I've taken all the floodlights to bits, so I might as well take one of the PIR sensors to bits too. Mainly to see how "waterproof" it is and how the mains side of things is handled.
It took me by surprise with a very odd bridge rectifier arrangement that serves both to rectify the supply and also to clamp the capacitor limited supply down to about 24V. It took me a moment to get my head round what it was actually doing. It's basically using two back-to-back zeners to shunt the AC supply to 24V while also rectifying it! The stand-by dissipation in the circuit is around 1W and I'm guessing that a lot of it is actually in those zeners, so I suppose by sharing the load between two operating on alternate cycles keeps them cooler.
Other than that it generates a smooth 5V supply from the main 24v one using a resistor and 5V zener, and then uses a common LP8072C PIR controller chip with associated circuitry to switch a 24V relay.
The circuit appears to have a design oddity. There is a small snubber network (quenches sparks and interference across switch contacts) but instead of connecting it across the relay contacts they have connected it across the load.
It took me by surprise with a very odd bridge rectifier arrangement that serves both to rectify the supply and also to clamp the capacitor limited supply down to about 24V. It took me a moment to get my head round what it was actually doing. It's basically using two back-to-back zeners to shunt the AC supply to 24V while also rectifying it! The stand-by dissipation in the circuit is around 1W and I'm guessing that a lot of it is actually in those zeners, so I suppose by sharing the load between two operating on alternate cycles keeps them cooler.
Other than that it generates a smooth 5V supply from the main 24v one using a resistor and 5V zener, and then uses a common LP8072C PIR controller chip with associated circuitry to switch a 24V relay.
The circuit appears to have a design oddity. There is a small snubber network (quenches sparks and interference across switch contacts) but instead of connecting it across the relay contacts they have connected it across the load.
Wow look at how clean your bench was.
Would it be possible to connect a capacitor between PIR sensor and LED to achieve fade in and fade out…?
I just love it when lights turn on smoothly.
It is what you are prepared to pay. it has nothing to do with China.
Mine point down, but it's failed now, so I will have a look inside to see if any water has got in, thanks for the video
Excellent deduction
Good info thanks
Hi Clive, please could you tell me why some electrical components hum and buzz, what is normal and what might be a sign that something is wrong?
I just got one of these. Specs say Rated Load : 60W LED lamp , 300W Tungsten filament lamp, why would it be different? I suspect its a cheaper scr version as I hear no click. The red wire drives out "mains" or 120V line voltage as we say over here. I don't think that the wire sizes are large enough to handle 300W either. Mine is glued together 🙁
Reverse engineering, yeah, but where can we get schematics?
Great video, after watching your video I fixed two PIR security lights that had stopped working. I took them apart and tested them, it seems that the Achilles heal of these light sensors is the switch and variable resistors. After years of being exposed to the weather, especially if they are mounted so that the switch and resistors are facing upwards. The circuit board, switch and variable resistors become dirty from air pollution and the PIR sensor stops working. After cleaning the circuit boards, switches and resistors both PIRs worked. Thanks Clive, for teaching us how things work!
It's the light outside your house still functioning?
Switch relais pir motion
Good to see the inclusion of a relay (not all seem to have this), which I assume would allow an override switch, which would apply 230v to the output without damaging it.
That is not a transistor, it is a voltage regulator from 24V to 5V. The zener diode is used to protect the regulator in a crowbar method. So the voltage get reduced from 230V to 24V to 5V. That 5V is used to supply the PIR circuitry on the second PC board. The 4th wire is the wire to control the relay's coil. I had a problem with my security light due to alot of load shedding in our country. So every time they switch on the power from the substation an inrush current occurs, but the crowbar could not handle this on off swithing and inrush currents and it went short circuit causing to have a 0V on the 5V supply. I removed the shorted zener diode and the 5V came back!
lol,,,nice,,like it…dip details….
Back to 'refresh' Input info, bcs now my PIR Input doesn't sense. Didn't remember you having a brain exercise – i was worried.
Not worried after 2 more views and I now understand, what had you 'asking', 'which way was OZ.'
Well I still ask, but not bcs I know; You Know, and W0W, I know why ~ You Rule! I DID Learn a bit more – Thanks Clive!