Change a selector switch to a push button switch... Is it possible?

Discussion in 'Automotive Electronics' started by Velyboy618, Aug 20, 2015.

  1. Velyboy618

    Thread Starter New Member

    Aug 20, 2015
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    I'm in the process of adding a under dash A/C unit into my car and I want to change the fan speed selector switch that came with the unit to a push button type switch unit by using these momentary push buttons and some relays. I want the push button switch that I'm trying to make to have 4 buttons total. 1 button for "off" and 3 other buttons for the "low, med & high" fan speeds & I would also like for each button to cancel the other one out when another one is pressed kind of like one of the A/V selector switches. I don't like the look of the switch that came with the unit & was thinking about mounting it inside the glove box out of sight but If you guys can help me out with something to use these buttons I am going to flush mount them somewhere on the dash where they are easily accessible. Thanks in advance!

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  2. Velyboy618

    Thread Starter New Member

    Aug 20, 2015
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  3. ScottWang

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    Aug 23, 2012
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  4. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    To do this with fewest parts requires you to learn how to apply a micro-controller to this project. The method with the quickest learning curve is to use an Arduino or PIC-Basic
     
  5. ScottWang

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    Aug 23, 2012
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    I bet you give him a heavy mission, I just thought that maybe I can suggest him to using CD4017 and some relays, but maybe it will more complicated.
     
  6. crutschow

    Expert

    Mar 14, 2008
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    You are looking for a Radio push button circuit.

    You can make one with a CD4078 NOR gate, a CD4042 4-bit latch, 8 resistors, 4 capacitors, and 4 transistors to drive the relays. If you are interested in such a circuit I can post the diagram.
     
  7. takao21203

    Distinguished Member

    Apr 28, 2012
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    A 16f54, some cheap mosfets and resistors, one coil for clocking.

    Or use a 4 relay board instead of the mosfets

    Cd 4017 isn't a bad idea just you have to cycle through all devices.

    The 16f54 costs less than a dollar, 20 pins ic. It doesn't need parts beside clocking, reset and the usual buffer capacitors. I'd use a switcher for the car to prevent the setting going off.
     
  8. ian field

    Distinguished Member

    Oct 27, 2012
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    Doesn't look heavy enough for automotive - some old washing machines had ganged latching push button selectors that would be more like it.
     
  9. ScottWang

    Moderator

    Aug 23, 2012
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    Yes, I'm afraid of the current maybe not enough, I saw the fan have the switches could be used, but I can't remember the name, they look similar as used in washing machine.

    There is one kind of push switches for fan - fan keyboard push button switch.
     
  10. ian field

    Distinguished Member

    Oct 27, 2012
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    Another possibility is a cheap halogen heater. They have various switchgear depending on make/model but I have seen one with a ganged latching push button bar.
     
  11. ian field

    Distinguished Member

    Oct 27, 2012
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    I'm still having problems with More options/email notifications.

    Its always greyed out and no matter how many times I tick the check box for watch thread, its cleared next time I post/edit.
     
  12. ScottWang

    Moderator

    Aug 23, 2012
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    I already asked Rob via PM, you just waiting for his reply, maybe you can describe some more details if needed.
     
  13. ian field

    Distinguished Member

    Oct 27, 2012
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    Thanks - the 2 check boxes can now be independently ticked, which looks like it should be working now.

    Too early to say whether any notifications will be forthcoming.
     
  14. crutschow

    Expert

    Mar 14, 2008
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    Here's a circuit I generated to perform the Radio Push Button function using only two ICs, which should do what you want.
     
    Last edited: Aug 31, 2015
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  15. absf

    Senior Member

    Dec 29, 2010
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    Can the 4514 be replaced with something smaller like 4028, 4555 or 4556?

    Allen
     
  16. crutschow

    Expert

    Mar 14, 2008
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    No. Those don't have a latch function, which is needed for this design.
    But if you can find a smaller binary or BCD coded latch, that should work.
     
    Last edited: Aug 26, 2015
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  17. absf

    Senior Member

    Dec 29, 2010
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    The only smaller decoder with latch I can find is the 74HC137, but then the Vcc has to be dropped to 5V which is not so good for automotive application.

    Allen
     
  18. crutschow

    Expert

    Mar 14, 2008
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    It just means you would have to add a 5V regulator to the circuit, such as a 7805.
    But then you start to lose the area savings that the 74HC137 gives. ;)

    Edit: Also the latch signal has inverted polarity on the 74HC137 so, in addition, you would have to add an inverter to the circuit.
     
    Last edited: Aug 27, 2015
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