I have a home project which involves using 17 small Christmas lights(2.5 v. ea.).
110 v. house current burns this few bulbs out. Can I use a dimmer switch(preferable)
or a transformer to reduce the current?
I have a home project which involves using 17 small Christmas lights(2.5 v. ea.).
110 v. house current burns this few bulbs out. Can I use a dimmer switch(preferable)
or a transformer to reduce the current?
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Replies
Terry,
2.5 volt bulbs? Expain please. Most christmass tree lighting is rated for 110 volts, unless they have a plug in type step down transformer on the cord which would reduce the voltage to the whole string of lights. Still, even those are sold as rated for 110 volt usage because the transformer is integral with the cord.
I think we need more information to provide any help.
Dave
Dave, I'm looking at the box the christmas lights came out of. The lights have a 5 amp, 120 v. fuse. It says" replace bulbs with only 2.5 volt push in type lamps".? It doesn't say what wattage they are. Does this give you any help? Terry
Terry, using Matts 7v figure, you could use a 120v to 12v transformer. Most thermostat and doorbells use a 24v transformer, but some use 12v. You probably have one in your house for your doorbell. A simple test would be to add a couple of wires to the secondary (12 or 24v) side of it, and hook up your lights. Worst that could happen is that you burn out a few more bulbs. If it works,your problem is solved.
Had another thought. My cell phone uses a 6v dc transforner. Maybe other plug in type transformer you have around the house would be closer to 12v ac. Calculators, kids games or toys, that sort of thing. Heck, maybe the lights will work on 6v dc current.
Let us know what your project is, and what you end up using.
Dave
Dave, Christmas bulbs are wired in series, not parallel like most household lights. So if there are 50 bulbs in the set, each bulb would be at roughly 2.4 volts.
Terry, What are these lights for? Is it possible to use higher rated bulbs (17 bulbs would have about 7 volts across each)? Otherwise it depends how the set will be used on how I would hook it up.
When people 100 years from now see my work, they'll know I cared. --Matt Mulka
Edited 4/7/2002 3:35:35 PM ET by Matt Mulka
Matt, My project, no kidding, is a display using the dash gauges out of a Nissan. The holes in the gauges for the lights are the same size as the small Christmas lights. Thanks for the help. Terry
A dimmer switch will not work well or might not work at all due to the way they are designed. It could end up blowing your bulbs out unpredictably. You may be able to wire the dimmer to a transformer with sucess, but I would try to use a wall transformer or ac adapter instead.
Wire the bulbs in series and multiply the number of bulbs x 2.5 to get the operating voltage. You can then buy (or scrounge up) an ac wall adapter of that or somewhat less volts to supply the voltage (AC or DC - either one ok). By the way, these adapters are rated at a output current, and if you draw less amps, the ouitput voltage may be higher than the rating. I believe the amperage is very low for these bulbs, the 5 amp fuse is used so that more strings can be plugged into the end socket.
You may be able to use 6 bulbs for an operating voltage of 15 volts, which will operate off a battery charger (typically at least 15 volts output).
Terry,
If I assume you are using these lights in their original series configuration and you want them all to work in unison, then yes, you could use a household light dimmer to drop the 110 vac household voltage to about 40vac. I get 40 volts(actually 42.5) from 17 (lights) multiplied by 2.5 volt rating you indicated. Keep in mind the 2.5 volt rating is a maximum so 42.5 volts total should be considered a maximum for the whole circuit.
If you want the lights to work individually then you need to supply 2.5 volt source(maximum) that can handle the current (i.e.amps) that the bulbs will draw and the hook the bulbs in parallel. I don't think a household dimmer is exact enough to give you 2.5 volts.
It has been a few years since I've dealt with this stuff but I think I got things BASICALLY right...Get a cheap Multi-meter from Radio Shack to play with and remember to always start with the meter set at a higher value than you might think be measuring! And, even though it might 'just' be 2.5 volts don't touch it to your tongue. It's not the voltage that'll kill you it's the amps. I've seen a 5vdc source put a 250lb guy flat on the floor.
Ron
It's not the voltage that'll kill you it's the amps.
Wrong. Neither amperage nor voltage kill. Power kills. While only a small amount of current in the wrong part of your body (the heart for example) will kill you, it wouldn't be there without voltage. So don't go thinking you are safe because amperage or voltage is low. Never handle something with voltage or current present unless you are trained and know what you are doing.
Now that I'm off my soapbox (sorry I had to do that). I think a transformer would be a good way to go. Stop by an electrical or electroncs store and tell them what the application is. They should be able to guide you in the right direction. Since I'm assuming this is for something fairly permanent, might as well get something heavy enough to take the load (albeit a small one) and last.
When people 100 years from now see my work, they'll know I cared. --Matt Mulka
Just saw your post about your project is using an instrument panel from a car. Well, couldn't you just leave the original bulbs in, find which wire or contact from the original harness powers these bulbs, and then just use a 12vdc battery charger to power to the correct contact?
Ron
Dimmers will not work because you must turn most of them to about 50% before they start up. Now you have about 60 volts, which is going to immediately blow the bulbs.
How about leaving the Christmas light string unchanged, and just hiding the extra lights where they won't be seen? All you'd need is enough space that you won't get too much heat building up. If you go the wall wart transformer way, be sure to check the current drawn by the lights, and get one that can handle the load.
-- J.S.
Thanks for all your suggestions. I'll let you know how it turns out.
This is the first time I've used this forum. It's great.
Terry
Mark...yeah, I thought about that problem but I thought it was somewhat less than 50% but I never really measured it, you're probably right. Ron
Radio Shack makes a handy plugin multilevel voltage output transformer.....not much money either........................take a look.
....................................Iron Helix