Best way to wire grain of wheat lighting?

[nick45326]

 Hello all,

  I am working on a faller carnival model that requires me to wire up a bunch of grain of wheat lights. My problem is if I wire them all together (continous) they are so dim that they render the lighting useless.  I was wiring them together, they were connected to an atlas connector then to my AC side of an MRC power controller.  My question is what is the best way to wire these small lights without the dimming effect and loss of power?  I am no electriation expert so plain terms would help a lot :)  Right now I need to wire up 5 grain of wheat bulbs for the model. However, I am sure I will need to wire up a lot more in the future... With plans to build an amusement park layout I want most of the lights to come on all at the same time with a flip of a switch (or two)..   Any help would be great. Thanks in advance. Nick

[narrow gauge nuclear]

You have wired the lamps in a series string.  You need to wire them in parallel. This means two wires need to run to every lamp.  This can be one long routed pair of wires going from lamp to lamp.  Depending on the number of lamps, you need to make sure that your power source can supply the current needed.

Example: Let's say you have 6 lamps that are 12 volt lamps and each needs 1/2 amp.  This means each lamp must have twelve volts across it to reach full design brilliance.  If this is done each will pull 1/2 amp of current.

In a series string like you hooked up originally ,each lamp would only have 2 volts across it. (very dim) and the current would only be less than 1/10 amp.   By hooking them in parallel as I instructed above using a 2 wire hook up running from lamp to lamp, the full 12 volts would light all the bulbs to full brilliance and the power source would have to supply at least 3 amps at the 12 volts.

Richard

[tstage]

Nick,

By your description above, you are wiring your bulbs "in series" - i.e. the wire from one incandescent bulb is connected to a wire of another incandescent bulb, which is connected to another incandescent bulb, and so on.  (Ex. A string of Christmas tree lights). 

Here's a diagram that may help:

The downside of this method is that you have to balance your power supply with your load.

Say you have three (3) GoW incandescent bulbs rated at 3 V[olts] each.  In order to operate those bulbs at full capacity (i.e. 3V), you would need 9 volts (9V) of power - e.g a 9V battery.  (3V x 3 bulbs = 9V)  If one bulb burns out, the entire string burns out because it breaks the circuit of electrical current.  And, as you have noted, the more bulbs you add to a "string" when wired "in series", the dimmer your output will be.  For example, six (6) incandescent bulbs would only receive 1.5V each and operate at 50% capacity with that same 9V battery.

Consequently, if you tried operating only two (2) of the 3V incandescent bulbs with your 9V, each bulb would receive 4.5V (33% more than it's rated capacity) and burn out in short order.

Nick, you may want to consider wiring your lights "in parallel".  This is where one side of a  incandescent bulb is connected to one side of another incandescent bulb.  Here's a diagram that may help you visualize that:

For incandescents, current can travel through them in both directions so it doesn't really matter which wire of Bulb A is connected to which wire of Bulb B.  What you need to be concerned about is the amount of amperage (amps or A) each bulb draws and what the total output of your power supply is rated at.

Say you are operating those same 3V incandescent bulbs with a 3V power pack, which has a 1A[mp] maximum output.  Each incandescent bulb draws 30mA (milliamps) or 0.030 amps.  You can add up to (33) 30mA incandescent bulbs wired "in parallel" to that power pack and all 33 bulbs will operated at 100% capacity @ 3V.  The power pack, however, is also running near full capacity at 0.99A and will overheat in short order.  When matching bulbs, bulb ratings (current draw), and power supplies, it's usually wise to not exceed 75% of the maximum load for your power supply.

I prefer to wire my interior and exterior lighting "in parallel" and operate it with good power pack - e.g. MRC.  I also prefer to wire it up to the DC terminals of the power pack (vs. AC) so that I can "dial down" the voltage.

Below is a freight station outfitted with 1.7mm 12V incandescent bulbs and operated @ 55-60% (or ~7V):

There's plenty of output at the lower voltage and it gives the structure a warm and inviting appearance.  There's also the added benefit that the bulbs will 1) stay cooler and 2) last much longer than if operated at 100% capacity.

Nick, I don't know if that helps you or not...or if it leaves you with more questions than answers.  I'm not an electrician either but I just learned a few things over the years.

Tom

[modelmaker51]

It's also best to operate lights from a separate power pack from your train power pack. If you operate your lights at or near the limits (Amps) of your power pack and try to run trains with it as well, you're going to find the power pack overloading and overheating and it will shut down. You might want to read up on using LEDs as they use less current (amps) and create less heat and last much longer, lightbulbs: 100-200 hours versus LEDs: 100,000 plus hours.

As a noobe to working with DC wiring, I would highly recommend picking up one of the Kalmbach books on DC wiring, getting a cheap multimeter and learning how to use it http://cs.trains.com/TRCCS/forums/t/208916.aspx  Both will save you a lot of grief and make this hobby a lot more fun.