30W LED with added 2.2UF film capacitor in series with Live wire.
Over the past year I’ve had to replace multiple LED lights with Day Night switch sensors in them. after multiple failures I decided to open one up to take a closer look at the cause for failure. Usually the LEDs are running hot and driven very hard from the factory so it’s not uncommon to see many black spots indicating burnt out LEDs in the light.
One way of extending the life of the led light is to reduce the power burning out the LEDs. This can be done easily by inserting an AC film capacitor in series with the live wire before connecting it to the light. this works great for reducing power and thus reducing the brightness of the light but it did not solve my issue.
2.2uf film capacitor helps reduce the power and strain on the LEDs.
In this case my light fails to switch on. when I opened it… The LEDs were still ok now on looking at the day night sensor I determined that the circuitry had failed. Failed how?
Well I had to investigate for a bit but eventually determined that the capacitive dropper was not supplying enough current for the transistor to swich from day to night. Why?
Day night sensor in the 30W light.
Well because the capacitor value had decreased somehow. seems that low quality film AC capacitors are used and their capacity drops maybe they deteriorate or loose electrolytic liquid I’m not exactly sure but when I replaced the capacitor with a new one everything worked again.
Faulty capacitor should be 220nf.
Replacement and faulty. Both questionable quality…
Inside the module I noticed the relay has no cover on it and a resistor and MOV were kind of in the way of the relay terminals…
Recently I had a Waco day night switch start to show faulty signs. Namely once dusk came the relay in the device would oscillate very fast for a few seconds effectively switching the light on/off very fast making a racket while stressing the LEDs out.
The relay would finally settle… mostly on the ON setting but sometimes it would settle on the OFF position. Then if you slightly bang the relay it would oscillate and settle on the ON position.
So I removed the switch and notices there was a lot of spider webs and critters close to the external AC connections. I cleaned the outer case and also notices a brown burn mark where the relay was located. This was due to sparks from the constant ON/OFF switching since the relay in this module had no cover.
The PCB was covered in a white powdery substance.
Now technically I did not have to open the module but I wanted to see if anything else was damaged. I opened the module and everything looked good except for the relay contacts which looked a bit beat up but were working ok..
I noticed that a resistor and a varistor were very close to the relay and could technically jam it’s opening/closing capability so I moved then away from the contacts and put everything back together again.
I now tested the module again and voila there is no more oscillations. So the grimy critters on top of the AC leads and the resister MOV combo close to the relay contacts were the likely culprits however my money is on the latter. So on re-installing I added extra tape and some silicon to seal the AC terminal blocks completely. A thin layer of silicone can still easily be removed for further maintenance and/or repair.
Testing the module to make sure the relay is getting the correct voltage etc.
The old meter has been through various toolbox banging battles..
Guts of the old multimeter. Very crusty with lots of through hole components and electrolytic capacitors. I replaced a damaged button as well as adjusting the voltage.
I have had the Major Tech MTD84 multimeter for 11 years now. Before I went off to another city far away for my first job my father purchased it for me as a parting gift. It was a low to mid range meter at that time and seems to be currently discontinued.
Now my meter is beat up but it reads just fine for the may DC projects I make however the voltage started to drift and has slowly become less accurate.
Luckily there is a few variable potentiometers on the PCB which can be adjusted to bring the accuracy back up to spec again. They allow for the DC, AC and Temp values to be adjusted no current option from what I could see. Even though I have a few multimeters I still can’t seem to throw this old one away…
Adjustable pots found on the back for easy access. Though they are very crusty…
So in order to set the correct voltage I had to connect a known working accurate multimeter to a battery along with the faulty one. For this I used the aneng8009 which has very good current and voltage accuracy for a cheapie.. Know I slowly adjusted the voltage variable potentiometer until the volts were mostly the same on each meter. (even though the MTD84 only has 2 decimal places it’s still close enough)
Very cool now the old multimeter is not so bad anymore with all it’s through hole resistors and electrolytic capacitors… perhaps next time I’ll have to replace a dry capacitor.
