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20 Feb 2015


BeagleLogic turns your BeagleBone [Black] into a 14-channel, 100Msps Logic Analyzer. Once loaded, it presents itself as a character device node /dev/beaglelogic.

The core of the logic analyzer is the ‘beaglelogic’ kernel module that reserves memory for and drives the two Programmable Real-Time Units (PRU) via the remoteproc interface wherein the PRU directly writes logic samples to the System Memory (DDR RAM) at the configured sample rate one-shot or continuously without intervention from the ARM core.

BeagleLogic can be used stand-alone for doing binary captures without any special client software.

The cape essentially consists of a TI 74LVCH16T245 16-bit buffer and associated power-on circuitry that ensures that the buffer does not come in the way of the power-up sequence of the BeagleBone (since the AM335x boot pins are shared with the BeagleLogic inputs). There is also a provision for cape EEPROM support that will be coming up shortly.

BeagleLogic – BeagleBone Logic Analyzer - [Link]

18 Feb 2015


by Vladimir Rentyuk @ edn.com

Suppose that you need to test a 1.5V, AA-size alkaline battery. You can apply a short circuit and measure current, or you can measure open-circuit voltage, but neither method properly tests the battery. A suitable test current of approximately 250 mA gives you a more reasonable test. You can use a 6Ω resistive load at 1.5V, which produces an output voltage of 1.46V at an ambient temperature of 25°C if the battery is in excellent condition. A poor battery might produce less than 1.2V. Given the load, the output current at 1.2V will be 200 mA instead of 250 mA. The battery will have just 80% of a full load current. Instead, you can use the circuit in Figure 1 to produce a constant-current load.

Circuit provides constant-current load for testing batteries - [Link]

18 Feb 2015


by Paul Galluzzi @ edn.com:

The Fig 1 circuit uses a Hall-effect sensor, consisting of an IC that resides in a small gap in a flux-collector toroid, to measure dc current in the range of 0 to 40A. You wrap the current-carrying wire through the toroid; the Hall voltage VH is then linearly proportional to the current (I). The current drain from VB is less than 30 mA.

To monitor an automobile alternator’s output current, for example, connect the car’s battery between the circuit’s VB terminal and ground, and wrap one turn of wire through the toroid. (Or, you could wrap 10 turns—if they’d fit—to measure 1A full scale.) When I=0V, the current sensor’s (CS1’s) VH output equals one-half of its 10V bias voltage. Because regulators IC1 and IC2 provide a bipolar bias voltage, VH and VOUT are zero when I is zero; you can then adjust the output gain and offset to scale VOUT at 1V per 10A.

Current monitor uses Hall sensor - [Link]

16 Feb 2015


Intersil’s application note (PDF) on building a battery operated auto ranging DVM with the ICL7106:

This application note describes a technique for auto-ranging a battery operated DVM suitable for panel meter applications. Also, circuit ideas will be presented for conductance and resistance measurement, 9V battery and 5V supply operations, and current measurement.


App note: Building a battery operated auto ranging DVM with the ICL7106 – [Link]

16 Feb 2015


by soldernerd.com:

If you’ve read my last post you’re already familiar with my Inductance Meter project: http://soldernerd.com/2015/01/14/stand-alone-inductance-meter/. At that time the hardware was ready but there was no software yet. That’s been corrected, the inductance meter is now fully functional.

From a high-level point of view the new software is very similar to the Arduino sketch I wrote for the Inductance Meter Shield (http://soldernerd.com/2014/12/14/arduino-based-inductance-meter/). If you look a bit closer, you’ll notice some differences for several reasons:

This project uses an entirely different microcontroller: A PIC 16F1932 instead of the Atmel Atmega328
This code is written in C (for the MikroC for PIC compiler by Mikroelektronika), not Arduino-style C++
The display I’m using here comes with a I2C interface rather than the familiar Hitachi interface

Stand-alone Inductance Meter - [Link]

7 Feb 2015


by electro-labs.com:

Have you ever been curious about the power consumption of an appliance? For example did you wonder how much it will cost you to leave your television in standby mode whole night? Or did you want to learn how much change your refrigerator settings will make on your electric bill? If your answer is yes, you can use a wattmeter to measure the power consumption of a device. In this project we are building one.

This is an AC Watt Meter which can measure the real power consumption of a device connected to the 230Vrms/50Hz mains line. The PIC microcontroller collects the voltage and the current information with the help of ADCs and then calculates the RMS voltage of the mains line, RMS current drawn by the device and the resulting average power consumption. All these information is then displayed on the dot matrix LCD.

DIY Digital AC Watt Meter - [Link]

26 Jan 2015

by mjlorton @ youtube.com

In this video I explain how a spectrum analyser (Tektronix MDO3000) can be used to view signals in the frequency domain vs an oscilloscope’s time domain.
I give an overview of the logarithmic scale and its benefits vs a linear scale.
I explain how compound wave forms like square and triangle are made up of harmonics.
I do a practical demonstration of how the spectrum analyser works with some example signals. I then show how this can also be done on an oscilloscope using the FFT (fast Fourier transform) maths function.

Spectrum Analyzer, Scope and FFT looking at Signals - [Link]

22 Jan 2015


by PeterHaban @ makechronicles.com:

I made a water level sensor a little while a go to measure the water level in my underground rainwater harvesting tank. Thanks to the Jubilee I found time to finally setup the first part of my Arduino/Xbee wireless sensor network and the first sensor node was also meant to read from this water level sensor. I was somewhat surprised when it only returned 0s so I went and had a closer look. How the slug got into the enclosure is still a mystery to me… but looking at the bright side (after the uncontrolled swearing) I now had a reason to build a much better water level sensor

Measuring a water tank level - [Link]

21 Jan 2015


A DIY dynamic electronic load by Jay_Diddy_B over at EEVblog Forum:

The dynamic load steps the load current so that the transient response of the power supply being tested can be observed.
0-5A maximum continuous current
0-5A pulsed current at 330Hz

DIY dynamic electronic load - [Link]

19 Jan 2015


by Joe @ hobbyelectronics.net:

This project was built to monitor the temperature of one of our computer rooms at work that has rather temperamental air-conditioning. The maximum temperature can be set, and if this is exceeded an alarm is activated.The unit gives a continuous display of current temperature and it’s possible for the constructor to change the device program firmware or display board.

LED display Over Temperature Alarm - [Link]





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