And the Relay is Called ...

[AlwaysLearning]

This is my first posting so I thought I'd use it to potentially demonstrate my ignorance.

The problem I want to solve is this: When a light is turned on, a relay connects for about 20s then disconnects. More precisely, on detecting 240vac, the DPNO relay switches a load of something like 12vdc @ 100mA for 20s. The relay doesn't trigger again until the 240ac is reapplied.

Now my electronics is rusty (25 years of corrosion) but I dare say I could build the circuit from scratch, and after letting some smoke out, get it working. But, there is a memory hiding in the back of my mind, that there already exists such a relay module, probably fitting an 11 pin base.

Before I dust down my 555 datasheet, can someone leap up and tell me the name of the relay thingy I need, preferably with a product code, though that might be pushing my luck.

 

[AnalogKid]

You are right about the 11 pin base industrial control relays. There are tons of time delay relays and timer modules on ebay.

ak

 

[KMoffett]

I need to do that very thing. In my case I used it to switch 120VAC. But with my circuit you could just the relay contacts to switch 12DC

Ken

 

[AlwaysLearning]

Yer, that's part of the problem I suppose; there are too many options and I don't have the terminology to select the right one.

Also lots of Chinese modules to switch on for a set length of time, but they only switch the main which would just make it an interface to a simple relay. Overkill lol

 

[kellys_eye]

Non-retriggerable monostable is the technical term.

There are multi-function timer relays that will have this as a function of their capabilities - they don't come cheap (if cost is an issue) - and if you can wave a soldering iron in the path of a handful of components you could achieve the same function quite effectively.

 

[BobK]

if you can wave a soldering iron in the path of a handful of components you could achieve the same function quite effectively.

Nice image of a soldering iron as a magic wand. Harry Potter's got nothing on us.

Bob

 

[hevans1944]

The relay is called (by Micromatic) an INTERVAL ON time delay relay. Their description of its operation:

Upon application of input voltage, the output is energized and the time delay (t) begins. At the end of the time delay (t), the output is de-energized. Input voltage must be removed to reset the time delay relay.

Read more about it on this Macromatic webpage.

Interestingly, the Macromatic relay that matches your specifications is not available from distributors. Contact the factory for information on how to buy one, which could be a TR-50521-07, TR-5021-08, TR-5021-09, TR-5021-10, TR-5021-12, or TR-5021-15, depending on what time resolution you need.

Macromatic (as well as other manufacturers) may have relays of identical functionality available in a different packaging configuration and with possibly a different nomenclature for the time delay function. Google freely for possible solutions.

Or you could get a large caliber soldering gun and intimidate a motley collection of components into an appropriate configuration. Smoke optional.

 

[AlwaysLearning]

Thanks for your guidance. It looks like I've sourced a suitable relay for a few pounds.

Mains to the coil, contacts stay made for the 20sec I wanted, then break. Out of curiosity I measured the current and found near zero in 0 to 20 sec, then 2mA afterwards suggesting that the relay is interval off rather than interval on, but it'll do the job and I can live with the relay energised for as long as the mains is applied; ~0.5W for 8hrs is going to be far less than the cost of sourcing the correct interval on model.