Controlling switch led's from two sources using transistors

Discussion in 'Automotive Electronics' started by deeknhays, Mar 27, 2016.

  1. deeknhays

    Thread Starter New Member

    Mar 26, 2016
    4
    0
    I'm designing a circuit for some indicating led's in a switch I plan on installing in my vehicle. My goal is to have one led come on with the dimmer circuit no matter the switch position. The other led comes on when the switch is turned on but also has to be dim-able. I found a DPDT relay board that suits my purpose but I don't want the mechanical sound in my vehicle as I'll be using this for 10 different switches. The first attachment is of the DPDT relay cicuit and the second one is of a MOSFET circuit I tried to design to accomplish the same thing. I'm not concerned about resistance values as of yet, just trying to get the circuit put together and then solve my values after.
    What should happen: When S1 is turned on Led1 is closed and dim-able. Led2 should not come on with only S1 closed. With S1 open and S2 closed, Led2 should come on. When S2 is closed and S1 is closed Led1 and Led2 should be on and on dim-able circuits.
    ME1 and ME2 are enhancement MOSFETs and MD1 is a depletion MOSFET.
    Is my transistor circuit even possible, or am I way off base here?
    Any help with this would be greatly appreciated. In the transistor circuit I'm using both enhancement and depletion MOSFETs, is there a way to only use enhancement MOSFETs? Or do I need to use both?
    DPDT RELAY DIAGRAM.png TRANSISTOR DIAGRAM.png
     
    Last edited: Mar 27, 2016
  2. eetech00

    Active Member

    Jun 8, 2013
    648
    110
    Hi

    What type of LEDs? Part number?
    What type of dimmer? Part Number?
    What type of relay? Part Number?

    Is this circuit supposed to just light LEDs? or does it also control something else?
     
  3. deeknhays

    Thread Starter New Member

    Mar 26, 2016
    4
    0
    Led1 will be a green 5mm pn 276-0304
    Led2 will be a blue 5mm pn 276-0311

    S1 and dimmer are integrated into my vehicle as they control the other interior lights. I'll be tapping into my dimmer circuit.

    The relay in the diagram will either be the RY5W-K or the RX12W-K

    S2 will also be driving a SPDT relay to turn on auxiliary lighting
     
  4. deeknhays

    Thread Starter New Member

    Mar 26, 2016
    4
    0
    For the purpose of a test circuit I'll be using pn 271-0215 as a dimmer
     
  5. deeknhays

    Thread Starter New Member

    Mar 26, 2016
    4
    0
    So after further review of my circuit I realized MOSFET ME2 isn't needed in the circuit. Attached is my revised transistor circuit. I was also wondering do I need to install a diode between ME1 and the junction where it meets with MD1 and a diode in between MD1 and the same junction?
    TRANSISTOR DIAGRAM.png
     
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