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Thread: Headlight Controller (PIC-based)

  1. #1
    Variable Bitrate Saab9-5's Avatar
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    Headlight Controller (PIC-based)

    This is a circuit in response to JBraddoc's request from thread Bluetooth as an RFID.

    The PIC will control the lights through relays that are optoisolated from the controller. Inputs from the vehicle are also optoisolated. A serial port is there to allow simple configuration changes (darkness value to turn lights on, delay for option 1, delay for option 2) that will be stored in the PIC's EEPROM. Other than that, it is a standalone circuit.

    I'll start breadboarding the circuit this weekend but wanted to put the schematic out there for people to see and comment on. And I created this thread so we can stop threadjacking the other one.

    NOTE: This circuit may change as I physically build it and run into design flaws.
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  2. #2
    Raw Wave rando's Avatar
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    This looks sweet!

    1) Could you use a PIC with a built-in resonator option to save a few parts?
    2) Will the linear regulator draw an excessive amount of current while the car is off?
    3) Current limiters at the PIC input/output ports connected to the opto-isolators?

  3. #3
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    Just some things I found, this what Ill do >>>

    1) The MAX232 is not really needed, you can simplify it just by taking the serial port RX line and bringing down voltage to what the PIC is comfortable with. This can be done by means of zener and resistor.

    2) No need for TX line, since you wont be reading the configuration stored in the PIC?

    3) Use a smaller PIC.

    4) Use the SW to emulate a UART if you can.

    5) If you can get away with it run the PIC at its internal 4Mhz clock.

    6) Use zener/resistor for voltage regulator.

    7) No need to opto isolate.

    8) The configuration can be done via a button and an LED. This will save you a DB9 connector and a level converter.


    Those are just some advice, I know you may not agree with them but those are some possible mods you may wanna consider.


  4. #4
    Variable Bitrate Saab9-5's Avatar
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    Quote Originally Posted by rando
    This looks sweet!
    Thanks. Especially coming from you with all the work you (and Seth, Racemeir, et al) are doing on the AM/FM radio project.

    Quote Originally Posted by rando
    1) Could you use a PIC with a built-in resonator option to save a few parts?
    Of course. I have a few of these from sample orders I've placed with Microchip. The design is very flexible, only requiring a PIC have: 1 analog input port, 1 serial port, 1 interrupt, 2 digital inputs, and 5 digital outputs.

    Quote Originally Posted by rando
    2) Will the linear regulator draw an excessive amount of current while the car is off?
    Won't know until I build it. My benchtop power supply has a display for current being drawn so I'll know then and tweak accordingly.

    Quote Originally Posted by rando
    3) Current limiters at the PIC input/output ports connected to the opto-isolators?
    I'll add those in. Thank you for the suggestions.

  5. #5
    Variable Bitrate Saab9-5's Avatar
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    Quote Originally Posted by Chris31
    2) No need for TX line, since you wont be reading the configuration stored in the PIC?
    Actually I do need the TX line. The circuit will be doing two-way communications, letting you know in real-time what the photoresistor value is. It will have a basic terminal interface.

    Quote Originally Posted by Chris31
    7) No need to opto isolate.
    I did this to provide a level of safety. But since it will need to operate off of the battery, that will go if the current drain is too much.

    Quote Originally Posted by Chris31
    Those are just some advice, I know you may not agree with them but those are some possible mods you may wanna consider.

    This is still very much a work in progress but I do appreciate all feedback and ideas.

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    No problemo...good luck

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    Low Bitrate jbraddoc's Avatar
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    Wow! I thought you said that you <i>just</i> got into this? LOL... I understand most of it, and it looks awesome :-) I am just glad I finally found someone that knows what I want to do.. LOL

  8. #8
    Low Bitrate jbraddoc's Avatar
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    I was going to post something, but I closed the window.. it was an edit.. I guess Ill type it all again when I can remember what I said... LOL

  9. #9
    Variable Bitrate Saab9-5's Avatar
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    Status Update

    The hardware has basically been breadboarded. I'm working on the software now. Unfortunately, I need to take a business trip to New York City so I have to pause this project for a week.

    Quote Originally Posted by jbraddoc
    Wow! I thought you said that you <i>just</i> got into this? LOL... I understand most of it, and it looks awesome :-) I am just glad I finally found someone that knows what I want to do.. LOL
    Thanks. I'm a quick learner.

  10. #10
    Variable Bitrate Saab9-5's Avatar
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    Note: The Power On LED in the Power Supply schematic is shown backwards. A new schematic will be posted when I return from NYC based on people's recommendations and any problems I run into while building it.

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