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My 9 volt dc regulator project . . .

Discussion in 'General Electronics Discussion' started by Rory Starkweather, Jan 15, 2015.

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  1. Rory Starkweather

    Rory Starkweather

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    Nov 13, 2014
    Is not turning out as I planned.

    I started out with a plain 120 VAC to 12 VAC, 1 A transformer connected across a 1.5 kOhm resistor. Results were just about as you would suspect. 14.8 vdc across the resistor.

    Then the fun began. I tried to put a W02M bridge rectifier Between the transformer input and the resistor. Measuring the voltage across the load resistor, I got 0 vac and 0 vdc. Something about that didn't seem right.

    After 3 days I finally decided that the breadboard was bad, and did some workarounds.

    The next thing I added was a 10 uF cap to ground from the output of the bridge, It popped because I hooked it up backwards. Well, actually I thought I knew where hot and ground were. I was wrong.

    I did notice that it took 20 minutes for the vac to drop from whatever the starting voltage was to 0.5 vac. RC time constant, I guess.

    So I plugged in the first 7809CV between the bridge and the load. It smoked. Hmmm.

    So I put in the second 7809CV. Output is 11.3 vdc with 6 vac riding on it.

    But wait. Isn't this a 9 volt regulator? I've checked it several times and it still says 7809CV.

    Lesson 1. It's hard to build a voltage regulator when all circuit values are unknown.
    Lesson 2. Breadboards don't seem to be appropriate for this kind of experimentation.
     
  2. davenn

    davenn Moderator

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    Sep 5, 2009
    I presume that was supposed to be ... Transformer output ? as in between the secondary and the resistor ?

    show us some photos ... sounds like you are connecting the bridge and other things incorrectly

    BB's are great but NOT for high current ... 1A or more

    Dave
     
    Gryd3 likes this.
  3. Rory Starkweather

    Rory Starkweather

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    Nov 13, 2014
    I don't have the technology to send pictures.

    The transformer is rated at 1 amp. The bridge is rated at 1.05 amps.

    The bridge has a + sign near one of the legs. I assume that is the positive output and the opposing terminal is something like a ground. The transformer is connected to the other two terminals of the bridge that I do not consider to be either + or -

    Is it possible that I may have blown up the bridge again, or the the regulator?
     
  4. Gryd3

    Gryd3

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    Jun 25, 2014
    Anything is possible, but it's hard to tell because we can't see it.
    You can always make your own bridge with discrete diodes.

    In any case, your transformer secondary, should be connected to the input on the bridge which should be marked with a tilde, or 'AC'.
    The + and - markings will indicate the rectified output.

    Connect the ground of the regulator to the negative output of the bridge.
    Connect the input of the regulator to the positive output of the bridge.
    Connect the output of the regulator to your resistor.
    Connect the opposite side of the resistor to the negative output of the bridge.

    You will be missing filtering!
    Connect a capacitor to the positive and negative of the bridge.
    Connect a capacitor to the output of the regulator, and negative of the bridge.

    * The negative of your bridge will be your new COMMON. So any circuit you construct will always have it's ground or common returned here.
    Consider your circuit now. The Primary side of the transformer is isolated from the secondary side.
    DO NOT connect any wires from the secondary side (Bridge and regulator) to the primary side of the circuit.
    Also, DO NOT connect anything after the bridge, to the secondary side of the transformer. Consider these two restrictions.
    Primary High Voltage AC -> Low Voltage AC -> Rectified Pulsed DC + Capacitor as filter + Voltage regulator.
    You do not want to cross these boundaries or you will find your circuit may behave in some unknown ways.
     
  5. davenn

    davenn Moderator

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    Sep 5, 2009
    seriously ?

    You have a mobile phone with a camera ?
    how are you accessing the www ? phone or computer ?

    Dave
     
  6. Rory Starkweather

    Rory Starkweather

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    Nov 13, 2014
    I don't have any phone at all. I don't have any cameras. No TV. I don't have a scanner. I really am a recluse. This is the only way I interact with the outside world. My choice, and I am happy with it.

    The thing that bothers me the most is that I used to be able to pop one of these out per day, but I never tried doing it on a breadboard before. The results were always as expected. I used fahnstock clips on wood bases for them.

    You would think that I had learned something from them, but not so sure anymore. This was supposed to be a one night project. One 12 vdc and one 12 vac wall warts, two 7809s from the same lot, one load resistor. The test was supposed to be filter caps and protection diodes for the 7809 as well as varistors for a little more protection. Maybe 'soft start' although the filter caps might take care of that.

    The point is that I am heading into day 6 and still don't have a clean output from the regulator.

    I am close to throwing this all away, except the transformers, and starting over using Brooklyn style techniques.

    One thing I didn't mention is this power supply is supposed to power several pieces of precision test equipment, like a true 1 VDC generator, a 1 Amp current source, a 1 Hz freq gen.

    Based on the principle that "You don't know what you will get out if you don't know what you are putting in." I really need a 9 volt regulator that actually does what I expect. I have 4 precision power supplies, but what a waste to put them to work on something like this.
     
  7. davenn

    davenn Moderator

    13,802
    1,941
    Sep 5, 2009
    You have to give us something to go on here ... no one likes playing the 20 questions game
    and unless we can see your construction we have no idea what you are doing wrong

    OK draw a pic of your layout in MS paint show how you have connected things onto the BB
    here is a breadboard ... save the image and load it into MSpaint and draw your components onto it
    and then load it back up to here

    BBoard.JPG

    you are probably just not using the board correctly

    Dave
     
  8. Arouse1973

    Arouse1973 Adam

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    Dec 18, 2013
    Do it the old way, get rid of the bread board and just connect the terminals with a bit of solder. Use short wires to connect points.
    Adam
     
    Rory Starkweather likes this.
  9. Rory Starkweather

    Rory Starkweather

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    Nov 13, 2014
    I'm sorry but I am nearly blind. I cannot live in the world that you do,

    I try to compensate by saying things like "Terminal A is connected to Terminal B, single wire link, soldered on both ends."

    If this causes you difficulty, I'm doing the best that I can.
     
  10. Rory Starkweather

    Rory Starkweather

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    Nov 13, 2014
    I've got a perfboard, and soldering iron in hand. :)
     
    Arouse1973 likes this.
  11. Gryd3

    Gryd3

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    Jun 25, 2014
    If you have enough vision to work on electronics, and read from schematics then surely you can draw something in MS Paint.
    There is also a free online service from Digi-key that will allow you to draw schematics : http://www.digikey.ca/schemeit

    It's very difficult for us to visualize how you may have hooked something up, but even more difficult for us to visualize on how you may have hooked something up incorrectly...
    That's why we would like to see something visual from a webcam, cell phone, scanner, or sketched layout.
    Drawings will give us a crystal clear idea of what you want to do, and will let us focus on correcting your circuit, or finding a fault in assembly.
    I would certainly try to get you to invest in a camera of some sort. It could cost anything from $0 for something used, to a couple grand for a High-end digital SLR. At the very least, take a look and consider it. It will help save our time and yours.
     
  12. Rory Starkweather

    Rory Starkweather

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    Nov 13, 2014
    Doesn't work. If I try to start MSPaint. The computer locks up.every time.I'm NOT a big Micketsoft fan.

    So I may be ready for Phase 2 10 x 100 uF and n10 x 3300 uF caps arrived today, with 40 X 1 amp varistors.

    All I need d to now is find a suitable perf Board and trash the new breadboard. As far as I am concerned , if it doesn't work once, it never works again.
     
  13. Rory Starkweather

    Rory Starkweather

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    Nov 13, 2014
    Thank you eating 2/3 of my post, editor.
     
  14. Rory Starkweather

    Rory Starkweather

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    Nov 13, 2014
    This editor is totally fucked up. I don't think I'll be back.
     
    Last edited: Jan 18, 2015
  15. Gryd3

    Gryd3

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    Jun 25, 2014
    That's not a very good outlook to have.
    Perhaps you should take the time to determine why something is broken before calling quits on it. It could be a simple error you are making.
    Regardless of your decision, I won't argue.
     
  16. Rory Starkweather

    Rory Starkweather

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    Nov 13, 2014
    It blew up? It smoked? What is your word for an object that has done both.
     
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