Adjustable Voltage Power Supply

Discussion in 'The Projects Forum' started by megawatts, Jan 13, 2009.

  1. megawatts

    Thread Starter Active Member

    Dec 24, 2008
    35
    0
    SgtWookie,

    The above kit you recommended to me for AC/DC conversion and output control arrived in the mail today. One problem I see at the moment is the output power socket that is supplied. This part will probably need to be soldered in place on the PCB, but will I have to use it in connecting two wires from one of the 2 pole edge connector blocks?

    Shouldn't I be able to run two wires, a -& a +, from the regulator output block to the -&+ on the timer board blocks, thereby not using the output jack on the regulator card? This jack looks something like what one would use when plugging in a wall charger or phone power jack.

    There will no doubt be other questions? Hope I have made these questions intelligible.

    Roland :confused:
     
  2. bertus

    Administrator

    Apr 5, 2008
    15,649
    2,348
    Hello,

    So you have made the K68 regulated power supply board.

    [​IMG]

    The input voltage comes from the transformer (12 Volts, as far as i remember).
    The output can be taken accros the output capacitor C4.
    You may use a couple of leads (red and black) connected at the output, if you do not want to use the terminals.

    Greetings,
    Bertus
     
  3. megawatts

    Thread Starter Active Member

    Dec 24, 2008
    35
    0
    Well, not exactly. I just purchased the kit and got it today's mail. The assembly comes next.
    Yes, I am using a railroad transformer which has primary and secondary posts with the secondary capable us have different voltage ratings.
    So, the socket shown in the drawing/schematic can be soldered, but not in fact used?

    Thanks for the quick response bertus
     
  4. bertus

    Administrator

    Apr 5, 2008
    15,649
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    Hello,

    The input socket is for easy plugging and unplugging.
    If you want to have a permanent connection this can be omitted.

    Greetings,
    Bertus
     
  5. megawatts

    Thread Starter Active Member

    Dec 24, 2008
    35
    0
    Bertus,

    Ah thanks, yes I want to make a permanent connection with most of the wiring as possible.
    Another question; Cap. C3 has a large down arrow with what appears to me a minus sign pointing towards the two leads, is the minus sign denoting negative? This shows the installer the correct polarity? I think this might be straightforward enough.

    Standby for more,
    Roland :)
     
  6. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Yes, it's a polarity mark. The leg nearest the arrow is negative.
     
  7. bertus

    Administrator

    Apr 5, 2008
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  8. megawatts

    Thread Starter Active Member

    Dec 24, 2008
    35
    0
    Ok, that was my first thought. Now, how about the tiny resistors. I know the colored rings are used to figure resistance or size of the resistor, but not sure about determing the polarity of each end. Is this something that is determined by using a digital voltmeter?

    I am doing just what the instructions say; look over and verify and check the pieces supplied in the kit. Familiarize yourself with each part.
    Next, I will be setting up a work space for the assembling portion of this project.

    Oh, is there polarity for the tiniest of caps? There seems to be one of the little tan colored ones here, C1, I believe.

    Thanks
     
  9. megawatts

    Thread Starter Active Member

    Dec 24, 2008
    35
    0
    Bertus,
    You must have replied while I was typing. I'll check out your suggestions now.
    Thanks again,
    Roland
     
  10. megawatts

    Thread Starter Active Member

    Dec 24, 2008
    35
    0
    Bertus,

    Just scanned over three links you referred to me. Thanks for the homework assignment, this will be good reading.

    Roland
     
  11. bertus

    Administrator

    Apr 5, 2008
    15,649
    2,348
    Hello,

    The .1uF (C2) has no polarity.
    Resistors also do not have a polarity.
    The diodes (D1 and D2) do have a polarity, the stripe or ring on the diode is the bar part of the diode symbol.
    The potentiometer has three connections, the two outer pins are the full potentiometer, the middle pin is the wiper (the arrow in the drawing).

    Greetings,
    Bertus
     
  12. megawatts

    Thread Starter Active Member

    Dec 24, 2008
    35
    0
    Bertus and beenthere,
    Thank you both for your help and guidance. I still have a lot of reading left, but am getting things pieced together. This should be a great project; I'll keep you advised.

    Roland :)
     
  13. megawatts

    Thread Starter Active Member

    Dec 24, 2008
    35
    0
    Bertus or beenthere,

    The instruction sheet supplied advises that IC1 is an LM317 which can draw up to 1.5A. If you need higher, then use an LM338T rated at 5A.
    Here's my question: my 3 color electronic timer card from the manufacturer declares the output from the card is 50W or 4A continous; should I substitute the LM 338T before assembly?

    Thanks,

    Roland
     
  14. bertus

    Administrator

    Apr 5, 2008
    15,649
    2,348
    Hello,

    Can the transformer you are giong to use handle the current ?
    If you want to draw more that 1.5 A the LM338 would be more suitable.
    It is also wise to enlarge C1 from 1000 uF to 4700 uf minimal.
    (10000 uf would probably work more stable).

    Greetings,
    Bertus
     
  15. megawatts

    Thread Starter Active Member

    Dec 24, 2008
    35
    0
    Bertus,
    Yes, I feel the transformer in question is capable of handling the needed current. Is there a way to test the transformer to see if I am correct?
     
  16. Bear_2759

    Active Member

    May 23, 2008
    120
    0
    Hi Megawatts,

    if it is an "off the shelf" transformer then there should be a label with all the info you need with input/output.

    it will have something like this (this is from my Nokia phone charger)

    input: 240VAC/50Hz/21mA/5VA
    output: 3.7VDC/355mA/1.3VA

    I'm in Aus so our mains supply is 240VAC, yours will be 110VAC, I think. also AC might be represented by "~" and DC might be represented by something that looks like an "=".

    the important parts you need is the output, with this example it would be 355mA. your's would be 1.5A or higher as the original circuit was meant to supply up to this current.

    hope this helps.
     
  17. megawatts

    Thread Starter Active Member

    Dec 24, 2008
    35
    0
    Bear,
    If you will refer to page 7 of this "the projects forum" you will see my first thread dealing with the transformer issue was discussed. This transformer is an industrial piece of equipment and not you typical "off the shelf" variety; I wish it were.

    Thanks for your reply and comments; I am going to put this project on hold for the time being and seek another option.

    For a side note, I had the privilege to visit Sydney, along with my fellow shipmates, back in the first week of August in 1970. We spent 5 wonderful days in Australia and then on to Auckland, New Zealand for 3 days before returning to the States. It was a first time visit for practically the whole crew.

    Thanks again :)
     
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