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AC Home Power Supply for Hobbyist/Small Projects

  1. May 9, 2013 #1
    Hello all! If you're reading this thread then thank you for taking the time to read and/or reply! I appreciate it!:biggrin::biggrin::biggrin:

    Onto the guts of the thread. Here I will list what I am trying to do, the associated questions that I have found reasonable to ask, and then any additional details I will note below.

    My goal is to make a power supply for my small electronics projects which are mainly for experimentation (e.g. circuit testing/analysis, small LED emitter/receiver circuits, etc.). Almost 95% of the time I am using Lantern Batteries (6V) or a 9V battery to power my breadboard for my small circuits. My next go is using my new oscilloscope (being shipped currently) and also my new LC meter to test some inductor/capacitor circuits and testing other wave forms. Obviously you can't have induction if you don't have AC supplying the juice to the coils. I also do a lot of experiments/projects for my family using electromagnets, which if were supplied with AC would eliminate the need for enameled copper wire eXacto knife scrapping.

    Some questions that I have wanted to ask and get answered since taking up this idea, is what is a relatable voltage in AC for what I am using currently (my DC batteries)? I would like to know because I am often touching my components and replacing parts, and I will always use a voltage appropriate for my environment, which is my wife & children. So with safety in mind I never use anything that will cause harm if one was to come into contact with the circuitry. I also power things that require very little amperage, such as LEDs, microcontrollers, DC motors etc. Basically what I want to know is what do I have to step down mains power (110VAC @ 60Hz) from my wall to a lower VAC, so that it is comparable to my 6VDC 20mA - 70mA draw?

    My circuit so far is rather simple, use a power cord to connect to my power outlet, which will be supplying a step-down transformer, which I will then have powering my breadboard at some reasonable voltage. I would like to integrate a fuse perhaps for safety, and I would like to keep the voltage stable and constant, so surgers don't kill my circuits.

    Any and ALL feedback is appreciated & welcomed. Thank you again for taking your time to read this thread! :biggrin:
     
    Last edited by a moderator: May 9, 2013
  2. jcsd
  3. May 9, 2013 #2
    OK, i think you need a signal generator, which is an electronics lab component that can generate an alternate voltage, usually you can choose between different forms like triangle wave, square wave, sinusoidal wave, you can adjust the duty cycle and add a dc offset, eand obviously change the frequency of the signal.

    Since the signal generator doesn't have sometimes an lcd showing graphically the signal you are generating, you can connect the output of the signal generator to your oscilloscope channel to view graphically the signal you are generating.

    Usually the signal you are generating has an amplitude <20Vpp .

    Just think that a basic electronics lab usually have :
    -An oscilloscope (to view voltages, current etc... is a very versatile instrument since even physicist use it)
    -A variable DC power source (to supply a dc voltage/current you can select the magnitude of the voltage/current from it.)
    -A multimeter, to get measurements
    -A soldering station
    -A signal generator (to generate a customized ac signal)

    And anyway if you want to make an ac generator yourself stabilized to for example 5V, from the 110VAC you must buy a transformer. You just go to an electronics shop and ask for a trasformer from 110VAC to 5VAC...

    I hope it could be useful.
     
  4. May 9, 2013 #3
    If you want to replace your batteries, you need a DC power supply. An AC power supply won't replace batteries.
    Your best replacement for batteries is probably a wall power supply.
    Wall power supplies (sometimes called a wall wart) are available from these and other sources:
    DigiKey, Search for Wall wart then AC/DC....
    Mouser Electronics, Search for Wall power supply.
    Good Luck
     
  5. May 9, 2013 #4
    I think he doesn't want really to substitute his batteries but i think he wants an analogous thing in AC , i mean a small active AC device...
     
  6. May 9, 2013 #5

    Danger

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    That's the impression that I got as well. Can he safely just remove the rectification circuitry from a wall wart to leave an AC output?
     
  7. May 9, 2013 #6

    Integral

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    Why not just get a step down transformer. Lots of old electronics have them.

    But you must know that you will not be able to use this as a SUBSTITUTE for batteries. It is not simply a matter of getting a similar current draw. Most active electronics components will only work correctly when you apply the correct DC voltage.

    Also not clear why you think:
    You will still need insulation on your wires and need to scrape the ends to make a connection.
     
  8. May 9, 2013 #7

    jim hardy

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    Carl suggested wall-wart supplies.

    th?id=H.4507448942133664&w=103&h=103&c=8&pid=3.1&qlt=90.jpg


    They're in every thrift shop. Read the fine print on them to see what they deliver.

    You'll find plenty of cell phone chargers in the range of 3 to 6 volts DC.
    You'll find plenty of 9 and 12 volt DC ones for various electronic radios and video games.
    You'll find plenty of 30 volt DC ones for home printers.
    You'll find battery chargers , be aware some of them put out unfiltered full wave rectified DC.
    You'll find some that put out low AC volts.
    They should cost you no more than a dollar or two apiece.
    Hobbyist electronics sites carry them as well.
    Some wall warts have internal regulators, some do not. You find out by testing them.
    If you want regulation on your board look into LM7900 series of regulators.


    Be aware it's not a precise transformation.
    It depends on how near the capacity of your transformer you are operating, and on your filtering.
    VDC = approximately Vac X √2 - 1.2
    5 volts AC when rectified and filtered will be in vicinity of 6 volts.
    7.2 volts AC when rectified and filtered will be in vicinity of 9 volts.
    Typically one makes a little more DC voltage than he needs and regulates it.

    Here is a tutorial on power supplies..
    http://www.ti.com/lit/an/snva006b/snva006b.pdf
     
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