Connect with us

New to electronics.

Discussion in 'Electronic Basics' started by anon, May 14, 2005.

Scroll to continue with content
  1. anon

    anon Guest

    Hi to all

    I'm just getting into electronics as a hobby because i've had to retire from
    work due to illness and thought i could do with something interesting to pass
    the time.

    I've decided to try my hand at some "breadboarding" to start me off.

    I saw a link for http://www.doctronics.co.uk/index.htm in one of these
    electronics newsgroups, so i had a look to find out if the website would be of
    any use to me.

    I noticed a project for a games timer which i thought i'd try my hand at. I sent
    off for the components, complete with instructions, and bought myself a couple
    of breadboards and some other bits and pieces to start me off.

    On ebay, i saw a new (and fairly cheap), bench top power supply which i thought
    would be better than having to keep buying batteries for the various projects
    that i would be undertaking.
    It is switchable between 3, 4.5, 6, 7.5, 9 and 12volts dc. The current rating is
    1500ma max.

    I was just wondering, as i'm new to electronics. Would the current of 1500ma
    max, be flowing whatever the voltage might be (ie: 3, 4.5, 6, 7.5, 9 or 12volts
    dc) - or would the current flow be dependent on the components being used in the
    circuit, upto a maximum of 1500ma using the above power supply ?.


    Thanks in advance for any help with this question.


    hermit50
     
  2. Tom Biasi

    Tom Biasi Guest

    The 1500 mA is the maximum rating of the supply. This means that no matter
    how you use the outputs the total current draw should not exceed 1500 mA.
    To better understand this do a search for E=IR, or Ohm's law. Learn the
    relationship between voltage, current, and resistance well.
    Good luck,
    Tom
     
  3. Hi,

    1500mA is the maximum that the power supply is capable of providing. The actual
    current drawn will depend on the circuit connected to it and the voltage you
    choose to supply it with. It is simply Ohm's Law which states (in the form you
    need) that the current taken will be equal to the voltage divided by the load
    resistance. The load resistance is that which the circuit presents to the power
    supply.

    Now this load resistance will vary widely from circuit to circuit but it is
    fairly safe to assume you will only need a small handful of mAs for that project
    and so have plenty of headroom. I suggest you spend just a little more money and
    buy a digital multimeter which will have a DC current range, so that you can
    monitor it and learn some basic theory in the process. They usually cost just a
    few dollars for a perfectly useable device and these days can even be found in
    supermarkets.


    Cheers - Joe
     
  4. Lord Garth

    Lord Garth Guest

    Look for a 5 volt regulated supply too.
     
  5. hermit50

    hermit50 Guest

    Hi again

    Thank you all for the replies answering my question.

    I have bought myself a digital multimeter, (i did already have an old analog
    one).
    I've also got a copy of Ohm's Law which i am currently (no pun intended)
    absorbing.

    Current = Voltage / Resistance. (I = E / R).

    Resistance = Voltage / Current. (R = E / I).

    Voltage = Current x Resistance. (E = I x R).

    Power = Voltage x Current. (P = E x I).


    I recently acquired a secondhand 20MHz Hameg 203-4 dual trace oscilloscope,
    including x1 / x10 probes and manual, which will come in handy at some point
    along the way in my new hobby.

    I expect i will be back on this newsgroup to ask other important questions in
    the (near) future but, for now, i'm off to do some more reading on this
    facinating subject - i think i'm getting hooked.


    Thanks again all


    hermit50
     
  6. Dwayne

    Dwayne Guest

    Others have answered your question. I will suggest four circuit concepts
    that should help get you started with DC circuits.

    (1) Ohms law:

    V=I*R

    Voltage (measured in Volts) is the product of current (Amperes or Amps for
    short) and resistance (Ohms). The important thing to realise is that you
    need a change in voltage to get a current to flow. The equation should
    actually read:

    V2-V1=I*R

    Think of a garden hose, if there is no difference in pressure between the
    water in the pipe and the air in the atmosphere then you would be hard
    pressed to water your plants.


    (2) Power

    P=V*I

    Power (in Watts) is the product of voltage and current. Ohms law can be
    inserted into the power equation to obtain equivalent statements namely;

    P=V^2/R
    P=I^2*R

    Also power supplied to a circuit will be absorbed by a circuit. If you apply
    too much power to a component it will smoke and fail. A resistor for example
    will have a value of resistance say 100 Ohms and value for power say 0.25
    Watts.

    P= V^2/R
    0.25=V^2/100
    V^2=100*0.25
    V^2=25
    V=5 Volts

    V=I*R
    I=V/R
    I=5/100
    I=0.05 Amps
    or
    I=50 mA

    So if you apply 5 Volts across (ie: V2-V1) a 100 Ohm resistor you will need
    to suppy 50 mA (milliamperes) of current.


    (3) Kirchoff Voltage Rule

    The sum of the voltages around any closed loop must equal zero. This is
    based on the assumption that your supply can produce enough current for your
    load/circuit. If not then your supply will only apply enough voltage to
    satisfy the maximum current.


    (4) Kirchoff Current Rule

    The [sum of the] current into a node (junction) must equal the [sum of the]
    current leaving the node.


    I hope this helps,

    Dwayne
     
  7. Charles Jean

    Charles Jean Guest


    Here's my list:

    Breadboard-hookup wire-wire cutters-wire stripper

    Digital VOM-cheap one-let's you measure the 3 variables in Ohm's
    Law-volts, ohms, amps. Gotta know Ohms law. The cornerstone of the
    electronics building.

    Good NiMH battery charger with AA size NiMH batteries. I use a Power
    Port Model BC-101-U. Individually charges up to 4 AA or AAA batteries
    at one time, based on deltaV/deltaT. Batteries can also be used for
    all the other battery-powered things around the house.

    Battery holders for the above. 1/2/3/4 battery capacities available.
    Lets you experiment with various voltages and power your early
    breadboard projects. 99% of your first efforts can be handled with
    either 5 volts(4 AA batteries, 4.8-5.2 volts, depending on charge
    state) or a 9 volt alkaline.

    A sprinkling of 1/2 watt resistors, spanning the range of 10 ohms to
    10 megohms. ~$0.05 ea.

    Various-colored LEDs. ~$0.05 ea.

    This will give you enough to learn about Ohms law, the correct way to
    wire in some LEDs and figure the resistor required for it to work
    without letting the magic smoke out, etc. Besides Ohms law, read
    about how to figure DC power. Later, you'll want to read about
    building your own power supply using a "wall wort", couple of
    capactitors and a 7805 voltage regulator chip.

    Welcome to the fray.

    Cheers!
    Charlie
     
  8. hermit50

    hermit50 Guest

    Hi Charlie

    Thanks for the reply.

    I've already got most of the items you listed above:

    Breadboard & hookup wire
    Digital VOM
    Various battery holders & connectors
    Various coloured LEDs
    Various types & sizes of Resistors, Diodes, Zener Diodes & Capacitors
    Various sizes of DIL Sockets
    Various transistors.

    I've also got a copy of Ohm's Law, i did a search on google & found a copy of
    "Kirchoff's Laws" as mentioned by Dwayne in a previous post.

    Now it's down to some experimenting with some circuits.
    The first of which is going to be a "games timer" as described on the following
    website:
    http://www.doctronics.co.uk/kits.htm#games


    Thaks again

    hermit50
     
  9. Charles Jean

    Charles Jean Guest


    Looks like an ambitious "first" project. The Dontronics kits are very
    good, and instructions are detailed, and theory well explained. With
    a kit like this you will be dealing with low frequencies, so you can
    "see" the pulses by using an LED and measure them with a stopwatch.
    When you get to frequencies much higher than 2-3 cps, though, this
    becomes pretty hard to do with just an LED. Then you're going to need
    either a frequency counter or an oscilloscope. The oscilloscope is
    more flexible. You can find used ones on EBay and the like.
    "There are known knowns. These are things that we know we know.
    There are known unknowns. That is to say, there are some
    things that we know we don't know. But there are also unknown
    unknowns. These are things we don't know we don't know."
    -Secretary of Defense Donald Rumsfeld
     
  10. hermit50

    hermit50 Guest

    Hi Charles

    I thought the Doctronics project would be a good starting point for me to get
    into breadboarding, and electronics.

    I recently bought a secondhand 20MHz Hameg 203-4 dual trace oscilloscope,
    including x1 / x10 probes and manual - which i got on ebay.

    I think it will come in handy with the projects.



    --
    hermit50

    /^\_/^\_/^\_/^\_/^\_/^\_/^\_/^\_/^\_/^\_/^\_/^\_/^\_/^\
    http://www.hermit50.pwp.blueyonder.co.uk
    ***************************************************
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-