GPS Interference

ljw2k

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...> Rayman Chan I would like the new revised GPS Mount please ....PM sent with address details.
 

USDashCamera

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Will the GPS interference cause problems with the image quality? i keep having clips at night where sometimes it looks really clear and other times it has a lot of grain. i can't think of why its happening unless it is interference of some sort. before i thought it might be because I had my joovuu x next to it running, but even when I don't have that up it happens.
 

jokiin

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Too many ¯\_(ツ)_/¯
i keep having clips at night where sometimes it looks really clear and other times it has a lot of grain. i can't think of why its happening unless it is interference of some sort. .

Have a look if you get the same results when the sensor is cold versus hot
 
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lacibaci

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Here is a test with the new housing:
There is still some interference but it looks better...
 
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lacibaci

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More data after the new enclosure with EMI shielding:

Total drive time: 424 minutes
GPS lock: 331 minutes (about 78%)

Raw data:
159 log files
19872 samples with GPS lock
5569 samples without GPS lock
 

bossev

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Thanks for sharing your research data lacibaci!

Does it create log files only when there is a GPS lock or it should create them any time?
I have tested mine the last few days and I didn't see any log files produced on the card (and I didn't have any GPS lock for few short 10-15 min. drives).

Thanks.
 
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lacibaci

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Make sure the GPS is set to logging in settings. Then check the GPS directory on the SD card.
 

Painter

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Hi all,

As expected i had the GPS issue with my recently purchased mini 903 dash cam...
I desided to have a look about how i can improve things.
After about 2 hours i can say that the problems are solved for me, i cannot say that the problem is 100% elliminated because i checked the gps satellites signal on my mobile with the nanoq on/off and there is still some signal decrease with the nanoq on but it seems that i have no issue at all.
No issue i mean that from the >5 minutes that the gps needed to lock, now it seems to be almost instant, just a few seconds.

As i have prepared about 15 photos let me say what i tried to do.
The issue was affecting the gps receiver (base) of the unit.
So the targets was two:
1) To reduce the interference emmited from the camera unit.
2) Reduce the interference reaching the GPS unit.

ΠΡΟΣΟΧΗ!!
I should warn you that i am not responsible if you try or if you attempt to do the below and destroy things, you car or yourself....

After i oppened the unit i realized that the plastic casing was already coated with copper based conductive paint.
Inittialy that made me thing that the "EMI 35 Electromagnetic Shielding - Spray that i ordered will probably not be needed.

1.jpg


As you can see the copperish spray is indeed conductive.


2.jpg

You will see that there are in total two elastic foam things with square cross section and condactive external braid that are used to electrically connect the "ground" of the two PCB's (printed circuit boards) with the conductive paint of the plastic casing.
To my liking it didn't seem that the below was making a good contact so i helped it with an elastic piece that i used capton tape to hold it in place on the top of one of the big capacitors.


3.jpg


I used 1cm copper tape on top of the existing copper paint in order to better "shield" the internal of the camera case, in the photo below you can see covered half of the cover side that is close to the copper tape roll.

4.jpg


In the photo below you can see the completed back cover of the camera.
I should note that the back of the display was already covered with a different type of shielding like a silver metallic cloth. Nevertheless i covered this as well with the copper tape.
Be carefull to cover it carefully with capton tape in order to insulate it, we don't want the copper taped parts to make electrical contact with the components on the PCB.


5.jpg


One of the important things that i noticed even before i had the camera completelly oppened was that this conductive foamy thing was NOT electrically conductive with the camera ground, that is for example the micro usb external side that is also soldered on the pcb. The soldering points are the two round holes between the micro usb connector and the "foamy" thing. That f thing is sticked in place with a sticky paper -as you can see in the picture below- but that sticky parer does not permit the electical contact.
That means that the back comera cover was not really using properly the internal shielding coating.


6..jpg


We don't want the foamy thing to make contact with any other pin on the PCB and also it should not move arround as it will mess up the camera.
So, i put some capton tape to insulate the nearby pcb parts.
7.jpg

I cannot post more pictures so i will continue on the next post.
 

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Painter

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And i used my soldering iron to solder the foamy thing on the micro usb ground (-) points.

8.jpg


Below you can see the completed shielding attempt, as you can see i didn't modify (apart of a small copper tape piece on top of the speaker) the front camera cover as it seemed to me that it had a decent amount of coating. From the other hand for the back cover i was expecting more coating but maybe your camera is a different story.

9.jpg

That concluded the camera part, now it is time for the gps base.
10.jpg
I soldered a small 100nf/63v capacitor between the ground and power supply pins of the base, that should help reduce some of the high frequency noise (interference) on the cable between the gps and the camera.
12.jpg
I folded the capacitor...

12.jpg

I shielded the back (attention, only the back cover, the front should remain as it is for the gps antenna to receive the satellites properly).
And as usually i covered the components with 1cm capton tape.

13.jpg

Probably an overkill but i have lot of tape and after i covered the capacitor with capton i put some more copper tape between the micro usb connectors.

14.jpg

I removed a plastic tab from the front gps cover that was reaching the capacitor and tape area.

15.jpg


So, i did the above and i have no issues at all.
Maybe not all the above was necessary but i didn't attempt any check in between the modification steps.

On the way to work threre are many tunnels where i was loosing the signal for good for a few minutes, i will check it again on Monday and post an update but so far so good.
 

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lacibaci

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Excellent write-up. Did you also have to refocus the lens?
 

Painter

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Excellent write-up. Did you also have to refocus the lens?
No, it seems to be ok. I did a couple thousand kilometers the last days and as i checked the recordings they have good focus but unfortunately many hot pixels.


Sent from my LG-H815 using Tapatalk
 

Dim_

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So, i did the above and i have no issues at all.
Painter, awesome!!!
I repeated the small part of your job only (last three pictures)
(I shielded the back cover of GPS platform covering the components with capton tape and I covered the USB connectors (the capacitor in your case) with capton and then some more copper tape between the micro usb connectors)
I noticed the result (the difference).
Now I catch the signal from time to time (before the GPS did not work at all)
I think the capacitor that you added is important as well.
 

Painter

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Dim, I’m glad the modification worked for you even with the small part of it.

Just, FYI after the extensive usage of the modified camera all that time I have no GPS problem at all.

But…. I could not stand it that it can be further improved so I’m continuing with the V2 of the modification.

Basically what I’m doing is :

A) more shielding on the casing of the camera (done)

B) more shielding and power filtering in the GPS (not started yet

C) check if it is possible to replace the small unshielded 3 wire cable from the gps connection pads to the power feed (inside the gps case).

D) Finally after better checking the videos I have a focus issue at about the 1/5th (right side) of the video (I know it was already discussed somewhere so I have to read more about it).


Step A is already completed and as it will probably take some time until is complete all the above let me show below what I’m talking about.


Here you can see the empty case as it was after the shielding with the copper tape two months ago.

Notice that there is no electrical connection between the two halves of the case – confirmed with the DMM (digital multimeter).



Let me explain this one. As I said I decided to put some extra shielding. Visible are the points at the clipping edges of the casing that there is no electrical conductive copper paint. As in the mean time I received the “Contakt Chemie EMI 35” spray I decided to use it.

I masked the areas that I didn’t want to be painted end voila!






So, I did it but it has some drawbacks:

a) The spray is expensive, I paid nearly 20€

b) In order for the conductive paint to adhere of a surface is slightly dissolves the material (plastic in this case and Of course I didn’t read that spray manual).

c) It didn’t adhere at all on the metallic ring with the magnet around the lens.

d) It clogged the small cooling holes so I had to release them again using a toothpick.

e) Some paint escaped my masking and is visible when the camera is re-assembled, not that I mind about it.




This is how the casing look like after painted with the copper spray and after I added a lot more of copper tape. Notice that also at the areas the two parts are clipping there is paint or copper tape. I very easily cleaned the metallic ring from the copper spray.

To conclude I believe that it is better, cheaper and easier not to use the copper spray at all. It doesn’t worth it.

Just press firmly the overlapping layers of the copper tape and make sure that there is electrical connectivity between them as the layer of glue under the tape does not ensure electrical continuity.










....continuing in the next post
 

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Painter

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Here is where I have the dashcam installed.



Have in mind that some cars have some UV protection film in between the two glass layers of the front windshield that greatly attenuate the gps signals.

For example, in my VW Passat (photo above) there is no issue at all at any position behind the windscreen but in my Peugeot 206 RC Le Mans the only area that the film is not present is behind the rear view mirror (usually black dotted area). It is possible that some of you having GPS issues the above film (not removable, it is sandwiched inside the windscreen triplex glass (laminated safety glass).

If you have French car It is more common to have that film implemented, it should be easy to search and find if it is present.

Also, the same issue happens if you install window tint film (usually not legal in windscreen and front door windows.


The outcome of the above modification so far is that I have GPS lock always when outside.

In the morning it takes about 2 minutes to first lock but afterwards even if I stop for some time it locks almost immediately. It probably depends on the charging status of the super cap in the GPS unit that keeps the ephemeris data.


Just FYI I feed the nanoq from the interior light unit.

The camera needs about 0,5A so the 12V to 5V/3A USB adaptor from ebay is ok and is not even getting hot.

Also have in mind that the connection point visible in the pictures are not the final ones as it seems that the ground point I used on the PCB depends on the door status.

Meaning that when I open a door te power to the camera is interrupted and comes back when I close the door. Anyway I have no idea about any noise on the specific feed line and I haven’t check yet if is also controlled by the battery disconnect relay that disconnects power some minutes after the car is locked (I hope it does, It will be very convenient for me).











As for the gps mods, the capacitor was an easy addon but probably some decent filtering with a ferrite core and coil/capacitors etc. if could fit will make a better job.

To be continued…
 

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lacibaci

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I also added shielding and 100k capacitor but it is still flakey. One thing I discovered was that the interference is most likely coming from the camera via the wire.
Here is how you can test it.
1. Remove camera from the mount.
2. Insert power cable to the GPS mount and wait about a minute.
3. Mount the camera and observe instant lock.

I can reproduce it 100%
 

jokiin

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Too many ¯\_(ツ)_/¯
I also added shielding and 100k capacitor but it is still flakey. One thing I discovered was that the interference is most likely coming from the camera via the wire.
Here is how you can test it.
1. Remove camera from the mount.
2. Insert power cable to the GPS mount and wait about a minute.
3. Mount the camera and observe instant lock.

I can reproduce it 100%

are you meaning you power the mount for a while and then add the camera?
 

jokiin

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Too many ¯\_(ツ)_/¯

ok, that's not really a valid test as such, the GPS only needs power to do what it does, it will pull a signal very quickly without the camera nearby but when you add the camera it's a hot start anyway which should be instant, if you power off while you're connecting it's a warm start after a few seconds which will also be close to instant, the camera as a cause of interference will far outweigh any interference from the cable that connects the two, someone asked in another thread why we use external GPS, situations like this is one of the reasons, having the GPS internal or very near to the camera as in a bracket mount is a lot more involved than people (some manufacturers included) appreciate
 
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