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Thread: Taking the plunge...

  1. #31
    Raw Wave treetop777's Avatar
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    I was thinking M2-ATX to power the hub? That should absorb the power spikes and supply clean constant power to the hub. (if the hub takes 12v)
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  2. #32
    Raw Wave
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    I didn't want to get involved... Hey man, then I'd have to read pages and have to THINK & understand, and probably review that every time - and I don't even review threads I'm active in (hence my stupid relies 'cos I'm confusing my threads)!
    Besides it seems like things are getting there...

    Just re power from "the cigarette lighter connector (behind the dash)", that sounds like a connection to the socket's wiring - ie, NOT using a cig plug.
    I was merely going to caution that (1) cig plugs can often be knocked or vibrate so power is lost & (2), my usual caution about some not handling more than a few Amps (despite alleged 15A ratings) and thereby a loss of entire vehicle (thru fire...).


    PhilG makes a good point about ACC going off during cranking. Now if a 2nd battery is used...
    You could keep power on during cranking - eg, a diode from STart, but probably to a relay used by ACC for your power straight from the battery for cleanest 12V and independence of other circuit loadings, or because you might need an RC delay to keep ACC on while moving to crank/STart (the ACC line should be disconnected BEFORE the starter motor gets its signal - ie, ACC & STart should NOT overlap).
    Or you could power on AFTER the engine has cranked - eg, the UIBI as used for dual batteries - but you want ACC power as well. (Ok, a UIBI into a 'latching' relay (SPST with feedback) which can also be manually controlled from ACC power etc.)

    The above depends on when it is to be powered eg, anytime, or IG key only; but not during cranking, etc.

    As I recall the M-series specs have VERY good performance and should ride thru cranking - ie, they operate down to 6V. (I often say automotive stuff should handle (if not operate) from 8-16V but down to 8V can be very difficult. But that M2 6V spec exceeds even my own design criterion!)

    Any switched-mode regulator/converter should clean up noisy or changing input voltage variation hence a direct fro battery feed may not be important. Most are switching at a few hundred kHz or even MHz (I think that mini converter I posted is 1.2MHz.)
    And yes, the M4 can be problematic, but I also read of some M2 noise issues.


    And I'd prefer one regulator supplying the end equipment (reliability, efficiency etc), but one as a pre-reg for others can also make sense - eg, you have the perfect splitter but it is 12V as opposed to automotive 12V. (LOL - I can confirm that "12V" LED tapes are 12V. My 5050 SMD license plate LEDs fried - sometime the series resistor; sometimes the 5050 LED itself. And yes, I I suspected that outcome.)


    Anyhow, must shower and work....

  3. #33
    Constant Bitrate
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    Well another way is to use the fuel pump fuse as a signal. From there trough a 3-5A fuse you could control a relay, which in fact will feed up your voltage regulator again trough a appropriate fuse.
    This way you eliminate the power loss during cranking because there is no fuel driven car in the world that cuts the power for it's fuel pump while the engine is trying to start . huh - that sounds like a professor wrote it . But you have to be sure your voltage regulator will survive the cranking.

    There are many ways to do that. It's up to you (and the real situation in the car) to decide which one to follow.
    My worklog: VOLVO S80 CarPC

  4. #34
    Raw Wave
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    Quote Originally Posted by VolvoCarPC View Post
    Well another way is to use the fuel pump fuse as a signal.
    Two major cautions:

    You'd want it powered after the fuel pump relay, not its (upstream) fuse unless you want it to behave the same as IGN.


    The switched side of a fuel pump (relay) might come on with IGN for a few seconds - especially Euro vehicles or those using typical VAG relays (Hella, Bosch etc with inbuilt circuitry 'smarts').
    Others may only come on during cranking and when the engine charge light extinguishes (ie, no IGN-on temporary turn on).
    And others may be wired any old how - whether oil pressure (stupid!) or non-OEM from (park) lights or IGN (bad!), etc.


    FYI - except for the initial IGN-on and any on-during-cranking, spark sensing and other fuel pump circuits make great battery isolator relay controllers.

  5. #35
    Constant Bitrate eugenweij's Avatar
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    Fuel pump sounds like a bad idea , I am thinking of either putting in a relay on the acc, that can switch on and off the 5v supply from the battery or a non-powered usb hub , gonna do some testing to see if that is a viable option
    View my worklog here

  6. #36
    Constant Bitrate eugenweij's Avatar
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    okay, been busy compiling the kernel, not been fully successful yet, so thats still 'under development'

    Another issue I ran into is that the battery pack isn't providing power to the odroid while it is charging, so I have been devising a way around that issue.

    I am planning on using a 5V supply rated 3A or more , one cable will run to the battery , another will run to a switch-like device I will be designing.

    From the battery pack, another cable will run to the same switch, and from the switch a cable to the odroid.

    The idea behind this is that when the car starts, thus charging of the battery starts , that same power supply will power the odroid while I am driving, and as soon as the ignition turns off , charging stops and the battery will take over powering the odroid.

    here a simple schematic of the idea, any input will be welcome as to the working of the switch unit
    what I am thinking of is that power to the odroid will come a second or so before power goes to the battery , making sure there are no interruptions, and when power is shut off , charging stops a sec before the power gets cut from the odroid.
    Tests will show if this will actually work

    Name:  odroid power.png
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    View my worklog here

  7. #37
    Raw Wave treetop777's Avatar
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    looks to me like it will blow-up! put arrows in the direction of the flow of power in your illustration and see. Looks like you will have back-feed somewhere..
    ****************************************
    OLD SYSTEM (DEAD)
    Intel D945GCLF2 Dual Core ATOM
    Lilliput 7" 629GL 2008 LED Backlight
    BU-353 USB GPS Receiver / iGuidance / IGO8
    M2-ATX Power Supply
    RideRunner Front End / Various Skins
    Windows XP SP3

  8. #38
    Raw Wave
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    As per treetop...
    Your problem is paralleling 2 power sources. That is very difficult to do without using diodes or static switches (as per AC UPS). Hence why dual source (UPS) systems etc are usually in series - ie, battery charger -> battery -> load.

  9. #39
    FLAC SNOtwistR's Avatar
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    I think I would buy this little gizmo and call it a day http://store.mp3car.com/Mini_Box_pic..._p/pwr-040.htm I am sure you can make this work like you want it (sort of) SNO


    Sorry wrong item this is what I was thinking of http://store.mp3car.com/Mini_Box_Y_P..._p/pwr-046.htm
    Last edited by SNOtwistR; 02-28-2014 at 04:26 PM. Reason: Wrong item in first link

  10. #40
    Constant Bitrate eugenweij's Avatar
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    the schematic I showed is merely to illustrate the idea, I am still working on making that switch unit work the way I want and restrict current flow so it doesnt flow anywhere I don't want it to.


    there will be a diode between battery and the switch so current only flows from battery to switch and not back. , also timed relays or something so the switch from battery to psu goes without intteruption of power to the odroid.


    The idea might seem simple but its a lot of googling and thinking before I get something that will work without damaging my stuff
    View my worklog here

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