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Thread: How to make an external battery pack?

  1. #101
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    Default Re: How to make an external battery pack?

    Just did up the circuit....failed.

    There no power to my DC plug...I used the single pole double throw switch, but when I switched to either side, both led light up???

    Sigh... Have to think of a way to solve it...

    Any suggestion for a parellel circuit with a single pole double throw switch, and led indication, and a DC output and USB output....all 5V?

  2. #102

    Default Re: How to make an external battery pack?

    Hi Max,

    You need to put the LED parallel to the line to the device. The led must be after the switch towards the plug. The LED must touch both the red and black lines. Better to put a resistor in series with the LED too, to prevent it from burning.

    EngHong

  3. #103
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    Default Re: How to make an external battery pack?

    Quote Originally Posted by enghong17
    Hi Max,

    You need to put the LED parallel to the line to the device. The led must be after the switch towards the plug. The LED must touch both the red and black lines. Better to put a resistor in series with the LED too, to prevent it from burning.

    EngHong
    Hmmm....? Can draw a diagram?.... I did have the led towards the plug after the single pole double throw switch.... Anyway the connection for the switch is positive wire of each pack on each side and the positive to the plug in the middle? Thats what I did actually... Its funny no matter which side I switch both led will light up also...

  4. #104

    Default Re: How to make an external battery pack?

    Hi Max,

    Think i know why the LEDs light up. Your red line from device should only be connected to the COM part of the switch. By the above drawing, you have nothing connected to the COM terminal of the switch. Below is my sketch......



    On how to connect the LEDs...


  5. #105
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    Default Re: How to make an external battery pack?

    Hi Enghong,

    Thanks for the diagram, really appreciate the effort.

    My circuit looked more like the first diagram but with the LEDs. I connect the both red wires of LED to the left and right metal piece of the switch. and the black ones were straight from the battery packs.

    Then 1 red wire to the centre of the switch to the DC output. 1 black wire were connected from the leds to the DC output.

    Correct?

    Here's my diagram, the centre grey box with 3 green strokes is the single pole double throw switch.


  6. #106

    Default Re: How to make an external battery pack?

    Hi Max
    after last nite's discussion, and after seeing the way you put ur LEDs.. haha.. I know why both lighted up. coz both LEDs are connected all the time. Both LEDs anode and cathode legs (+ and - legs) see a voltage difference larger than 3v, that's why lighted up.

    the rough schematic provided by enghong can work to have LED light up to show which pack being used, provided there are 2 SPDT switches.

    However I made up some kinda schematic myself. using 1 DPDT switch, and 2 diodes



    only drawback is, the diode introduces voltage drop. how much voltage u lose due to the diode there depends on which type of diode u use. normal silicon one would cause 0.7v whereas schottky has 0.3v across the anode and cathode.
    meaning, if u have 4.8v batt pack, ur device will only see 4.1v or 4.5v, depending on which type of diodes being used. so, must see if ur devices will work at such voltage. IIRC, they shd work.

    you got my number, so in any doubt, give me a call lah

  7. #107

    Default Re: How to make an external battery pack?

    Hi Max,

    I realised that using your diagram, you would not be able to light up the LEDs to indicate which batt pack is being used. You will only be able to light it to show that there is power ON/OFF. Relised that when i tried drawing the SPDT switch, thus the 2 drawings.

    The drawing by Squalle looks good. Only drawback is the diode voltage drop.

    Squalle, the diodes are for protection against power surge from device? Any other uses? Also why 2, not 1?

    EngHong

  8. #108

    Default Re: How to make an external battery pack?

    diodes are there to prevent the LED being ligthed up by wrong batt pack

    not surge protection. surge protection would be using bypass capacitor at the point after the switch, bypass the current to the ground.

  9. #109

    Default Re: How to make an external battery pack?

    Quote Originally Posted by squalle
    diodes are there to prevent the LED being ligthed up by wrong batt pack

    not surge protection. surge protection would be using bypass capacitor at the point after the switch, bypass the current to the ground.
    Oh.....i see the picture now......yea, why din i think of that.....haha cracking my head on how to light up 1 LED......yea i thot surge protection is using capacitors too but there have been cases where diodes have been used to protect device from connection of wrong polarity that's what i thot u were using it for, din think of the LEDs.


  10. #110
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    Default Re: How to make an external battery pack?

    Quote Originally Posted by squalle
    Hi Max
    after last nite's discussion, and after seeing the way you put ur LEDs.. haha.. I know why both lighted up. coz both LEDs are connected all the time. Both LEDs anode and cathode legs (+ and - legs) see a voltage difference larger than 3v, that's why lighted up.

    the rough schematic provided by enghong can work to have LED light up to show which pack being used, provided there are 2 SPDT switches.

    However I made up some kinda schematic myself. using 1 DPDT switch, and 2 diodes



    only drawback is, the diode introduces voltage drop. how much voltage u lose due to the diode there depends on which type of diode u use. normal silicon one would cause 0.7v whereas schottky has 0.3v across the anode and cathode.
    meaning, if u have 4.8v batt pack, ur device will only see 4.1v or 4.5v, depending on which type of diodes being used. so, must see if ur devices will work at such voltage. IIRC, they shd work.

    you got my number, so in any doubt, give me a call lah

    Wah pai sey bro, dun understand your diagram leh...Can draw simple layman style or not? I not EE student leh. you mean I cannot use 1 spdt switch lah? Like that I just use 2 normal switch can already lah
    Last edited by TrailsofLife; 26th October 2005 at 02:17 PM.

  11. #111

    Default Re: How to make an external battery pack?

    which part that u're unclear about?

    what you need to get are DPDT switch and 2 diodes. which diodes to get? hehe that one u gotta ask the uncle there. get the one that will withstand 4A (A stands for ampere, a unit for electric current).
    I think we should meet again then I give u a crash course for eletronics things.

    btw, I myself not an EE student either . you can pick these things up fast. dont worry

  12. #112
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    Default Re: How to make an external battery pack?

    I think better to have 2 normal switch, solve all the problem.

    Any idea about the polarity of USB?

  13. #113

    Default Re: How to make an external battery pack?

    ok
    a lot simpler
    tho' u gotta be careful dun on both at the same time. might burn ur batt due to short circuit within batteries themselves

    abt the USB, not yet.. sorry...

    btw, still interested to make those 8 batts in series then step down the voltage? can guide u in which exact parts u shd hunt for.
    the regulator, u can use LM350, rated for 3amp. so it's safe for ur usage.
    it's adjustable, too

    here's the schematic, ripped off the suggested layout from the LM150/350 data specs


    LM350 according to farnell sg costs S$4+
    http://sg.farnell.com/jsp/endecaSear...SKU=412302&N=0

    the rest are cheap stuffs
    3 capacitors (non-exotic types of course. costing less than SGD1 each for sure)
    and get a trimmer for the R2. then u can adjust to watever output voltage u want it to be (min of 1+v, and max that's the same as ur input minus the drop out voltage due to the linear regulator)

    tell me if u're still interested to get the DC-DC voltage converter realised

    EDIT: changed the ampere rating. 350 has lower rating (i.e. 3amp instead of 5amp of its sister LM150)
    Last edited by squalle; 26th October 2005 at 07:05 PM.

  14. #114

    Default Re: How to make an external battery pack?

    USB pinouts: http://pinouts.ru/data/USB_pinout.shtml

    the website is very good to get the pinouts layout of many many plugs or protocol

  15. #115
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    Default Re: How to make an external battery pack?

    Hello bro,

    your diagram all got funny symbol I dunno one. ha ha...

    íf dun use all the resistor and whatever, just a simple circuit, possible?

  16. #116

    Default Re: How to make an external battery pack?

    for ur switch? then LED will burn out very fast due to too much current flow.

    the resistors are placed there to limit the current flowing thru the LEDs

    about the voltage regulator? you cant avoid those resistors. they're needed to set the output voltage

    so, now tell me. which one r u more interested in?

  17. #117
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    Default Re: How to make an external battery pack?

    Actually dunno also lah...I have 2 battery cases, some wires, 1 SPDT switch, 2 leds... What else do I need or change?

    Yo bro, when you draw diagram hor, dun use symbol can? just simple simple like my one, can?
    Last edited by TrailsofLife; 27th October 2005 at 12:35 AM.

  18. #118

    Default Re: How to make an external battery pack?

    simplest way?

    get 1 more SPDT
    one each to disconnect each pack
    possibility will be:
    1. both off
    2. pack A on
    3. pack B on
    4. both A and B are on

    then the two centre legs from two SPDT switches u've got, u just join them
    for the LED, each + leg at the centre leg of the SPDT.
    but, without the diodes. hahaha very high chance that both LEDs will light up as before
    you still have to go with the diodes in order to show which pack is being used.

    the diodes are there just to prevent backflow
    e.g. pack A switch is open, pack B is connected. at the jack there, u have to join them together right? that's the point where the LED for pack A will get light up too. it's all due to them being connected to the same wire. so to break this off, use diodes. diode won't let any current flow if the polarity is reversed.

    anyway..... if u want simplest way. just take away the LEDs hahaha
    do u really need them anyway? just simply put 1 to show whether it's on or totally off.

    like I've said lor, if you wanna learn, maybe saturday when I need to go to SLT, meet me there? got time?

  19. #119
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    Default Re: How to make an external battery pack?

    saturday I shoot wedding leh...

    why need two SPDT switch, 2 normal switch cannot meh? Can draw diagram or not? Simple layman one lah, no symbols one?
    Last edited by TrailsofLife; 27th October 2005 at 01:10 AM.

  20. #120

    Default Re: How to make an external battery pack?

    here

    take a look:


    still need those resistors and diodes.

    for diodes, I cant tell now which type to buy. try to ask the seller which one that's rated 3amp and above.
    Like I've said, without those diodes, both ur LEDs will light up no matter which pack being used
    DPDT is the same as SPDT, just that you've got 6 legs instead of 3
    see how I connect those wirings at the legs. shd be able to understand already rite?

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