Arne van Iterson's Display Upcycles an Analog Multimeter and an ePaper Panel Into Something More
With an ePaper background and a swinging needle, this smart display links in to Home Assistant for live readouts.
Electrical engineering student Arne van Iterson has blended one of the most modern display technologies with one of the oldest, combining an analog gauge's needle with an ePaper background display.
"I got a very very cheap multimeter a while ago at school and I didn't have any leads that fit, and I already had a multimeter so it was somewhat useless to me," van Iterson explains by way of background to the project. "However, the size of its analog face did closely match the size of the 2.13" [ePaper] display commonly found on cheap development boards like the T5 E-[Paper] from LILYGO. I decided to combine the two and make an analog display that has a changeable face."
The multimeter in question lacks the usual LCD display, favoring instead a classic swinging-needle analog gauge. As the measurement under test increases in value, the needle swings further to the right — a classic and easily-read display. Behind this is a printed sheet with the scales required to turn the needle's position into an actual reading — and it's here that van Iterson's project takes off.
Taking only the needle part of the multimeter and placing it in a new housing, van Iterson's dual display swaps out the pre-printed background for a LILYGO T-5 e-Paper Display. The position of the needle is controlled through a voltage divider, while the ePaper display — which uses electrophoretic technology, requiring power only when changing states — can be set to display any desired scale.
"It connects to Home Assistant through MQTT and the value can be updated using the included automation. It can display any numeric value with a little configuration," van Iterson explains, with his build currently being used to provide a live reading of the output of a home solar power system. "Of course, the arm is not all that accurate and the display is always going to be slightly off but it's a quite a fun display piece while still being useful."
The project is documented in full in van Iterson's Gitea repository, along with the source code and 3D-printable housing under an unspecified license.