Showing posts with label night. Show all posts
Showing posts with label night. Show all posts
Tuesday, April 9, 2013
Night Lamp
This simple night lamp required very low current as 350mA. So you can operate this lamp using one normal 1.5V battery. But we recommend using alkaline batteries as you can operate long time without any headache.
When you buy a IC for this circuit make sure it is Cmos type. To get best results do not use an ordinary LED cheap bulb, use a good one. You can build this lamp without the photo resister but it will be then affect to the duration of the battery you can use, there for use photo resister to double the running time as mention in the diagram.
When daylight comes the photo resister will automatically disconnect the circuit and with the darkness it will be switched on again.
Monday, April 8, 2013
How to Make a Light Activated Day Night Switch Circuit – Science Fair Project
This is the circuit diagram of a light activated switch based on National Semiconductors comparator IC LM 311 and a LDR. The circuit is based on a voltage
comparator circuit wired around IC 1.The non inverting in put of IC1 is
given with a reference voltage of 6V using resistors R3 and R4. The
input to the inverting input will be the voltage across the LDR that is
light dependent. At darkness the resistance of the LDR will be high and
so do the voltage across it.
At this condition the voltage at the inverting input will be higher than the reference at non inverting pin and the out put of the comparator will be low(~o V). When the LDR is illuminated ,its resistance drops and so do the voltage across it.Now the voltage at inverting input will be lower than that at non inverting input and the out put of the comparator goes high (~12 V). This makes transistor Q1 on and it drives the relay.As a result we get a relay switching according to the intensity of the light falling on the LDR.
At this condition the voltage at the inverting input will be higher than the reference at non inverting pin and the out put of the comparator will be low(~o V). When the LDR is illuminated ,its resistance drops and so do the voltage across it.Now the voltage at inverting input will be lower than that at non inverting input and the out put of the comparator goes high (~12 V). This makes transistor Q1 on and it drives the relay.As a result we get a relay switching according to the intensity of the light falling on the LDR.
Light Activated Switch Circuit Diagram with Parts List .
Light Activated Switch Circuit Diagram
Notes.
- Adjust POT R1 to set the desired light intensity for switching the relay.For this illuminate the LDR with the desire intensity light.The relay will be either on or off.Adjust POT R1 slowly so that the state of the relay changes.That’s it.Now the circuit is set for the given intensity of light.
- Assemble the circuit on a good quality PCB or common board.
- You can use either a 12 V battery or a well regulated & filtered 12V DC mains operated power supply.
- The pin 5&6 (Balance & Balance/Strobe ) of IC LM311 are shorted to minimize the chance of oscillations.
- The pin out of LM311 is also given together with the circuit diagram.
Subscribe to:
Posts (Atom)