Raspberry Pi Forums

Hello,
at the begining I would like to apologize for my bad english , now to the point.
I got this setup:
- Raspberry Pi from farnell
- about 15cm usb powercord connected to
- RouterBoard 433UAH ( datasheet says Max current 2A ) which got installed in miniPCI slot
- DBII F52N-PRO which is an WiFi AP card

Internet to RPI is connected to RB433UAH via ethernet cable about 20cm long ( maybe a bit more )

Now here is the problem scenario:
1. everything working fine
- RPI power on and working normally
- RB433UAH power on and working normally ( CPU load 0-5% ), set to only G WiFi connectivity
- Laptop with AR5B95H card ( chip AR9285 )
2. problems
- to point 1 we add another WiFi connected device, samsung gt-i5510, somekind of broadcom WiFi chip
- RPI working normally
- RB433UAH starts to go mad, CPU load 20-40%, log's says that phone is connecting and disconnecting all the time
- connectivity from the phone is not stable, putting ping command in the console of the phone, outcome, very unstable ping
- connectivity on the laptop, unstable, ping, same as on the phone, unstable
3. everything working fine ( not the phone problem )
- disconnecting laptop via WiFi
- connecting only Samsung GT-i5510, ping, stable, connectivity, stable
- RB433UAH, CPU load 0-5%, working stable
4. problems
- already connected GT-i5510
- connecting another phone via WiFi to RB433UAH, Samsung GT-s5570
- ping on both phone unstable, connection is unstable
- RB433UAH, CPU load as before, 20-40%, working very unstable
5. everything is back to normal
- powering of RPI thinking that it draws to much power via usb
- connecting two phones and one laptop via WiFi to RB433UAH
- ping, stable on all three devices, connectivity stable
- RB433UAH, CPU load 0-7% ( normal ), working stable
6. everything is still normal
- scenario as in point 5
BUT !
- I plug back RPI to RB433UAH BUT ! on a longer cable and put it away from RB433UAH + I made a simple bash script with for((;;)) to put it in 100% CPU load on RPI
- ping on all three WiFi connected devices still stable and CPU load on RB433UAH is normal
7. Finding the problem
- everything is still as in point 6
- second after I put RPI on top of the RB433UAH everything goes MAD ! ping, stable connectivity, normal CPU load on RB433, everythings gone ( this is what my set is looking like: http://net-aztek.pl/rpi_rb.jpg , so no short circuits [this was made before I put RPI on a long cable and far away from RB433UAH ] ) it does not matter where I put the RPI ( on the front of the RB433UAH, on the middle [where the CPU is] or on the back [where F52n-pro is] ) if RPI is powered on and putted within distance of 5-10cm of RB433UAH, the other device ( RB433 ) goes mad.


Can you tell my why is this thing happening? Please keep in mind that if only one device is connected via WiFi to RB433UAH and RPI is putted on top of it and powered on, everything is fine ( just like described in point 1 of this post ).

The Raspberry pi is a completely unshielded computer board. You will notice that other
computers usually come in metal cases which provides shielding and even mobile phones
have built in shielding. You must keep the pi as far away from other wi-fi devices as possible.

Or you can install it in a metal case and join the metal to the negative power line, This
should provide shielding for other wi-fi devices.

Oooook but RPI is certified to have europien electric noise standards and beside that the RB is in metal case (not grounded but still in metal case).
Do you thing putting a layer of aluminum or copper between RB and RPI will help?

fredjam wrote:You must keep the pi as far away from other wi-fi devices as possible.

Mine is sitting right next to my wifi router and seems to cause no issues.

By writing that RPI is certified in europien electric noise standards I ment that it have CE so it should not interfere with another devices. Can someone from RPI staff can answer my questions? It'll be nice

it may be compliant
however putting anything that close to the aerials is going to cause problems
try it underneath the router
try it covered in tin foil both under and over

chiken wrote:By writing that RPI is certified in europien electric noise standards I ment that it have CE so it should not interfere with another devices. Can someone from RPI staff can answer my questions? It'll be nice

RPi Foundation team have written extensively on this - see http://www.raspberrypi.org/archives/tag/ce-compliance

There are two levels of CE certification, and the Pi was tested to the lower one.

Also, there are two parts to CE certification - transmission and reception.

So your Pi must not radiate more than a certain amount of RF - it shouldn't interfere with the working of anything else
And your Pi should keep working when subject to a certain amount of RF

Is placing a Pi that close to a source of RF - the wifi aerials - really fair?

All the certifcations assume a reasonable distance, like saying something can be warmed or kept hot but putting into a an open log fire is beyond its scope.

As far as I remember the original CE/FCC basis for radiations started with the benchmark of should not cause interference to an analog TV from 3m. This then got refined to what frequencies and energy levels.

Placing two aerials close together is asking for trouble, just like two loud talkers next to each other in a room talking at same time.

Ok, I got my answer, RPI is certified with CE but even though I put it much to close to other device, ok I get it .
But now the solution, I was asking earlier if putting a sheet of aluminium ( or tin foil ) on the botton of RPI or between RPI and RB, or even putting a sheet of copper ( which sould isolate it even better ) will help, get in mind that I want only cover the bottom half of the case of RPI, not the whole thing, it would look ugly if i wrap it around with tin loid P.