NOV7
Timer for PCB exposure box with ATtiny2313
When doing more than one thing at the same time it is very easy to lose track of time. Exposing PCBs to UV light is delicate work and overexposing will result in, well, you know what.
Exposing is usually done with UV fluo-tubes but compact fluorescent lamps are also safe way to go and result in excellent PCB quality. Housing for the exposure system shouldn't be a problem because those old broken PC scanners come very cheap. The only thing missing here is the timer to turn off those lamps after pre-set (experimentally determined) time, but this also is not a problem any more because this solution with ATtiny2313 is excellent!
NOV6
Make arduino image scanner/sequencer
Here is a cool project for all of you Arduino lovers (not me, by the way). Even if you are not into Arduino or electronics per say, you might find this little thing interesting if you are into music or strange music instruments.
This here is actually a piece of hand-held hardware designed to create music by scanning a provided image or a drawing. The scanning sensors are LDRs (photo-resistors) and their values are read by Arduino with A/D channels. Those values are than converted to MIDI notes and music is born. This device can also be used as a scanner to scan images with very low resolution.
Source: Gijs Gieskes
NOV4
Voice powered crystal controlled radio transmitter
In case you have missed this before (I sure have) here is a radio transmitter that doesn't require any power source. Well, at least not any classic power source like batteries.
This radio transmitter is powered by the operator's voice alone! The speaker connected to the device converts audio signal to low voltage at the end contacts. Naturally, amplitude of the generated voltage corresponds to the amplitude of the speaker's voice, hence making this an amplitude modulated power source. This power source is used to power the high-level DSB modulator/crystal-controlled RF oscillator. The interesting part is that the range of this transmitter is around 160km/100miles!
Source: El Silbo
NOV3
Spectrum analyzer for 2.4 GHz band
The spectrum analyzer can be described as a frequency-selective, peak-responding voltmeter calibrated to display the magnitude of an input signal. Spectrum analyzer is not a power meter, even though it can be used to display power levels. In RF (telecommunications) spectrum analyzers are used to determine occupied bandwidth and track interference sources.
Spectrum analyzers are not cheap devices and here we will see a DIY RF spectrum analyzer for 2.4 GHz. It is based on Cypress CYWUSB6935 RF radio-module for 2.4 GHz which has one key component: internal RSSI meter (registers) that measure receiving signal's strength on selected frequency. This chip is directly connected to LPT port of a PC that runs plotting software that is built in Qt so it is available for both Linux and Windows. This is very useful tool to test WiFi channel occupation!
Source: Jason Hecker
NOV2
Color-changing halloween pumpkin
Halloween is behind us but it's never too late to scare people off with some crazy invention.
This is a remote controlled LED pumpkin. Channel buttons 0-8 on the remote toggle the colors of built-in LEDs inside the pumpkin. Button 9 activates the "angry mode" that flashes red LED for a few seconds. In the "angry mode" there is also a vibration motor implemented in the top cover, but it doesn't seem to shake that well. It is based on PIC18F2550 microcontroller with built-in USB bootloader which is a pretty large overkill for this project.
OCT30
DIY hot air soldering station
For all those who are not able to afford themself a new SMD hot air soldering station, there is a pretty simple solution. By using heater, hair dryer, plastic bottle, some pipes and electronics you could make a hot air station that works just as well as the real one.
With little automation and smart electronics this could make a serious hot air soldering/desoldering station. There is another version of the same thing after the break and the build instructions are on the project page.
Source: Alfred73
OCT29
Hand held electrocardiogram (ECG) with ARM uC
Electrocardiogram is based on STMicroelectronics STM32 Primer development board which has onboard LCD, USB support and STM3210B 32-bit microcontroller. On dev-board's housing two copper plates were added for skin contact and measurement signal input. Inside the dev-board there is a custom built PCB with signal amplifiers and step-up (boost) converter. Source code is available for download on project page.
This device can be used as standalone portable ECG or even as a lie detector, and there is also a PC application for real-time data plotting via USB.
Source: Jingxi Zhang
OCT28
Capacitance meter with ATmega8
It is often required to know the precise capacitance of some capacitor which is in most cases different than the rated value.
This capacitance meter measures capacitance with 1pF resolution and in 1pF to 10000uF (10mF) range. Before initial measurement a calibration should be performed which is than saved in EEPROM of microcontroller. The device is realised on ATmega8 AVR and firmware is written in C which is available for download on the project page.
Source: Lars
