Interference of LED driver with gps unit?- Mtbr.com
Results 1 to 12 of 12
  1. #1
    Alles komt goed!
    Reputation: gijsberg's Avatar
    Join Date
    Dec 2005
    Posts
    82

    Interference of LED driver with gps unit?

    I am going to build myself a LED light, but I am worried about the possible interference towards my Etrex Vista GPS unit. I want to put the LED Light on top or bellow the handlebar, but it is certain within a 5 cm radius of my GPS unit fitted on the stem.
    .
    Are there any things I have to think about: choosing the right type,brand of driver, LED Driver combo, placing of the driver (inside the LED housing, or near the battery?) The LEDlight is not going to be a big quatro Lumen BBQ but I am a control freak about good functioning ot the GPS.
    Last edited by gijsberg; 12-09-2010 at 08:52 AM.
    ---------------------------
    Gijs, from the mountain

  2. #2
    mtbr member
    Reputation:
    Join Date
    Jan 2010
    Posts
    291
    I doubt very much that you'll have any issues. GPS signals are in the >2GHz range and due to the spread spectrum nature of their transmission are VERY hard to jam/interfere with by conventional RFI sources.

    cheers,
    george.

  3. #3
    mtbr member
    Reputation: TTGV's Avatar
    Join Date
    Oct 2008
    Posts
    49
    Hello, LED drivers are often EMC (ElectroMagnetic Compatibility) "noisy" stuff, because of the electronical principle and behavior. As Georges80 said, GPS is about 1 or 2 GHz, so the GPS waves won't be disturbed; but what about the inside computer process ?
    Make a test with your stuff wired "in the air", without metallic box. FM radios are disturbed.
    A good way for the job is to place the driver in the Aluminium box with the leds, and use a shielded cable, grounded to the same box, to go to the battery. You can use metallic connectors, as Troutie's lights. The final touch should be done with a front glass with a metallic antireflective coating, pressed on the box, to give a front shielded surface... My lamp don't have this....

  4. #4
    mtbr member
    Reputation:
    Join Date
    May 2010
    Posts
    333
    My Garmin edge sits about 2-3" from my light. No problems here.

  5. #5
    mtbr member
    Reputation:
    Join Date
    Feb 2009
    Posts
    169
    Quote Originally Posted by georges80
    I doubt very much that you'll have any issues. GPS signals are in the >2GHz range and due to the spread spectrum nature of their transmission are VERY hard to jam/interfere with by conventional RFI sources.

    cheers,
    george.
    Actually GPS can be jammed by a rather low power noise source. You can even buy jammers at DX. The reason is the very low power level of the GPS signals so it does not take much to jam them. However, I am pretty confident that there is little interference generated by a LED driver at the 1.575 GHz of the GPS signal. You should be fine

  6. #6
    mtbr member
    Reputation:
    Join Date
    Jan 2010
    Posts
    291
    Quote Originally Posted by vroom9
    Actually GPS can be jammed by a rather low power noise source. You can even buy jammers at DX. The reason is the very low power level of the GPS signals so it does not take much to jam them. However, I am pretty confident that there is little interference generated by a LED driver at the 1.575 GHz of the GPS signal. You should be fine
    I did write "conventional RFI sources" and by that I include the RFI generated by the typical switcher IC based LED drivers.

    cheers,
    george.

  7. #7
    Alles komt goed!
    Reputation: gijsberg's Avatar
    Join Date
    Dec 2005
    Posts
    82
    So with EMC protection (alu housing and shielded cable) there wil be no expected problems?

    About the frequencies:
    Quote Originally Posted by georges80
    .........GPS signals are in the >2GHz range and due to the spread spectrum nature of their transmission are VERY hard to jam/interfere with by conventional RFI sources.
    I was reading a article @ page 28
    These GPS frequencies are designated as L1 (1575.42 MHz) and L2 (1227.60 MHz)
    Is there any information of the frequency working range of the LED driver, internet resources, search(keywords)

    Update: Meanwhile i sended a mail to Taskled for EMC information
    Last edited by gijsberg; 12-09-2010 at 08:52 AM.
    ---------------------------
    Gijs, from the mountain

  8. #8
    mtbr member
    Reputation:
    Join Date
    Jan 2010
    Posts
    291
    Quote Originally Posted by gijsberg
    Is there any information of the frequency working range of the LED driver, internet resources, search(keywords)

    There are 2 flavours of LED driver:

    1) linear regulator or 'resistor' based - essentially all DC and no EMI/RFI.

    2) switching regulator, generally <2MHz and most often <=1MHz. These will radiate some EMI/RFI, better drivers will have shielded inductors and good PCB layout to minimize trace lengths from the switcher and inductor. Good quality ceramic capacitors to bypass/filter the input and output.

    Some drivers with modes etc will have a microcontroller. The uC will be running <20MHz and typically below 10MHz (no need for lots of computing power). All the high switching stuff will be inside the uC since they have internal ram/flash/eeprom, so very little EMI/RFI generated there. There might be a higher frequency signal to run PWM etc to the switcher core for dimming. This is a low energy signal and filtered very close to the uC.

    Finally, just for grins, I fired up my bluetooth GPS (in a plastic case) and draped the LED wires (test jig) over the BT GPS and also ran a maxflex driver with test jig (i.e. just sitting on the bench and NOT in a case) about 1" from the GPS. I saw NO change in received signal strength or fix quality.

    You're basically worrying about a problem that doesn't exist with any 1/4 decent GPS or bike light. Heck, if GPS was that easy to 'mess with' the BT link in my BT GPS would cause the GPS to not work - oh and the WIFI from my laptop that is 10" from my BT GPS would compound the problem

    cheers,
    george.

  9. #9
    Alles komt goed!
    Reputation: gijsberg's Avatar
    Join Date
    Dec 2005
    Posts
    82
    Received a reply to my email:
    Quote Originally Posted by Taskled-email
    driver stuff is a NON-ISSUE for your GPS reception. You should be more worried that you'll fall off the bike and get hurt than getting a bad GPS fix


    Georges80 thanks for your explanation and experiment
    ---------------------------
    Gijs, from the mountain

  10. #10
    mtbr member
    Reputation: Ofroad'bent's Avatar
    Join Date
    Jul 2010
    Posts
    1,475
    Umm, probably off topic, but should we be worried about RF and health effects from a regulated LED if it's on your head running for an hour a day or so, or is it sufficiently shielded by an aluminum housing?

    I know the jury's out on holding a cell phone next to your brain for that long.

  11. #11
    mtbr member
    Reputation:
    Join Date
    Jan 2010
    Posts
    291
    Quote Originally Posted by Ofroad'bent
    Umm, probably off topic, but should we be worried about RF and health effects from a regulated LED if it's on your head running for an hour a day or so, or is it sufficiently shielded by an aluminum housing?

    I know the jury's out on holding a cell phone next to your brain for that long.
    I'd be a lot more worried about my laptop being on my lap - oh, but I've already contributed to the construction of two healthy boys so I guess my two spherical mates are no longer needed

    cheers,
    george.

  12. #12
    mtbr member
    Reputation: Sarguy's Avatar
    Join Date
    Sep 2010
    Posts
    808
    My Magicshine light is just left of my center mounted Garmin Oregon GPS. No problems; however, I had to put the battery pack on the head tube to move it away about a foot. It kept interfering with my wireless speedometer to the right of my Garmin. First time it happened I looked down and saw I was going 40 mph up hill. Hmmm.
    2010 Trek Rumblefish
    2013 Trek Cobia

Members who have read this thread: 0

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  

THE SITE

ABOUT MTBR

VISIT US AT

© Copyright 2020 VerticalScope Inc. All rights reserved.