Relay for continuous on-off operation? - Page 1
Forum section: electronics / beginners

author: fubar.gr
author_rank: Unknown
timestamp: December 29, 2015, 04:50:16 pm
content: I have a project that requires two 100W incandescent lamps flashing alternatively, one second on, one second off.My first thought was to use a relay with NO and NC contacts, so when one lamp is turned on the other is off, and so on.But the relay will be switching on and off 1800 times per hour, 12 hours a day, 6 days a week.That's 130 thousand switchings per week!Are there relays that can handle such a thing or should I use a solid state solution?

author: dom0
author_rank: Super Contributor
timestamp: December 29, 2015, 04:52:02 pm
content: > for continuous on-off operation?Absolutely. They are called solid-state relais.

author: babysitter
author_rank: Frequent Contributor
timestamp: December 29, 2015, 05:05:10 pm
content: You might consider a mercury blinking relay like the Siemens RB108. These have been used for signal lighting of railway crossings.

author: cponcsak
author_rank: Contributor
timestamp: December 29, 2015, 05:17:58 pm
content: Quote from: dom0 on December 29, 2015, 04:52:02 pmThis. I have used these in the past and they work really well.http://www.ebay.ca/itm/24V-380V-40A-250V-SSR-40-DA-Solid-State-Relay-Module-3-32V-DC-To-AC-/201414937205?hash=item2ee5440a75:g:0MoAAOSwD0lUduWtI cant seem to find the current required to activate them though but I know I have a few kicking around and could try to locate one and test if you needed.

author: Ice-Tea
author_rank: Super Contributor
timestamp: December 29, 2015, 05:18:42 pm
content: Seems like a job for a triac?

author: picandmix
author_rank: Frequent Contributor
timestamp: December 29, 2015, 05:24:33 pm
content: Quote from: fubar.gr on December 29, 2015, 04:50:16 pmThink you question / problem will be finding a 100w incandescent lamp that will withstand that amount of on/off cycles.

author: Richard Crowley
author_rank: Super Contributor
timestamp: December 29, 2015, 05:29:20 pm
content: Quote from: fubar.gr on December 29, 2015, 04:50:16 pmThere WERE mechanical relays like that many decades ago.But they were replaced by solid-state switches for a generation now.This seems like a perfect application for your common SSR (solid-state relay)For such a modest 500mA load, you could use two of the little SIP relays.And you could make a simple 2-transistor multivibrator to drive them.

author: Kleinstein
author_rank: Super Contributor
timestamp: December 29, 2015, 05:42:05 pm
content: Even mechanical relays can stand this for quite some time, e.g. longer than a pair of lamps.The way to go would be triac's or solidstate relays, which are often triacs controlled through an optocoupler.With EU regulations, getting the 100W incandescent lamps might get difficult. No more calssical 230 V - 100W incandescent lamp are supposed to be sold for household lights.

author: Ice-Tea
author_rank: Super Contributor
timestamp: December 29, 2015, 05:44:12 pm
content: Quote from: picandmix on December 29, 2015, 05:24:33 pmCan't be that hard? Fairground attraction lights seem to do that all the time?

author: dom0
author_rank: Super Contributor
timestamp: December 29, 2015, 06:04:35 pm
content: They will probably have a, don't know the English term, "warm keeper" circuit. Like a dimmer set to a very low level, so that the filament stays warm (and high resistance) without emitting much light. This also reduces the time to full light output.

author: cponcsak
author_rank: Contributor
timestamp: December 29, 2015, 06:22:51 pm
content: Is it possible to just switch it to LEDs? That would solve both of those problems.

author: Zero999
author_rank: Super Contributor
timestamp: December 29, 2015, 07:21:26 pm
content: Quote from: cponcsak on December 29, 2015, 06:22:51 pmI agree and if aesthetics are a problem, there are LEDs available which look like incandescent lamps.http://www.yandiya.com/path0379/path0386/

author: poorchava
author_rank: Super Contributor
timestamp: December 29, 2015, 07:35:17 pm
content: Dunno how about other countries, but here in Poland since the EU banned 100W bulbs, there has been an incredible flooding of 99W bulbs. I wonder why...BTW, SSRs of all kinds can be had for really cheap from China.Sent from my HTC One M8s using Tapatalk.

author: Richard Crowley
author_rank: Super Contributor
timestamp: December 29, 2015, 07:47:47 pm
content: Quote from: dom0 on December 29, 2015, 06:04:35 pmIn English (at least AmEnglish) it is called "keep-alive". Probably a technique that is rapidly disappearing as incandescent lamps go extinct.

author: Ice-Tea
author_rank: Super Contributor
timestamp: December 29, 2015, 08:37:54 pm
content: Quote from: Richard Crowley on December 29, 2015, 07:47:47 pm... and I learn something new. Thanks fellas!

author: SeanB
author_rank: Super Contributor
timestamp: December 29, 2015, 09:20:17 pm
content: Look for sign flashers, they are designed to do that, so you get a module with a simple capacitive power supply, a 555 timer and a 4017 chip and selectable 2 to 4 outputs, with each being a 16A triac as switch, using some zero cross switches to drive them. Typically limited to 5A total by the fuse, as the traces are not going to survive more.Otherwise a Faraday motor sign switch is totally electrical and mechanical, using a homopolar or eddy current motor, as a slow drive for a set of large mechanical switches on an eccentric cam. Those run for decades on 27/7 with almost no maintenance.If you want good incandescent lamp life simply connect the primary of 2 small transformers ( secondary voltage irrelevant as you only are using the primary magnetising current) of around 10VA rating across each relay, to provide a small current flow in each lamp so the filament stays warm when off. NTC in the supply lead as well to limit cold inrush on initial switch on so the cold lamps warm up slower. Only works with relay drive, but a relay will easily do 100 million cycles mechanically if you are running it at low current, so use a 10A rated relay, preferably a 24VDC one, to drive your 100W lamp load. Use a plug in Omron one, so you can change it easily, and use the NO contacts only on the relays, do not rely on the CO contacts providing a good lifetime, as the NO contact is rated better than the NC contact.

author: fubar.gr
author_rank: Unknown
timestamp: December 30, 2015, 03:57:19 pm
content: Thanks for all the ideas!I want to make two amber lights that flash alternatively. This contraption will be installed near the exit of a parking lot, along with signs and a speed bump, because some motorists exit too fast and pose a threat to passing pedestrians.Commercial traffic light solutions are way too expensive IMO. Each light costs €100, lamps not included. I believe these use special lamps that are more expensive than a typical household incandescent.Also the flasher unit costs something like €300It is just a small board with a micro and a couple of relays.The LED version of the lights is even more expensive. I think I'll build something from scratch.

author: Richard Crowley
author_rank: Super Contributor
timestamp: December 30, 2015, 04:09:11 pm
content: Here in the US, the LED replacement lamps for traffic signals are available on the surplus market.Is anything like this availble in Europe?Giant Yellow Traffic Lighthttp://www.goldmine-elec-products.com/prodinfo.asp?number=G20803(Also available in green and red)

author: fubar.gr
author_rank: Unknown
timestamp: December 30, 2015, 04:39:59 pm
content: The best I could find locally was this:http://www.accessories-eshop.gr/shop-products/axesouar-fortigwn-lewforeiwn-fanoi-fortigou-lewforeiou-flas/led-fanos-flas-9-33v-140ch71-5mm-20led-45776This is a 24 Volt truck indicator LED light, 14cm in diameter.I'll post some photos when it's done!

author: cponcsak
author_rank: Contributor
timestamp: December 30, 2015, 07:31:07 pm
content: I was going to suggest a truck or trailer light. It seems like you have this all under control. I'm looking forward to seeing the finished project. Make sure you take video.