# Lights keep going out



## PatD (Feb 4, 2015)

I have about 18 mini bulbs I put in buildings and 6 lamp posts (included in the 18). I am using a separate transformer for just the lights. I have them wired parallel, positives together etc. I have tried 3 different transformers with the same results. They come on for about 5 seconds then go off. After a couples of minutes I can light them again with the same results. I have tested all the wiring with my volt meter etc. I'm guessing I need a stronger transformer. Do they have a circuit that shuts them off if overloaded? I have a large 12v - 13.7 volt power supply I could use but the voltage is not variable. Thanks for any help.

PatD


----------



## johnfl68 (Feb 1, 2015)

PatD:

Are these incandescent lamps, or LED's?

It's an odd behavior, sounds like perhaps a thermal breaker on the transformer, if all 3 transformers are the same, but I am only guessing.

Do you know how much current each bulb draws? What is the voltage of the transformer?

John


----------



## PatD (Feb 4, 2015)

HI John 

Incandescent lamps. Voltage unknown. If I hook 1 up to test it it lights very bright at full bore and doesn't burn out.

AHM 15 VDC 2.7 VA (circuit breaker projected.)

Bachman 17 VDC 7VA

Bachman 16VDC 1000mA

I'm attaching photos. Thanks for your help. I have a nice 12v dc power supply but i am afraid to use it because I can't cut the voltage down. :dunno:


----------



## johnfl68 (Feb 1, 2015)

OK:

If I remember correctly...
I(A) = S(VA) / V(V)

2.7/15 = 180ma (10ma per lamp for 18 lamps)
7/17 = 412ma (22ma per lamp for 18 lamps)
(16VA?)/16 = 1000ma (55ma per lamp for 18 lamps)

These are just guesses, as we don't know the current draw of the lamps.

Looking around, a 40ma draw is common for some mini bulbs, so that is probably why the first two power supplies had issues.

The third power supply should be able to supply 55ma a lamp, which should be ok if they are 40ma lamps. But if they are 60ma lamps, then again there is not enough current to drive them all.

Unfortunately not knowing the Voltage and the Current Draw of the lamps poses the problem.

If they are all wired in Parallel, then the Voltage is the same for all of them and the Current adds up. So you have already fed them with 17vdc, then the 12vdc supply should be ok, as long as it supplies more than 1000ma.

So hopefully this will help some in explaining the problem.

I just can't speak with any certainty with unknown lamps.

John


----------



## PatD (Feb 4, 2015)

That makes sense. I tired to wire them in series but to much drain the bulbs were dim. But in parallel they were bright. That was before they all were wired. I think you are right about the transformers being to weak to power all the bulbs. That was my theory. I am going to try the 12v-13.7 volt PS I have I think that will light them without burning them out. I attached a pic of the one I have. Thanks for all your help. I will let you know the results.

PatD


----------



## Howard1975 (Jan 6, 2014)

That power supply you show, the 12v-13.7 one, will be much more powerful then all three of your small power packs (AHM and Bachmann) combined together. That is because the "LAKE" brand power supply is rated at 3 amps. Combined, your 3 other packs equal only about 1.6 amps, if my math is correct (and the figures posted by John above in his calculations). 

The 13.7 volt power supply should be perfectly fine, as long as the bulbs can handle 13.7 volts. Otherwise, you would need to wire a limiting resister into the circuit, to lower the voltage to whatever the bulbs are designed for.


----------



## PatD (Feb 4, 2015)

I wired 3 spare bulbs parallel for a test and it worked fine. They lite bright and didn't burn out. So I hooked it up to the layout and it looks great! Thanks to all for your advise. I attached a few photos of the grand lighting. This is my first attempt at model rr and I am having a great time with it. I chose N scale due to limited space as we live in elderly housing. This forum is the greatest.

:appl: :smilie_daumenpos:


Pat D


----------



## johnfl68 (Feb 1, 2015)

Good to hear, PatD! Have fun!


----------



## Howard1975 (Jan 6, 2014)

That is good to hear, that everything is working good for you. Also it's great to hear, you are enjoying the hobby. The lights sure make the scene look nice. Have fun.

Howard


----------

