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23 Mar 2015


The circuit shown is a microcontroller based Energy Meter that uses MCP3905A as its main component, which is an energy-metering ICs that supplies average power information through a pulse with direct drive for mechanical counter. It includes a higher-frequency output supplying instantaneous power information for calibration while conforming the IEC 62053 International Metering Standard Specification. The energy meter provides exceptional accuracy in measuring the amount of energy consumed by an electrically powered device. It can significantly read immediate power usage, which may be used to perceive future energy consumption.

Microchip’s MCP3905A energy meter reference design is a standalone, single-phase residential meter for active energy meter design. In addition, MCP3906A can be used in the project. For calibrating the frequency output, a voltage divider calibration circuit was optimized. Each meter must be calibrated using the voltage divider circuit going into Channel 1 of the MCP3905A/06A. The MCP3905A/06A has appropriate bypass capacitors on VDD coming from the DC power supply circuitry and has its input logic pins connected to user-selectable jumpers, with the exception of the HPF pin. For this system, the HPF is turned ON with this pin connected to VDD. Moreover, the DC power supply is created from a half-wave Zener diode limited AC signal feeding a 7805 +5V regulator. The Zener diode D2 however, limits the peak voltage to 15V while the optical isolator is included in the reference design as an additional level of protection for other circuitry.

Energy meter system had been widely used to measure the energy consumption to residents, industries and businesses benefiting the power usage. It is typically calibrated in billing units such as kilowatt-hour and periodic readings of electric meters, which establishes billing cycles and energy used.

Energy Meter based on MCU - [Link]

20 Mar 2015


by ohnitsch.net:

While trying to create a circuit that detects whether water is flowing through a pipe by measuring the vibration with a piezoelectric sensor, just to see what happens I taped the sensor around my finger and – to my surprise – got values that were a very noise-free representation of my heart rate!

Measuring Heart Rate With A Piezo - [Link]

20 Mar 2015


The simple project can be used as test gear. Its easy way to monitor the battery voltages, especially dry cell, NICAD, NIMH, supply up to 1.5 Voltage. Battery Monitor range 0.15V to 1.5V. The project is built around Texas instruments LM3914, The LM3914 senses the voltage levels of the battery and drives the 10 light emitting diodes based on the voltage detected on input connector. Circuit works on 5V DC. J1 Jumper is used to select the DOT mode or bar graph mode.

NiCad-NiMh Battery Monitor - [Link]

18 Mar 2015


Martin’s DIY Internet connected smart humidifier project:

The project uses a DHT22 temperature sensor mounted to the side of the enclosure for better ventilation and reliable reading:
I threw in a ultra-cheap I2C OLED status display to get a visual reading. Milling the box so that the OLED shows was pretty nasty, hated it. I cut a piece of paper and placed it on top of the cover, below the transparent lid to cover up for the lousy milling job
The humidistat switches on and off the humidifier as needed, the humidifier itself is plugged in to a plug in the relay. The  auto detects when water is out and stops, so I didn’t have to care about that.

Internet connected smart humidifier - [Link]

5 Mar 2015


A thermometer is utilized to quantify the temperature of solids, liquids, or gases. A thermometer contains a fluid (normally mercury or a liquor arrangement) in a supply whose volume is directly reliant on the temperature (as the temperature expands, the volume increments). At the point when the fluid is warmed it ventures into a thin tube that has been aligned to demonstrate the temperature. Temperature can be recorded in Celsius, Fahrenheit, or Kelvin, accordingly it is imperative to note which scale the thermometer is balanced for.

This Do It Your Own (DIY) digital thermometer circuit can measure temperatures up to 150°C with an accuracy of ±1°C. The temperature is read on a 1V full scale-deflection (FSD) moving-coil voltmeter or digital voltmeter.

Operational amplifier IC 741 provides a constant flow of current through the base-emitter junction of NPN transistor BC108. The voltage across the base-emitter junction of the transistor is proportional to its temperature. The transistor used this way makes a low-cost sensor. You can use silicon diode instead of transistor. The second operational amplifier is amplified by the small variation in voltage across the base-emitter junction, before the temperature is displayed on the meter. Preset VR1 is used to set the zero reading on the meter and preset RV2 is used to set the range of temperature measurement. Operational amplifiers operate off regulated ±5V power supply, which is derived from 3-terminal positive voltage regulator IC 7805 (IC1) and negative low-dropout regulator IC 7660 (IC2). The entire circuit works off a 9V battery. Assemble the circuit on a general-purpose PCB and enclose in a small plastic box. Calibrate the thermometer using presets RV1 and RV2. After calibration, keep the box in the vicinity of the object whose temperature is to be measured.

Digital Thermometer Circuit - [Link]

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]





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