By Dean Segovis @ makezine.com:
A transistor is an electrical component that functions, most basically, as a switch — in principle not so different from a light switch. Instead of a physical movement, however, a transistor is controlled by a flow of electricity. And unlike your basic light switch, a transistor can be on, off, or somewhere in between.
Non-Contact Voltage Detector - [Link]
If you are doing any electrical work, one of these Non Contact Voltage Test Pens can be quite handy. Just touch the wire that you want to make sure isn’t live and check that the tester doesn’t beep and start flashing. This test pen is on all the time monitoring for AC between 90V and 1000 V. I would have preferred the device to have an on/off switch which would allow the battery to last even longer but I guess they figured that the 1.5 year life that they rate this for when in standby was good enough. This impressive life is because they got the current draw down to under 10 micro amps! Even when operating it only draws a handful of milli amps.
Non Contact Voltage Test Pen Teardown - [Link]
Mooshimeter: The Wireless Graphing Multimeter with Data Logging and Multichannel Simultaneous Sampling
The Mooshimeter makes multi-channel measurements possible in situations that are too fast, too slow, too sensitive, or too dangerous to use a traditional multimeter. And by harnessing your smartphone’s hardware, it does so at an insanely low price.
The Mooshimeter was born out of our frustrations as electrical engineers at the limitations of the “standard” digital multimeter.
Almost every digital multimeter will only let you use one mode at a time, meaning that to watch relationships in an active system you need to use multiple meters. Most have a front panel dominated by a numeric LCD display and a gigantic mode selection knob. And having the display mounted on the measurement hardware makes it very difficult to measure moving or enclosed systems, because the user must have clear line of sight to the meter to be able to read it.
Mooshimeter – Measure 600V and 10A with 24 bit precision through 50 meters - [Link]
SUF shared his voltage reference project in the forum:
To achieve the things above I designed a small battery good indicator circuit with a zener an opamp two LEDs and a few resistors. If you switch it on and the battery fall below 8V the red LED will lit instead of the green. I wanted to have a SOB style case. I designed a new one with a trick on it. I used a third acrylic plate what has a hole inside. The hole can accommodate the battery and the battery clip. This setup keeps the battery in place.
Voltage reference project - [Link]
A team of Columbia Engineering researchers, led by Mechanical Engineering Professor James Hone and Electrical Engineering Professor Kenneth Shepard, exploring the properties of graphene have demonstrated a new electro-mechanical resonant component.
The resonator’s structure consists of a 2-4 micrometer long strip of graphene suspended over a metal gate electrode. The strip of graphene has a natural resonance governed by its physical dimension and is used in the demonstration as the frequency determining element in an RF feedback oscillator circuit. Applying a voltage to the gate electrode stresses and deflects the graphene strip changing its resonant frequency. The team applied baseband audio and tones to the gate electrode to produce a 100 MHz FM signal.[via]
Tiny FM Transmitter uses Voltage Controlled Graphene Resonator - [Link]
startingelectronics.com has a very clear tutotrial on how to read analog voltages using Arduino:
Analog channels A2 to A5 on an Arduino Uno are used to measure four different voltages. The measured voltages are displayed on a 16 character by 2 line LCD. The four channel Arduino multimeter can measure four independent DC voltages that can each be in the range of 0 to 50V. Voltages are displayed with one decimal place, e.g. 5.3V, 12.8V, etc.
Arduino LCD Voltmeter with 4 Channels - [Link]
Have you ever wanted to take a standard voltage op-amp and turn it into a high voltage output circuit? Here is a technique that requires some shunt regulators to power the chip and some current limiting transistor circuitry for the output. This example should work upto +/- 120V.
Make an Op-Amp High-Voltage Output Circuit - [Link]
Kerry Wong shows how to make an adapter circuit for measuring very low voltages with a multimeter.
A typical 3 ½ or 4 ½ multimeter can measure voltage in the low mV range and current in the low mA range. Voltage measurement in the µV range and current measurement in the nA range are typically only available in the more expensive lab bench multimeters. In this post, I will show you a simple adapter circuit that can be used for precision voltage measurement down to the µV range. Using this circuit along with the current adapter circuit I discussed earlier you will be able to perform most of the low level measurements with a 3 ½ meter.
Precision Voltage Adapter For Low Voltage Measurement - [Link]
The INA230 is a current-shunt and power monitor with an I2C interface that features 16 programmable addresses. The INA230 monitors both shunt voltage drops and bus supply voltage. Programmable calibration value, conversion times, and averaging, combined with an internal multiplier, enable direct readouts of current in amperes and power in watts.
INA230 – Precision digital/current/voltage/power monitor - [Link]
When specifying a reference, keep in mind that initial accuracy, temperature coefficient and long-term stability all play a role in overall accuracy of the finished product. By taking some care in applying the reference, and by avoiding some key pitfalls, the reference’s inherent accuracy can be preserved.
Using and understanding voltage references - [Link]