Hi everyone! I’m on a project where I try to get an old telephone switch (in German “Hebdrehwähler HDW 27”) to work again. I took a SparkFun MicroView, connected an old (modified) telephone (just the wires from the dialer & cradle), two electromagnetic relays, a power adapter with 48V/60W and a stepdown converter for 5V, put them all together on a 3D printed board… and it works like a charm! The display tells me to pick up the speaker, then it wants me to dial a 2-digit number. While I’m dialing, the MicroView live-reads out the dialer and works the magnets on the HDW 27. After that I have to hang up and the HDW will be triggered a few times to get reset for the next call…
The only problem: at the second or third use of the magnets (dialing the 2nd number or hang up-reset) the MicroView screen goes black, but everything else works perfectly, only “blind”. When I pull the plug and start over, the display comes back like nothing happened. I tested three different MicroViews, all with the identical behaviour. For cross testing I removed the power from the step down converter and connected the MicroView directly with a seperate power adapter (5V), which fixes the problem. Since I have no equipment to thoroughly measure the current from the converter, I wanted to ask: what conclusion can you draw from that behavour (screen goes blank, but works)? Is it a spike in current or an “outage”? The integrated Arduino keeps working without interruption or reset…