Faded Beauty DMM Gets An OLED Makeover

When a fine piece of lab instrumentation crosses your bench, you’ve got to do your best to put it to work. But even in the highest quality devices no component lasts forever, especially vacuum tubes. For some vintage instruments with vacuum fluorescent displays, that means putting up with less-than-perfect digits in order to get that sweet, sweet precision. Or not – you can always reverse engineer the thing and add a spanking new OLED display.

The Hewlett-Packard 34401A digital multimeter that fell into [qu1ck]’s lap was a beauty, but it had clearly seen better days. The display was full of spuriously illuminated dots and segments, making it hard to use the 6.5 digit DMM. After a futile bit of probing to see if a relatively easy driver fix would help, and with a replacement display being made of solid unobtanium, [qu1ck] settled in for the long process of reverse engineering the front panel protocol. As luck would have it, H-P used the SPI protocol to talk to the display, and it wasn’t long before [qu1ck] had a decent prototype working. The final version is much more polished, with a display sized to fit inside the original space occupied by the VFD. The original digits and annunciator icons are recreated, and he added a USB port and the bargraph display show in the clip below.

We think it looks fabulous, and both the firmware and hardware are on Github if you’d like to rescue a similar meter. You may want to check our guide to buying old test gear first, though, to get the most bang for your buck.

Continue reading “Faded Beauty DMM Gets An OLED Makeover”

Router/Twitter/Arduino clock

ledclock

[Kyle] decided to build the above LED clock for his church. Though it may look impressive enough, it is also hiding loads of features. [Kyle] wanted to make the clock as easy to control as possible, so rather than use buttons or dials to control what is being displayed, he used Twitter. The clock is connected to the internet through a Linksys WRT54GL. The router was hacked so not only does it supply the connection to Twitter, it also parses all of the replies the clock’s feed gets. The clock responds to commands to turn it on or off, run a countdown before service, display the number of viewers on the church’s live stream, and display a sequence of numbers. The time never needs to be set, as it is synched from the internet. The circuit for actually driving the display is based off a PIC, but it was changed to run off an Arduino.