Resurrecting the Antique Pressure Gauge to Display Internet Bandwidth

Resurrecting the Antique Pressure Gauge to Display Internet Bandwidth

Who doesn't like old technologies? For example, a Motorola cell phone as heavy as a brick and built to last centuries (literally)? I do like old stuff, my dear readers. That's why when one day I came across a cool looking (and rightly priced!) antique pressure gauge on eBay I bought it with very little hesitation. Presumably, gauges like this had been used on steamboats and locomotives. I had the idea to upgrade it to use this piece of ancient technology for modern purposes, specifically to measure my home internet bandwidth utilization.

This is what I got in the mail a few days later.


Not cool. I was not ready to hang this at my desk, being too ugly even for me, not to mention my wife. What I really wanted to see was a brass bezel and black body instead of this rusty bezel and gray rusty-dusty body. I desperately needed some magic and I found it at the local hardware store: sandpaper, paint remover, and spray paint!

After applying my newly acquired magic the gauge started to look much more appealing.

That was better, but I still needed a different kind of magic to make it measure something more useful for me than steam pressure. I thought about creating an application (running on the PC) to calculate bandwidth utilization and somehow send this information to the gauge via USB.
But how would I make the needle move? The answer came from China in form of the miniature RC servo. RC servos are typically used by hobbyists in radio-controlled models and robotic applications. It’s a perfect fit for this project because:

  • It’s small, so it fits the gauge easily
  • It needs 5V power supply (since I am planning to use USB and it provides 5V)
  • It’s easy to control
Here is the downside - an RC servo needs a precise PWM (Pulse Width Modulation) signal for positioning. PC/Windows was born to be almost useless for generating any precise timing/pulses, so I needed something else to generate it. I elected an Atmel AVR microcontroller for this job. Why AVR? Simply because I've used it before, know this platform reasonably well, and love it (well, sort of). Unfortunately, the smallest/simplest AVR microcontroller I had planned to use didn't support USB communication, so I had to add a USB-to-serial converter to the mix since serial protocol is easy to implement even on the tiniest microcontrollers.

Now I am ready to put it all together:
  • The PC runs a .NET application which calculates bandwidth utilization and sends it to the gauge. It sends the utilization as a percentage since the gauge is calibrated 0-100
  • Inside the gauge, there is a USB-to-serial converter that talks to the AVR microcontroller via asynchronous serial communication (this is just a fancy term for serial port)
  • The microcontroller converts the utilization percentage to the PWM signal and sends it to the RC servo
  • The RC Servo controls the needle position utilizing parts from the original mechanism

Completed gauge with scale removed.Completed - Opened

In the picture above: RC servo (blue thing, covered with whitish mass), USB to Serial adapter (green board), and microcontroller (small 8-pins chip, to the right of the green board).

Everything was mounted inside the gauge using my favorite method - glue gun (I am pretty sure Wikipedia knows a better term for it, but "glue gun" just sounds dangerous).

Now back to the .NET application. It turns out that it's very easy to read a whole bunch of the statistical data from my home wireless router because it supports SMNP protocol. SNMP is a standard network management protocol supported by most of the network devices (computers, routers, printers, etc.). It provides access to the device's internal status/variables/parameters.

The most important variables to me were sent/received byte counters. There is one set of counters (upload/download) per each Ethernet port (my router has 5 ports), but I cared only about the Ethernet port connected to my DSL modem. By querying these counters every second it's trivial to calculate upload/download speeds. However, in order to calculate bandwidth utilization, I also needed to know my maximum Internet upload/download. is a hero of determination of true Internet speed.

Cool, I can calculate both the upload and download bandwidth utilization, but which one should I use for the gauge? I tried a few options and found out that I personally like a maximum between upload and download because it tells me when to expect web surfing bog-downs.

The .NET application interface is pretty simple, nothing fancy.
PC Application

This is how completed gauge looks.

Thank you for reading my humble blog and have fun hacking the stuff.

Ah right, I forgot the video of the completed system, enjoy:

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Great video. Unfortunately, I must be missing somheting because I can only get the servo to respond to one of the photocells. When I reverse the wiring it responds to the other photocell. I have adjusted the servo adjuster and the potentiometer. The results are the same. Any thoughts, suggestions?
asian antique
dont know what is gauge but it sounds nice.
Boris Cherkasskiy
# Boris Cherkasskiy
Thank you for the comment, but unfortunately I am not a collector. This was my one-off project based on pressure gauge. Although, I noticed that vintage gauges seem to be highly-desirable items on Ebay.
Kathy Little
# Kathy Little
We have 12 antique pressure gauges from 2 1/2 inches to 12 inches in diameter. Would you be interested in buying them or is there a market somewhere out there for them? Thanks, Kathy

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