How does this circuit works?

Thread Starter

praveenmax

Joined Apr 26, 2016
14
Hello All,
I got this small circuit out of a toy lamp. It basically has a LED with an pot core i guess. Please check the image below.
circuit_topview.jpg

Another view:
circuit_sideview.jpg

As per my observation,
When Power ON : The LED lights up . But after 1 second, the pot core deflects any nearby metal pieces. ANd it happens for every 1 second.

My Doubt: Since there is no uC, how the pot core is triggered to magnetize for every 1 second.

Thank you.
 

KeithWalker

Joined Jul 10, 2017
1,789
There must be more than what you are showing us to create the 1 second pulses. What is on the other end of the yellow and white wires? Are there any components oh the back of the circuit board?
 

AlbertHall

Joined Jun 4, 2014
11,318
Did the coil have a magnet above it on some kind of string, like a pendulum?
In that case the movement of the magnet would induce a voltage in the coil and perhaps trigger the transistor to conduct briefly and repel the magnet until it swings back again.
 

Thread Starter

praveenmax

Joined Apr 26, 2016
14
Did the coil have a magnet above it on some kind of string, like a pendulum?
In that case the movement of the magnet would induce a voltage in the coil and perhaps trigger the transistor to conduct briefly and repel the magnet until it swings back again.
It seems like that only :). But i cant understand how it happens so precisely .
 

Yaakov

Joined Jan 27, 2019
3,190
It seems like that only :). But i cant understand how it happens so precisely .
What do you mean by "deflects any nearby metal pieces"?

The normal operation depends on the time constant of the pendulum. If you were to hang a little magnet from a long string above the coil, the time constant would depend on the string length.
 
Last edited:

SamR

Joined Mar 19, 2019
3,425
What is triggering the transistor without a capacitor? Or is that not a transistor turning the coil on and off? Yes, it is faux flickering candle. Never saw one before like that. Most use a more modern flickering LED. A piece of metal on the bottom of the plastic flame blade. Coil turns on and off displacing the metal on the end of the flame blade. Blade is supported by an axle through near its center of gravity to rotate on. Flickering effect caused by the changing angle of light from the LED reflected off the wiggling blade.
 
Last edited:

Yaakov

Joined Jan 27, 2019
3,190
What is triggering the transistor without a capacitor? Or is that not a transistor turning the coil on and off? Yes, it is faux flickering candle. Never saw one before like that. Most use a more modern flickering LED.
It‘s the same circuit as the ”perpetual motion machine” desk toy. When the magnet passes the coil it induces a current which turns the transistor on powering the coil, which kicks the magnet. If it’s a simple pendulum, it will keep very accurate intervals.
 

AlbertHall

Joined Jun 4, 2014
11,318
Hello All,
I got this small circuit out of a toy lamp. It basically has a LED with an pot core i guess. Please check the image below.
View attachment 239918

Another view:
View attachment 239919

As per my observation,
When Power ON : The LED lights up . But after 1 second, the pot core deflects any nearby metal pieces. ANd it happens for every 1 second.

My Doubt: Since there is no uC, how the pot core is triggered to magnetize for every 1 second.

Thank you.
Can you read any numbers/letters on the transistor?
 

SamR

Joined Mar 19, 2019
3,425
Interesting simple circuit! I was wondering if the coil charge and collapse might somehow drive the transistor switching. Interesting and novel concept (to me at least). So that would be a magnet on the end of the blade and not just a piece of iron.
 

Yaakov

Joined Jan 27, 2019
3,190
Interesting simple circuit! I was wondering if the coil charge and collapse might somehow drive the transistor switching. Interesting and novel concept (to me at least).
They are fun. Not too hard to build and properly packaged, very “mysterious”. They can also be in a rotary configuration.
 

Yaakov

Joined Jan 27, 2019
3,190
It’s a variant of a Kundo clock.

hi Sam
I would say its a variant on the Esaki osc, using that Inductor and reverse breakdown.

E
It could be. Since it is a candle it might move only periodically. Looking carefully I don’t see the expected sense winding of a Kundo pendulum.

1622369256296.gif
 

SamR

Joined Mar 19, 2019
3,425
That's why I asked as to what was in the middle of the coil that I saw. The sketch I found just shows a magnet being moved over the coil. The magnet on the end of the flame blade isn't going to be doing a great deal of moving relatively compared to a pendulum, very short radius of swing from its axle. Is there an iron element in the center of the coil that might be moved by the magnet? Also, I keep seeing these kinds of oscillators with a capacitor (which I expected but is missing here). Balancing all of this out to make it work is quite a little feat, even as simple as it looks. I am impressed.
 
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