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Yes-Circuit: Misunderstood or malfunction

Ed8ElectronicDe

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Hi, I am a Newbie here and concerning electronics!

I think I have understood some basic principles, concerning volt/ohm./amp.,
and I am learning from a lab kit, with described experiments..

Since this kit is out of date, I think, I am allowed to post it here,
concerning only my question.
Why doesn't this work out, as described? "Push button, led alights, and remains lighted.."

In the circuit I have built from the instructions, the LED goes out, after releasing the button. Only lights up during pressing the button.

Resistor Values are: R1=1kOhm, R2=33kOhm, R3=220kOhm, R4=100kOhm, R5=5,6kOhm, R6=470 Ohm, Transistors: npn BC 546B
Battery: 9V, red cable (technical plus)

circuit_plan_66.jpg

this is what I've plugged together according to the instruction:

circuit_built_66.jpg

Thanks kindly, for helping out...
(I am from Germany, so language corrections might also be helpful)

Daniel :p
 

betwixt

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Your language skills are perfect!

From what I can see, you have built it correctly and the values look good.

If pressing the button makes the LED light up it means T1 is working. What should happen is T2 should stop conducting and instead of the button providing base current to T1 through R1, it comes from R4 and R5 instead.

So something is wrong around T2. Can you swap it with T1 in case the transistor itself is faulty. Do you have a test meter?

Brian.
 

Ed8ElectronicDe

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Your language skills are perfect!

From what I can see, you have built it correctly and the values look good.

If pressing the button makes the LED light up it means T1 is working. What should happen is T2 should stop conducting and instead of the button providing base current to T1 through R1, it comes from R4 and R5 instead.

So something is wrong around T2. Can you swap it with T1 in case the transistor itself is faulty. Do you have a test meter?

Brian.
Hello, Brian! At the moment I do not have a test meter, yet. But I have got a lot more electronic components, like resistors,
transistors, selled and shipped by an ebay-member. And I can also do some math, on this, if you have a suggestion for finding out, what is wrong on T2.

Thanks. :)

- - - Updated - - -

So something is wrong around T2.
I tried this out, marking T2 with a "hat", and distinguishing T1 "works", and both T1 and T2 "work",
"work" meaning "LED lights up".

So I made six photos with my smartphone:

T1 working positions: rotated 90°/180° counter-clockwise
T1working.jpg T1working_2.jpg

T2 not working positions: rotated 90°( photo missing, cause upload limit) ,180° counter-clockwise
T2notworking.jpg

T1 and T2 working positions: rotated 0°/270°
T1andT2working_2.jpg
T1andT2working.jpg

Perhaps this is helpful to an electronic wise man... :cool:
 

Audioguru

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We cannot see your schematic clearly.
The transistors have no part number so how do we know which wire is emitter, base and collector? A European transistor wires are CBE, an American transistor wires are EBC and an Oriental transistor sometimes has the C wire in the middle.
 

betwixt

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Be careful, transistors can be damaged by swapping their connections over and they will only work when wired correctly.

What Audioguru said is quite right, did these transistors come pre-wired on the little circuit boards or did you mount them yourself?

The plastic package is called TO-92 (Transistor Outline number 92) but different manufacturers bring the wires out in different ways. Some are three wires in a row, some have the middle wire offset to make a triangle and the E,B and C can come out in a different order. It may be that the E B and C marked on the circuit boards does not tie up with the actual pins on the transistor. Working out which pin in which needs either a transistor tester or at the very least a test meter. It would be a worthwhile investment to get one, even a very cheap one is better than nothing.

Brian.
 

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