Design me a circuit please

[Marvo]

I'm trying to do it on my notepad still it's annoying the hell outta me now. At this point, I've added a second relay to the other beacon, I seem to think you have to link each relay out to not set the other beacon off. or am I wrong?

Heres a pic of where I am.... But whether I'm on the right track or not I have no idea.

There's a couple of minor hicups with the circuit. On the 12vdc control circuit you've linked both beacon lights together so if one of the beacons operates when a fence zone alarms then both beacons will come on together. The beacons have separate 12vdc supplies from the fence control box and need to come on independently to indicate which zone is alarming, linking them together will not allow this to happen.


The second problem is on the 230v side. The neutral directly to the floodlight is fine but the live needs to be switched to the floodlight when either relay operates. The switch contacts of the relays need to be wired in parallel.


Think about a basic light circuit with two switches. If you wire the switches in series you need to operate both switches for the light to come on. If you wire the switches in parallel then either switch will operate the light. These are referred to 'AND' and 'OR' circuits and form the basics of boolean algebra which no doubt you'll be taught at some stage.

 

[Marvo]

We'll have another brainstorming tomorrow evening. I think that now the ball is rolling I should be able to give the client a decent progress report on thursday and maybe even get a stage payment for the early design phase.

 

[Happy Jack]

My attempt at a circuit will go up later tonight. I do have a question, though, regarding the preset time for the floodlight to remain on. What came to mind when I read the brief was that that end of the circuit would need to be fed via a 555 timer, a watchdog timer or something similar and a latching relay. That seemed a little excessive for the exercise. And I've since read that such circuits have the tendancy to fail over such relatively long periods of time.

However. This time-delay relay set to interval mode from RS appears perfectly serviceable. Can someone confirm that it is? Clearly a cheaper alternative will need to be found.

Buy Time Delay Relays Timer relay switchoff delay 2W CT ARS 22 ABB 1SVR630120R3300 online from RS for next day delivery.

 

[Marvo]

So you're already adding a timer...nice.

The timer you have linked will work but I think stick with the simplest timer possible, one with a single changeover contact like this one. Timers with multiple contacts, multiple functions and remote potentiometers can get confusing especially if you're unfamiliar with them.

As you can see in the operation drawing when power is applied the timer relay remains dormant for the preset length of time, then it operates and stays operated until power is removed again. It has a changeover contact so it can be used as a delay-on or delay-off depending which contacts you use.

 

[Marvo]

Just to explain the operation graph above;

 

[Happy Jack]

The timer you have linked will work but I think stick with the simplest timer possible, one with a single changeover contact like this one. Timers with multiple contacts, multiple functions and remote potentiometers can get confusing especially if you're unfamiliar with them.

Thanks for the link Marvo, you are quite right. I'v never had to spec a device like this, so cheers for the heads up.

 

[Marvo]

It's difficult to know what level to pitch these projects at. To be honest I thought you might have had a little experience with relays but I suppose those who haven't are just going to learn more.

Happy Jack, if you have a circuit that will operate the floodlight when either of the fence zones alarm then attach it for the others to see. You can always add a revised version in another post once you've added the timer.


I actually don't have a solution to this myself yet. There's so many ways it can be done with relays and a timer you'd run out of fingers trying to count them so there isn't just one correct answer. Different designs and circuits will all have their good points and bad points so it's more about the process of the design than actually coming up with the right answer as such.


The thought process for me would be that the LED floodlight is going to be operated by a relay. This relay would get it's initial operation from one of the 12vdc beacon lights.....but.....it would need a self hold circuit because that 12vdc supply is going to disappear when the alarm panel is reset.

So you need a relay that operates (indirectly) to a 12 vdc signal then holds itself in via one of it's own contacts (poles).

This self holding circuit can then be interrupted by a delay timer and by a manual reset button with a normally closed contact.


One other consideration is that once the fence alarm condition is reset you no longer have a 12vdc supply.....so....the relay that switches the floodlight would need to be a 230v relay and the self hold circuit would be 230v.

 

[Happy Jack]

Hey Marvo, I'm won't be at home until a little later; if my Teamviewer connection was active via my home desktop I'd retrieve my drawing and upload it now. It is reassuring to know that the arrangement you describe is essentially what I've drawn. Not that there won't be errors or suggestions, of course but...

There's so many ways it can be done with relays and a timer you'd run out of fingers trying to count them so there isn't just one correct answer. Different designs and circuits will all have their good points and bad points so it's more about the process of the design than actually coming up with the right answer as such.

This is why this particular exercise has been brilliant, so again I really appreciate your efforts. Once my drawing goes up I'll respond in kind, as it may not be terribly clear.

An edit just to add that I may have had an advantage. Our last unit we covered motors and motor controls in some depth and, as such, I have the DOL circuit etched into my subconscious. It was the arrangement there between contactor and N/O, N/C contacts that informed my response.

 

[Marvo]

Okay so once I've got my head around the requirements I usually draw a plan on paper. The plan isn't a circuit diagram it's just a very rough schematic of who's who in the zoo. It might suggest what components are going to be used and their relationship to each other ie what is controlling what.

Here's the 'Plan A' schematic that I've come up with;



It's called 'plan A' for a good reason...mainly that Plan B and usually Plan C end up superseding it at some stage.

What it shows is the two 12vdc alarm beacons on the left which will each operate a relay. These relays are configured so either of them will cause the 230v relay that supplies the floodlight to operate. The 230v floodlight relay will have one of its contacts supplying its own coil, this is a 'self hold' arrangement. The self hold circuit will include the timer contact and the reset-button contact both of which are normally closed.

And that's as far as the plan goes. Next step for me would be to split the circuit into two pieces, the 12vdc side and the 230vac side. I'd start drawing these circuits separately to start with, then when it looks like they both might work I'd look at connecting them together.

 

[Happy Jack]

Haha. Even down to the orientation of the relays...

I'll try and upload my drawing later. Thanks again Marvo, that really makes it crystal clear.

 

[Marvo]

.... Our last unit we covered motors and motor controls in some depth and, as such, I have the DOL circuit etched into my subconscious. It was the arrangement there between contactor and N/O, N/C contacts that informed my response.

The way a DOL starter self holds is very similar to the way it would work in this circuit. It's great to see you're using existing knowledge and adapting it to new challenges, this is what designing new systems is all about. You already know all the bits and pieces it's just a matter of rearranging them into a new bigger picture.

There's no mad rush to get your circuit finished, I'm hoping some of the other tear-aways like Floody and Resu are going to pitch in with an attempt as well

 

[Happy Jack]

Below is my first attempt along with a number of products that are referenced to it. I shall run up this materials list over the next day or so, as well as explain my circuit and reasoning in a bit more detail, even if it is proven to be incorrect.

What struck me is that, in fact, the N/C override switch could be located in a number of positions. But something irks about where it is currently, and I just can't place it. Anyway.



12V-R1 & 12V-R2 -
PT2S7LB2 - TE CONNECTIVITY / SCHRACK - RELAY MODULE, DPCO, 12VDC | Farnell United Kingdom

230V-R1 -
RT3S4T30 - TE CONNECTIVITY / SCHRACK - POWER RELAY, SPDT, 230VAC, 16A | Farnell United Kingdom

230V-TR1 -
M1SMT 24/230V - BROYCE CONTROL - TIMER, MULTIFUNCTION, 6 FUNCTION | Farnell United Kingdom

 

[Marvo]

Wow, looks impressive!! I'll have a good look at it later when I have some spare time.

What struck me is that, in fact, the N/C override switch could be located in a number of positions. But something irks about where it is currently, and I just can't place it. Anyway.

Often the final layout decision is influenced by the layout of the existing system being retrofitted or even keeping cable runs short as possible etc. These decisions can often be made later on in the life of a project, even as late as during the actual installation. Like I said there's not necessarily just one correct answer.

Good work Jack

 

[Marvo]

Okay, looking at your circuit when either of the zone alarm beacons get 12vdc power it operates one of the two 12v relays. Both of these relays contacts are wired in parallel (both the common contacts have a permanent 220v supply) so it works as an 'OR' arrangement where either will operate the 230v relay (R1).
So far so good

Operating relay R1 will perform 3 different functions. 1. It will supply the LED flood with a 230v supply. 2. It will supply the normally open timer contact with a supply. 3. It will supply the timer to start the timing process.

You've used a multifunction timer so I'm going to assume it's set so it will operate the contacts immediately on receiving supply and hold them for a timed period before dropping them out.


If this is the case then the timer will self hold over its own contacts and those same contacts will keep the LED flood illuminated.

Any time the reset button is pressed the timer and the relay will both drop out as long as the initial alarm has been reset and the 12vdc signal has stopped.

It's a very nice circuit. As far as I can see it will work as per requirements. Well done and congratulations on a successful circuit.

The only thing I would suggest is that you could get rid of the relay R1 entirely. If the timer contacts operate immediately on power-up then relay R1 could easily be made redundant with very minor changes, the only purpose it's serving at the moment is to supply the timer with power. I've added a clue in the drawing below.

 

[Happy Jack]

Yes I see it now, thanks for the pointer, Marvo. With your comments, R1 does appear redundant. I should have reproduced the DOL a little more accurately, in hindsight. And I think that was what was bugging me.

Thanks for all your efforts. Will come back early next week with a price. Haha.