Capacitive Discharge circuit for switch machines - WOW!

[MisterBeasley]

I was having trouble with one of my PECO switch machines. Sometimes it would flip, sometimes not. My layout is still in chaos, so the wiring is is mish-mash of solid, stranded and alligator clips. The machine in question is much further from the power supply than the others. I also wired up a couple of cheap relays to control signals, and they were working poorly, too. I wasn't too surprised about the relays, since I was running AC for the switch motors, and the relays were designed for DC.

I found a capacitive discharge circuit diagram, and today I hit Radio Shack after my LHS and picked up the parts. It's just a diode bridge, 2 resistors and 2 capacitors, so I had it built in in hour.

Like I said, "Wow!" The switch machines all throw with an authoritative SNAP when I hit the button. The relays for the signal lights are now rock-solid, too.

I picked up a circuit board and a couple of nice screw terminals for the input and output wires, but the basic thing costs about 10 bucks. I connected the input to the AC supply of my old powerpack, which I had been using for the switch machines anyway.

[stokesda]

I just built one of those, too! (for my Atlas machines) Haven't had a chance to try it out in practice yet, since my layout is still in progress, but I was rather pleased when everything worked properly after I put it all together. I'm guessing you got your plans from the website www.awrr.com. The site also features a circuit for turnout indicator lights that I'm now chomping at the bit to build.

One thing I'd do differently this time is look at ordering the parts from Jameco online. They seem to be much cheaper than Radio Shack.

Anyway, glad to hear somebody else has made a CD system and is happy with it!

Cheers, and happy circuit building!

[TomDiehl]

Wow, does that bring back memories. I remember a schematic published for these back in the '60's. For a twin coil machine, they can give them some snap.

[MisterBeasley]

Gee, Dan, you're a mind reader. Me, I'm a google reader, but that's how I came across the same site.

[stokesda]

Acutally, I found that site purely by accident from reading this forum a little while back, from this topic:

http://www.trains.com/community/forum/topic.asp?page=-1&TOPIC_ID=38901&REPLY_ID=402410#402410

Prior to that, I'd never heard of capacitive discharge circuits... so I didn't even know what I was missing, let alone know what to Google [:)]

[Anonymous]

Another excellent source for circuits is:

http://home.cogeco.ca/~rpaisley4/CircuitIndex.html#index

Mike Tennent

[rrinker]

Told ya's! Really easy to build and they WORK.

[:D][:D][:D]


One of the ones on Rob's site is close to the one I built a long time ago from Practical Electronic Projects for Model Railroaders. It has a transistor in it to speed recharge time on the capacitor. You can throw turnouts as fast as you can hit the buttons - without the transistor it take a bit of time to recharge. I built one when I was in N scale and from that moment on NEVER burnt out another of the fragile Atlas N scale switch motors.

--Randy

[Anonymous]

I worked at a Radio Shack store back in the mid 1970s and we used to sell a kit for a capacitive discharge device for your auto ignition to help with cold weather starting. All these shade tree mechanics would come in and ask for "that CAPTIVE discharge" thing. I'm glad to hear that the CD circuit works well on the layout. Now....how do I keep that discharge captive? This net ought to do it....hmmmm....let's see now.......

[rrinker]

I remember those. Going back even further, early 70's at the latest, my Dad installed one on our 66 Chevy. Not the RS one, but the same thing. Basically those were retrofit electronic ignitions that changed your old points and coil ignition into the same electronic ignition found on most modern cars.

--Randy

[Anonymous]

I'll bet your dad was sharp enought to know it was CAPACITIVE discharge! What do you model, Randy. Seems like you're in the right part of the country to model PRR or maybe Conrail.

Ed

[rrinker]

QUOTE: Originally posted by ebriley

I'll bet your dad was sharp enought to know it was CAPACITIVE discharge! What do you model, Randy. Seems like you're in the right part of the country to model PRR or maybe Conrail.

Ed

Yeah I'm pretty sure he knew the difference.

See my signature line - I model Reading. I used to live a couple blocks from the East Penn main line, which is the primary east-west route to New Jersey for Conrail/NS. Now I live not far from the old C&F branch, which still sees a train now and then, except few of the new transfer warehouses they've put up around here have rail service - go figure. During they day it's hard to move around here with all the crazy truck traffic.

--Randy

[Anonymous]

Boy, do I miss distributors with points and stuff. I used to set the dwell with a match book cover, and off I drove.

Now , if my 2002 F-250 stops on me on the side of the road, I have no idea whats wrong.

AAhhh, the old days.

Jim

[Seamonster]

You said it, Yardgoat46! I bought a 1992 model car, trading in my 1985 that had served me so faithfully, and when I opened up the hood on the dealer's lot, I just stared. Nothing was familiar. The engine was facing the wrong way, what's the fan belt doing snuggled up to the right fender, where's that big round air cleaner, where's the carburator I used to tweak with a screwdriver, where's anything familiar??? [:O] The backyard mechanic has been put out of business--the car has to be serviced by a technician, not a mechanic now. I'm reduced to topping up the fluids now, not that anything other than the washer fluid needs it with 3 month service intevals on my 2004 model to keep up the warantee. I've still got fond memories of my old 1958 VW Bug that I could fix with baling wire and chewing gum.

Just to keep the post on topic (sort of) I remember those add-on CD ignitions, and I use CD supplies for my turnouts. I built Peter Thorne's CD unit years ago, but now I'm going with Rob's. They're a little violent on N scale turnouts, but they get those points over with authority!

[rrinker]

Thorne's is the one I built for my N scale layout, served me well. I think there's 3 in that chapter of Thorne's book - a super simple one, the fast recharge with a 2N3055 transistor, and one that has the complete power supply to plug into the wall. I built the second one and hooked it to my old power pack while the (then) new Tech II ran my trains. Worked like a charm. Probably still works if I knew where it was.

--Randy