Can anyone explain me this circuit

  • #1

Main Question or Discussion Point

 

Answers and Replies

  • #2
NascentOxygen
Staff Emeritus
Science Advisor
9,244
1,071
This is a homework exercise?

It should be in the homework subforum.
 
  • #3
This is a homework exercise?

It should be in the homework subforum.
no, this is my project for school
 
  • #4
NascentOxygen
Staff Emeritus
Science Advisor
9,244
1,071
What is the circuit supposed to do?
 
  • #5
Svein
Science Advisor
Insights Author
2,025
649
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).
 
  • #6
What is the circuit supposed to do?
this is the circuit of a laser security system
 
  • #7
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
 
  • #8
Svein
Science Advisor
Insights Author
2,025
649
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"
 
  • #9
Another thing I would like to add is the thyristor is BT-169
 
  • #10
NascentOxygen
Staff Emeritus
Science Advisor
9,244
1,071
What can you tell us about the Speaker?

Have you bought the components? How does the laser get used?
 
  • #11
Svein
Science Advisor
Insights Author
2,025
649
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 [Broken]

A slight problem: BT-169 is not specified for DC operation.
 
Last edited by a moderator:

Related Threads on Can anyone explain me this circuit

  • Last Post
Replies
8
Views
1K
  • Last Post
Replies
1
Views
3K
Replies
3
Views
2K
Replies
4
Views
2K
  • Last Post
Replies
1
Views
15K
Replies
12
Views
2K
  • Last Post
Replies
6
Views
2K
  • Last Post
Replies
17
Views
3K
Replies
3
Views
701
Top