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Thread: Fusion Brain digital output for HVAC.

  1. #1
    Maximum Bitrate stonestatue's Avatar
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    Fusion Brain digital output for HVAC.

    I'm in the process of installing the car PC in my van and want to incorporate HVAC control into it. It has the Fusion Brain 4.0 which has 16 digital outputs and 13 analog inputs. I have already done some analysis of the situation in this thread:

    http://www.mp3car.com/vbulletin/gene...mc-savana.html

    I realized the Fusion Brain's digital outputs are not variable. It's either 0 volts (off) or 5 volts (on). That's good for turning on and off switches, but I want to control the temperature. This is done via a servo motor which opens a flap to determine how much heat to let in. The servo is controlled by a controller. The controller determines how far the temperature blend door is open based on a signal from the temperature dial. The temperature dial acts like a rheostat or potentiometer and has 21 different inputs it can send to the controller.

    I determined that it is a variable resistor logic input. This means that it starts out with zero resistance and goes up to full resistance. I'm not yet sure which one is full open and which one is full closed, but that won't be hard to figure out.

    All that being said, I would need the Fusion Brain to output a signal of varying resistance (21 "buttons" in Road Runner) to mimic the temperature dial. Since the digital outputs can only be on and off, it can't vary the voltage. I did notice that it has PWM capability, however I'm not sure if that can help me achieve my goal. Any help is greatly appreciated. (Greenman perhaps?)
    Check out my GMC Savana worklog.

    Remaining tasks to facilitate vanputer installation codename "Enterprise":
    - Edit skin to liking.
    - Get compatible phone for mobilephone.net.
    - Facilitate HVAC control.

  2. #2
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    VegasGuy's Avatar
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    Quote Originally Posted by stonestatue View Post
    I'm in the process of installing the car PC in my van and want to incorporate HVAC control into it. It has the Fusion Brain 4.0 which has 16 digital outputs and 13 analog inputs. I have already done some analysis of the situation in this thread:

    http://www.mp3car.com/vbulletin/gene...mc-savana.html

    I realized the Fusion Brain's digital outputs are not variable. It's either 0 volts (off) or 5 volts (on). That's good for turning on and off switches, but I want to control the temperature. This is done via a servo motor which opens a flap to determine how much heat to let in. The servo is controlled by a controller. The controller determines how far the temperature blend door is open based on a signal from the temperature dial. The temperature dial acts like a rheostat or potentiometer and has 21 different inputs it can send to the controller.

    I determined that it is a variable resistor logic input. This means that it starts out with zero resistance and goes up to full resistance. I'm not yet sure which one is full open and which one is full closed, but that won't be hard to figure out.

    All that being said, I would need the Fusion Brain to output a signal of varying resistance (21 "buttons" in Road Runner) to mimic the temperature dial. Since the digital outputs can only be on and off, it can't vary the voltage. I did notice that it has PWM capability, however I'm not sure if that can help me achieve my goal. Any help is greatly appreciated. (Greenman perhaps?)
    Where you get in trouble is trying to run inductive loads (motors, servos, incandescent lights) off the digital ports. Your probably going to need some additional circuitry and hardware between your fusion brain and the systems you want to control.

    Do a search, because there are people that have done it on this board. You might want to check out RelayPros.com for some more robust controller options. Good luck!

    VegasGuy

  3. #3
    Fusion Brain Creator
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    you need a digital pot. look them up. you want the "pushbutton" type, then emulate pushbuttons with digital outputs.

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    Bugbyte's Avatar
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    Can you replace the servo with a standard R/C servo? They use PWM to control position.
    Quote Originally Posted by ghettocruzer View Post
    I was gung ho on building a PC [until] just recently. However, between my new phone having internet and GPS and all...and this kit...Im starting to have trouble justfiying it haha.
    Want to:
    -Find out about the new iBug iPad install?
    -Find out about carPC's in just 5 minutes? View the Car PC 101 video

  5. #5
    Maximum Bitrate stonestatue's Avatar
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    I am not sure how easy it would be to fit.
    Check out my GMC Savana worklog.

    Remaining tasks to facilitate vanputer installation codename "Enterprise":
    - Edit skin to liking.
    - Get compatible phone for mobilephone.net.
    - Facilitate HVAC control.

  6. #6
    Maximum Bitrate stonestatue's Avatar
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    Regarding the digital potentiometer, how exactly would that work?
    Check out my GMC Savana worklog.

    Remaining tasks to facilitate vanputer installation codename "Enterprise":
    - Edit skin to liking.
    - Get compatible phone for mobilephone.net.
    - Facilitate HVAC control.

  7. #7
    Constant Bitrate
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    Why not having a look at the eyeR interceptor pro. It has many dedicated HVAC features and also a back up custom infrared remote for when you PC hasn't booted up yet or fails. Though if you already have a fusion brain, and like the idea of a dedicated HVAC remote you can now buy the remotes seperately. It's has intergrated servo and PWM control.. Just a thought.

  8. #8
    Maximum Bitrate stonestatue's Avatar
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    It looks interesting, but can it emulate variable voltage outputs?
    Check out my GMC Savana worklog.

    Remaining tasks to facilitate vanputer installation codename "Enterprise":
    - Edit skin to liking.
    - Get compatible phone for mobilephone.net.
    - Facilitate HVAC control.

  9. #9
    Maximum Bitrate stonestatue's Avatar
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    Quote Originally Posted by greenman100 View Post
    you need a digital pot. look them up. you want the "pushbutton" type, then emulate pushbuttons with digital outputs.
    Could I use one digital potentiometer that outputs different voltage levels or would I need one digital potentiometer for each dial setting (21)?
    Check out my GMC Savana worklog.

    Remaining tasks to facilitate vanputer installation codename "Enterprise":
    - Edit skin to liking.
    - Get compatible phone for mobilephone.net.
    - Facilitate HVAC control.

  10. #10
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    Can you hook up an RC/PWM type servo to the mechanical Temperature dial? System would be something like this.

    Front end > FusionBrain > PWM Servo > Temperature dial > Controller > OEM Servo

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