In this project, I designed a nightlight that automatically dims and turns itself off. A lot of people find it difficult to fall asleep when they suddenly transition from a brightly lit room to complete darkness. A dim source of light such as a nightlight helps them to adjust to a lower brightness and fall asleep more easily. But the down side of most nightlights is that they waste electricity because they are on all night when you really only need them to be on while you are falling asleep. So I designed a nightlight that will automatically dim and turn itself off after a certain period of time that is set by the user

Step 1: Materials

Jumper wires
Printed circuit board
IC1: 741 OP AMP
IC2: 741 OP AMP
Terminal Connectors
R1: 1MΩ
R2: 5kΩ variable
R3: 2.2kΩ
R4: 3.3MΩ
C1: 2200µF 10V
C2: 2200µF 10V
D1: 1N4001
D2: D3: D4: 3.5V LED
S1: SPST latching switch
S2: momentary switch
Plastic project box
T1: 6V 400mA DC power supply
It may also be helpful to have some glue and heat shrink tubing.

Soldering Iron
Wire cutters
Screw driver
<p>I have made the circuit on breaboard and checked several times to make identical to this one. I have provided 9V-10V in power supply from DC adapter. The problem is that, the Op-Amp (from timing circuit) is giving a fixed output of about 0.38 V in pin 6. That means it is not working as a comparator and this voltage is not enough to charge C2 and lit the LEDs up. What could be the possible reason behind this? Thanks in advance. </p>
<p>Keep in mind that the output is of the first op amp is supposed to be low until the button is pressed. When you do press the button, hold it down for a while to ensure that the capacitor charges all the way. If that still doesn't fix it, check each of the components individually to make sure that they are all working at the correct values.</p>
<p>Oh I'm sorry, I didn't mention that I got the low voltage even after pushing the button (momentary), the C1 (pin 3) charged to about 8.68 V and the voltage dividing network (pin 2) was providing 2.3 V. So it should work as a comparator but it doesn't. Still low voltage (0.38 V) output at pin 6 (tried with 3 different 741s). Did you face similar problem? </p>
<p>This isn't explicitly show in the diagram, but pin 7 should be connected to Vcc and pin 4 should be connected to GND. These pins supply power to the IC.</p>
sir instead of potentiometer.. i would like to use a fixed time (0, 15, 30, 45) using selector switch. what would be the timer circuit look like?
<p>The circuit would be identical except instead of a variable resistor, you would put a set of fixed resistors and a selector switch.</p>
Thanks sir! ?
This project has a built-in light source. Sir, is it possible to use LM741 as a dimmer to any light bulbs (e.g. lamp dimmer)?
the LM741 is a very low power device. It can only out put 40 max. So you can directly control only lights that draw 40 mA or less. If you want to control higher current lights you will need power transistors.
<p>Really nice idea. I'll be building this before too long. Thanks!</p>
<p>Thanks for designing just a simple timer/dimmer circuit. So many 'bles use an arduino or other microcontroller, and for the most part, they are overkill.</p><p>Kudos!</p>
Thank you very much! Your explanation was really helpful.
a very good idea-proyect :) <br> I only have one question, how do you power the 741? its supposed they must be powered with a dual voltage supply
Dual power supplies are only needed if you want to be able to output positive and negative signals such as in a pure AC signal. When working only with DC, a single positive supply is fine.
Sir can i use 5V DC?.. what do you mean is has an operating voltage of 9.8V?..where can i get that?.. my light source cannot cannot more than one..please help me
is the power supply connected to the outlet all night?.. is that ok?..
Yes. I have been using it for over a year with no problems. It does use a little power by being plugged in but it is perfectly safe.
neat project! what should the voltages of those 2200&micro;F capacitors be?
You're right. I did forget to mention that. I will update the materials list to include that. It doesn't really matter as long as they are rated for more than the supply voltage. The power supply that I used had an operating voltage of a about 9.6-9.8V with this circuit. So I just used a couple of 10V capacitors.
Forget the circuit, where can I get one of those cool lanterns? :-)
I think that we got that one from Earth Bound a couple of years ago. They have a number of similar lanterns in stock most of the time. But once or twice a year they will go on clearance for half price. We also found some similar ones at World Market last year.
Very cool project and I'm totally digging that lantern.<br><br>As much space as it provides, I would look at making two more lights on the same pattern, but with differently colored LEDs. Putting them all on different time differentials with the variable resistor would make an impressive light show in the room as they all faded away.
I find that it is a lot cheaper to buy super bright white LEDs. Then you can color them yourself to whatever you want. Liquid highlighters work fairly well for that.

About This Instructable


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Bio: My name is Jason Poel Smith I am a Community Manager here at Instructables. In my free time, I am an Inventor, Maker, Hacker, Tinker ... More »
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