Circuit for constant to momentary relay for insulated rail operation

Gunrunner

i knows this is off topic and I apologize, but I have been trying to do a work around on the ERR whistle relay board. Since the SSR is not available I’ve been trying to sub a relay in it’s place with no success. Could you look at my modification to the circuit and advise me where I went wrong.

michael

The diodes will set you back 2-cents a piece so why not just put them in. 

I agree with GRJ that the effect will be minimal and in all likelihood unnoticeable.  Note that the coil is driven by a half-wave signal.  So even when the coil is energized, at least half of the time there is no energy in the coil and hence no energy for the proposed new diode to re-circulate!

The capacitor could indeed add more delay, but as George points out you can hear the AC half-wave buzzing if the switch is jammed in-between - what amounts to a free audible warning/alarm.  A large capacitor would smooth the AC so you would not hear a stuck solenoid if the switch jammed in no man's land! 

So if the discussion turns to the jammed switch scenario, in addition to the original time-out method, you could install a 25-cent PTC resettable thermal fuse that would cut power to the coil if active for more than a few seconds.  Of course the train might still derail if the switch is stuck in no man's land but at least the switch coil would not burn up!   

And, then, to peel even more layers of the onion, I suppose one could concoct a scheme to cut track power if the switch is stuck.  Then the train would stop dead in its track, not derail at the switch, user gets some kind of fault indication, user clear the fault, resets the electronics and away we go...

I got it working on one switch. However, it is not consistently throwing completely. I increased the voltage on the accessory transformer, which helped. I may need a beefier transformer. The 5ms. delay time may be a little short. However, I may also be having mechanical problems with the switch and how I attached the switch machine. The manual switch normally takes heavy spring, which I removed. I found some lighter springs from my RC car parts bin. I may try that. I still don't have the timer relays, so I can't try those yet. I could add a capacitor. GRJ, where would I add that, and is there a value that would work best at 18V half wave DC? Thanks!

George

To delay the relay dropout, you add the cap right across the relay contacts.  As for what value to use, that is dependent on a lot of factors, I'd start with around 100uf 35V and see if that gives enough delay.

Thanks again. 

I'm going back to troubleshooting 101. I need to get the switch working with the regular switch control, before I get the anti-derail working. Once that is working flawlessly, then I will see if I need any updates to the anti-derail circuit.

George

I want to report back and thank everyone for their help. I got the circuit working consistently. First, I read about these LGB switch machines and supplementary switches. The supplementary switch, being mechanical, creates mechanical resistance on the switch machine, which was causing me problems. Fortunately, LGB solved this problem with a crazy device called an EPL-Booster (LGB 52750). I bought one of these and ran the AC to the switch machine through it. It makes the switch machine "snappier". I have no idea how it does it. I found a schematic and it is loaded with diodes. Right now, I am using 24VAC accessory power, which is beyond the stated specs for the unit. I may try backing that down. 

Second, the switch threw great in one direction, but had problems in the other. It seemed like the power was cutting too soon to the relay, as we discussed earlier in the thread. I tried Keith's method of adding a diode across the relay. It did seem to add a delay, but it was too short. I then added a capacitor as John suggested. I had the 47uF caps that Stan recommended and used one of those. It did the trick! The switch throws great in both directions!

George