A part of my engineering project involves a L.E.D tubelight staying on for 16 hours continuously. I am connecting the light to a relay module. Is it ok, if the relay stays on for so long? I mean, is it designed to sustain for such a huge period of time?
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Well, if you are doing an engineering project, of course you need to do some engineering research, make some educated engineering guesses, and then some engineering experimentation, and finally some engineering tradeoffs. I am an hobbyist and wish to become an engineer, so I am interested to do some research. Can you let me know which LED tube light and relay you are using? Are you using the popular home/office use, 4ft 20W tube, and those cheap relays claiming 200VAC 10A, from Amazon?– tlfong01Commented Apr 14, 2019 at 8:12
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3 Answers
To add to @Ghanima's excellent answer, you may also wish to consider a latching relay. Briefly, a latching relay has two stable states (i.e. it is a bistable device, similar to a flip-flop). This means that the relay can be latched into an OPEN or CLOSED state, and it will remain in that state until commanded to change by the input. This avoids the necessity of supplying input voltage and current to maintain (for example) a NORMALLY OPEN relay in a CLOSED state for an extended period of time. Latching relays typically find application in situations similar to the one you've described in your question - where they must be in an OPEN or CLOSED state for extended periods of time.
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1Just to mention that the input signal changes from a permanent signal to a short pulse. The control must be changed. +1– IngoCommented Apr 14, 2019 at 8:21
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1And it's common to use a second throw to short a GPIO to GND so you have feedback as to the relay state on your controller otherwise they might get out of sync. Commented Apr 14, 2019 at 8:48
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Both true statements, and thank you for adding to the answer.– SeamusCommented Apr 14, 2019 at 10:15
The first stop to answer such questions should be the datasheet of the part in question. This is where the manufacturer lists the operating conditions of the device.
That aside it is usually safe to have a relay active for longer periods of time, assuming you're within the operational range of current and voltage (again, as laid out in the datasheet).
Wear and tear of an electromechanical relay is usually due to switching under load, i.e. with a voltage applied to the terminals, not being permanently on or off. For more on the issue of contact degradation see here https://en.wikipedia.org/wiki/Relay#Arcing (which I won't make part of this answer as it does not address the question).
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Thank you so much for your help @Ghanima. Btw does a timer relay also have the same working? Commented Apr 13, 2019 at 14:48
Engineering project, LED tubelight staying on for 16 hours continuously connecting the light to a relay module. Is it ok?
Yes, no problem. Common LED tube is only 200VAC 20W, or about 1A. 5V relay boards can safely pass 6A.
You may also like to consider latch relays, or timer relays. Latch relay saves Rpi's time constantly keeping relays's state. Timer relays are solid state and can pass 5A. But timer relays are only manually set, up to 16 hours, not by Rpi.
Amazon 20W 4-Foot LED Tube Light, 45W Equivalent, White, 1943WH
Amazon HiLetgo 5V 1 Channel Latching Relay Module with Touch Bistable Switch - $6.09
Ali Express Solid State Relay Module (manual, not Rpi) - US$2.54
1. Manual setting, not Rpi compatible
2. 0.1 seconds (min) to 999 minutes (max) infinitely adjustable.
3. Power MOSFET 5A, 400W
There is another Capacitive Touch Latching Self-Locking Relay. It seems there are too many to select!
AliExpress Capacitive Touch Latching Self-locking Switch Relay Module
