Time Delay Relay

This might do it: Cebek 28-6176

This is the Adjustable Timer I used on the fire scene I built. I used the one pre-assembled and tested price 14.99 works great.

That looks like just the ticket.  Do you use it with AC or DC?

Here it is from the manufacturer, as the eBay listing stated "last one"

http://galakelectronics.com/VG-301B.htm

Thanks Dale.  I think I've found a few pre-assembled kits for short money that I may try.

http://www.ebay.com/itm/DC-12V...;hash=item3a87052f11

http://www.ebay.com/itm/TIMER-...;hash=item4ab5d66b2b

http://www.ebay.com/itm/COMPAC...;hash=item4ab3b247c3

Boy, you can see the difference in prices based on location!  You can see why the Chinese have captured the cheap electronics high ground!

I ended up with this timer http://www.ebay.com/itm/251373...e=STRK%3AMEBIDX%3AIT and it gets me half way there.  When 12VDC is applied the relay closes for the chosen duration then opens.  The 12VDC must be supplied during the whole time the relay is closed.  I want to be able to use a momentary switch to supply the 12VDC to power the relay.  Can I do this by either inserting a capacitor between the momentary switch and the board or some other means?  If so, how do I determine the size of the capacitor?

I think I am making this more complicated than it is.  If I use a momentary switch that is normally closed it will power the relay through the cycle.  When the cycle is done the relay opens and waits for power to be removed and reapplied to re-set it.  When the momentary switch is activated (opened) it will break the circuit re-setting the timer and activate the relay again.  Is there a normally closed switch similar to a Lionel 90 controller?

How much time delay do you need? 

Yes you can momentarily charge a capacitor thru the momentary switch and have it hold the relay.  There is a formula to size the capacitor but for long time delays the capacitor is going to be quite large (and expensive).  If you have 12VDC available "all the time" you can get a time delay module that can be triggered by a momentary pulse from a switch.

I have suitable timers,not commonly available described below. Email me privately if interested.

link

You can also do most anything with the more common Mars timers and relays shown here,but they are at least 18 volts.

link

Dale H

How long do you want the relay to stay closed?  You can place a large capacitor across the coil of a 12 VDC relay and some some delay on opening.  I use one on my gantry crane circuit, a 2200 mfd, wjhich hold the coil in for about 2 second (to give motor a chance to stop before solenoid shift releases.  GRJ could probably advise of a supercap to give a substantially longer hold.

What I am anxious to find at a reasonable price {CHEAP!} is a relay to break a circuit that stays on more than 5-10 seconds, to save uncoupling tracks.

Back in the 60's, I experimentes using a cap to trigger a power transistor to get longer hold periods, but I have completely forgotten how I did it.

you can do that with 2 relays

The idea is discussed here in a different application. 

LINK

Dale H

Thanks for the replies.  I do think the timer I bought will work if I use a constant 12VDC source and a normally closed momentary switch.  I think a Lionel 88 controller will do the trick.

What is reasonable?

The OP's eBay module is about $5-6 and if used in the Delay-OFF mode, it will do what you want.  That is, when power is applied to the uncoupler it powers the timer module relay.  The relay instantly closes (applying power to uncoupler).  After 5-10 sec (or whatever you set) the relay opens and stays open until power is removed.  Of course if you are power the uncoupling track with AC 14V accessory voltage you must convert this to ~12V DC but this has been shown many times on OGR usually for isolated-rail occupany detection to trip a 12V DC relay.

OTOH if 50 years later you're still game for component level tinkering you could dust off your notes and charge a cap which drive a transistor to trip the relay after 5-10 sec of power.  That would probably be $2-3 in parts but a bunch of soldering.

What is "reasonable" is defined by the large number of uncoupling tracks and solenoid-activated accessories I have on my layout.  My layout is large because I've been acquiring stuff for almost 75 years, not because I've plowed large amounts of kilodollars into it in the past few years.

With Chinese 10-amp relays going for a dollar (I got a few dozen) and capacitors cheap, somewhere there's a schematic.