrete Circuitry”
[Sylvio] decided to buy one of the cheap alarm systems you can find on the internet to have a look at its insides. The kit he bought was composed of one main motion sensor and two remote controls to arm/disarm it.
Communication between the remotes and the sensor is done by using infrared, requiring a direct line of sight for a signal to be received. Modern alarm systems typically use RF remotes with a typical frequency of 434MHz or 868MHz. In his write-up, [Sylvio] first tries to replicate the IR signal with one of his ‘learning remote controls’ without success and then proceed to reverse engineering the remote circuit shown in the above picture. Hackaday readers may figure out just by looking at it that it is a simple astable multivibrator (read ‘oscillator’). Its main frequency is 38.5kHz, which is typical for IR applications. Therefore, if one of your neighbours had this ‘security system’ one could just disarm it with any of the same remotes…
[Sylvio] then explains different ways to replicate the simple IR signal, first with an Arduino then with a frequency generator and finally using the USB Infrared Toy from Dangerous Prototypes. We agree with his conclusion: “you get what you pay for”.
Now [Kevin] claims he built this robot for his 3-year-old son but we know he just used that as an excuse to spend way too much time in his workshop. The robot is a roundup of all the interesting things you can do with hobby electronics. It’s a great example of what you can teach yourself in one year, as [Kevin] only started tinkering with electronics about fourteen months ago.
The robot centers around an Arduino which manages to control a plethora of auxiliary boards. The alarm clock part of the build has a readout in the center of the robot’s chest. There are a bunch of sounds which can be played as the alarm, including a lot of iconic movie sound bytes. Add to that some playful features — like a tone generator which is altered by the column of potentiometers on the left, motion activated eyes, and sound activated ears — and you’ve got a dream-come-true of a toy for your kid.
As a side note, we wrote this several days ago, but ended up bumping it a couple of times in the publishing schedule. We reached out to [Kevin] to let him know a feature was on the way. When he learned that we bumped it in order to feature [Jamie Matzel’s] giant robot he had to laugh. The two met at a mini Maker Faire about a year ago and that interaction is what gave [Kevin] the confidence to start the project.
Continue reading “Zappo the robot mixes tone generator, sensors, alarm clock and more”
Most of the homes in the area where [Raikut] lives have tanks on the roof to hold water. Each is filled from a well using a pump, with gravity serving as a way to pressurize the home’s water supply. The system isn’t automatic and requires the home owner to manually switch the pump on and off. [Raikut] made this process a lot easier by designing an LED bar indicator to monitor the water level.
The sensor is very simple. Each LED is basically its own circuit controlled by a transistor and a few resistors. A 5V signal is fed from 7805 linear regulator into the tank. The base of each transitor is connected to an insulated wire, each extending different depths in the tank. As the water rises it completes the circuit, illuminating the LED.
[Raikut] is conservation minded and built a buzzer circuit which is activated by the LED indicating the highest water level. If someone walks away from the pump switch while it’s filling the alarm will sound as it gets to the top and they can turn it off before it wastes water.
We’ve got some friends who have two sump pumps. One is a backup and sounds an alarm when it is switched on. But this only works as long as they’re home to hear it. [Felix Rusu] came up with a solution what will text him if the sump pump fails. This way he can head home, or call someone to check in on the problem if he’s away.
We saw a pretty complicated monitoring system back in January. This one uses a single ultrasonic rangefinder which we think is much simpler. It’s accurate to about 1cm and is simple to use — it’s very popular with the hobby electronics crowd which helps with price and availability of sample code. We hem and haw about the use of a Raspberry Pi board with the project. On the one hand it’s a cheap way to get the sensor on the network and provides the infrastructure you need to send any number of alerts. On the other hand, it’s a lot of power for this particular application. But we figure it can be extended to monitor other utilities in [Felix’s] home, like a sensor to alert him of a leaking water heater. And we think everyone can argue that a monitor like this is well worth the time and effort he spent to develop it.
Still trying to solidify that reputation as the office Grinch? This project will let everyone know you’re a complete jerk in no time. It’s called the 8-bit Annoying Person Remover. It detects when someone enters your office at which point it starts to play the Super Mario Bros. theme song while the display counts down 400 seconds. Just like in the game the music gets faster at the end and when it stops they know it’s time to get the heck out.
The hardware inside isn’t too complicated. An Arduino and a Wave shield do most of the work. The song played is stored on an SD card and can easily be changed. There’s a speaker mounted under the top heat vent of the enclosure. The device defaults to displaying the time of day, but monitors a motion sensor on one side to detect when someone comes through the door. This also works when someone leaves, cutting off the music and resetting the display. Don’t miss a video of it in action after the break.
It’s as if this was made specifically for the Comic Book Guy
Continue reading “NES annoyance timer makes no friends at your work”
This sunrise alarm clock was made in a bit different form factor than we normally see. Instead of a box next to the bed it’s a bar above the headboard which slowly illuminates every morning. This was [Holly’s] first electronics project. She spent pretty much all summer working on it and accumulated a skill set that included designing for and operating the laser cutter and assembling and programming the electronics.
She didn’t start from square one. The hardware and programming were greatly simplified by the availability of RGB LED strips and the Monochron clock which drives them. [Holly] altered the code to bring up a blueish hue over a 35-minute time period. Since this will be used to wake her at 5:30am she was also obliged to include some backup sounds just in case. But after the project was finished and mounted she forgot to turn them on and was pleasantly surprised that the lights woke her up on time. The mounting bracket seen above uses t-slot rail with laser cut brackets to hold the half-cylinder shade for the sconce. The final product looks fantastic!