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Cat-sized Cardboard Dome
Written by Instructables   
Friday, 05 August 2011 15:05

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This 'ible was heavily influenced and inspired by supersoftdrinks awesome Cardboard Play Dome she made for her kids. (Can be found in http://www.instructables.com/id/Cardboard-Play-Dome/ ) I was impressed and wanted to make one myself, but as an "adult" it would have had to be huge and it would ta...
By: Nelyan

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Last Updated on Thursday, 11 August 2011 22:50
 
Arduino TNC
Written by Dangerus Prototypes   
Friday, 05 August 2011 09:00

Authors: Dangerus Prototypes

Amateur radio operators use various digital data modes for radio communications. One such mode is known as packet radio, which transmits data in groups or “packets” of bytes. As described by the ARRL, “packet radio allows improved throughput and error control. The basic protocol for packet radio is AX.25. Transmission speeds typically range from 300 bps on the HF bands to 1200 and 9600 bps on VHF or UHF.” The necessary interface hardware between the radio and the computer is known as a Terminal Node Controller (TNC).

KI4MCW reports on the status of his project to implement a TNC using the Arduino:

The goal of this project – the creation of a simple but effective TNC using Arduino hardware – has been achieved a couple of different ways. Because of the precise timing required to sample and decode AX.25 audio, it was not possible to build a working solution using the standard Arduino libraries. Instead, each solution has involved software written in C, calling AVR-libc libraries or manipulating register values directly.

Currently, my efforts are focused on an implementation that uses the freely available BeRTOS package, a collection of integrated libraries and drivers for embedded platforms. The AX.25 and AFSK modules included with BeRTOS form a high-performance packet engine that can be modified to function as a KISS TNC. I am working with the BeRTOS team to integrate KISS functionality into the main package, so hopefully those functions will be available in future versions of their product.

Progress reports and a working example of the code (both source and binary for an ATmega328p-based Arduino) can be found at the KI4MCW website. A simple test circuit is available from the BeRTOS website.

Read more: http://dangerousprototypes.com/2011/08/05/arduino-tnc/

Last Updated on Saturday, 27 August 2011 03:31
 
24 LED Police Flasher
Written by Electronics lab   
Wednesday, 03 August 2011 04:35

Authors: Electronics lab

Dual color (4 line x 3 column) led, 12 white and 12 blue are intermittently switched controlled by two NPN transistors BC337.  The speed and duty/cycle timing of lighting duration is determined by NE555 oscilator. The number of repetition of sequential lighting of each group of led is determined by 5-stage divide-by-10 Johnson counter with 10 decoded outputs and carry out bit (CD4017).

The intermittent lights from two group of led imitate the police car strobe lights.
The speed of switching off and on of led are continuously regulated by variable trimmer resistor.

24 LED PoliceFlasher - [Link]

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Last Updated on Wednesday, 31 August 2011 00:52
 
Geiger Tube Simulator
Written by Administrator   
Wednesday, 03 August 2011 00:00

Enrico Mathesar writes:

This little gadget will simulate a 500 volt or less Geiger tube when driven by a signal generator of sufficient amplitude, typically 5 volts p-p or greater. The purpose is to generate a steady, precise number of counts per minute so that the Geiger counter’s meter may be calibrated.

Geiger Tube Simulator –[Link]

Last Updated on Wednesday, 03 August 2011 18:40
 
Geiger Tube Sensors
Written by Administrator   
Wednesday, 03 August 2011 00:00

ladyada.net writes: 

Geiger Mueller Tubes – Handy for people looking to make random number generators or detect radiation. Tubes tend to be Cold War old stock from Russia/US, and tend to be used for detecting Gamma and Beta radiation. You’ll need a high voltage boost supply – check nixie tube projects for some HV supply designs

Geiger Tube Sensors – via

Last Updated on Wednesday, 03 August 2011 18:42
 
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