Tube amp monitor
Sparkfun contributor [Pete] really loves tube amps, but he’s a very safety-conscious guy who doesn’t like being electrocuted. This is a problem, since tube amps are usually very high voltage, and a...
View ArticleLED battery level indicator
[Kc7fys] came up with a this simple battery level indicator. It uses a single LED to display a battery’s voltage; if the voltage exceeds 12V, it glows green. If it is below 11V, the LED glows red....
View ArticlePIC programmable power supply
This programmable power supply is the perfect addition to your bench tools. [Debraj Deb], who previously built a whole house power monitor, designed this build around a PIC 18F4520 microcontroller....
View ArticleAdjustable voltage and polarity tester
Instructables user [Rudolf] wrote in to share a handy little tool he created with ham radio operators in mind. Now and again, he found himself connecting to an unknown power supply, and rather than...
View ArticleAutomotive battery voltage monitor
[Rajendra’s] car had just about all the bells, whistles, and gauges he could dream of, but he thought it was missing one important item. In an age where cars are heavily reliant on intricate...
View ArticleLight bulb, diode, and capacitor step mains down to 12V DC
[Todd Harrison] needed a way to run a 12 volt PC fan from mains voltage. Well, we think he really just needed something to keep him occupied on a Sunday, but that’s beside the point. He shows us how...
View ArticleFrom the readers: low battery cutoff solutions
We got a lot of really great feedback about low battery cutoff options in the comments section of Monday’s replacement battery post. To refresh your memory, some power tool batteries were replaced by...
View ArticleAC vs DC human pain test
Ever wondered just how much being zapped by electricity hurts? Curious if AC is worse than DC? Want to know just how many volts a human body can take? Although many people might cringe at the shear...
View ArticleAfroman Demonstrates Boost Converters
If you need to regulate your power input down to a reasonable voltage for a project, you reach for a switching regulator, or failing that, an inefficient linear regulator. What if you need to boost the...
View ArticleAdding a Battery Gauge to a Project With Zero Parts
The typical way of doing a low battery detector is throwing a comparator in the circuit, setting it to measure a certain threshold voltage, and sending that signal off to a microcontroller or other...
View Article“Who is John Galt?” Finally Answered
For those who haven’t read [Ayn Rand’s] philosophical tome Atlas Shrugged, there’s a pretty cool piece of engineering stuffed in between the 100-page-long monologues. Although fictional, a character...
View ArticleIsolated Voltage Measurements Through Frequency
This one’s not a flashy hack, it’s a great piece of work and a good trick to have up your sleeve. Sometimes you’ve got a voltage difference that you’d like to measure, but either the ground potential...
View ArticleBuilding Transistors with Transistors
Since the 1940s when the first transistor was created, transistors have evolved from ornery blocks of germanium wrangled into basic amplifiers into thousands and thousands of different devices made of...
View ArticleSay It With Me: Root-Mean-Square
If you measure a DC voltage, and want to get some idea of how “big” it is over time, it’s pretty easy: just take a number of measurements and take the average. If you’re interested in the average power...
View ArticleLightning Generator from Electric Lighter
Generating high voltages isn’t too hard. A decent transformer will easily get you into the 100s of kilovolts, provided you’re a power company and have access to millions of dollars and a substation to...
View ArticleCustom Circuit Makes for Better Battery Level Display
Isn’t it always the way? There’s a circuit right out of the textbooks, or even a chip designed to do exactly what you want — almost exactly. It’s 80% perfect for your application, and rather than...
View ArticleOld Wattmeter Uses Magnetics To Do the Math
Measuring power transfer through a circuit seems a simple task. Measure the current and voltage, do a little math courtesy of [Joule] and [Ohm], and you’ve got your answer. But what if you want to...
View ArticleYou Didn’t See Graphite Around This Geiger Counter
Even if you don’t work in a nuclear power plant, you might still want to use a Geiger counter simply out of curiosity. It turns out that there are a lot of things around which emit ionizing radiation...
View ArticleFive Channel Monitor Keeps Boat Batteries Shipshape
While those of us stuck sailing desks might not be able to truly appreciate the problem, [Timo Birnschein] was tired of finding that some of the batteries aboard his boat had gone flat. He wanted some...
View ArticleIf You Need a Measurement Tool Just Build A Measurement Tool
[Darlan Johnson] was working on a wearable project and needed a way to measure the change in voltage and current over time. Most measurement tools are designed to take snapshots of a system’s state in...
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