# Confusing Circuit- How Can this Be?

Discussion in 'General Electronics Chat' started by Grandmasterpeg, Nov 30, 2005.

1. ### Grandmasterpeg Thread Starter New Member

Nov 30, 2005
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So my teacher was showing us this circuit he made in class today, and he wont tell us how it works. This is the picture of the circuit:
http://img517.imageshack.us/img517/7576/trickcircuit1tb.jpg

Its an AC circuit, one wire going through two switches, and then two light bulbs. He showed us, with both switches closed, both lights went on, as normal. Then he opened both switches, and neither light bulb lit up, as expected. Next he opened the right switch, and closed the left, the left light bulb went on, but not the right. How was this possible?? This also worked vise versa. He wont tell us what he put in the circuit to do this. Does anyone know how the circuit was able to do this, is it a trick? ( I thought it might have something to do with the light bulbs, since both were frosted and you couldnt see inside them, also he wouldnt let us touch the circuit after he demonstrated). He did say there was something that we couldnt see that was important. What was it?

Sep 20, 2005
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3. ### Grandmasterpeg Thread Starter New Member

Nov 30, 2005
7
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Hey, im trying to understand this, I don't see how the diode in switch one effects anything other than making it avoid the switch altogether. Also When you open switch 1 and close switch 2, how does that enable for bulb 2 to go on but not bulb 1?

4. ### kurios Member

Sep 29, 2005
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but wait a minute the circuit that big master has shown in his preview is different from that of kubeek u know the bulbs in bigmaster's circuit are connected in series while in the shematic diagram that the kubeek has shown the bulbs are in parallel.
well according to me there would be a game of capacitor that is charged while one switch is closed and is discharged while other switch is open i will show u the circuit diagram in future.

5. ### Grandmasterpeg Thread Starter New Member

Nov 30, 2005
7
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By future I hope you mean, by tommorow morning Unfortunately the secret will be revealed tommorow afternoon, unless I can figure it out before, I actually made a simpler solution, tell me what you think...
http://img400.imageshack.us/img400/8805/circuit0bl.jpg

Benefits will be given to the person to figure this out before it is revealed

6. ### p3flyguy New Member

Nov 30, 2005
5
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Consider the above diagram, but put the lights in series. Parallel branch diodes off each lightbulb so that it looks just like the switches, but with light bulbs.

Then when you close one switch, the positive half flows through and around to the light bulbs. it will continue through one diode since this is seen as a "short" and not through that bulb. When it gets to the other diode, it sees an "open" and flows through the bulb instead lighting it up. A similar situation for the other switch, and with both switches closed, they both light for their respective halves of the input sine wave, but since the device runs at 60 cycles per sec, you do not see the flash. Only lit bulbs.

Does that make sense?

Nov 30, 2005
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8. ### p3flyguy New Member

Nov 30, 2005
5
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yes and here is the flow if i can figure out how to add the pic

9. ### p3flyguy New Member

Nov 30, 2005
5
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yes and here is the flow if i can figure out how to add the pic

10. ### p3flyguy New Member

Nov 30, 2005
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[attachmentid=994]

11. ### p3flyguy New Member

Nov 30, 2005
5
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sorry about the bad graphics. I hope you can see the flow in red

12. ### Grandmasterpeg Thread Starter New Member

Nov 30, 2005
7
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sorry, you misunderstood. This is showing the right bulb (the circuit is turned the other way, bulbs on top)... the right bulb lit up with both switches open... In the circuit im talking about when the right switch is closed (which is the left switch in your picture) and the left switch opened, the right bulb is lit, left bulb is not lit, and when the left switch is closed, right switch opened, the left bulb is on, not the right.

13. ### kubeek AAC Fanatic!

Sep 20, 2005
4,670
804
the right switch is closed, look at it more careful.

When you swap either the diodes on bulbs or the diodes on switches, the lit bulb will swap too (L/R).

14. ### Grandmasterpeg Thread Starter New Member

Nov 30, 2005
7
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but the diagram is showing when both switches are open, the right bulb is lit.... this is not what happens. When both switches are open, no light bulbs are lit.

Nov 30, 2005
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Jan 22, 2004
1,437
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hi

bingo B)

17. ### kubeek AAC Fanatic!

Sep 20, 2005
4,670
804
isn´t it the same circuit as in post #10? (except swapped diodes on bulbs)
notice there is written "close" above the right switch.