Hi.
Today I'd like to design one of those night light circuits that turns on a night light when the room gets dark.
I came up with a simple circuit it reduces the AC level and rectifies it with the "FULL BRIDGE RECTIFIER!!!"
Which is really just called a bridge rectifier.
It powers the circuit which senses the light and switches light on and off
Please see my website Electroboom.com for more details on the circuit.
This circuit is a bit of an overkill because it's an industrial-grade nightlight.
Imagine a Hells Angels biker wants to stay overnight in an abandoned factory, and he's ascared of the dark.
So he uses this circuit. Here's my creation. Let's plug it in.
Amazing, usually sh** goes haywire at this point. Oh, I forgot to turn on the
Oh, sh**, SH**! [person] "What the F*** was that?"
I said I'm sorry!!!
Always always double "chick" and triple "chick"...check che...
Check your circuits to make sure there's nothing shorted especially when dealing with power circuits. I fixed it. Let's plug it in
Turning the lights off
The hell..? Nice. I added a feature. It's blinking. Oh... I know...
See it's feeding back into the circuit. What happens is that when the light turns on the sensor sees light and turns off its output
And when the light turns off the room gets dark the sensor turns it back on again and the loop continues
Now if I cut the feedback by blocking the light it stays on forever. It's working
Now let me discuss the power supply side of the circuit and show you some waveforms.
Now if I probe the input A...
[Screams] Sh**!
I have mentioned it before. The ground of the probe is shorted to the Earth terminal of the power plug through the scope and this circuit
Is pretty much riding on the live wire. So when you connect your probe ground to this circuit
You're just shorting the 120 volt AC output. It is a safety feature, but for applications like this you need to insulate your earth
So you can put some tape around it or use an insulating transformer, which I don't have.
OK, here's the 120 volt AC input to the circuit
And this is the output of the capacitor divider and as you can see it's much smaller. Let me zoom in...
You also see that it's a little bit deformed because it's loaded by the circuit. Now if I measure the output of the rectifier
It is AC
What about the ground
That's AC too. What the hell?!
Something I forgot to mention is that the rectifier output is only DC between its power and ground output not reference to the input wires
So I have to move the probe ground to the rectifier output ground. Which is I think this
You might want to turn things off before moving things around to avoid shorts
Okay fixed. Now, this is the output of the bridge rectifier which is around 13 volts
But it can change to around 7 volts depending on the loading of the circuit on the voltage supply
Now I feed that voltage into my 5 volt regulator which provides a fixed 5 volt output and doesn't change by input fluctuations
And that supplies to my sensor circuit and the sensor circuit turns the light switches on and off. That's it
I'm done with this circuit
It's all fixed and functional
so I'm gonna pass it on to one of my
Eligible Patrons at Patreon.com. If you also like to support my channel you can go to
Patreon.com/electroboom to become my patron and potentially win one of these giveaways
"Potentially"... Get it? Because everything is potentially charged around here which means that this might be a liability to send to anyone
It's like sending Anthrax by mail
Well, I'm going to send it to the draw winner anyways, but it's for educational purposes only, right?
So if you kill yourself using it don't go around and Badmouth me okay?