Monday, December 12, 2011
A negative voltage is derived by shifting gnd with two diodes, i feel this did not work very well. Two pins of CD4028 pins are also used to boost the reference to get two extra ranges as 4051 has a 100E on resistance.
The 555 clock makes 4029 counter count. But the clock can be clamped to gnd by a TL062 window comparator. The clock is frozen when the input value to comparator pin 5-2 is within a lower limit and upper limit "window" pin 3-6.
The 4029 counter BCD is decoded to decimal by 4028 which drives the LEDs, keep LED drive within 3mA or chip will be loaded. Use high efficiency extra-bright LEDs.
The 4029 BCD also controls a shunt resistor array with CMOS switches 4051. The voltage across shunt is a sample of leakage current. This is compared in the window comparator to freeze the Clock and LED display to give a reading of the leakage current or Insulation Resistance.
Thursday, December 08, 2011
The Femto OS is a very concise portable real time - preemptive operating system (RTOS) for embedded microcontrollers with minimal ram and flash, say 2KB .. 16KB flash and 128 .. 1024 bytes ram. The main target is the Atmel AVR architecture, such as the ATtiny or smaller ATmega series.
Femto OS is specially made for small embedded devices. For example, the 'Smallest application' is the application called 'Bare' compiled for the ATmega8. It solely runs a 16 bit led counter on the idle task hook. It consumes 258 bytes of flash and 10 bytes of ram.
- Ruud Vlaming
Read More -
Tuesday, December 06, 2011
My Start as a Ham - Ralph's Story - "I suppose my interest in things electrical began when at a very young age I poked a metal hairpin into an electrical outlet. To this day, I vividly remember the amazing flash and bang that resulted! Of course, I wanted to know why that happened. It was a few years more before I learned to read, and found out about electricity."
Ananth Notes- Thank god you survived to tell the story, this was a Jolt of a start. Very few people survive this. I would like to add …
All Mains Inlet Sockets should be Shuttered, so that such a thing does not happen again to any child again. Another Law, No Mains Socket should be less that 5 feet above the ground level.
Then we should all move to a 24V home voltage standard, Read more at my Tech blog..
Then ralph has many projects with educative information. A RF Ammeter the Easy Way. A 400 Watt 60 Hertz Power Inverter. These are interesting to study.
The design of switching supplies is a bit more involved than traditional "big iron" transformer power supplies. When taken step-by-step, however, it is quite possible for an amateur to design and build a working high power switching power supply. This article describes a high power, high voltage switch mode power supply designed to operate a KW level RF power amplifier.
Home brew Litz Wire
The Litz wire was fashioned by taking two parallel strands of #18 AWG wire about 115 feet long and twisting them together in a clockwise direction with an electric drill until the twisted wires had about two turns per inch. The twisted wire was then cut into four equal length and laid side by side.
Vicacopter - Open Flight Robotics
Vicacopter uses a ground computer for flight control. An 8 bit airborne microcontroller handles rate damping, PWM, & sensor capturing. The ground computer handles navigation & provides a simple instrument panel. This was the cheapest & most flexible way to fly. The system can be converted to a completely airborne autopilot very simply.
- Automated landing & takeoff
- Sonar position sensing for indoor flight
- GPS position sensing for outdoor flight
- Ground station instrument panel
- Untethered communication from pilot to ground station
- Curved or linear paths
The Tri-Roter one used 3 gyros for short term rotation sensing, 2 accelerometers for long term tilt sensing, 3 magnetometers for long term heading sensing, a high quality GPS module for horizontal position, a barometer for altitude sensing. A 3rd accelerometer was too sensitive to vibration & altitude changes to be any good. Because of the long term sensors & the very stable gyros, the orientation was always pretty accurate & didn't drift.