I’m going to need 50 potentiometers, all panel mounted, with a 6mm diameter knurled split 15mm long shaft (or close to it). I will be using them as dimmers on my layout for house/street incandescent lighting. Each bulb (grain of wheat) is between 6 and 12Vdc and draws between 23 and 85ma. There will be no more than 10 bulbs on each circuit. The power supply is 13.7Vdc. Anybody know what type of pot I need and where I can buy it???
mkepler954
I have found Digi-Key to be an excellent source with great service, fast delivery and good prices. Here is a link to their potentiometer selection:
http://www.digikey.ca/product-search/en/potentiometers-variable-resistors/rotary-linear/262965?k=potentiometer
Hopefully you can find something suitable.
Dave
Edit: Re pots not being suitable - My bad - I don't know enough about electronics so I should have kept my mouth shut.
I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!
A potentiometer isn't going to cut it here. You need wire wound rheostats. Do you really need to constantly adjust the brightness of your street lamps and building lights? You can keep the voltage low on multiple circuits using voltage regualtors or even just groups of diodes in series for th require voltage drop. Even with a rheostate that cna handle the load, the drop will vary depending on how many bulbs are in a given circuit, because the voltage drop depends onthe load current. Same reason old (non-transistorized) power packs meant for HO scale don;t work on N scale or many modern HO locos- the motors are more efficient and thus create less of a voltage drop across the rheostat.
If you really must dim all the lights like thi, your best bet would be some circuits designed for this, with a power tranistor or simialr output. A potentiometer would then be the control.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
The typical carbon potentiometer used as a volume control in a radio, TV, etc. cannot handle the current load that will result from incandescent bulbs. You will need wire-wound power rheostats for this, and they are not cheap or easy to find.
Just a thought, it might be cheaper to try a used cheap transformer for trains, just vary the track voltage. Depends on draw vs power pack capabilities. But maybe worth a test since you can get those sometimes pretty cheap.
Richard
Yeah, I also don't see the need for dimming house and street lights. You just flip them on, then dim your overhead lights and vise versa; you raise the overhead lights and then turn off the layout lights with another flip of a switch(es).
If you absolutely had to dim the lights, you might consider a stepped dimmer using rotary switches and resistors, They can be had with 12 and 16 poles (steps). You would use a different resistor value for each step. It would be cheaper than buying 50 dimmers!
In DCC it would be fairly easy although not cheap to do it with stationary decoders with or without an automated program.
Jay
C-415 Build: https://imageshack.com/a/tShC/1
Other builds: https://imageshack.com/my/albums
Thanks all! I guess I bit off more than I can chew. As they say, a little bit of knowledge is a dangerous thing. I actually wanted to do this for my 11 grandkiddies to get them involved and have fun at the same time. After listening to you guys and doing some more research, I've decided to scrap the idea. I will hook most of the lights to a buss powered by a variable power supply (1.5v to 12v) and selectively use dimmers on a separate 12v buss to power spotlights, an occasional house or a closed business. This will still keep my younguns happy and still look pretty cool.