I have a set of 60 “rice style” bulbs with a 24volt power unit. There are 3 and sometimes 4 wires to each of the bulbs. I believe they are hooked up in parallel. They burn with a dim orange light rather than bright white.
I would like to add a string of 30 lights (in series) to my roundhouse. I have an old transformer to supply dc power if necessary.
Could I use these lights with the proper resister or should I junk the lights?
Doc
Lots of open-ended specifics make this rather hard to answer ....
What is the current draw per bulb ? What is the voltage rating of the bulbs ? What is the current rating of your power supply ? Are the bulbs all wired in parallel or series or a mixture of both ?
Just some initial suggestions .... A 24 volt supply is not the best for powering low voltage bulbs (1.5 to 12 volt). The ideal arrangement is to use a power supply that is at least close to the voltage the bulbs require. If you are using 12 volt bulbs, use a 12 volt supply. Also, series wiring bulbs should be avoided. First of all, 30 bulbs that are rated even at 1.5 volts will require 45 volts at the source to light them properly. Then, if one bulb burns out, they all go out !!! Wiring them in parallel will avoid that. Then comes the current draw - if each bulb draws even 250 milli-amps, 30 bulbs would require a supply of over 7 amps !!!
My suggestion (and this is just me) would be to scrap the bulbs and go with LED lighting. You could run hundreds of LEDs off the same power supply, and get a much more realistic lighting effect over-all. That many bulbs in an engine house would look for all the world like the inside was on fire !!!
Mark.
¡ uʍop ǝpısdn sı ǝɹnʇɐuƃıs ʎɯ 'dlǝɥ
Maybe I should have explained the problem a bit differently. If I knew what the voltage of the bulbs were I would not have sent the e-mail.
I thought someone might know what voltage a 3mm bulb (not LED) might be. If 60 produce a dim light on 24 volts I thought the bulbs would be at least 24 divided by 60 or 0.40 volts apiece. In addition my stated needs of 30 bulbs would allow me to use a 12-volt power source, which I have plenty of.
The construction of the roundhouse prevents my use of parallel wiring. A series string of lights would work well since the whole string could be pulled out and replaced easily if one burnt out and replaced.
Does anyone know what voltage 3mm incandescent bulbs usually run on or how I could test them to find the voltage?
Doc,
The quick and dirty method obviously would be to remove one of the bulbs, attach it to the DC terminals of a power pack with wires, then - starting at "0"- gradually turn up the voltage of the power pack. If you have an MRC power pack with nice incrimentations labeled on the outside of the knob and you know the output of the your power pack, you can get a reasonably accurate idea what the bulb is.
Course, this is probably not an option for you since I'm guessing you'll want to keep the string intact. You could always take the last one...
Tom
https://tstage9.wixsite.com/nyc-modeling
Time...It marches on...without ever turning around to see if anyone is even keeping in step.
As Tom indicated, that's probably your best approach. Your opening statement about some being wired in series and some in parallel have me thinking something similar to a string of Christmas lights. A string of 60 12volt bulbs could have 10 bulbs in series with 6 of those series wired in parallel to run of 120volts. Conversely, you could have 20 6volt in series and 3 of those inparallel.
You won't find any common bulbs with a voltage rating under 1.5 volts. So unless you can mathematically decipher how they are all originally connected to their intended power source, our guess is just as good as yours.
Do as Tom suggested, and when you have the bulb at the desired brightness, remove the bulb and take a voltage reading at the power pack's terminals. With that known reading, you can proceed from there as to how many bulbs inseries you can run from a given power supply.
I took the advice and used a VOM meter on 1 bulb. I cranked up the power to 2.5 volts and the bulb burned as bright as I would want it. This was twice as bright as it was in the string.
I guess I should first try 15 bulbs with 12 volts and see how that looks and proceed from there. Are there any better ideas?
Thanks, Doc
Well, you're on the right track !
Based on your finding 2.5 volts is where you want the brightness to be, you are only going to get FIVE bulbs in series and still maintain the same brightness ( 2.5+2.5+2.5+2.5+2.5 = 12.5 volts) Using your original 24 volt supply, you could in theory double the amount of bulbs to a maximum of TEN.
Simply put, divide the number of bulbs into the voltage supply and that will get you the volts each bulb will receive. There's also the current draw to consider as well - too much of a current draw will cause your supply to ultimately go into melt-down.
Something else to consider. If you operate your bulbs at a lower voltage, they will last longer.
I usually try to wire my indoor or outdoor layout lighting "in parallel". This way I can hook them to the DC terminals of my power pack and "dial down" the lighting so that I operate the lights at 50-60% peak capacity. The bulbs both last longer and they give the layout out a warmer glow to it.
For example, here's my freight house using Miniatronic 1.7mm 12V bulbs @ 60% power for both interior and exterior lighting:
For me this is plenty bright enough and gives the building a more inviting look to it.
Doc, since you will be wiring your roundhouse "in series", adding a couple more bulbs to your string should accomplish the same task. The other thing to keep in mind is that, if your roundhouse is plastic, the lower voltage output of the bulbs will allow them to run cooler and be less likely to cause any sort of melting, if a bulb should make contact with a surface.
To be honest with you Tom, I'd run those outside lights even LOWER. Unless that's just the wya your camera adjusts to the light.
I've seen charts on the internet that show the amount of increasd life from running th ebulbs below their rated voltage. It's pretty incredible. Pretty much to the point that if you run them at 50-60% of their rating, they theoretically won't burn out in your grandchildren's lifetime. Even doing 75-80% greatly extends the life. Those Edison bulbs that are still burning after 100 years? Those thick filaments are probably good for 400-600 volts, running them on 120 is a good part of why they've held up.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
rrinker To be honest with you Tom, I'd run those outside lights even LOWER. Unless that's just the wya your camera adjusts to the light.
Randy,
That's exactly what's happening. I took the picture just after sunrise, with the basement lights out and the camera on a timer. The lights would normally look softer and less "glarey" than that.
Will pray you have a good surgery and speedy recovery, Doc. Keep us posted how you are doing. The important thing is to get better.