MAR21
VCR cassette clock
Although you probably don't have a VCR anymore, you must have a few VHS cassettes laying around somewhere. By using one VHS tape, LED diode and an old quartz clock you can make pretty unusual clock.
What must be taken care of is that the numbering should be anticlockwise since the transparent disc holding the numbers is being rotated from left to right. The numbering of hours is accomplished by etching or engraving the transparent disc so it can catch light from an LED below. Engraving could be done by using hot soldering iron and steady hands.
Source: lemonie
MAR10
Magnetic sniffer probe
If you are working with magnets and you need to figure out the polarity or even "see" the magnetic field around it, you should really build this simple magnetic probe. It is made out of NE555 timer configured as VCO, piezzo buzzer, hall effect sensor and a few passive components.
NE555 produces a constant distinctive sound when hall effect sensor doesn't sense any magnetic field. As soon as the sensor picks up magnetic field, it will result in voltage change on it's output pin that is further connected to NE555's input pin which will finally result in change of sound pitch on the buzzer. The pitch differes when sensor is closer to south pole than the north, so you can easily figure out it's polarity as shown in the video.
Source: pronteon
MAR3
Very simple light following robot
This simple light following robot consists of a minimum number of components: two transistors, four resistors, a photo resistor, LED and a motor. Of course, this all is required for driving only one motor so you need to multiple these components by two so that your robot can move left and right - towards a light source.
There are more versions of this robot and here is another one which we have all seen earlier. Check the video of robot in action.
Source: dunnos
FEB26
GPS tracker using two-way radios
It should take just a few minutes to complete this crude GPS tracker. It is made out of FRS or PMR446 two-way radios and a Garmin GPS receiver. You could probably use any other GPS receiver and the range of this tracker is around 2-3km - depending on the two-way radios range.
What's interesting to me is that this configuration actually does work: RS232 output from Garmin is connected to microphone input of one radio with only two wires. At the other (receiver) side, instead of a speaker, a wire with a COM port connector is soldered and connected to PC with Google Earth and Earth Bridge installed.
It is a very simple hack that works but I would really like to see some opto-isolators here.
Source: V-Man737
FEB21
Megaphone with no batteries required
Here is a very original megaphone that doesn't require any batteries. It is built around a shake flashlight that is powered by its own internal electrolytic capacitor that we previously charged from the energy of our muscles - by shaking hands of course.
Inductive circuit inside a flashlight is kept as-is and a simple LM386 audio amplifier was constructed on a proto-board. A speaker is mounted inside a plastic cup (acting as a sound funnel) and glued at the other end of a flashlight.
Now, all you need to do is make sure you don't run out of energy whilst making a very important speech for the masses.
Source: prizepony
FEB18
LED lightbulb mod
You must admit that this is pretty unusuall situation - LED in a lightbulb, and it's all powered from mains. Old lightbulb was degutted and replaced with two LEDs in anti-parallel connection, with a capacitor and resistor in series. This resistor with capacitor is used to limit current through LEDs. Two LEDs were filed down to half-size and glued together to form a single LED. This step probably is not necessary but it looks cool this way.
Please bear in mind that this device is powered from mains, so it requires a lot of respect when testing.
Source: Tool Using Animal
FEB15
Interface rotary phone dial to PIC
It is very likely that you have an old rotary phone dial lying somewhere around the house for no reason. Well, it is about time to connect it to PIC microcontroller and find some use for it, maybe a digital combination lock with no keypad?
Firmware is written in MBasic and it is available for download. Microcontroller used in this example of interfacing the rotary phone dial is Microchip PIC16F877, but you can use any other microcontroller you like with a few modifications of firmware source code.
Source: randofo
FEB14
Wireless pulsating Valentines heart
If you don't know what to give your loved one for Valentine's, this might interest you. It is a wireless pulsating heart that activates when it's other half gets close. The heart consists of a radio receiver and in the other half you will find a small radio transmitter. Transmitter sends a signal every 0.5s for as long as it is switched on and it is controled with PIC12F683 microcontroller. When receiver senses the transmitter it will blink an LED embedded in heart. Transmitter and receiver are small RF modules that operate on 433.92 MHz whose schematics equivalent can be found here.
So, you give a hart and keep the transmitter for yourself.
Source: daenris
