I am planning to install a few of the PECO switch machines on my N-Scale layout. It is sounding like I will need a Capacitor Discharge Unit for best performance. I am not likely to build my own - where can one be pruchased? Are they really needed? Any info would be appreciated. Thanks.
Hi
Yes I used one on my last layout. I used SEEP turnout motors to throw PECO switches. The CDU throws the switch fast rather than slowly like a Tortoise. It’s a British company but have a look at their website. Scroll down the page to view the CDU. www.gaugemaster.co.uk/modules.html (I live ten miles from them.)
I’ll be using Tortoise on my new layout.
Anyway, hope it helps.
Cheers!!
The Circuitron Snapper is available several places.
And you could build one:
Awww, c’mon, you can build one! It was my first time back in soldering after many years. Believe me, a CDU is an excellent first-project to get your feet wet on soldering and wiring. You will do far more complicated projects as your layout progresses. Mine took me maybe an hour to put together and solder. (And yes, I’ll admit it, about 3 months to find the loose wire I forgot to solder.)
Another good reason to build one: All the parts are cheap. If you fry one (pretty difficult, actually) then you can get another one without breaking the bank.
If you can dig up a copy of the book Practical Electronic Projects for Model Railroaders, there is a whole chapter on CD power supplies, and I believe the second one is the one that is the same design as the Circuitron Snapper. It used to be that allt he required parts were avaialble from Radio Shack, that might still be true.
I agree with Mr Beasley. Maybe because I said it before too [:D] A CD power supply is a great first time electronic project, it’s very simple and hard to mess up, and most of the parts are quite robust in that if yo hold the heat on for an extra second or too it won;t fry the part. You can’t go nuts and heat for as long as you like, or use a big 100 watt soldering gun, but neither is it a delicate circuit. I built mine in 1979 to power the Atlas turnouts on my N scale layout and it still works to this day. I was 13 at the time (athough to be honest it was far from the first thing I soldered together - and the following year I built a computer from a kit). The Circuitron device is a quality product and will work fine, but if you want to expand your skill set a bit, this is a perfect way to do it.
–Randy
Here’s a pretty simple CD I got from someone on one of the forums (Maybe Don Gibson??)
How hard can it be?
I have this book, “Practical Electronic Projects for Model Railroaders” if you need the pages scaned on the CD discharge unit sent me an email. Great book for beginers electronics. Built the SS throtles from this book. Just retiried these after twenty five years of service. DCC all the way now
Ineed that will work, but the difference between the slightly more complicated circuits with the transistor is that the transistor ones will recharge the capacitor about 10x faster, maybe more. This could be important when you suddenly realize you hit the wrong turnout and you’re about to dump your favorite loco on the floor. The simple resistor/capacitor circuit will take significant time to build up enough of a charge the throw the turnout. That can be adjusted somewhat by altering the value of the resistor, but the point of the resistor, besides preventing the capaciotr from being a dead short on the power source, is to limit the current that flows when you accidently hold the button down too long. With a higher value resistor this current is low and won’t even warm up the relatively delicate Atlas N scale switch machines. The purpose of the transistor is to bypass that resistor during the charge cycle so the capacitor charges up quicker.
Probably more circuit theory than you wanted to hear, but with the transitor version I built I was able to push switch buttons on my N scale layout as fast as I could move my fingers and always had enough juice to snap them over. That would not have been the case with the simple version.
–Randy
I’ve been looking for one lately also. Here’s the least expensive I’ve found so far:
http://www.1stplacehobbies.com/cgi-bin/prod.asp?pn=800-5303&x=13&y=10
I’ve had very good results buying from this company.
Tom
They are easy to make and quite cheap, less than $3 if you buy your parts right. Here’s a how to on making them.
http://www.2guyzandsumtrains.com/Content/pa=showpage/pid=27.html
Even though power is only a short pulse, the solenoids in the switch machines draw quite a bit of amprage. Two amp power supply is good enough to work reliably, especially when activating more than one switch machine. Voltage should be about 18 to 22 volts.
Allelectronics has a 20vdc, 3amp table top power supply for $14.
Thank you for the link, Gary. I’ve been looking to replace the power supply tthat runs my transistor throttles.
Tom
Thanks for all the imput. I think I need a clarification on one point. How many CDU do I need for a layout? Is it one simply hooked up to the power supply and then to the bus that powers the switch machines or one per switch machine. Now my budget is as tight as the next guys but time is a premium and if I only need one, $23 and time savings sounds like a good deal. If someone could point me toward a diagram and a key as to what the symbols represent I may change my mind. Thanks - from an electrically challenged train lover. Oh ya - my 7 year old just wants the DCC hooked up and to keep the trains running.
The number of CDUs depends on the layout. I have two (probably because I bought 2 at different times) and they are in stations at opposite ends of the layout. If you are just one operator, you can get away with one.
If you will have multiple operators, you may want one for each yard/station. This eases the problem where one operator empties the CDU just before the other tries to use it.
The other consideration is the power of the capacitor. The more switches you throw at the same time, the bigger you need it. (someone else will have to come up with a formula!)
You can throw a whole route at once with a single button push. Search for “diode matrix”.
I use 1 per turnout as it simplifies wiring and they are just so cheap to build yourself. One DC power supply can power them all, so each unit requires one 1K resistor and one 2200 mfd cap. The cap is 65 cents and the resistor is 5 cents at http://www.allelectronics.com/index.html . No board is needed. Fred