Qualification > Sciences
need help with Reed relay, Reed switch and LDR
NotAbod:
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
SauD~:
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.
::)
NotAbod:
--- 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.
::)
--- End quote ---
thanks a alot, nut actually our school physics teacher told us that a normal closed relay is used. :-\
so which one is correct ????????
SauD~:
--- 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 ????????
--- End quote ---
Won't a closed switch gets open? In open circuit current doesn't flows.
NotAbod:
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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