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Thread: Help with AC/DC-DC powersupply from Timeline

  1. #1
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    Help with AC/DC-DC powersupply from Timeline

    I guess I should start a new thread on this, since the other is getting long.

    I recieved my AC/DC-DC powersupply from timeline today, and I'm looking at the spec sheet and it says:

    "Note 2 - Normal output is TTL high goes to TTL low if AC input is lost

    Note 3 - TTL High will shut down power supply if operating in battery mode - AC input required to restart power supply"

    I plugged the AC in, hooked up the battery, and put a multimeter on the ouput lines... when the AC in is removed, the battery kicks in and supplies power, however if the battery is unplugged and reconnected, the output voltages don't return until the AC is reconnected. Any ideas on how the supply can be restarted without supplying the AC power, or maybe it can be tricked into thinking there is an AC source.

    I wish I had a circuit diagram, but all I have are the pinouts, and it shows that there are three pins that communicate with the computer about the powersupply status. I will get a picture of the board sometime soon. Did any electronics guru's by this powersupply? From the looks of it, the board is basically seperated into two sections, and AC-DC part, and then a DC-DC part that ouputs the regulated voltages.

    This powersupply would work great with an inverter, because you wouldn't lose power on startup, etc. However I would really like to be able to use it as a DC-DC supply... which works great as long as I don't interrupt the DC input.
    Still setting it all up:
    FV24 with celeron 900, super tiny custom case, Datalux 10.4 touch screen in the Subaru Outback

  2. #2
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    here's the past thread about this supply:
    Cheap DC-DC PSU - Be quick!

    and the pinouts:
    Still setting it all up:
    FV24 with celeron 900, super tiny custom case, Datalux 10.4 touch screen in the Subaru Outback

  3. #3
    FLAC mp3z24's Avatar
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    try a couple of experiments and measure the voltages on pins 1, 2, and 3 of connector p-2. i would be interested to see what is happening with these wires when the AC is lost and the DC kicks on. also, what happens to tell the board that the AC has been re-connected. there has to be some sort of signal to the power supply.

    my guess at the moment would be this:

    pin 2 normally shows ttl high (whatever voltage value that is), when the ac is lost, the psu detects this signal loss and changes the voltage to ttl low (whatever value that is). when the ac is restored, ttl high is sent into pin 3, signaling the psu to switch to ac mode, at the same time ttl high is sent across pin 2.
    hmmmmm
    well, there has to be a relay or switch that is triggered by the ttl high, when the switch detects the ttl high, the ac is pulled for the supply. wouldnt ttl high be associated with the voltage from the ac? so when ac is lost, the relay switches to the other source, in this case the 12v dc. the voltage on pin 2 would show the ttl low voltage associated with the dc operation. so in order for the psu to switch back into ac mode, ac voltage would have to be detected by the relay, resulting in the switch back to ac operation, and sending ttl high across pin 2.

    that is my take on what is happening i dont know if any of it makes sense. it did in my head could you possibly take some pictures of the boards. top and bottom, maybe that would shed some light on the components. also, see if you can get a data sheet or schematic. ideally a schematic!!

    in my opinion, if you wanted to use this as a dc-dc psu with an internal dc battery backup, i would think that you are going to have to replace the ac portion of the board with a dc-dc supply.

    i am by no means a circuit expert so take this info at whatever value you feel comfortable.

    if i were designing this circuit, i would think about a dc-dc with a fast acting switch/relay between the inputs to detect the main dc from the battery as the main power source, and then if that source fails, the relay would switch the input to the backup battery. but, you would have to prevent the voltage drop during the source switch with something like a tank circuit.

    my $0.02 and ramblings....

    ~mike

    edit: if im right, im gonna be scared of myself!!!
    Single Member of the "1000 Post and No MP3 Car" Club
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  4. #4
    Variable Bitrate
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    Smoothswiss,

    could you measure the voltage that the AC-DC section outputs?
    I would like to know what input the DC-DC section needs to be supplied with, in order to trick it into thinking that it is powered by AC all the time.

    Also what will happen if you use a diode (MBR3045) in between to connect the PSU's battery terminals in parallel with the car's battery? Will the car's electrical system overcharge and destroy the small battery when the engine is running?
    What if you don't use the small battery at all and substitute it with the car's battery and have the PSU running on DC all the time? You'll need AC to restart the PSU only if you disconnect the car's battery or even after cranking the engine (due to the voltage drop)???.

  5. #5
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    unfortunatly I don't have my digital volt meter with me, so I'm using a cheap analog meter. I measured the voltage going into the DC section, and it looks to be about 3 volts?... but I'm not sure if my meter is working correctly. It's hard to work on stuff in a dorm room cause I have very little tools here. I will try my best to get a picture up soon. The only components interfacing between the 'AC' and 'DC' section is one large transformer, and 2 small IC chips.

    I don't think just putting a diode between the car battery and the small (2.2 AH) would be a good idea, a charging circuit which stops charging at a certain voltage would probably be much better.

    Also, the 3 ouput/input pins work just like the sheet says. If the AC goes out, pin two goes low. Pin 3 is used to shut off the supply while opperating in DC mode, it doesn't signal it to switch to AC... the supply automatically switches to ac when plugged into the wall. There are also no relays, there's something that looks like it's in a relay case, but it's just a capacitor.

    Thanks for all the help on this, I hope I can get it working sometime!
    Still setting it all up:
    FV24 with celeron 900, super tiny custom case, Datalux 10.4 touch screen in the Subaru Outback

  6. #6
    Variable Bitrate
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    What if you connect the car's battery to the PSU instead of the battery that came with it (with a diode in between)?
    It still doesn't work right?

  7. #7
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    Originally posted by Dimitris1976
    What if you connect the car's battery to the PSU instead of the battery that came with it (with a diode in between)?
    It still doesn't work right?
    I haven't had the chance to hook it up directly to my car battery yet, but theoretically it should work the same as the little battery, you still need the AC to start it up.
    One option I'm looking at if we can't figure out how to get it to work without ac, is to hook up a low wattage inverter to kickstart the powersupply, and then just run it off the 12 volt. I'm wondering how long the powersupply can run off the small 12 volt battery if it is not supplying current to the motherboard (computer turned off). I would think it would be able to stay on for a long time, since it's not powering anything, then maybe it wouldnt need the AC everytime. Not a very small solution, but I think it may be practical to have an inverter on hand in my car anyways, and I will still be using the efficiency of the DC-DC supply to run the computer.
    Still setting it all up:
    FV24 with celeron 900, super tiny custom case, Datalux 10.4 touch screen in the Subaru Outback

  8. #8
    Variable Bitrate
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    Is there an easy and efficient way to reduce the car's 12V to 3V needed to supply the DC-DC section of this PSU?

  9. #9
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    I feel bad, cause my knowledge of electronics is very limited... I just hope someone who knows what they are doing also bought one of these...

    as far as the 3 volts I measured, I bet you also need to do something with those tiny IC circuits... they must be controlling something?
    Still setting it all up:
    FV24 with celeron 900, super tiny custom case, Datalux 10.4 touch screen in the Subaru Outback

  10. #10
    Variable Bitrate
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    This 3V sourse does not have to be rated at many Amps. Only some mAmps, just to make the DC-DC section think that there is being supplied by AC - then the battery takes over.

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