wiring a relay ( dual) to operate 2 electromagnets

Hi , i'm firstly going to link to a thread I posted recently as it will help in understanding what i'm trying to achieve https://www.electro-tech-online.com...lway-dcc-accesory-decoder.162255/post-1411560 ,most of the relevant info comes toward the end of that thread , as you can see I solved the problem by using a ready made product that had only recently become available but a couple of problems have occured to me in that whilst the unit will energise either of the 2 relays and hence energise one or other of the 2 electromagnets via a DCC switching command it will depend on the model railway automation software to issue the DCC commands and if that experiences a hiccup it could result in a relay remaining energised after it should have switched off and subsequently lead to an electromagnet remaining switched on with the subsequent risk of fire as they can get quite hot ,I think I need some sort of variable timer to switch a relay off after a given number of seconds has passed (approx 3) even though the software is telling it to stay on , any ideas or comments will be most gratefully received . here is a link to the dual relay board , http://www.train-tech.com/index.php/accessories-extra/relay-controller .

Do you have 9.5V on a 6V relay coil? That will make it hot. But not if you stay within spec (?) Or is it the electromagnet getting hot.

Define clearly what you have, and need to change, with links to datasheets.
Input:
Function:
Output:

I did'nt say that I have 9.5V on a 6 volt coil , I have DCC voltage which in my case as the layout is in N gauge I have apprpx 14 volts which is fine for these relays , this is what the manufacturer say's , "The RL1 works on analogue or digital layouts and is powered directly by DCC or 12-16 Volts smooth DC. When on digital the relays can also be controlled by DCC accessory addresses which are easily set up using One-Touch DCC" .

I misread your question so my answer does'nt answer it properly , i'm not concerned with the relays getting warm because basically they don't but I am concerned about the 2 electromagnets which are used to uncouple railway wagons remotely , they get quite hot when energised for the 5 seconds that I have now determined is neccessary for a succesful uncoupling , I simply want to make sure that they can get no power once the relay has switched off as insurance against one remaining energised even though the control software should have told it to turn off .I should add that the uncouplers( electromagnets) will never be used both at the same time .

garyd said:

I think I need some sort of variable timer to switch a relay off after a given number of seconds has passed

Click to expand...

A common way to do that is with a one-shot circuit with the desired duration (typically built with a 555 timer).

How much current does the relay require?

Hi , i'm not sure if you mean power to the coils or the power that the relays will be supplying ? but i'll give both - the power to the coils is 14 V DCC which is a modifified DC waveform and the power supplied to the COM and NO contacts is 20 V regulated DC from an old laptop psu , I hope this helps ?.here is the manufacturers blurb -(The RL1 works on analogue or digital layouts and is powered directly by DCC or 12-16 Volts smooth DC. When on digital the relays can also be controlled by DCC accessory addresses which are easily set up using One-Touch DCC. Relays are a great way to switch on and off relatively high power devices such as motors and solenoids because they act like a switch contact and so are safely electrically isolated from other signals. The Relay Controller incorporates two separate relays, each with single pole changeover contacts which can switch up to 3 amps at 24 volts AC or DC, so can be used to control DC or AC models.)

Okay, I read the relay data sheet and better understand what you are doing. but I'm not familiar with DDC control.
It seems that if you are activating the relays with one DCC command, then it requires another DCC command to de-activate it.
Is that correct?

It's DCC (digital command and control) and is the way most model railways are controlled these days although the older DC system is still widely in use .You are correct in that it takes 2 commands to activate and deactivate either of the 2 relays and this can be either via a DCC handset which is linked to a computer like command station through the rails that the trains run on or automatically via Computer control software , at the moment I do the switching using a handset as the control software is not yet fully configured , the RL1 twin relay board has what is known as a DCC decoder built into it so that it can be given a unique DCC accessory address that the command station can issue commands to usually via a wired or wireless hand controller , in the case of the 2 relays I utilise a DCC "switching " command that is mostly used for changing points (uk) or switches (usa) but can be used for many things such as level crossing gates or working cranes .In addition to DCC accessories there are also DCC Locomotive decoders and the 2 types are completely seperate so that you can use say address number 10 on a Loco but also use address 10 on an Accessory decoder as the 2 types of decoder are seen entirely seperately by the command station or the Automation software .

So if it requires a DCC command to de-activate the relay, then I don't see an easy way to do that.
Are you using the S input or the M inputs for control?

You could perhaps use a timer to cut off the power to the relay or the electromagnetic after the desired number of seconds following activation.
Does that sound feasible?

I don't need to use the S or M inputs as the board is fed with DCC current and commands to switch the relays on and off are sent through there , "
You could perhaps use a timer to cut off the power to the relay or the electromagnetic after the desired number of seconds following activation.
Does that sound feasible?" this is precisely what I am wanting to achieve ie I want the power to the relays to be switched off 5 seconds after a relay has been activated but then say 15 minutes later for it to allow a relay to be energised again .

garyd said:

I want the power to the relays to be switched off 5 seconds after a relay has been activated but then say 15 minutes later for it to allow a relay to be energised again .

Click to expand...

So you need two timers.

If you reapply power to the relay will it always start in the relay off position?

I think you are probably right in that I would need 2 timers and yes it will always be in the off position when the timer allows the power to be restored .

A CD4060 timer circuit (here) could be modified to generate both times.
Is that something you could build with the modifications I can supply?

Here's something you can try. It is untested but should work. The circuit is a discrete "one shot" interface between the relay board and the EM coil.
When the output of the Relay board energizes, it triggers the one shot, energizes K1 for 5 seconds, then resets.
R3 reduces the voltage so a 12v relay (K1) can be used, its value will depend on the coil current rating required for K1.
The pulse width depends on the values of C1/R2 (and mosfet Vgs(th)) but the width can be adjusted just by changing the value of R2.
The circuit relies on the output of the relay board to de-energize, then re-energize, to enable the one shot to re-trigger. One circuit would be needed for each coil.

eTech said:

Here's something you can try.

Click to expand...

In post #10 the TS stated he wanted a 5s delay to turn it off and a 15m delay to turn it back on.

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Hi , Crutschow and eTech , i'm sorry for the delay in replying but I had a pressing matter to attend to , I really appreciate your help but I have to say that I know already that constructing electronic circuits is beyond my capabilities , I had in mind something off the shelf and have come across this https://www.alibaba.com/product-det...0.7724857.normal_offer.d_title.50841888aMXCRP , I have no idea whether this would do what I want so i'm asking you what you think ?.

garyd said:

I had in mind something off the shelf and have come across this https://www.alibaba.com/product-det...0.7724857.normal_offer.d_title.50841888aMXCRP , I have no idea whether this would do what I want so i'm asking you what you think ?.

Click to expand...

You may be able to use two of those to generate both the delays.
I'll have to give that some further thought.

Yes I thought it may take 2 , they are readily available in the UK via Ebay and would cost just £13.00 delivered .I'm in no rush so take your time .

Unfortunately, I can't really understand the chinglish explanation of how it works, so I'm not sure if you can connect it for your requirements.
It does look like it can be programmed for both ON and OFF times of the output, but it's not clear if it will do exactly what you want.

It may be better to get a delay module such as this, since it has a SPDT relay, which allows more flexibility in configuring the ON/OFF times of the output.
It appears to have the same timing modes as the one you picked.
The P2 or P3.1 mode may do what you want.