Results 1 to 5 of 5

Thread: RC Filter for Fuel Gauge

  1. #1
    Newbie
    Join Date
    Apr 2009
    Posts
    13

    RC Filter for Fuel Gauge

    i've shelved my idea of an incar PC and touchscreen for now, it was looking to be too expensive. So i'm sticking with my current set up - but, what i would like to do is fit a different fuel gauge to the one i'm using.

    I bought a 52mm TIM gauge and sender unit (when i fit all my existing gauges in the car), but the sender unit doesnt fit the classic mini tank, and the original sender pulses so the TIM gauge gives a bouncy needle. I've check the resistance on both the TIM sender and original sender unit, and they're pretty much the same 20 - 260 Ohms. I did discuss this issue on a different post when i was wanting to set it up with a PC, i was told i'd need an RC filter to smooth it out. can anyone help me with the components and layout i'd need?

    thanks

    Jon.

    ---------- Post added at 08:42 PM ---------- Previous post was at 07:19 PM ----------

    you can ignore this, i've solved it.

  2. #2
    Raw Wave
    Join Date
    Nov 2009
    Posts
    2,118
    Although solved, a common solution is to replace the gauges bi-metal voltage-regulator with a "smooth" one (or non-digital as some jokingly say...).
    Such gauges are typically ~8V so an 8V regulator (7808 etc), or a 317 adjustable set for 8V or 8.5V whatever...
    Though an RC filter is also possible - but usually R has to be smallish hence C must be BIGgish. Or a filtered-input voltage follower/buffer....

  3. #3
    Newbie
    Join Date
    Apr 2009
    Posts
    13
    i just wired it up to a spare battery, with a spare fuel sender and it worked fine!? not entirely sure why it initially pulsed when i'd tried it a while back. i guess the original "wire in" for the old gauge isn't the same as the ignition +ve and could be source of the pulse, and just looking at a wiring diagram, would come from the voltage regulator. I'm guessing the TIM gauges (i have also water temp, oil pressure, RPM and the instructions are to use the ignition +ve) most likely have some sort of regulator built in?

  4. #4
    Raw Wave
    Join Date
    Nov 2009
    Posts
    2,118
    Oh yes.... D'oh!

    I referred to traditional OEM gauges without even considering that aftermarket would be raw 12V!

    For OEM gauges/vehicles, fuel & temperature are usually voltage regulated whereas oil pressure is not (it is 12V).
    The regulators are traditionally bi-metal things - like old flasher cans - that pulse +12V for an average of 8V. (Yes - it is PWM.)
    One beauty of them is that they are not polarity sensitive - connect the car battery the wrong way and they still work fine.

  5. #5
    Newbie
    Join Date
    Apr 2009
    Posts
    13
    ah, thanks for clearing that up. yeah, i've fitted it in the car now and it's working fine.

Similar Threads

  1. Air Fuel Gauge gives loud whine / feedback
    By dhantiflag in forum General Hardware Discussion
    Replies: 1
    Last Post: 05-27-2010, 07:53 AM
  2. Reading Gas and Fuel Gauge
    By mdawg in forum Engine Management, OBD-II, Engine Diagnostics, etc.
    Replies: 2
    Last Post: 09-11-2008, 11:45 AM
  3. Replies: 7
    Last Post: 02-18-2007, 03:54 PM
  4. How to calibrate Fuel Gauge?
    By PatO in forum Off Topic
    Replies: 3
    Last Post: 01-17-2005, 05:38 AM
  5. Air Filter and Fuel saver
    By Scorpnstail in forum Off Topic
    Replies: 14
    Last Post: 04-14-2004, 10:08 AM

Bookmarks

Posting Permissions

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