Can anyone explain me this circuit

[gaurav_dua]

http://prntscr.com/60xcwx

Thank you

 

[NascentOxygen]

This is a homework exercise?

It should be in the homework subforum.

 

[gaurav_dua]

This is a homework exercise?

It should be in the homework subforum.

no, this is my project for school

 

[NascentOxygen]

What is the circuit supposed to do?

 

[Svein]

Seems a bit odd. If you connect the battery when there is no light on the LDR, the thyristor will turn on, the LED will start glowing and there will be a click in the speaker. When the LDR gets illuminated - it depends on the thyristor and the speaker (a thyristor will not turn off if the load current is large enough).

 

[gaurav_dua]

What is the circuit supposed to do?

this is the circuit of a laser security system

 

[gaurav_dua]

Seems a bit odd. If you connect the battery when there is no light on the LDR, the thyristor will turn on, the LED will start glowing and there will be a click in the speaker. When the LDR gets illuminated - it depends on the thyristor and the speaker (a thyristor will not turn off if the load current is large enough).

Can you explain in more detail?
Thanks

 

[Svein]

Can you explain in more detail?
Thanks

From http://en.wikipedia.org/wiki/Thyristor :
Thyristors have three states:

1. Reverse blocking mode — Voltage is applied in the direction that would be blocked by a diode
2. Forward blocking mode — Voltage is applied in the direction that would cause a diode to conduct, but the thyristor has not been triggered into conduction
3. Forward conducting mode — The thyristor has been triggered into conduction and will remain conducting until the forward current drops below a threshold value known as the "holding current"

 

[gaurav_dua]

Another thing I would like to add is the thyristor is BT-169

 

[NascentOxygen]

What can you tell us about the Speaker?

Have you bought the components? How does the laser get used?

 

[Svein]

Another thing I would like to add is the thyristor is BT-169

Look at http://www.nxp.com/documents/data_sheet/BT169_SER.pdf

A slight problem: BT-169 is not specified for DC operation.