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Thread: EMI? Gremlins?

  1. #1
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    EMI? Gremlins?

    OK to begin with I don't have a Gremlin. I have a 2007 Honda Ridgeline. I use a Car2PC adapter to connect my Dell 5100 laptop thru the OEM head unit, mainly to play mp3s. (Yes, the 5100 is a brick & yes, it overheats & yes, I have thermal shutdowns on occasion.)

    Here's the story: Running the laptop off battery only, everything is cool, except of course that the battery lasts less than an hour due to its age & the draw from the sound & hard drive. Running the laptop using a DC-DC cigarette lighter adapter (admittedly an el cheapo from eBay), again, everything is cool ... almost. The laptop runs fine & the sound is great. But after about 10-15 minutes running with the DC-DC converter, the Tire Pressure Monitoring System (TPMS) indicator comes on.

    [For background, the Honda Ridgeline has a "TPMS" indicator that displays if there is a fault in the overall system, as well as separate indicators to show if a particular tire is low. If I unplug the adapter, the TPMS indicator will go back out. I have not used a Scangauge or other tool to read any fault codes that might be in memory. From my research, it appears that the individual tire sensors work on some radio frequency.]

    Does this sound like an RF interference issue with the cheap DC-DC converter? Does anyone know what frequency the tire sensors might operate on? (Nobody on my favorite Honda board seems to know...)

    I don't know if there's a solution, but the light is annoying. (And yes, the first time it happened I stopped & checked the tire pressure all around )

    T.I.A.

    Joe

  2. #2
    Low Bitrate ajscomp372's Avatar
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    It could be that the DC/DC converter is causing some sort of interference in the power system. Interference like that sometimes causes sensitive electronics like radio equipment to stop working. You should buy a better DC/DC converter if you have the money (I bought a good one and it hasn't given me any trouble). If not, you might want to look into putting together some circuit between the converter and the power source to cut the interference.

  3. #3
    Constant Bitrate
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    Sep 2004
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    I highly doubt the TPMS works on RF. Think about it logically. Those sensors need electricity, which means getting a wire to them, while theres a electricity wire there, why not put a few data cables there and do away with the whole RF??

    If you have a 2007 Honda, doesn't that mean the car is brand new, which also means the battery is as well??

    I believe the DC-DC converter on ebay is at fault here. A ciggerette lighter is supposed to only power certain things.....such as a ciggerette lighter.....they were not and never have been designed to power stuff that continuously draws alot of power.

    The TPMS sensors most likely work on voltage to guage the pressure. I.e, High pressure = low resistance = high voltage output on the sensor wire, and vice versa.

    If the battery goes flat, then the TPMS sensors will be working at a lower voltage, therefore acting like the pressure is low. But then again, I may be wrong, as I have no idea how TPMS sensors work!

    My advice to you, is get a proper DC-DC converter, stop skimping! If you have enough money to buy a brand new honda, im sure you have enough to buy a decent PSU and computer!!
    Secondly, measure the voltages from the battery, if it is dipping too low, get a bigger better battery.
    Thirdly, if the battery still dies, then take the alternator and get it upgraded!

  4. #4
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    Checked with a Honda Tech... The pressure sensors do use RF to transmit to the "body control module" which in turn links to the dash indicators. The tech wasn't sure whether it might be interference on the power line or RFI, though.

    Addressing other questions: vehicle battery is 1 yr old & good. No worries there. I'm reluctant to invest in a more expensive power supply if there might still be an issue, since "el cheapo" runs the laptop just fine & other than the idiot light coming on, there are no malfunctions.

    My secretary reported that her 2007 Honda Odyssey had a similar TPMS issue (indicator on) when her kids had either their video game or a DVD player running off the cigarette lighter.

  5. #5
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    I would recommend a cleaner more direct from the battery power source for the cig DC-DC adapter. You could buy a cigarette lighter/power outlet kit from rat shack and wire it directly to the battery (throw in a relay to keep it ignition hot) and that may solve your problem. However I had a cheapo ebay cig adapter that would draw too much power and eventually it smoked it self (thank god i was testing it at the time and watching it) those things arn't always the most reliable of power sources and i wouldn't be surprised if its putting out some nasty interference somehow. Try the direct wired outlet, if that doesn't work get a quality adapter from targus or even dell and you'll probably be set.

    HTH
    Matt
    Hardware: [-------- ]30%
    Software: [----- ]20%
    Install:[------- ]70%
    2005 Subaru WRX - New 1.83 GHz Mac Mini - OSX/parallels is my front end - K301 InDash monitor

  6. #6
    Low Bitrate
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    Jul 2007
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    If you are still having this problem, try plugging something that draws less amps into the DC converter. Maybe a cell phone charger or something. If it doesn't create the problem, the current draw may be overloading the board. If the problem does reoccur, the converter may be causing some RFI. Understand though, RFI, while possible, is unlikely. Scan through your radio stations to see if you are getting any interference there. This may be able to confirm your suspicions. Other than that, I'll have to think more. I'm actually at work trying to figure out my own RFI issues...you wouldn't happen to be driving anywhere near BWI airport in Baltimore would you?

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