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Author Topic: need help with Reed relay, Reed switch and LDR  (Read 4173 times)

Offline NotAbod

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need help with Reed relay, Reed switch and LDR
« on: March 23, 2011, 01:22:20 pm »
hello
i need help with Reed relay, Reed switch and LDR.
How does street lights work using LDR and a normally closed reed relay?
help me please
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Offline SauD~

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Re: need help with Reed relay, Reed switch and LDR
« Reply #1 on: March 23, 2011, 07:57:52 pm »
Street Lamp working:
LDR (photoresistor) resist the flow of electricity, but their resistance drops when light hits them. The more resistance in a circuit, the less electric current flows through. In a LDR powered street light, a small current runs through the resistor. When it becomes dark, the resistance increases and the current drops. Now the Reed relay which consists of "Normally Opened" relay switch is used. The low current in the circuit makes the reed relay to power the lamp with the battery in the another circuit.
::)
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Offline NotAbod

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Re: need help with Reed relay, Reed switch and LDR
« Reply #2 on: March 23, 2011, 08:25:10 pm »
Quote from: $~SauD~$ on March 23, 2011, 07:57:52 pm
Now the Reed relay which consists of "Normally Opened" relay switch is used. The low current in the circuit makes the reed relay to power the lamp with the battery in the another circuit.
::)
thanks a alot, nut actually our school physics teacher told us that a normal closed relay is used.  :-\
so which one is correct ????????
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Offline SauD~

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Re: need help with Reed relay, Reed switch and LDR
« Reply #3 on: March 23, 2011, 08:42:47 pm »
Quote from: Abod on March 23, 2011, 08:25:10 pm
thanks a alot, nut actually our school physics teacher told us that a normal closed relay is used.  :-\
so which one is correct ????????
Won't a closed switch gets open? In open circuit current doesn't flows.
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Offline NotAbod

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Re: need help with Reed relay, Reed switch and LDR
« Reply #4 on: March 23, 2011, 10:07:00 pm »
i donno
there are 2 circuits
     
During night time this circuit is drawn
     _________________________                 ___________street lamp______
     |                        |                  |                |                                             |
     |                        |                Relay coil    Relay(NC relay)                          |
     |                      resistor           |                |                                             |
    ____                   |__________|                |__________240v___________|
      _    12v             |
     |                        LDR
     |_____________|                         
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Offline SauD~

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Re: need help with Reed relay, Reed switch and LDR
« Reply #5 on: March 24, 2011, 09:32:55 am »
Quote from: Abod on March 23, 2011, 10:07:00 pm
i donno
there are 2 circuits
     
During night time this circuit is drawn
     _____________________________                 _________street lamp________
     |                        |                   |                |                                        |
     |                        |                Relay coil        Relay(NC relay)                     |
     |                     resistor              |                |                                        |
   ____                     |____________|                |__________240v___________|
     _    12v               |
     |                        LDR
     |_______________|                         
Oh, Sorry sorry
You are correct :-[
Yes, normally closed switch works in it
I am sorry.
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Offline NotAbod

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Re: need help with Reed relay, Reed switch and LDR
« Reply #6 on: March 24, 2011, 03:14:46 pm »
no problem bro ;)
we didnt get any questions about LDR and relays today, it was phyiscs mock exam.
i was so worried about LDR, Relays and transistors xd xd
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Offline SauD~

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Re: need help with Reed relay, Reed switch and LDR
« Reply #7 on: March 24, 2011, 03:30:57 pm »
Quote from: Abod on March 24, 2011, 03:14:46 pm
no problem bro ;)
we didnt get any questions about LDR and relays today, it was phyiscs mock exam.
i was so worried about LDR, Relays and transistors xd xd
i had physics on Wednesday, mocks :P
Gave it without studying because i was sck >:(
i had a transistor question :-[
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Offline NotAbod

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Re: need help with Reed relay, Reed switch and LDR
« Reply #8 on: March 24, 2011, 03:56:39 pm »
actually i have no idea about transistors.
i dont have a good physics textbook to study about transistors from it :(
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Offline SauD~

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Re: need help with Reed relay, Reed switch and LDR
« Reply #9 on: March 24, 2011, 04:25:00 pm »
Quote from: Abod on March 24, 2011, 03:56:39 pm
actually i have no idea about transistors.
i dont have a good physics textbook to study about transistors from it :(
Study notes and check a book named "Physics for you" by Keith Johnson. Its a good book :)
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Offline NotAbod

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Re: need help with Reed relay, Reed switch and LDR
« Reply #10 on: March 24, 2011, 06:03:21 pm »
ok i will.
thanks for the advice.
is it availabe as ebook?
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Offline SauD~

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Re: need help with Reed relay, Reed switch and LDR
« Reply #11 on: March 24, 2011, 06:31:05 pm »
Quote from: Abod on March 24, 2011, 06:03:21 pm
ok i will.
thanks for the advice.
is it availabe as ebook?
I am not sure,
Let me search,
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Offline NotAbod

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Re: need help with Reed relay, Reed switch and LDR
« Reply #12 on: March 24, 2011, 06:51:26 pm »
i am searching too....
nothing till now
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Offline The Golden Girl =D

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Re: need help with Reed relay, Reed switch and LDR
« Reply #13 on: March 26, 2011, 04:27:10 pm »
I've got some notes on this just give me ur e-mail ID since I was not able to upload it here.
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Offline SauD~

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Re: need help with Reed relay, Reed switch and LDR
« Reply #14 on: March 26, 2011, 04:36:32 pm »
Quote from: ~ The Golden Girl ~ on March 26, 2011, 04:27:10 pm
I've got some notes on this just give me ur e-mail ID since I was not able to upload it here.
IGCSe? :o
Send me too, mom :D
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