I am having a home automation setup of following major components:
- Arduino Nano as main controller
- ESP-01 as Wi-Fi module
- HI link 5M05 5v 1Amp supply
- 5v 7Amp 220v sugar cube relay
- BC547 transistor as relay driver
- TSOP1738 as IR Remote receiver
I am facing a weird behavior with the relay in my home automation project.
Relay is working fine with loads like filament bulb, tube light, fan etc. But I am facing problem with LED lamps, specifically Ceiling LED lamps over 12W rating.
Basically the problem is after few switchings (say 2-3) the relay contact stayed ON for ever. When i am trying to switch Off with IR remote, it doesn't respond but when i switch it using Blynk App, it works fine. And this behavior only comes with LED lamps over 12W.
Could somebody can explain me why this is happening and how can I solve it.
Try using a diode (eg. 1N4007) in the relay coil terminals
This is not as simple as it first appears. Is it possibly that you can give us a schematic, not a frizzy thing? Just guessing but there is no input resistor to the base of the transistor maybe something in the 300 to 700 Ohm range. This missing causes heating giving unpredictable results. If you want it guaranteed off during reset put a resistor something in the 10K range from the micro pin to ground. Assuming you are switching lowside (ground). You can use a inexpensive diode such as a 1N4001 across the relay coil, cathode to positive. I use avalanche (UIS) rated MOSFETs hence no diodes or gate resistors needed. Since you are switching AC you need to use a snubber circuit such as a .1uF and a 150 ohm resistor in series across the contacts. I am guessing that your LED lights have an inductive component causing reverse transients. You will probably have to adjust this. Do not put a diode across the contacts as it will give you 50% power minimum all the time.
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