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15 Feb 2012

Sergei Bezrukov writes:

This project is based on the Function Generator described on Mondo Technology web site. I just did very slight changes and fixed some obvious typos in schematic. The code is rewritten for the Microchip MPLAB IDE syntax.

Device features

  • Frequency range: 11Hz – 60KHz
  • Digital frequency adjustment with 3 different steps
  • Signal forms: sine, triangle, square, pulses, burst, sweep, noise
  • Output range: ±15V for sine and triangle, 0-5V for others
  • Sync output for pulses

The device is powered from 12VAC which provides a sufficiently high (over 18V) DC voltage needed for a normal operation of 78L15 and 79L15. The 12V power supplies are replaced with 15V ones. This is done in order to LF353 Op-amp could output the full range of signals to a 1K load. By using a ±12V supply this resistor must be at least 3K.

60kHz PIC Function Generator - [Link]

14 Feb 2012

Sergei Bezrukov writes:

My goal was to design a simple and user-friendly frequency counter which would be capable to handle radio FM frequencies and have an autonomous power supply. Powering it from batteries benefits to the device portability and makes working with it more convenient by eliminating a mess of power cords in a home lab. I use it just occasionally and a small size is a bonus simplifying its storage in a table drawer.

Most of similar devices I have found on the Internet use an LCD module with a built-in controller. Such a device draws pretty much current. Also, many high-speed counters use power-hungry ICs which makes it difficult for a battery operation. Finally, many projects are poorly documented which makes any modification unnecessary difficult. So, I started my own design which uses modern high speed and low-power ICs and can work from a single AA cell.

150MHz PIC Frequency Counter - [Link]

Fast Frequency Counter - [Link]

12 Feb 2012

Test Thyristor and Triac using this circuit. Pay attention on mains voltage!

Thyristor – Triac Tester - [Link]

12 Feb 2012

www.adafruit.com writes:

After spending quite a bit of time selecting a scope that matched my budget and requirements, and looking (importantly!) at the ecosystem around that scope, I settled on Agilent’s new MSOX2000/3000 series — specifically, the Adafruit Christmas Elves picked out an MSOX2024a (the screenshot above was taken on this scope).

These scopes (in my opinion) are an excellent value for a mid-range scope, and really raise the bar for the competition in the $2-5K range. I’d like to write a few blog posts on the reason behind that choice and the thinking behind the whole list of items above, but as a first foray into that I thought I’d try to explain some of the details you should keep in mind if you’re thinking about a scope yourself (probably the most useful tool on any EEs workbench after a multimeter).

Why Oscilloscope Bandwidth Matters - [Link]


11 Feb 2012

Eric built himself a battery monitoring system based on the ATmega328 Development Kit. He drained a 9V battery with 100mA of current and monitored the voltage drop until total depletion. He used this data to estimate how much time is left until depletion – [via]

The 100mA constant load was chosen because my ProtoStack Arduino Clone with LCD draws about 92mA and I wanted to write a sketch to display a battery bar and the approximate hours battery life left. Since all batteries have an internal equivalent series resistance (ESR), it is important to take that into account when only using a battery’s voltage to monitor its state of charge. Since we discharged the battery through a load that is similar to the ProtoStack board with LCD, the ESR of the battery has automatically been accounted for in the voltage measurements.

Monitoring battery voltage to calculate capacity with an Arduino - [Link]

11 Feb 2012

With the recent increase in solar storm activity, Alexander Avtanski bring our attention to his DIY magnetometer project – [via]

The activity of the Sun varies on a cycle with a period of approximately 11 years. Periods of low solar activity are followed by a few years of sharply increased number of solar spots, flares, and coronal mass ejections (CMEs), disrupting Earth’s magnetic field and causing magnetic storms. With the next Solar cycle maximum approaching I wanted to get on the fun too, so I set to build my own device for detecting and recording those magnetic storms, a.k.a. a magnetometer.

DIY geomagnetic storm monitoring - [Link]

10 Feb 2012

Here is an app note from Microchip explaining how to interpret various analog to digital converter specifications. This article covers how attributes of ADCs are calculated and how they apply to it’s performance and precision –  [via]

The purpose of this application note is to describe the specifications used to quantify the performance of A/D
converters and give the reader a better understanding of the significance of those specifications in an application.

App note: Understanding ADC specifications and attributes - [Link]

9 Feb 2012

dangerousprototypes.com writes:

We’ve been researching various component testers, and BrentBXR tipped us about this high-resolution capacitor meter. It’s accuracy is claimed to be around 0.2%, which is much lower than typical capacitor tolerances.

Internal comparators in a PIC16F628 create an oscillator with the capacitor under test. The oscillator frequency is proportional to the value of the capacitor. An internal timer measures the period of oscillation and calculates the capacitance. Most high-accuracy capacitor meters seem to use this technique, it’s something we’ll look at closely in the coming weeks.

High resolution capacitor meter - [Link]

9 Feb 2012

This is a simple inductor and capacitor measurement tool. The part to test is connected to an oscillator circuit, and the frequency of oscillation corresponds to the value of the capacitor – [via]

All I do is use the LM311 square wave output as pulses to a 16bit counter, and another 100mS periodic timer to count how many pulses per 100mS interval, to calculate the oscillation frequency. BTW, the PIC32 is running off a 16MHz crystal. I average the results from 5 consecutive readings, so I have a 0.5second measurement repeat rate. Good enough. It seems to be accurate enough for my needs, which is basically identifying components that I salvage, or coils that I wind myself.

LM311 oscillator based LC meter - [Link]

9 Feb 2012

freecircuits.org writes:

AS with many tinkerers and junk electronics collectors, a variety of “acquired” power supplies wind up on the author’s shelves to await attention. But are they worth keeping? Testing them with a resistive load is messy and difficult, and with high current supplies it is nearly impossible, unless you have a carbon pile! The tester whose circuit diagram is shown in Fig controls supply currents to 20A, and voltages from 1·7V to over 50V. Current control is so stable that once the current is set, a supply voltage can be varied across this range and the current will remain constant. Maximum power will depend upon how well the pass transistors utilize heatsinks.

Power Supply Tester circuit - [Link]



 
 
 

 

 

 

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