An AVO 8 Teardown

July 22, 2024 by Al Williams 7 Comments

AVO meters — literally amp, volt, ohm meters — are not very common in North America but were staples in the UK. [TheHWcave] found an AVO 8 that is probably from the 1950s or 1960s and wanted to get it working. You can see the project in the video below.

These are very different from the standard analog meters many of us grew up with. [TheHWcave] shows how the dual range knobs work together to set the measurement. There are three separate ohm settings, and each one has its own zero pot. We were surprised that the meter didn’t have a parallax-correcting mirror.

Other than dirty switch contacts, the voltage measurements still worked. After cleaning the contacts, most of the ranges worked well, although there were still some issues. Some of the resistor ranges were not working, either. Inside the case were an old D cell and a square battery, a B121 15 V battery. Replacing the 15 V battery with a bench supply made things better.

Some plugins are available to allow the meter to read low resistance or high currents. We thought using the soldering gun as a current source was clever. Once he gets it working, he opens the box around the 14:30 mark.

The inside was all hand-wiring and power resistors. Of course, there are also a ton of contacts for the switches. So it isn’t just an electrical design, but a mechanical one, too. The electrical design is also interesting, and an analysis of it winds the video down.

[Jenny List] has a soft spot for these meters, too. Why use an old meter? If you have to ask…

Continue reading “An AVO 8 Teardown” →

Giant Analog CO2 Meter Sweeps Away Doubt

November 14, 2019 by Kristina Panos 11 Comments

Most of us are aware that trees turn CO₂ into oxygen, but we’d venture to guess that many people’s knowledge of this gas ends there. Is it feast or famine out there for the trees? Who can say? We admire [rabbitcreek]’s commitment to citizen science because he’s so focused on making it easy for people to understand their environment. His latest offering, a giant analog CO₂ meter, might be our favorite so far.

The brains of the operation is an Adafruit Feather Adalogger. It reads the CO₂ sensor that’s mounted close to the business end of the nautilus, and becomes the quill that writes the CO₂ value to a FeatherWing e-ink screen. For the giant needle, this lovely meter uses one of those fiberglass poles you mark your driveway with so you can find it under a blanket of snow. The needle is counter-balanced with washers encased in printed plastic.

As you can see in the GIF, there’s a decent delay between the CO₂ blast and the needle response — we like to imagine the CO₂ spiraling slowly through the nautilus like a heavy, ill wind on its way to gravely move the needle.

Want a way to monitor air quality that’s a bit more discreet? Slip this portable meter into your pocket.

Current Meter Shows Current Time

January 5, 2016 by Anool Mahidharia 16 Comments

This isn’t the first of its type, but [Daniel]’s MSP430 based Analog Gauge Clock certainly ticks off the “hack” quotient. He admits an earlier Voltmeter Clock we featured a while back inspired him to build his version.

[Daniel] was taking an Embedded systems class, and needed to build an MSP430G2553 microcontroller based final project. Which is why he decided to implement the real time clock using the micro-controller itself, instead of using an external RTC module. This also simplified the hardware used – the microcontroller, a crystal, three analog ammeters, and a few passives were all that he needed. Other than the Ammeters, everything else came from his parts bin. Fresh face plates were put on the ammeters, and the circuit was assembled on a piece of strip board. A piece of bent steel plate served as the housing.

The interesting part is the software. He wrote all of it in bare C, without resorting to using the Energia IDE. He walks through all of the important parts of his code on his blog post. Setting load capacitance for the timing crystal was important, so he experimented with an oscilloscope to see which value worked best. And TI’s Application Note on MSP430 32-kHz Crystal Oscillators (PDF) proved to be a useful resource. Three PWM output’s run the three ammeters which indicate hours, minutes and seconds. Push-button switches let him set the clock. See a short demo of the clock in the video below.

Continue reading “Current Meter Shows Current Time” →

Hackaday Links: March 12, 2013

March 12, 2013 by Brian Benchoff 28 Comments

Thankfully saved from steampunkers

meter

[Chris] found a really cool pocket watch-style multimeter in a box of junk that was passed down from father to son. There aren’t any markings on it, so he’s looking for any information he can get on it. It’s a cool piece of vintage tech in any occasion; check out the pics he sent in below:

Here’s a fix for your illegal stuff

[Don] ‘acquired’ one of those China-only Raspberry Pis, but after plugging it in, only the power light would stay on. The fix, apparently, is putting these three files in the /boot folder of a Red Pi SD card.

Not a pocket watch

meter

[Tom] picked up an old DC volt meter in an antiques shop. He quickly gutted it to make an analog meter display for his Raspberry Pi. There’s a few status lights to remind [Tom] of something he hasn’t figured out yet. Bonus points for a cheap buck boost converter, though.

Smashing monitors? Really?

NESIT Hackerspace

The Meriden, CT hackerspace, the New England Society of Information and Technology, was vandalized last week. They’re dealing with some real punks here; their computers weren’t stolen, they were just smashed. NESIT is looking for donations (both money and equipment), so if you have a few monitors or old boxxen and live around there, consider donating them.

Help a guy out here.

survey

[Jonathan] is a real cool dude that’s working on his master’s thesis on ways to build a sustainable company through the development of open source hardware. He wants you to take a survey. How do we know he’s cool? He had something posted on HaD back when we had the old black and white and scotch tape images.

Monitoring The World’s DNS Status Using A Display Straight Out Of WarGames

July 31, 2011 by Mike Szczys 14 Comments

Nothing says Cold War like a map of the work with LEDs embedded in it. Throw in some analog dials for good measure and you’ve got a piece that would be comfortable mounted next the WOPR in everyone’s favorite ’80s-computers-run-amok movie. We think [Dima] really hit the mark when building this status panel for OpenDNS datacenter monitoring.

[Dima] works for OpenDNS and wanted to make something special for its upcoming 5 year anniversary. He’d already been toying with making boxes from laser-cut wooden pieces. This was just a matter of choosing a size that would fit the dials and leave a suitable area for a laser-etched map. Each of the twelve panel meters gets a PWM signal from the Arduino Mega that he used to bring the device to life. It shows a comparative server load for each data center based on the previous day’s numbers. There is an LED in the map for each of these centers. Right now they’re all red, but he used RGB LEDs and plans to upgrade the capability soon. He should have no problem doing this as he sourced some TLC5940 drivers to extend his I/O capabilities.

Don’t forget the check out the clip embedded after the break. Continue reading “Monitoring The World’s DNS Status Using A Display Straight Out Of WarGames” →

CPU Tachometer

August 7, 2009 by Caleb Kraft 35 Comments

[youtube=http://www.youtube.com/watch?v=3nAeftaUWYw]

Recently, analog displays have come back in vogue. This is partially due to the common steam punk theme that is popular right now. [Cristiano] has done an analog display, but instead of brass and polished wood, he’s gone automotive themed (Internet Archive Cache) with it. He purchased a cheap tachometer from ebay. A circuit had to be designed to give the tach the signals needed for it to operate, and you can download the schematic from his site. As you can see in the video above, it works well. We think that “shift” light might get annoying pretty quickly.