Voltmeter Clock Looks Great On Display

Voltmeters are cheap, and have a great industrial aesthetic about them. This makes them prime candidates for hackers looking to do a clock build. [Brett Oliver] went down this very road, and built a very stylish timepiece along the way.

[Brett] initially wanted to go with 240-degree voltmeters, however the cost was prohibitive, so settled for the more common 90-degree models. New dials were produced by first sanding down the old dials, repainting in an old-fashioned off-white, and then applying the new graphics with inkjet transfer paper.

The attention to detail continues with the case. [Brett] aimed to build the clock with an old-school lab equipment aesthetic. A large piece of mahogany was crafted into the base.  A clear plastic cover was sourced from eBay, which really makes the piece. Large buttons and toggle switches were chosen to complete the look.

On the electronic side of things, it’s all run by a PIC16F628A, which controls the voltmeters via PWM. Running with a 20MHz crystal, the PIC is not a great timekeeper. Instead, the whole show is synchronized to [Brett]’s master clock we featured a few years back.

Building a clock is a rite of passage for a hacker, and [Brett]’s example goes to show how craftsmanship can really pay off in this pursuit. Video after the break.
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Building A 6.5 Digit Voltmeter From Scratch

After initially working to create a modernized replica of a Czechoslovakian 4-digit Metra M1T242 voltmeter, [Jaromir Sukuba] figured that while he was at it, he might as well create a voltmeter that would be slightly more capable. This led to the design and construction of a brand-new, 6.5 digit voltmeter design, which [Jaromir] has documented over at EEVBlog.

Employing an MSP430FR5994 MCU for the digital board, and an Altera/Intel EPM240T100 CPLD plus ADC on the input side, the design has been undergoing validation for a while now. The current revision uses an OPA140 op-amp in an integrating ADC setup in a multi-slope run-up configuration, but [Jaromir] has plans to replace this input board with another op-amp in a more efficient topology in the future.

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Tiny Voltmeter Uses DNA

We use a lot of voltmeters and we bet you do too. We have some big bench meters and some panel meters and even some tiny pocket-sized meters. But biological researchers at the University of Chicago and Northwestern University have even smaller ones. They’ve worked out a way to use a DNA-based fluorescent reporter to indicate the voltage across cellular membranes.

We don’t know much about biology, but apparently measuring the voltage on the membrane around a cell is easy, but measuring the voltages across membranes inside the cell isn’t. Previous work disrupted cells and measured potentials on isolated organelles.

The indicator — called Voltair — can target specific parts of a cell and includes a reference indicator so that a ratiometric measurement is possible. In fact, there are three main parts to the 38-base pair DNA duplex. One module contains a voltage-sensing dye that fluoresces in a way that indicates voltage. The second module is a reference dye that allows researchers to judge the voltage level. The final module identifies where the probe should attach.

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Analog Meters Become A Clock For Father’s Day

Around Father’s Day each year, we usually see a small spate of dad-oriented projects. Some are projects by dads or granddads for the kids, while others are gifts for the big guy. This analog meter clock fits the latter category, with the extra bonus of recognizing and honoring the influence [Micheal Teeuw]’s father had on him with all things technological.

[Michael] had been mulling over a voltmeter clock, where hours, minutes and seconds are displayed on moving coil meters, for a while.  A trio of analog meters from Ali Express would lend just the right look to the project, but being 200-volt AC meters, they required a little modification. [Michael] removed the rectifying diode and filtering capacitor inside the movement, and replaced the current-limiting resistor with a smaller value to get 5 volts full-range deflection on the meters. Adobe Illustrator helped with replacing the original scales with time scales, and LEDs were added to the meters for backlighting. A TinyRTC keeps time and generates the three PWM signals to drive the meters. Each meter is mounted in its own 3D-printed case, the three of which are linked together into one sleek console. We love the look, which reminds us of an instrument cluster in an airplane cockpit.

Bravo to [Michael’s Dad] for getting his son into the tinkering arts, and cheers to [Michael] on the nice build. We like seeing new uses for old meters, like these server performance monitoring meters.

[via r/DIY]

Hackaday Prize Entry: A Minimal ATtiny Voltage And Frequency Counter

Sometimes when you build something it is because you have set out with a clear idea or specification in mind, but it’s not always that way. Take [kodera2t]’s project, he set out to master the ATtiny series of microcontrollers and started with simple LED flashers, but arrived eventually at something rather useful. An ATtiny10 DVM and DFM all-in-one with an i2c LCD display and a minimum of other components.

The DFM uses the ATtiny’s internal 16 bit timer, which has the convenient property of being able to be driven by an external clock. The frequency to be measured drives the timer, and the time it returns is compared to the system clock. It’s not the finest of frequency counters, depending as it does on the ATtiny’s clock rather than a calibrated crystal reference, but it does the job.

The results are shown in the video below, and all the code has been posted in his GitHub repository. We can see that there is the basis of a handy little instrument in this circuit, though with the price of cheap multimeters being so low even a circuit this minimal would struggle to compete on cost.

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Retrotechtacular: Weston Electrical Instruments

A ‘meter is one of the most important tools on any electronics bench. After you’ve exhausted your five senses trying to figure out what’s happening in a circuit, firing up the old ‘meter is usually the next step. Meters are largely digital nowadays, but their analog ancestors are still widely available. We have a chemist and inventor named [Edward Weston] to thank for the portability and ubiquity of DC measuring equipment.

After immigrating to the United States from England with the degree in medicine his parents wanted him to earn, [Edward Weston] asserted that he was more interested in chemistry. His career began in electroplating, where he soon realized that he needed a reliable, constant current source to do quality plating. This intense interest in power generation led him to develop a saturated cadmium cell, which is known as the Weston cell. Its chemistry produces a voltage stable enough to be used for meter calibration. The Weston cell is also good for making EMF determinations.

Within a few years, he co-founded the Weston Electrical Instrument Corporation. The company produced several types of meters along with transformers and transducers known for their portability and accuracy. In 1920, [Weston & Co.] created this 1920 educational film in cooperation with the United States Navy as part of a series on the principles of electricity.

The viewer is invited to consider the importance of measurement to civilization, most notably those fundamental measurements of length, mass, and time. [Weston] positions his electrical measuring instruments at this level, touting them as the international favorite. We get the full tour of a Weston meter, from the magnet treated for permanence to the specially designed pole pieces that correctly distribute lines of magnetic force. What education film about electromagnetism would be complete without an iron filings demonstration? This one definitely delivers.

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Voltset Multimeters At World Maker Faire

Many tents at World Maker Faire were divided up into booths for companies and various projects. In one of these tents, we found the Voltset booth. [Tom, Ran, and Michael] were on hand to show off their device and answer any questions. Voltset is essentially a multimeter which uses your phone as a display. It connects to an Android phone via USB or an optional Bluetooth module.

Now we’d be a bit worried about the risk of damaging our phones with a voltmeter electrically connected via USB. However, many people have an old phone or retired tablet kicking around these days, which would be perfect for the Voltset. The Bluetooth module alleviates this problem, too – though it doesn’t fix the issue of what happens to the multimeter when someone decides to call.

Voltset isn’t new; both the Voltset team and the similarly specced  Mooshimeter were also at World Maker Faire last year. In the interim, Voltset has had a very successful Kickstarter. The team is accepting pre-orders to be shipped after the Kickstarter backers are sent their rewards.

voltset-2[Tom] told us that the team is currently redesigning their hardware. The next generation prototype board with more protection can be seen in the far right of the top photo. He also mentioned that they’re shooting for 5 digits of accuracy, placing them on par with many bench scopes. We’re skeptical to say the least about 5 digits, but the team is definitely putting their all into this product. We’ll wait until the Kickstarter backers start getting their final devices to see if Voltset is everything it’s cracked up to be.