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Thread: Hp tuners monitor a ground switch?

  1. #1
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    Hp tuners monitor a ground switch?

    I have mpv1 pro and want to know if it can monitor a hobb switch.

    The switch completes a ground circuit.

    I can have that turn on a led too, but want to know if I could set up in the scanner to see it go from on/off.

    Grounded vs open

    What I mean is:

    Can I hook up the ground wire from the switch that triggers the pump to the scanner.

    Read it in the scanner as on (ground present) off (no ground present)

    Would look like this in the chart. ____/````````````\______ (up its on (1) at bottom is off (0)
    Last edited by Tarendor; 1 Week Ago at 10:05 AM. Reason: Additional info

  2. #2
    Advanced Tuner dhoagland's Avatar
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    I do not believe so. From what I can see the MPVI 1 has 4 analog inputs, the MPVI 2 has 2 analog and 2 CAN inputs...

    Can your Hobbs switch output a 5V analog signal?
    If so you maybe could input that just like a wideband.... Then set a chart to monitor that voltage, with a range of 0-5... Zero being your Off, 5 being your On.

    Possibly put a pressure sensor in (I'm assuming you are monitoring if an aux fuel pump is running) and do the same thing with whatever then on/off numbers are for fuel pressure. There are quite a few predefined in the MPVI 1 transform options
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  3. #3
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    What is the voltage range on the analog inputs? What you would be looking to read is simply a high/low status bit. High = voltage present, low = no voltage present. Might possibly need to add a pull-down resistor to make sure there's no stray floating voltage when the circuit is off but this is standard stuff.

    I'd ask support (open a ticket) for specifics on the analog inputs. Also ask, if it's limited to reading 0-5v, would it be 'safe' with battery voltage applied. Lots of inputs are protected and current-limited, but the circuitry (and code/firmware) is limited to displaying a smaller range of voltage.

    If it is truly limited to 5v, one workaround could be to feed 5v to the Hobbs switch, have it activate a 5v relay, that then activates your current 12v relay. Most low-voltage relays are much lower current than typical 12v relays, hence the reason for the two in series. Sounds clunkier than it would be in reality but it'd work.

  4. #4
    Advanced Tuner dhoagland's Avatar
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    Quote Originally Posted by blindsquirrel View Post
    What is the voltage range on the analog inputs? What you would be looking to read is simply a high/low status bit. High = voltage present, low = no voltage present. Might possibly need to add a pull-down resistor to make sure there's no stray floating voltage when the circuit is off but this is standard stuff.

    I'd ask support (open a ticket) for specifics on the analog inputs. Also ask, if it's limited to reading 0-5v, would it be 'safe' with battery voltage applied. Lots of inputs are protected and current-limited, but the circuitry (and code/firmware) is limited to displaying a smaller range of voltage.

    If it is truly limited to 5v, one workaround could be to feed 5v to the Hobbs switch, have it activate a 5v relay, that then activates your current 12v relay. Most low-voltage relays are much lower current than typical 12v relays, hence the reason for the two in series. Sounds clunkier than it would be in reality but it'd work.
    Great points on getting true input limits
    I thought about something like this, but concerned with the 3 AMP output. (Obviously not knowing the safe limits of the MPVI input)

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  5. #5
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    I = V/R

    That doesn't change just because it's solid state components instead of plain resistive loads. The MPVI analog inputs are going to draw a minuscule amount of current, otherwise they would pull down the circuit being measured. You can connect a dinky little test light direct to B+ and B- and nothing explodes even though that same battery is capable of delivering 1000A or more, given the right (or wrong!) resistance.