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Thread: Hardwire VM70 Display

  1. #1
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    Hardwire VM70 Display

    Using a VM70 in my CarPC build. From reading around here and prior experiences with cigarette/aux adapter power I know that it can be dirty and noisy power.

    I would prefer to hardwire into the chosen power source. The directions for the VM70 are not top notch. There is an AC/DC adapter, an auto(cigarette) adapter and what appears to possibly be a hard wired connection for the display.


    I'm unsure if the wires labeled +12V & Ground are for hard wiring the display or for something related to video inputs. I don't want to go connecting power if it is not proper. I contacted Carl at short-circuit.com but have not heard back as of yet. Thanks for the input!

  2. #2
    MySQL Error soundman98's Avatar
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    4&5 should be for monitor power-- so just connect these to your regulated source.

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    Quote Originally Posted by soundman98 View Post
    4&5 should be for monitor power-- so just connect these to your regulated source.
    Thanks soundman98. It seems to be working well on bench supply using those two connections.

    Now for your last statement regulated source. This monitor is designed for 11.5-14.5V DC input. My charging system in cold weather will reach up to 15.4V. I asked Carl and he said they have never tested above 14V and the VM70 probably would not handle the 15+ volts. This is normal for my vehicles charging system so no issues there.

    I plan on using my radio circuit to power the VM70 and not tapping into the AUX circuit. I am reserving the AUX circuit for the DC-DC adapter for the laptop. The radio circuit is rated for 10A which is more than enough to power the VM70.

    Using a 12V Sharp LDO regulator to play it safe. It has a four pins the fourth of which can be used as an on/off switch. Grab the 12V switched signal from the radio harness for the on/off switching on the vreg. Then power source will come from the 12v fused(ALWAYS HOT) wire in the radio harness. Does this sound like a good plan of action for protecting the display?

  4. #4
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    Went with the Sharp vreg and utilized the on/off pin to do the switching. Here is the completed switchable vreg module:

    Vreg Module:



    Vreg Module and Pigtails:



    Finished Module:



    Here is the schematic I used. With output going to VM70 not LEDs and I did not include an LED monitor as it won't be visible when installed.




    Problem Solved I'd say!

  5. #5
    Variable Bitrate djvillar's Avatar
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    Just use the 12v (yellow line) from your power source. And fuse it of course. That is regulated 12v. Look at the fuse in the cigarette adapter the the size.

    Edit:
    If its like the lilliput you'll use a 250v 2amp fast acting fuse. Available at any radioshack. They'll have line in fuse holders too. And you'll need a barrel plug... for a Lilliput is an "M" size one at Radio Shack... 5.5mm OD 2.1mm
    Last edited by djvillar; 05-15-2011 at 02:59 AM.

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    MySQL Error soundman98's Avatar
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    ^ ah i see, the laptop is using it's own car power adapter, so you don't have a 12v reg source on the dc-dc psu..

    it's just like your recent led projects-- while voltage regulation is not required, it is a couple extra steps that can extend the life of any electronic device, so why not do it?


    i don't believe that you need to use the switching capabilites of the vreg, though, there isn't a specific reason other then the added complexity. i think it would be fine to connect the vreg to the switched power wire..

    and if you do want to do it use the constant power w/ 4th pin control, remember that the 4th pin needs to get pulled to ground to turn the vreg off, so you'll need to use a relay to activate it.

  7. #7
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    Quote Originally Posted by soundman98 View Post
    ^ ah i see, the laptop is using it's own car power adapter, so you don't have a 12v reg source on the dc-dc psu..

    it's just like your recent led projects-- while voltage regulation is not required, it is a couple extra steps that can extend the life of any electronic device, so why not do it?


    i don't believe that you need to use the switching capabilites of the vreg, though, there isn't a specific reason other then the added complexity. i think it would be fine to connect the vreg to the switched power wire..

    and if you do want to do it use the constant power w/ 4th pin control, remember that the 4th pin needs to get pulled to ground to turn the vreg off, so you'll need to use a relay to activate it.
    I had replied with a post last night about the vreg but it seems it was never posted...


    EDIT:
    It's there now!
    Last edited by sall; 05-15-2011 at 09:09 PM.

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