Delorean project

Discussion in 'Automotive Electronics' started by Rissy, Nov 23, 2015.

  1. Rissy

    Thread Starter Member

    Nov 23, 2015
    84
    2
    Hey there, I'm working on designing a circuit which I wish to incorporate into my DeLorean.

    I only need help with one aspect of this circuit. The conversion of a pulsed ON-OFF-ON-OFF (12V) signal into a constant ON signal (12V) whilst the ON-OFF-ON-OFF (12V) is continuing to happen, and then a constant OFF.

    I found this solution on the web:

    http://www.the12volt.com/relays/relaydiagram22.html

    BUT, you can see that it requires a lot of capacitance there to hold on the 12V during the OFF part of the cycle. I was wondering if I could do the same thing with either a transistor or a SPST on IC in place of the automotive relay and therefore hopefully reduce the necessity for such a huge amount of capacitance. Can anyone give me a design, or help me put together one?

    I was thinking something along the lines of this:

    [​IMG]
     
  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
    1,066
    Your circuit has a serious flaw; the output is grounded:(

    Even if the emitter of the NPN is ungrounded, it will not do what you need.

    I'll post something in a few min...
     
  3. Rissy

    Thread Starter Member

    Nov 23, 2015
    84
    2
    Thank you. I can't wait to see what you come up with. I've been advised by a friend that I could probably use a 555 timer IC to do what I want to do, but he's not willing or able to give me more information than that. I'm currently hunting for an appropriate 555 timer project on the web which will fulfill my needs lol! (It's easy to find something to do the opposite of what i'm trying to do! It's obviously easier to destroy a constant signal than create one from a broken signal! lol!)
     
  4. atferrari

    AAC Fanatic!

    Jan 6, 2004
    2,645
    759
    An awful short circuit as is.
     
  5. Rissy

    Thread Starter Member

    Nov 23, 2015
    84
    2
    I realise there is a short to earth there. I only put together this drawing very quickly in order to convey my intention better (a picture speaks a thousand words as they say) If i had put the yellow output on the other side of the transistor (emitter side) then the IC which I have on the other end of that yellow wire would simply be permanently live, which is not what i want. But thank you for your input. No one else needs to point out my ground short now. lol.
     
  6. KeepItSimpleStupid

    Well-Known Member

    Mar 4, 2014
    1,138
    200
    So, this pulsed signal is continuous at some rate? Is this rate known? A "missing pulse" detector is usually used.
     
  7. Rissy

    Thread Starter Member

    Nov 23, 2015
    84
    2
    It's an indicator (turn signal) pulse produced by a CF13 JL-02 LED flasher relay.
     
  8. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
    1,066
    I had to guess at the pulse timing, but some variant of this will work. Follow the voltages on the plot and see what node they match in the schematic.

    Note how the PFET is connected, source on top. It will switch several Amps.

    147.gif

    Need better definition of pulse freq and pulse duration, and how long you want it to hang on after the last pulse... That will affect R4 and C1.
     
  9. Rissy

    Thread Starter Member

    Nov 23, 2015
    84
    2
    Okay, So now i need to expose my lack appreciation of this circuit now. lol!

    The triangles. Those are? Down to earth?

    what is that "HAT1072H"?
     
  10. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,773
    1,103
    That will be the flux capacitor then :). Seriously, 1000uF isn't 'huge' by today's standards, and is available in quite compact forms.
     
  11. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
    1,066
    Yes, tie all of those together, and then to the car chassis. (Assuming a neg ground car).

    A modern PMOS field-effect power transistor I call a PFET. Any of these in an easier-to-work-with TO220 package would work in this circuit. Depending on how much load current you are switching, you need to bolt it to metal for heat-sinking using an insulating mounting kit.
     
  12. Rissy

    Thread Starter Member

    Nov 23, 2015
    84
    2
    at "Your Load" will be two 4011 NAND gate IC's, a couple of resistors, an NPN and the final end customer for all the trouble....an LED indicator. BA9S, drawing nothing more than 2-2.5W (if that!) but an incandescent would be about 2-2.5W i think, so if the LED was whipped out and replaced with an incandescent, then i want the circuit to handle this increased load without melting or blowing up.
     
  13. Rissy

    Thread Starter Member

    Nov 23, 2015
    84
    2
    So with such a low power draw, is the power transistor still necessary?
     
  14. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
    1,066
    Here is another version using an automotive sugar-cube 12Vdc relay.

    148.gif
     
  15. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
    1,066
    You never stated what the load is. I was assuming a load of several amps, like a lamp.

    It sure would help us if you put in a country when you register for the web site and put in ALL of your requirements in the first post!
     
  16. Rissy

    Thread Starter Member

    Nov 23, 2015
    84
    2
    Ah yes. You can really see the difference in the power drain there during the OFF part of the cycle. It drops really low. Can you model this, but show the voltage trace out the far output? (Your Load) for BOTH versions?
     
  17. Rissy

    Thread Starter Member

    Nov 23, 2015
    84
    2
    I'm sorry Mike. I've just joined, so have not gotten used to the site yet. I'm in the UK. I like dabbling in Electronics from time to time when i have a project goal, but i'm not an expert by any stretch of the imagination. My lack of detail in my original request is nothing more than innocent ignorance i'm afraid. Please have patience with me. :)
     
  18. JoeJester

    AAC Fanatic!

    Apr 26, 2005
    3,373
    1,157
    Do you want the same output if a bulb burns out and the flash rate changes?

    You basically need a retriggerable monostable.
     
  19. MikeML

    AAC Fanatic!

    Oct 2, 2009
    5,450
    1,066
    Here is a lower output current version:

    147a.gif
     
  20. Rissy

    Thread Starter Member

    Nov 23, 2015
    84
    2
    I can't figure out how to reply to individual people's quotes!?

    JoeJester
    For each side of the car, there will only be one LED/Bulb. So if it goes, then there wont be any others on that part of the circuit to keep flashing/illuminating. So a changing rate should not be a problem.

    MikeML
    This is looking good. I guess i'm gonna have to buy some components and get testing this bad boy! lol! I REALLY appreciate your help with this people, especially Mike who's gone to all that hard work simulating (i'm wondering how i can do that myself, and maybe even simulate my whole designed circuit in one go!?).

    I'll definitely come back and let you all know how i got on with this, and also maybe ask for some more advice on other parts of my design if they don't check out during testing. I'm not sure how long it will take for me to get a test together. I'm gonna have to order components off ebay etc before i'm in a position for testing.
     
Loading...