Car radio and audio player buttons don't behave correctly. - Page 1
Forum section: electronics / general

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: November 19, 2022, 10:32:47 am
content: Hi. I've got a pair of identical small cheap mp3 players as well as a radio in a 20 year old car that suffer the same annoying symptom. Though unlikely I can fix even if I could be bothered, I wonder if you can explain why the volume buttons/controls seem to fight with each other in functionality.The car radio has a rotary encoder volume control as well as buttons on the steering wheel. It's only annoying because when I want to turn up the volume sometimes no matter what your pressing or dialling, the volume ends up at zero. Same problem, yet on completely different devices.I wonder if I'm cursed.I figure it's some kind of resistive matrix with the buttons but would like a more detailed example or explanation of how it's supposed to work and why it isn't.

author: Jeff eelcr
author_rank: Frequent Contributor
timestamp: November 19, 2022, 06:11:12 pm
content: Volume switches can collapse, most of the time they will "feel different".Rotory encoders will loose contact and reverse direction or skip.Bad solder connections can also cause these problems.Rarely the IC they control is the problem.Jeff

author: David_AVD
author_rank: Super Contributor
timestamp: November 20, 2022, 08:38:04 pm
content: Many times I've seen rotary encoders with worn out or dirty contacts cause the adjustment to only go in one direction no matter what way it was turned. It's never been the electronics itself.With tact switches, a lot of times they are all arranged to shunt an ADC line to 0V via a resistor, with a different value per button. You can see one resistor per switch, usually located adjacent to it. When the switches wear out, their contact resistance rises and adds to the shunt resistance. This then mimics other switches or puts them out of a valid switch reading range.

author: MrMobodies
author_rank: Super Contributor
timestamp: November 20, 2022, 09:03:39 pm
content: Reminds me of this video:EEVblog #1360 - REPAIR - Aircon Control PanelQuote

author: sokoloff
author_rank: Super Contributor
timestamp: November 20, 2022, 09:44:04 pm
content: To add to David_AVD's reply above, the steering wheel controls also go through a slip ring and wiper arrangement that often wears or otherwise causes trouble. My '96 Jeep was terrible for that. The buttons would only work if you turned the wheel off-center a fair bit. This was particularly annoying as that was the only way to engage the cruise control.

author: BradC
author_rank: Super Contributor
timestamp: November 21, 2022, 12:38:05 am
content: Quote from: Ed.Kloonk on November 19, 2022, 10:32:47 amI had a Blaupunkt in my old Audi that use to do similar. It had an EEPROM that it used to store settings, and each time you moved the volume knob or used the steering wheel controls it would write the new setting to the EEPROM, then read it back and use the value. It only took a couple of years out of warranty and most of the time it would wind up at zero. Occasionally it would wind up at full volume, which was startling and mostly unpleasant. They'd obviously never heard of wear leveling.It got to the point I could only reliably change the volume on a really hot day after the car had been sitting in the sun.