N900 sensitive to magnets. Magnetic case latches can wake device.
 

I just noticed something about the N900:

If you place a magnet near the center of the N900 screen while it is in sleep mode, it temporarily wakes up. If you remove the magnet, it goes back asleep.

I noticed this because I have a leather phone/PDA holder with a magnetic clip, which wakes the N900 up whenever I insert or remove it from the case. It is impossible, with even the utmost care, to insert the N900 without it waking up. It then is easy to press the screen or top buttons and launch an undesired program.

So avoid cases with magnetic clips!!!

I wonder if there is a reed switch inside the N900 which is closed (shorted) by the proximity of a magnet when then keyboard tray is open, and if that explains the waking up behavior.

I also wonder if this can be worked around in software. If sliding the keyboard tray open can be prevented from waking up the device, then it might be enough to prevent magnetic fields from waking it up as well.

Re: Sensitivity to magnets?
 

sweet works with a magnetic money clip. If you "just" touch screen goes back to sleep. If you move magnet screen stays on. Also does it on N97,but you have to be much closer to the switch.

Re: Sensitivity to magnets?
 

Magnets induce voltages when moved, and otherwise only affect active parts of the circuit (i.e. which have a current flowing through).
Can you check if the wake-up happens only when jiggling the magnet around or also when standing still?

Re: Sensitivity to magnets?
 

I opened up my N95 quit often and the sliding screen had a magnet inside. when it moved over the pcb, the pcb would know the screen was open. probably something similar is going on in the N900.

Re: Sensitivity to magnets?
 

I think Nokia is using a magnetic switch on the back of the screen and on the inside of the case, rather than other mechanical switches (i.e. plungers, etc.) as the magnetic variety will not get filled with dust, etc. I had noticed the same behavior but had not yet gotten the time to write it up. A magnet also holds the kickstand in place... On the N800 a magnetic switch would tell the unit when the back-plate was on or off. It is a very clever way to do it. I would suspect that the camera may work in a similar fashion (although I have not tested that yet.

Re: Sensitivity to magnets?
 

When the keyboard tray is closed, I notice that the magnet wakes up the N900 temporarily, but it goes back to sleep when the magnet is removed.

When the N900 is asleep, but the keyboard tray is open, the magnet wakes up the device and it stays awake even after the magnet is removed.

It seems so sensitive to magnetic fields, that maybe it uses Hall Effect sensors instead of reed switches.

(70% right, 60% down) as viewed in landscape mode is the location where it is the most sensitive. If Device Lock is enabled, that would be the bottom right of the <- soft key.

Re: Sensitivity to magnets?
 

I have submitted Bug 6689 as an enhancement request.

Re: Sensitivity to magnets?
 

I noticed this when using a sideways case that had a magnet in it. My battery life totally sucked.

The magnet is making the phone think the keyboard is open. If you turn on the onscreen keyboard and close the slider - place a magnet at the back of the device then do a dmesg from the shell you will see the message:

slide (GPIO 71) is now open

So the phone thinks the keyboard is open when it's not.

Sucks for me since I liked the case with the magnet.

Re: Sensitivity to magnets?
 

You realize it's impossible for software to distinguish parasitic magnetic fields from the useful ones, right? Don't expect your bug to be fixed too soon

Re: Sensitivity to magnets?
 

Confirm. I have this issue on N900 and n85....

Re: Sensitivity to magnets?
 

I vote for Hall effect sensor, usually you can hear a tiny ping when a reed switch operates. A compass brought near the N900 shows strong fields near the ends of the device, particularly the end near the headphone jack. But this could also be the motor for the vibrator.

The camera door is sensed by a optical sensor that triggers on the reflective white patch on the cover.

Re: Sensitivity to magnets?
 

If you actually read the bug, you'd see it was a request for an option that opening the keyboard tray not wake up the device, which it does currently.

If the software is changed to not wake up the device when the tray is opened, it presumably will not wake up when a parasitic magnetic field passes through it, either.

But as for parasitic vs. non-parasitic fields -- it would actually be possible to tell them apart if they were modulated by the hardware, e.g., frequency detection. Instead of a fixed magnet, an electromagnet would emit a small signal which the Hall Effect device could detect and demodulate to distinguish it from background noise.Of course emitting the modulated electromagnet would use up more power.

(OT: I once submitted a bug against a paper shredder company whose shredder thought that the bin was full whenever any light passed through the bin window, and refused to shred. I had to tape up the window to keep it from picking up parasitic light. Had they simply used a modulator-demodulator for the LED transmitter-receiver pair, they could distinguish parasitic light from their own LED's.)

Re: Sensitivity to magnets?
 

I believe it does have something to do with how Nokia determines if the devices keyboard opens. The same thing occurs with the N810 but not the N800.
The N800 had an optional leather case/cover that used magnets. When I tried this thing on the N810 it would wake it up as soon as the cover was lifted. Not so with the N800.
At first I thought the dang light sensor had something to do with it.
Perhaps someone can find the code in an N810 and a work around might be the same for the N900.

Re: Sensitivity to magnets?
 

@YoDude: I tested it, and it's definitely not the proximity or light sensor, but is magnetic. Like you, I hope someone came up with a workaround for the N810 which can be transferred to the N900, but I wouldn't hold my breath :mad:

I was shopping in the store tonight, replacing my nice leather magnetic-clip case with a cheaper-but-okay slip-in case. 95% of the cases in the store were magnetic, so I had to keep searching :mad:

I'll probably eventually get a Piel Frama or similar.

Correction: Piel Frama is also magnetic. S**T!!!

Re: Sensitivity to magnets?
 

It may help to insert a piece of iron plate as a shield. Not even sophisticated but better than always empty battery. Care that you don't shield the GSM antenna area (see the manual)!

Re: Sensitivity to magnets?
 

A hall effect sensor needs a constant current flowing through to work. This would surely kill the battery quickly, and be a useless drain. I'm betting it's a small coil, which generates an impulse every time a magnet is moved around it. This makes it impossible to modulate the impulses, to distinguish between internal and external fields.
Even if modulation were feasible, it would surely require some hardware changes. So i'm afraid no fix from nokia on existing devices.
A metal plate should reduce the device's sensitivity, but possibly not enough to block it out. The device will also only lose gsm signal if it's completely encased in metal

Re: Sensitivity to magnets?
 

Even a coil requires a circuit to detect and amplify its signal, which requires no more current than a Hall effect circuit.

Nokia may not fix the hardware, but the firmware/software can be fixed to avoid turning on the device when the sensor thinks that the keyboard tray opens.

That is, for all intents and purposes, a fix.

The other possibility is hacking your device by opening it up and cutting a wire or trace, thus stopping the sensor from working.

Re: Sensitivity to magnets?
 

Apparently Nokia agrees :)

Please add your votes!!!

Re: Sensitivity to magnets?
 

I voted for this bug on bugzilla. My nice new case will be useless unless a fix is made available in software. I really hope Nokia adds an option.

Re: Sensitivity to magnets?
 

The software solution to this hardware bug is to have an option to "Not wake on keyboard" or "only wake from switch" or somesuch.

Re: Sensitivity to magnets?
 

Me got this issue as well. I found there is bug exists in bug tracker - see bug 6689. I have idea how to workaround this in software, see comments to a bug.

Nokia N900 problem with magnatic fields
 

The N900 has a problem with magnets. The screen goes on when you hold a magnet nearby the screen. This happened also by the back of the N900. If you have a case with magnet closing (my old E90 case from Carrymobile) like i have , see my YouTube film. Has somebody the same problem ???
http://www.youtube.com/watch?v=kaYT-cqCjdw

Re: Nokia N900 problem with magnatic fields
 

Oh yeah. You have to test a lot of cases. I finally found one -- a cheap off brand -- with a lightly weaker magnet that seems to work. Most cases have a stronger magnet that will set off the N900.

And you can;t find a case without a magnet, it seems.

Good luck.

Re: Nokia N900 problem with magnatic fields
 

When i use my magnetic pouch for the n900 i face the screen inside instead of outside because of the magnetic field. This prevents my n900 from turning on whenever i try to pull it out. I've have tested it many times already. I have an original Blackberry pouch for my n900 which fits perfectly. It's a slide down pouch unlike the one in that video. I recommend it.

Re: Nokia N900 problem with magnatic fields
 

I have a case from Tmobile (USA) store and has no magnet. the case is just like ones with magnet but has no magnet. Width is just fine but is a bit longer than n900. But it's a good fit. I used to use it for G1.

Re: Nokia N900 problem with magnatic fields
 

i prefer the invisible protection like zag and a leather slip case.

Re: Nokia N900 problem with magnatic fields
 

this has been discussed before - the hardware for detecting keyboard slide is most probably based on some kind of a magnetic detector...

Re: Nokia N900 problem with magnatic fields
 

And for the back - the camera slider has a similar setup.

Re: Nokia N900 problem with magnatic fields
 

will this mess the phone up over time?

Re: Sensitivity to magnets?
 

Threads merged.

magnetic closure on case activates device
 

Hi I have a fine leather case from piel frama, with a magnetic closure.

I always thought that my N900's battery life sucked, but now I know why. The magnetic closure system activates the device!! It just switches it completely on, just like sliding out the keyboard.
I checked this with another magnetic closure case (from my E90) and the same happen!!!
This is a design flaw in the N900!!

Re: magnetic closure on case activates device
 

@mtjioe, this 'bug' has been already discussed on this forum, you can join this thread :)

This is actually a problem of many sliders using magnets to discover keyboard slides. My ooold HTC Wizard had the same issue.

Re: magnetic closure on case activates device
 

Or in the case.....

Which sensor is it activating?

Re: magnetic closure on case activates device
 

http://talk.maemo.org/showthread.php?t=36194 is the other topic on this subject :)

Re: N900 sensitivie to magnets. Magnetic case latches can wake device.
 

Threads merged.

Re: magnetic closure on case activates device
 

Hmm..yes, this is interesting. I wonder if it is possible to access this magnetic sensor and read its values...? If N900 can detect magnetic fields, that might have some applications..

Re: N900 sensitivie to magnets. Magnetic case latches can wake device.
 

Ha! Now I know why mine got ridiculously hot and the battery discharged while in the pouch with a magnetic closure.

Re: magnetic closure on case activates device
 

The desing flaw is using a magnetic closure on case. Magnetism causes interferences to electronics, discharges batteries, etc..

A small magnetic exposure for a short time is harmless, but can cause serious damage like data loss if the exposure time increases.

Sorry for bad English.

Re: N900 sensitivie to magnets. Magnetic case latches can wake device.
 

Vote for bug 6689 - https://bugs.maemo.org/show_bug.cgi?id=6689

Re: N900 sensitivie to magnets. Magnetic case latches can wake device.
 

I had this problem before, and my solution is put the N900' s screen face to you body in the leather case. That can avoid your phone is waken up by magnetic clip :D