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Need some help understanding a schematic

Discussion in 'Automotive Electronics' started by Tom Stark, Mar 4, 2017.

  1. Tom Stark

    Tom Stark New Member

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    High all. I posted a while ago I needed help coming up with a sequencer for my tail lights. Everyone was very helpful and I got a schematic from one of the kind folks here. Well I ordered some parts, and I have some questions. The schematic calls for CD4027B flip flop switches but on Digikey I was only able to find CD4027BE flip flops. On the schematic they look like (to me at least! LOL!) 7 pin chips. When I got them they are 16 pin chips. So I did some searching on the net to get more info, and found a pinout for them. So if I am correct J is pin 10, CLK is 13, K is 11, Q is 15, Q (with the line over it, sorry can't do that on computer!) is 14, But I did not find PRE or CLR, but I did find SET pin 9 (perhaps is PRE?) and RESET pin 12 (perhaps CLR?).
    The timer I got is an NE555P not just NE555, but sure that is the same.
    I am wondering am I correct with the pins on the flip flops? Also what do I do with the unused pins, just leave them alone? Would I be wise to put sockets on my board rather than solder the chips? I see "K" is shown to "B3" B3 would be my 3rd tail light bulb, is K connected to the bulb like Q on the last flip flop? The "PRE" on the flip flops, are those connected to ground? I assume the vcc on the 555 chip gets my +12v supply. And what is that round circle (as opposed to square circles I guess!) on the lower left hand corner? Is that simply what ever switch I use to turn these on? and lastly if you have any advice for someone like me I would appreciate it. I have built electronics before, like the Megasquirt that runs the fuel injection and ignition on my Corvair but that was pretty easy as it came with a PCB and was all pretty straight forward. I have talent and ability, just lacking in the education to do this all on my own. so any help is appreciated!
    TIA
    Tom Stark sequencer.png
     
  2. alec_t

    alec_t Well-Known Member Most Helpful Member

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    A CD4027BE (CD4027B-anything) is the right part. You have the pinout correct (including the Set and Reset). Pin 8 is ground (Vss) and pin 16 is the positive supply pin (Vdd). Since you are using only half the IC, connect pins 3,4,6 and 7 to ground. Leave pins 1 and 2 floating.
    This is a CMOS part, so anti-static precautions should be taken.
     
  3. Tom Stark

    Tom Stark New Member

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    Thank you very much! Do you have any idea what that is in the lower left of the schematic? I am thinking it is just what ever I use to switch power on or off, and do the "PRE" go to ground?
    Thanks again!
    Tom
     
  4. dave

    Dave New Member

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  5. alec_t

    alec_t Well-Known Member Most Helpful Member

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    V-turn is a simulated pulsed voltage source, used for resetting the '555 IC. Normally, C2 would be connected instead via a resistor (say 10k, not critical) to Vdd to provide power-on reset.
    Yes, the PRE pins go to ground.
     

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