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please help me build a circuit

Discussion in 'General Electronics Discussion' started by cuda65, Nov 5, 2009.

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  1. cuda65

    cuda65

    10
    0
    Oct 17, 2009
    Iam using a radio shack kit model#28-278 . Usins the 1000 ohms inductor & 2 220 resistors & 2 leds. What size capacitor will i need balance to the circuit out ? Iam using a 10 volt dc power source if that makes a diff. I really could use all the help i can get thanks
     
  2. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    And we really need help from you if we are to be able to help you. You make as much sense here as in your other post on the same subject, but at least here you provide one more clue. So I searched the net for that kit, and found it contains 75 projects. You do have the 98-page owners manual? Which of the circuits are you referring to (page #)? Or please provide a link to what you are trying to do.
    (And inductors are not measured in ohms, although they do have a resistance.)
     
  3. cuda65

    cuda65

    10
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    Oct 17, 2009
    ok it is not in manual, henrys kit has it in ohm,s when capactor discharges it charges the inductor cut power the magnetic field collapes & reverses polarity & charges the capactor backinforth the resistors are for the LEDs & the LEDs show the current flow backinforth thanks & i said i was new at this
     
  4. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    Well, that's ok, but we'll still need detailed information, like a picture of the inductor, or a real detailed description of it. A 1000 "ohms" inductor could be anything. It's like telling someone to come see you in Toronto, Mexico.
    Yes, I guessed the operation in your other thread and stated you'd probably need a rather large capacitor - but got no more leads to go on from you. I'm forced to play PI here, don't be so tight on the information..
    So you say Henry's kit, that's a clue - what more?
     
  5. cuda65

    cuda65

    10
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    Oct 17, 2009
    if you could see this kit you would see the inductor is built in and a spring connector on each end labled 1000 ohms the capactor has to balance the inductor & support the resistors & LED's this all i can tell you iam doing the best i can idont what else to tell you if i cant find this out i will fail the class
     
  6. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    If it's labeled Ohms then it's not likely to be an inductor. Does it look different from the other resistors you have there? The Radio Shack kit you refer to has no such inductor.
    So the henry kit has no name? And no clue as to where the "inductor" came from, what shape it has or how big and heavy it is?
    Do you have any idea what frequency you want this thing to oscillate with? Do you need to see each cycle or just the decay?
    Anyway, Googling brings up a couple of links you might find useful.
    Here's some tank theory:
    http://www.allaboutcircuits.com/vol_6/chpt_4/15.html
    Here's a calculator:
    http://chemandy.com/calculators/tank_resonance_calculator.htm
    If the "inductor" should happen to be 1000mH then a 1000uF capacitor will give it a resonant frequency of 5Hz. Each cycle back & forth should then be visible on the LED's.
     
  7. cuda65

    cuda65

    10
    0
    Oct 17, 2009
    maybe another ball game i looked it up in the manual and its a transformer it consists of two coils of wire wound around a form made from thin plates of iron a signal flowing through one coil is induced into the second coil circuts that cannot connected directly to the speaker (built inthe kit) because of their low resistance are connected to the speaker through transformer inductor and decay will work just see them blink will be better more balanced now their is another one on the kit that is a 8 ohm transformer but i dont know if it would get the job done
     
    Last edited: Nov 6, 2009
  8. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    Ok, I see, it's a transformer, labeled 1000 ohms on one side and 8 ohms on the other side. The high-impedance side of it can have a significant inductance if the speaker is not connected to the other side. Exactly how much inductance is hard to say without measuring it.
    One problem to keep in mind is that small transformers have a limited low-frequency response, so it may go into saturation at the frequencies you are aiming for, giving poor response on the LED's. It migh work better with a higher frequency.
    So just hook up any capacitor you can get your hands on and try it out. But if you do want it to swing at a few Hz I figure you'll need at least 4700uF.
     
  9. cuda65

    cuda65

    10
    0
    Oct 17, 2009
    they are 2 diff. transformers, if you look at the tank circuit at allaboutcircuits.com just add the LEDs & resistors my ? is will the 1000 ohm transformer work as the inductor if so what cap will balance the circuit where to put the LEDs & resistors & what polarity 470 is the bigges cap i have
     
    Last edited: Nov 7, 2009
  10. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    Did you obtain an extra transformer? The kit has only one. A transformer by definition has at least two windings, and this one has one winding intended for 1000 ohms and one intended for 8 ohms impedance. The 8 ohm winding needs to stay disconnected from the speaker during the experiment or else the oscillations will decay rapily. The 1000 ohm side of it will then behave as any other inductor.
    If you want a cap to balance a coil then you also have to specify the frequency it is to be balanced at. A tank circuit will by definition oscillate (& be balanced) at the frequency its component values decide. So, any values you put in there will be balanced all by itself by the nature of the thing.
    You can insert the LED's at any place in the circuit, but if you do it in the Rstray position it will represent the current.
    I guess you already know the LED's are to be connected in anti-parallell (both pins together but with the LED's in opposite directions) and that you only need one resistor in series with them.
    The polarity of the cap will not matter in this case since the applied voltage will be so short. An electrolytic cap will take some time to be damaged by AC or reverse polarity. The voltage rating of it also matters. It will stand reverse polarity up to 10% of it's normal rating indefinitely.
    Just try the 470uF one, and the 1uF too. If you connect the speaker to the 8 ohm side it will make a sound with the self-resonant frequency of the circuit each time you "ping" it. If it decays too rapidly to hear you can put a resistor in series with the speaker to reduce the damping effect it has on the tank circuit.
     
  11. cuda65

    cuda65

    10
    0
    Oct 17, 2009
    did u look at the web site u told me about all about circuits (tank circuit) using my 1000 ohm transformer instead of that 1 where 2 put the LEDs & resistors 2 make it work right & do u know how much resistance the diff color have i know it will not be much but i will need 2 know total resistance of total circuit
     
  12. Resqueline

    Resqueline

    2,848
    2
    Jul 31, 2009
    I was referring to that page when I told you where to put the LED's. 220 ohms like you suggested should be fine.
    Why don't you just try it out and experiment a little? That's what the kit is meant for. This is not exactly rocket science that will blow up in your face if you do it a little wrong. Sometimes all data neccessary to make "perfect" calculations are simply not available, and then one just have to use the "cut & try" method.
    If you want to know the total resistance of the circuit you'll have to buy yourself measuring instruments, "no-one" knows the resistance of that transformer.
    It's also "impossible" to define the resistance of LED's as they are non-linear devices.
    Also, "no-one" knows if you'll actually be able to make the LED's light at all with the parts available, you'll just have to try it different ways and see. Seeing how it works also makes estimates & calculations easier afterwards.
     
  13. cuda65

    cuda65

    10
    0
    Oct 17, 2009
    thanks for all the info.
     
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