Decade counter/555 for use as a push button ignition switch

Discussion in 'The Projects Forum' started by MATTY B, Jan 26, 2008.

  1. MATTY B

    Thread Starter Active Member

    Jan 26, 2008
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    Hi Im attempting to build a push button start system for my car and I plan on using a decade counter and a single button to trigger the counter and I need help with how I should design it to take into account a few details of this type of circuit that a normal 4017 decade counter wont do on its own. The way it needs to work is as follows:

    1. Press Button once and release, circuit goes from OFF to ACC which is first position.

    2. Press Button and release again, circuit keeps ACC on and turns on IGN which is second position

    3. Press Button and HOLD for start, IGN (position 2) must stay on and the start fuction should only function while the button is held on.

    4. After Button is released from start position, ACC and IGN both are active.

    5. Press Button and release and circuit resets to off position.

    I figured using a circuit similar to the LED sequencer with the 555 timer to debounce the switch would work as the basis of the circuit. Tying the different outputs together and isolating them with diodes would help seperate the funtions of the different positions of the counter and would solve the issue of the counter not being able to count up and retain certain positions together (such as IGN and ACC staying on together after pressing the button twice"i hope this isnt confusing") As far as triggering relays I figured I could use a set of transitors to trigger relays for each individual circuit. My main concern though is how to momentarily trigger the START circuit and then go to the next position after it is released since I do not want the STARTER to have to be pressed on and then have to be pressed off again. Im hoping this problem is easily solved with an additional circuit or posibbley just an extra component.
     
  2. Søren

    Senior Member

    Sep 2, 2006
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    Hi,

    What's wrong with the loads of answers you got on the other board?
     
  3. MATTY B

    Thread Starter Active Member

    Jan 26, 2008
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    huh? Im not sure I follow you. I came across this board today searching google for help on my car. Until now Ive been using a circuit based off of a latching relay, problem is that the starter funtions when you press the button to the on position. You may have me mistaken for somebody else but if there are answers to my questions on another board send me that way. Until reading about decade counters Ive never even heard of one till today but they make sense and I looked at the circuits on this site at the led sequencer and it looked really close to what I needed to do.
     
  4. weegee

    New Member

    Jan 22, 2007
    4
    0
    you could learn to program a small pic, im using the pic12f629 to do what you describe here, with the button debounced in software makes it a very small, neat circuit, by watching the tach signal you can have it so you just press the the 'start' button and it turns on the starter motor until the revs rise (up to a max of 15 seconds, before giving up), then push again to switch off.
     
  5. MATTY B

    Thread Starter Active Member

    Jan 26, 2008
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    Id prefer to build something without delving into software. I think im really close using this setup, I just gotta figure out how to make one of the outputs momentary, is there possibly a capacitor setup that could be triggered off of that output so as soon as it is turned on and the switch is let go it pulses again and will go to the next position? if something lke that would work then id have it whiped. Hope someone can chime in on this.
     
  6. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Why not just a toggle switch for the ignition, and put the starter button under the accelerator like the 1950 Buick?

    How were you planning to unlock the steering wheel? If ya gotta use the key to work the lock, why not just twist it and start like the rest of us? No key and no lock sez "Steal me!".
     
  7. Søren

    Senior Member

    Sep 2, 2006
    472
    28
    Hi,

    Might be for some track speeder.

    Anyway, This should fit the bill, with a few (optional) extras thrown in for good measure.
     
  8. MATTY B

    Thread Starter Active Member

    Jan 26, 2008
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    thanks a ton for that schematic!! The car is a 1964 Chevelle without a locking column. FYI the push button starts have become very popular since alot of new cars have gone to passive RFID keys that sense when you are near the car and the ignition switch is replaced with a single button. Problem is nobody makes an aftermarket device that does this so alot of people are having to make their own and due to component integration on new cars its not very easy to use the existing parts from a new car and put them in an older car since I did heavily research. What I do plan on using for security is the key system from a new corvette since the parts that are necessary for passive keyless entry cost about 200 dollars for the module, antennas and fob. That unit is great since it is self contained but it does not have a built in provision to control the ignition switch, that is handled by a body computer and the engine computer $$$$. Soren, could you tell me what site you grabbed that from Id like to read about what features it has. I can tell it has the all the relays for switching aong with leds I assume to indicate switch position and such but I didnt know if there was any additional info in the thread regarding the circuit. If not this should be fine and I do appreciate all the help. Thanks again, Matt.
     
  9. rwhite692

    New Member

    Feb 7, 2008
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    0
    Hi Matty, you are trying to accomplish the same thing as I (69 Camaro!) I will be watching this thread for your progress and will post mine as well, I think Soren's circuit implementation is quite good!
     
  10. Søren

    Senior Member

    Sep 2, 2006
    472
    28
    Hi,

    Sorry for the late answer, I seldomly remember to get email notification ticked off and a bit too exhausted when I get home these days.

    I didn't grab it anywhere :eek: I read your wanted specs. added a bit for the heck of it and made it (business as usual ;))

    If you have questions about it, or want changes, just give me a yell.
    (If you want the quickest possible reply, then drop me a mail at Spambox(at)im26y(dot)com)

    And that goes for rwhite692 or anybody else with such interests as well of course.
     
  11. Søren

    Senior Member

    Sep 2, 2006
    472
    28
    Darned, now I forgot the subscription once more :(
     
  12. MATTY B

    Thread Starter Active Member

    Jan 26, 2008
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    0
    ok so I built that circuit and it didnt work correctly :( I do have a few questions before I try something different. First according to the schematic the schmitt trigger and the decade counter dont have ground and power hooked to either well Vss and Vdd. I dont know if those should be hooked up or not. Also this is more or less an assembly thing but is there a simpler way than the schmitt trigger to debounce the switch or is it functioning in a way that its a necessary part? At this point when I press the button it only triggers the starter and nothing else. Better description is I press the button and the starter lights up as long as im holding the button on. Thats it so at this point it doesnt work at all. Im wondering if anything was left out but its a good chance that I may have screwed up too. Hopefully someone can help me out with this cause at this point I have absoultely no other avenues to making this work.
     
  13. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    Don't know when he's going to be back, but this should get you going.

    1) Yes, both the 4093 and the 4017 must have power (Vdd) and ground (Vss) connected to their respective pins. Additionally, there should be a 0.1uF (100nF) capacitor (ceramic or tantalum) connected between each of those IC's power and ground pins to bypass power spikes.
    4017: Vdd/power is on pin 16, Vss/ground is on pin 8.
    4093: Vdd/power is on pin 14, Vss/ground is on pin 7.
    Power and ground connections (with bypass caps) are often not shown on schematics, as they are implied; they tend to simply add clutter.

    2) The 4093 Nand Schmitt triggers as shown are connected in a standard fashion which eliminates switch contact bounce. Without this, the 4017 would be clocked a random number of times (perhaps dozens of clocks) for each single button press and release.
     
  14. MATTY B

    Thread Starter Active Member

    Jan 26, 2008
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    you know what the more I look at this the more I think its not setup right (the schematic) biggest issue is that Q4 resets instead of going back to IGN and ACC. Secondly I dont think that there is any way to make Q3 momentary. What I need is for Q1 to be ACC, Q2 to be ACC and IGN, Q3 to be IGN and START but has to be MOMENTARY and when release go to Q4 IGN AND ACC then Q5 resets. Is there a way to make Q3 momentary and when the button is released do something to step the 4017? If you think of this circuit as a regular ignition switch it makes it a ton easier to understand the functioning required. You go from off to ACC to ACC and IGN then START is momentary where when you let go of the key it steps back to IGN and ACC. Also is it possible to just use a 555 as a monostable vibrator? It would require half the amount of traces as the 4093. I dunno this is complicated for me, maybe someone could help me with a PIC based setup if that would work better
     
  15. Søren

    Senior Member

    Sep 2, 2006
    472
    28
    Hi,

    You specified:
    And that's what it does - please don't blame me for you changing your mind ;)

    It works as you specified!
    If you changed your mind, post new specs and I'll make you another circuit.

    If you need a PCB layout - tell me.

    Don't blame me for not having paranormal abilities :D
     
  16. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Matty,
    Transistor Q1 is ACC. When IC2 is reset (or first powered on), transistor Q1 is off.
    There are diodes attached to IC2's Q1, Q2, and Q3 outputs, which keeps transistor Q1 biased ON for button presses 1, 2, and 3. The 4th time the button is pressed, IC2 is reset, and transistor Q1/ACC turns OFF.

    Transistor Q2 is IGN. When IC2 is reset (or first powered on), transistor Q2 is off. There are diodes attached to IC2's Q2, and Q3 outputs, which keeps transistor Q2 biased ON for button presses 2 and 3.

    Transistor Q3 is Starter. IC1D's output will be high unless both inputs are high, then it will be near 0v. IC1C's output inverts IC1D's output, which makes the combination of the two NAND gates an AND gate. IC1D pin 12 will only be high when the button has been pressed the 3rd time. IC1D pin 13 will only be high when the button is DOWN; when pushed down for the 3rd time both inputs to IC1D are high, causing the output of IC1C to go high, causing transistor Q3 to turn ON; as soon as the button is fully released IC1D pin 13 will go low, causing IC1D pin 11 to go high, causing IC1C 's output to go low, causing transistor Q3 to turn OFF.

    It really will do what you need for it to do, if you wired it up as shown in the schematic (plus the power/Vdd, ground/Vss connections and bypass capacitors, of course)
     
  17. MATTY B

    Thread Starter Active Member

    Jan 26, 2008
    45
    0
    ok maybe Im just looking at it wrong, sorry soren, I will do the hook ups for the 4093 and 4017 for Vdd and Vss. Its probable that since they arent there nothing is working correctly. Also Im not expierenced with the schmitt triggers so Im probably confusing my self and its designed exactly as I asked and I just cant tell. I will do those hookups and keep you informed.
     
  18. Søren

    Senior Member

    Sep 2, 2006
    472
    28
    Hi,


    Here is an updated PDF with:
    • The old schematic.
    • A new schematic less the relays (since they should probably be mounted away from the PCB) and with a reset cap added.
    • PCB overlay.
    • PCB layout in 1:1
    • A timing diagram to make the logic clearer to you.
    This should get you a working circuit going.
     
  19. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    On further thought, there is one small change that would help starting go more smoothly; that is to turn the ACC circuit OFF while the starter is engaged, and back on when the starter was released. This would make maximum battery power available for turning the engine over, and would mimic the operation of a typical ignition switch.

    This could be as simple as installing an NPN transistor between D3 and IC2 Q3; collector on IC2 Q3, emitter on D3, base connected via a 10K resistor to IC1D pin 11.

    I marked up just the affected portion of the circuit to illustrate the changes - if you'd want to do this; original on the left, mod on the right.
     
  20. MATTY B

    Thread Starter Active Member

    Jan 26, 2008
    45
    0
    soren you are THE MAN, do you have a paypal account I will pay you for that. That is so helpful and way beyond what "Id expect from someone online. Sgt. Wookie- that is a very good idea and I think I can implement that quite easily and thats how a normal switch works anyways although its not completely necessary to have it seperated during starting if you have the heater and stuff like that it can affect starting. Ill print out two of the pcbs and put a transitstor on one and the normal setup on the other. But I have to say that this is the most help I have ever gotten online and Im trully grateful
     
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