Surely this should be easy...!

Discussion in 'The Projects Forum' started by Thorfinn, May 23, 2012.

Thread Status:
Not open for further replies.
  1. Thorfinn

    Thread Starter New Member

    May 23, 2012
    3
    0
    All I need is a circuit that, when 12V is applied, passes 12V at about 0.25A to a miniature bulb, then after about 5 seconds, cuts power to the load and only resets at the next power down/power up cycle.

    It is an automotive requirement; I need a dash bulb to light when the vehicle is started, then extinguish after about five seconds.

    Obviously a 555 timer springs to mind but the circuits I have seen so far assume a mechanical reset button.

    Am I missing the obvious?

    Regards,

    Simon
     
  2. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,769
    969
    quick... remove your second sentence including the part after the semicolon.
     
  3. mcasale

    Member

    Jul 18, 2011
    210
    12
    Nothing is EVER easy .... and don't call me Shirley.

    Automotive stuff is not permitted in this forum.

    Run away ...... run away ......
     
  4. MrChips

    Moderator

    Oct 2, 2009
    12,414
    3,353
    Use a 555 timer and a HEXFET. It can be done despite what you have seen so far.
     
  5. wayneh

    Expert

    Sep 9, 2010
    12,086
    3,024
    I'd consider adding an RC on the gate of fet to give a soft fade out once the timer has turned it off. Much cooler than just going dark.
     
  6. Thorfinn

    Thread Starter New Member

    May 23, 2012
    3
    0
    OOOPS...I prob'ly should have read the posting requirements and rules more carefully - assumed they would be standard boilerpate.

    Apologies all. I admit that although I can swing a mean soldering iron, the niceties of circuit design are not my strength...

    Regards

    Simon
     
  7. MrChips

    Moderator

    Oct 2, 2009
    12,414
    3,353
    Soft fade...ooh, we're getting fancy.
    Ok then, use an 8-pin MCU and PWM the output to the HEXFET.
    No external RC required.

    If you're willing we can make this an AAC community project and someone can send you the code or even a programmed MCU. That's all you need, an MCU and a MOSFET.

    In fact we know someone here who would even make a PCB for you.
     
  8. Thorfinn

    Thread Starter New Member

    May 23, 2012
    3
    0
    I'm perfectly willing to lend my personal problem to the world (well, the AAC community) if it's of interest! Be my guest, everyone!

    Meantime, many thanks for all suggestions so far. I LOVE the "soft-fade" suggestion....:D

    Simon
     
  9. bertus

    Administrator

    Apr 5, 2008
    15,638
    2,343
    Hello,

    I am closing this thread as it violates AAC policy and/or safety issues.

    Quote:
    6. Restricted topics. The following topics are regularly raised however are considered “off-topic” at all times and will results in Your thread being closed without question:

    • Any kind of over-unity devices and systems
    • Automotive modifications
    • Devices designed to electrocute or shock another person
    • LEDs to mains
    • Phone jammers
    • Rail guns and high-energy projectile devices
    • Transformer-less power supplies
    This comes from our Tos:
    Terms of Service
    There will be enough sites where automotive questions can be discussed :
    Member selected automotive forums

    Bertus
     
Loading...
Thread Status:
Not open for further replies.