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Thread: easiest way to build this circuit?

  1. #1
    MySQL Error scott_fx's Avatar
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    easiest way to build this circuit?

    Im trying to use a single momentary button to cycle these two functions.

    first press = momentary pulse 12v to contact A
    second press = momentary pulse or latch 12v to contact B (if latching, it would have to reset/unlatch upon the next button press)
    (rinse and repeat)



    bonus points if there could be a delay on each button press. i.e. you have to hold the button for 2 seconds in order to reduce unintentional presses.


    could this be done with relays and a simple resister capacitor circuit?
    Last edited by scott_fx; 03-28-2011 at 06:28 PM.
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  2. #2
    MySQL Error soundman98's Avatar
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    this is about as close as i can find-- requires 2 momentary switches:


    (taken from here)
    555/556 Bistable (flip-flop) - a memory circuit
    The circuit is called a bistable because it is stable in two states: output high and output low. It is also known as a 'flip-flop'.

    It has two inputs:

    * Trigger (555 pin 2) makes the output high.
    Trigger is 'active low', it functions when < 1/3 Vs.
    * Reset (555 pin 4) makes the output low.
    Reset is 'active low', it resets when < 0.7V.

    The power-on reset, power-on trigger and edge-triggering circuits can all be used as described above for the monostable.






    then there is this thread:
    http://forum.allaboutcircuits.com/sh...ad.php?t=33897


    actually, the link in ^that thread seems to be exactly what your looking for:
    http://www.discovercircuits.com/DJ-C...-off-latch.htm

  3. #3
    MySQL Error scott_fx's Avatar
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    Quote Originally Posted by soundman98 View Post
    this is about as close as i can find-- requires 2 momentary switches:


    (taken from here)
    555/556 Bistable (flip-flop) - a memory circuit
    The circuit is called a bistable because it is stable in two states: output high and output low. It is also known as a 'flip-flop'.

    It has two inputs:

    * Trigger (555 pin 2) makes the output high.
    Trigger is 'active low', it functions when < 1/3 Vs.
    * Reset (555 pin 4) makes the output low.
    Reset is 'active low', it resets when < 0.7V.

    The power-on reset, power-on trigger and edge-triggering circuits can all be used as described above for the monostable.






    then there is this thread:
    http://forum.allaboutcircuits.com/sh...ad.php?t=33897


    actually, the link in ^that thread seems to be exactly what your looking for:
    http://www.discovercircuits.com/DJ-C...-off-latch.htm

    thanks for the links but i only need to pulse the contacts. maybe explaining my application will help.

    im building a pushbutton start for my boat using a dei remote start module. it needs a 12v pulse on one lead in order to start the engine then to shut off the engine it looks for another 12v pulse (from your brake light) on another lead.

    im trying to accomplish this with a single momentary button.

    actually.... i could use a latching button and a spdt relay. but... that wont 'pulse' the 'engine start' lead.

    ---------- Post added at 06:27 PM ---------- Previous post was at 06:01 PM ----------

    i found this:
    use a latching relay with two common SPDT relays

    When the coil of the latching relay it is momentarily energized, one contact and the common are closed and stay closed even after the coil is no longer energized. When it is momentarily energized again, the other contact and the common are closed.

    For each actuator, connect one motor lead of the actuator to #30 of an SPDT relay and #87a to ground. Connect the other motor lead of the actuator to a second SPDT relay and wire as above. On the first relay connect #86 to one of the contacts (non common) of the latching relay and connect #86 of the second SPDT relay to the other contact (non common) of the latching relay. Connect #87 and #85 of both SPDT relays and one side of the coil of the latching relay to 12V+. Connect the (-) output of one momentary switch to the cathode sides of two diodes. Connect the anode side of one diode to the other side of the coil of the latching relay and connect the anode side of the second diode to the common contact of the latching relay.

    When you press the momentary contact switch, the motor should move in one direction for as long as you hold it and stop when you release it. When you press and hold it again, it should move in the opposite direction.
    from here:
    http://www.the12volt.com/installbay/...=19&TPN=1&PN=1

    now to figure out how to get that 'long press' function
    Last edited by scott_fx; 03-28-2011 at 09:09 PM.
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  4. #4
    Maximum Bitrate kegobeer's Avatar
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    Would something like this work?

    http://www.digitalguarddawg.com/2GOKEYLESS2.html

    It is advertised for boat use. Or, is this not compatible with your remote start module?
    Last edited by kegobeer; 03-28-2011 at 11:03 PM.

  5. #5
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    From the12volt's momentary pb to constant on.

    Since you'd have 4 inverters (or 2 other gates) spare, you could add an RC delay...

  6. #6
    MySQL Error scott_fx's Avatar
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    Quote Originally Posted by kegobeer View Post
    Would something like this work?

    http://www.digitalguarddawg.com/2GOKEYLESS2.html

    It is advertised for boat use. Or, is this not compatible with your remote start module?
    thanks, but that is more then what i need and more then i want to spend. I rarely leave my boat unattended and i'll be adding a simple hidden kill switch so rfid isn't necessary for me. I'm confident i can achieve the same results using a remote starter module and a simple pushbutton circuit


    Quote Originally Posted by OldSpark View Post

    From the12volt's momentary pb to constant on.

    Since you'd have 4 inverters (or 2 other gates) spare, you could add an RC delay...
    thank you oldspark. one thing that confuses me (still learning about building circuits) is how will this toggle between two outputs. the schematic only shows one output.

    i looked up the pdf and it didnt help me much.
    http://www.produktinfo.conrad.com/da...-en-74HC04.pdf

    and for future searches. here is a tutorial with examples for a rc start up delay circuit:
    http://www.electronics-tutorials.ws/rc/rc_1.html
    could be used for a amp delay
    Last edited by scott_fx; 03-29-2011 at 02:27 PM.
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  7. #7
    Raw Wave
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    Quote Originally Posted by scott_fx View Post
    one thing that confuses me is how will this toggle between two outputs.
    Use it to switch a relay that toggles between the two outputs....

    The circuit merely toggles for each press of the button, ie, flips between hi & low (like a T-type flip-flop).
    Either hi or low can be used to controls a relay - eg, low turns on a hot (+12V) relay by grounding it; hi supplies voltage (+12V) to a relay, or you use a single SPDT (changeover) relay etc.

    Just be wary of what current the relay requires compared to what the gate (inverter) can supply (sink or source).
    That depends on what package is selected, and - of course - what relay....



    PS... Good RC reference - a great combination of text, formulae & pics - it makes it sound less daunting (even if the significance of a differentiator isn't understood - you see how a cap (RC) can edge-detect; and there's the old time & frequency domain again....)

    And I can help with driver current - ie, what is needed to drive what relay.
    I might even review your desire to figure a circuit... time permitting, and memory remembering!
    Last edited by OldSpark; 03-29-2011 at 03:59 PM. Reason: PS...

  8. #8
    MySQL Error scott_fx's Avatar
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    Quote Originally Posted by OldSpark View Post
    Use it to switch a relay that toggles between the two outputs....

    The circuit merely toggles for each press of the button, ie, flips between hi & low (like a T-type flip-flop).
    Either hi or low can be used to controls a relay - eg, low turns on a hot (+12V) relay by grounding it; hi supplies voltage (+12V) to a relay, or you use a single SPDT (changeover) relay etc.

    Just be wary of what current the relay requires compared to what the gate (inverter) can supply (sink or source).
    That depends on what package is selected, and - of course - what relay....



    PS... Good RC reference - a great combination of text, formulae & pics - it makes it sound less daunting (even if the significance of a differentiator isn't understood - you see how a cap (RC) can edge-detect; and there's the old time & frequency domain again....)

    And I can help with driver current - ie, what is needed to drive what relay.
    I might even review your desire to figure a circuit... time permitting, and memory remembering!
    oh great. that is a lot of help. my one concern though, if im using a spdt relay, i need just a single pulse for the 'engine start' lead. would you suggest just using a monostable 555 timer circuit between the spdt relay and the 'engine start' lead? or did i misunderstand your explanation?
    Last edited by scott_fx; 03-29-2011 at 04:29 PM.
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    My Car Pc Install
    My Boat Pc worklog

  9. #9
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    Aha! Now that I read your OP a bit better....

    Yes - you are correct, though maybe spare gates instead of a 555.

    (Don't get me wrong - I love the 555 - but in retrospect I realise it was overused when simpler or alternatives were possible. Plus the 555 has a relatively high current drain - it's only 10mA, but that is significant in solar etc applications, and can drain car batteries in a few weeks; 10mA being equivalent to a LED, or ~1/20th of a 3W bulb - why have that if 0.1 or 0.01mA is possible?).

    Alas the problems of using ONE switch for multiple things... did I mention PICs? (Nah - far from needing that as yet... speaking of current consumption...)


    But only recently did some clever person put me on to a good site, and from MOSFET as a Switch I saw its reference to an experiment Using a MOSFET as a Switch which has a delayed off circuit down the page...
    ...from brunningsoftware.co.uk

    Not that that is the full solution (because we need the "toggle" to be a pulse), but in combination with a capacitor differentiator...
    (Don't you hate people that give me the big words to use?)


    But more later.... I'm late for elsewhere (my other reality).

  10. #10
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    It would make things easier if you could add a second button to shut down the Engine. When you use the same button it becomes complicated real quick.
    A a switch a resistor and capacitor in parallel and a relay is all you need for each circuit.

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