Inductance Capacitance Meter

We all know that the most troublesome components in electronics are inductors and capacitors. Usual ones have high tolerance, time has an effect on them and their cost can be quite big. Besides that, i believe there are other people like me, who have boxes full of salvaged components from things that couldn’t be repaired. Now, from those components, you can measure capacitors and inductors with the tool presented in this project.

The L/C meter presented has a pretty good accuracy, +/- 1% of reading +/- 0.1pF or +/- 10nH. The measurement method is not the usual one but it’s very interesting, first the microcontroller measures the frequency of the oscillator, then measures the frequency of the oscillator with an added known capacitor and last time it measures the frequency of oscillation with the unknown component added.

In my opinion this method is a good approach if you can measure the frequency accurately. If we look at the equations described in the project that gives us the value of the unknown component we observe it only depends on those three frequencies and the value of the added capacitor. So we have only one element in our equation that isn’t measured, Ccal which can be chosen to be a higher quality capacitor with low tolerance and thus each time you calibrate the meter the frequencies are measured again and the calculations will be more accurate in case some component from the oscillator changed its value a bit because of temperature for example.

Another good function it that it can show you the difference between two components, very useful for matching. The oscillator is done using a LM311 comparator with the resonant circuit in the positive feedback loop. The microcontroller used is a PIC16F84, the assembler code is available as well as the hex files and schematic.

Inductance/Capacitance Digital Meter: [Link]

controlling the flight of a zeppelin

A teams of students from Colorado State University have designed and built a PIC-based circuit to control the flight of a blimp. You can control it manually by remote or let the zeppelin find it’s own path to a specific destination that is designated by an infrared beacon.

The remote control has a 204 LCD display which shows the commands and a 12 key keypad from which you can control take off, land, forward, reverse and steering commands. The zeppelin also has an altitude controller with ultrasonic sensors. This makes it go higher if it detects the ground too close or go lower if it’s altitude increases too much.

The thrust is given by two motors, each set at the end of a horizontal bar. A servo motor controls the angle of this bar and thus the direction of the thrust. There are four IR sensors each placed in the four cardinal points. These sensors serve the autonomous flight mode. The IR sensors output a low pulse when it “sees” the beacon so the zeppelin will follow the direction of the sensor which gives out the most pulses. The beacon is made with 16 IR LEDs driven by two 555 circuits.

The altitude control is been taking care of by a PIC16F84 designated IC2 in the schematics, steering is done by a PIC16F88, IC3, and all communicate with the control center a PIC16F874, IC4. Thrust motors are driven by SN754410, IC5 in the schematics. In the remote control you will find a PIC16F877P who takes care of all the RC functions, reading the keypad, displaying characters on the LCD, sending audio message to speaker and sending serial commands to the zeppelin.

Controlling the flight of a Zeppelin: [Link][Via]

 PIC16F84 Countdown timer for PCB exposure unit

The purpose of this timer is to provide a countdown time from 1 second to 99 minutes & 59 seconds. I use it to control the lighting for the Ultra-Violet exposure of photosensitive PCB material. The project provides also an audible alarm at the end of the countdown time and switches the UV lights by means of a relay. It is based on a Microchip microcontroller, the 18 pin PIC16F84(A). This microcontroller contains 1Kbyte of flash memory for program code, 64bytes of static RAM memory, and 64bytes of EEPROM memory which are used here to store up to 15 different (user-programmable) countdown times.

PIC16F84 Countdown timer for PCB exposure unit: [Link]

April 19th, 2008

Tiny LED Projector

 Tiny LED Projector

The basic idea of TinyProjector is to create the smallest possible character projector that can be either integrated into mobile device, or linked dynamically with wireless RF connections like serial low range transceivers. Compared to all the earlier versions, which used laser diodes salvaged from cheap key chain laser pointers, the current prototype has smaller low-cost low-output laser diodes that allow for just one row of eight lasers instead of two interlinked rows of four lasers, making cumbersome primary deflection mirrors obsolete.

Tiny LED Projector: [Link]

 PIC16F84 12-bit, 8-channel analog to digital converter

This project is a simple 12-bit, 8-channel analog to digital converter (with 4 additional digital inputs), which may be connected to the PC through the serial interface (RS232). The sequence of sampled channels, and sampling frequence are programmed by the PC while the maximal sampling frequency is limited by the data transmission rate, and at 115200 baud is equal to ca. 3kHz for 1 channel without digital inputs, and to ca. 500 Hz for 8 channel with digital inputs.

The analog input voltage range is -2.5V to 2.5V. The digital inputs may be used for recording additional digital signals, eg. the time code used to synchronize the recorded data with other events. The project is based on PIC16F84 (or 166C84) microcontroller, and MAX190 (or MAX191) ADC. The device is mounted on a small single-sided printed circuit board, easy to prepare even at home.

PIC16F84 12-bit, 8-channel analog to digital converter: [Link]

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