I'm working with the 4 relay Arduino shield, and all was going swimmingly. I have my desktop lamp blinking based on Relay 1. However - occasionally, and I do mean very sporadically, the light doesn't switch off. The LED on the shield goes out - but the lamp stays on. Then after about 3 cycles, it will go back to blinking normally. It's almost as if the relay is not resetting, but I can HEAR it still clicking away. I suspect some sort of hardware issue - anyone else seen this?
Household circuit - 110v (120 measured with meter) -
Regular desktop incandescent 100w lamp.
Leads to Common and NO
My understanding is that the 4 Relay Shield includes appropriate transistors and flyback diodes for each relay. Am I just over-powering the relay with 110V?
I managed to catch it failing and recorded a video. i started recording when it failed - the light is on at the beginning of the video. Then it cycles once successfully and fails again. The it resumes normal operation for the remainder of the video:
There are multiple Arduino 4 relay shields, so a link to YOUR shield would have been nice. The shield that I am familiar with is limited to 48 volts and 60 watts (presumably resistive, which an incandescent bulb is NOT). 100 watts incandescent is excessive. It seems to me that you are occasionally welding the contacts together weakly. Your relays will not last long like this. Your relays should drive other relays (or triacs, etc.) that are rated for your load.
By the way, relays have a limited cycle life. Flashing can quickly use up that life. 0.1M, 1M, or 10M cycles are possible lifetimes. How many days will it take you to reach 10 million cycles?
Hi,
Why do not use Solid State Rrelay. They last almost forever and can be turn on/off reputability and do not burn the contacts. Also they are compatible with Arduino.
Sorry - I was not aware there were multiple versions of the shield. However, a review of the specs on my particular shield reveals a limit of 48V and 60W as you mentioned. Lucky I didn't burn the place down. Mom would've killed me. Thanks for the pointer.
You need contact arc suppression ... the arcing is worse when the contacts open and this is usually when problems happen (as in your case). When switching AC, its very beneficial to add an arc suppressor. I would suggest connecting this MOV across the NO and COM contacts that switch the lamp. It will reduce contact arcing (EMI/RFI), prolong the life of the relay and most likely resolve the problem.
