Hello,
I am working in a home automation project that require controlling led strip using both relay and switch in parallels. Led strip require power adapter to convert from 220 V AC input to 12 v 12.5A DC output to power the Led Strip.
this adapter can be powered either by relay or by separated in switch. so if relay not work switch can do the job.
when switching both the relay and switch I noticed that relay contacts shut and not return back again when switch off relay. the COM and NO remain contacted.
do I have to apply a diode to prevent current flow on NO after closing relay.
I have included the wiring of the circuit.
thanks in advance for help.
That sounds like a welded contact probably caused by to much current when the contacts closed. I will take a SWAG and say the relay is rated at 10A Maximum and 12.5A exceeds the maximum rating by 25%. Guess what caused that?
If your relay is in a blue plastic box, take some time and do an autopsy. You will discover the current rating for the relay is based on the diameter of the contacts. BUT! the contacts are round so there is only a tiny pin point sized contact being made and welding will occur with a very small current.
yes my relay is in a blue plastic box, but do you mean that welding of contacts happened due to over current or low current back when turn off the power supply?
From what I have seen here I highly recommend you STOP this project before you or somebody gets hurt or possibly killed. The reason for this statement is you do not appear to have even the basic skills to works with mains power.
Looking at your sketch you need all new parts, nothing is connected correctly. You have two AC sources, + into the Arduino nano ground and ground connected to Arduino +. What part of the relay circuit is damaged, the contacts cannot be as they are not connected to the same circuit.
At this point I highly recommend you spend some time with basic electronics tutorials and get a copy of the Arduino Cookbook and skim it cover to cover. Surprise in store, you will probably find what you want to do in there.
Could be either, but most likely the arc when contacts bounce on closing. over current is a relative term. Almost and thing like one Ampere is too much for those tiny contacts. Please take the dead one apart and learn how much they are over rated. The reason for the rounded contact points is the design allows the moving contact to be anywhere. Very sloppy design, but can be quickly assembled by untrained Chinese people.
Hello @gilshultz
thanks for your reply,
Actually I do not connect AC power to nodeMCU board it was just drawing mistake,
I have corrected the sketch also with only one AC power source (I added two just under impression I simplify it for reading).
Project used Ac to DC adapter to power the NodeMCU and relay module
in the same time I have another AC to DC adapter to power the led strip.
it is required to use the relay OR the switch to give AC power to led strip adapter
Appreciate if you revisit the updated wiring and help me identify weakness on it.
I suggest you use proper industrial relays designed for decades of service, not the hobby/learning type relays that are used in "don't care" projects. When they fail, they are just replaced. When building a home automation system, you do not want to be testing and replacing components every few days!
