I think my charger is trying to hack my phone

January 14, 2015 5:34 AM

Sometimes when I put my phone on my wireless charger, numbers and characters constantly appear in the "Enter pin:" field.

Qi charger, Android phone. Occasionally, but consistently through different versions of Android, my phone behaves weirdly when put on the charger, like the charger is determined to brute force my pin (luckily I don't have wipe after 10 attempts enabled). Random characters appear to be entered, and I get a lot of "wrong pin" messages. It's strange to watch. What's going on?

posted by devnull to Computers & Internet (7 answers total)

That's a common behavior of a noisy power supply. The capacitive touch screen on your phone depends on the electrical ground being "quiet". A cheap wall brick charger can disrupt the sensing circuit and fool the touchscreen into accepting false touches.

Your Qi charger isn't a cheap charger, per se, which is kind of odd. What happens when you put it on a decent wall power supply?
posted by JoeZydeco at 5:49 AM on January 14, 2015 [5 favorites]

Is there torsion being applied to the connector in your phone through the charging cable?

I've had this issue before with previous Android phones where when the cable was plugged in, the on-board connector had gotten loose or damaged somehow and wiggling the cable/connector would result in erroneous keypress signals.

For mine, the connector was screwed up in such a way that just flipping the phone over (face-down) and hanging the cable off the edge of whatever surface it was on stopped the keypress events.

Try another cable - they wear out over time - or other positioning to try to reduce the flex applied to your connector.

Edit: I actually looked up the Qi charger and looks like it's an induction charging pad rather than a connector-based one (I assumed it was a brand-name plug-in charger). So my above answer is less-useful in this use case but may still provide debugging ideas.
posted by bookdragoness at 7:53 AM on January 14, 2015

Seconding JoeZydeco - this is behavior I'd expect from a cheap wall charger, but not a wireless charger.

My best guess? The charging field from your charger is somehow causing interference with a component in your phone that is manifesting as touch events on the screen.

If possible, try to test with both a wired wall charger and another Qi charger - if you experience the same thing with other types of chargers, it may be time for a warranty replacement.
posted by trivia genius at 7:56 AM on January 14, 2015 [1 favorite]

Best answer: I've occasionally noticed this on my Nexus 4 when charging wirelessly, but only when the screen was particularly dirty/smudged (I don't use a screen protector). After cleaning the screen, the problem went away. I always attributed it to the extra oils somehow changing the electrical properties of the glass just enough to confuse the touch sensor, but don't know if that's actually what was happening.
posted by yuwtze at 9:56 AM on January 14, 2015

I had this issue with a low-power charger on newer phones. If plugged into a 500 mA charger (such as a bluetooth headset charger), my phone would register touches randomly and/or not respond to actual touch on the screen.

The Qi charger supplies a lower power level than the standard plug. My guess - if you have a case based Qi charger, plugged into the regular charging port, than the low power will result in this issue.

I have a Note 3 with Qi pad installed internally, and don't have any issues.
posted by shinynewnick at 10:04 AM on January 14, 2015

does the qi charger take a custom power supply? or just a microusb one. because if it just takes microusb, replace the power supply with the best cheap power brick ever made.
posted by emptythought at 6:36 PM on January 14, 2015

Response by poster: So it turns out the interaction between my screen protector and the screen (as well as the carger supply, as most of you have written) was the problem. If the screen protector is clean, I don't get the problem.

I was able to visualise the phantom touches by enabling developer mode and enabling "show touches".
posted by devnull at 1:01 AM on February 5, 2015