Electrical help needed - building lighting

[Butlerhawk]

I wired a building for lighting - used 2 bulbs from a 35 bulb C'mas light set; hooked up to a 12 volt power pack; in less than 5 minutes both bulbs burned out simultaneously. What happened? Not enough bulbs hooked up for 12 volts? Your help will be appreciated. Thanks.

[richg1998]

This question should really be in the Electrical and DCC question.

First of all, I can see you know nothing about electricity. The 35 lamp string with 120 volts has all lamps in series. That means 3.5 volts rating for each bulb.  Do the math. Two bulbs in series ( 7 volts) would be very bright for 12 volts and probably burn out fairly rapidly. A single 3.5 volt lamp with 12 volts will probably burn out instantly.

 

Rich

[7j43k]

Or, in a friendlier way, you can divide 12 by 3.5 and get about 3 and a half bulbs. Four in series sounds right. If you want the lights dimmer, add more bulbs. In series.

Ed

[larak]

Butlerhawk

hooked up to a 12 volt power pack; in less than 5 minutes both bulbs burned out simultaneously

 

Likely only one bulb burned out if they are wired in series. If any series component burns out, current flow stops through the entire circuit. (That's why it's called series.)  Toss the other one too since it's been heavily stressed. Do not reuse it.

Line voltage is 120V nominal.  120 / 35 = 3.43 volts per bulb. Probably 3-1/2 volts each.

Use four or five in series and you'll be OK. More would work but likely be too dim. Experiment - they're cheap!

Karl

[prrsd45]

If you have a spare DC power pack, you can hock up these bulbs in parrelle and turn up the voltage until the bulbs light. Check your voltage to insure they do not exceed 3.5 volts. Then tape the knob on the power supply to that voltage. You can continue to add more of the same bulbs through out the layout with the proper voltage already set.

 

[Seamonster]

I agree with everyone else, those were likely 3.5 volt bulbs and were burned out by 12 volts.  Here's a couple of alternate solutions.

The Christmas tree lights were likely the miniature kind with little wire leads that press-fit into plastic sockets.  Check out the stores for replacement bulbs rated at 12 volts.  Now's a good time to do this because the stores will be trying to get rid of their Christmas stock--if they haven't already taken it off the shelves.  Try to find clear bulbs.  The colouring won't come off those bulbs!  (Don't ask how I know!)

Or you could get a 3 volt "wall wart" power supply and use the bulbs you have.  You will likely be able to operate only a few bulbs off this power supply before you reach its current limit.

Hint: operate the bulbs in structure lighting at 10 to 20 percent lower voltage than they are rated for.  They will be plenty bright enough (at full voltage they are glaringly bright) and they'll last much longer too.  It's always a good idea to paint the inside of the walls flat black so the light doesn't shine through the plastic and make the structure look like a glowing radioactive haunted house.