Powering 1.5v lights for billboards

Th question here is whether the bulbs are wired in series or parallel. If they are in series, then 3 vac is just fine. If they are in parallel then 1.5volts is the requirement.

Al

Half wave the 3VAC with a single diode 1n4001 is OK. That will give you about 1.5 V equivalent pulsed DC. However if you accidentally move the tap to a higher voltage (easy to do on the power chief) you can burn out the bulbs.

Another way is to get a small bridge rectifier. Connect the + and - and put the 2 AC leads (marked ~) in series with any light bulb on the layout. For example a street lamp run on 14 volts. When the street lamp is powered it will receive 12.8 volts. Tapping the 2 AC leads of the bridge will yield 1.2 VAC whenever the street lamp is on. Hook this to the 1.5 volt bulb(s). This is burnout proof regardless of transformer voltage.

Dale H

Guys,

The diagram is here: circuit. Is this how the diode should be wired?

Thanks,

George

Those bulbs are in series in the diagram, so the 3V tap directly should work fine. Connect a 1.5V D battery to them and see if they're very dim, that will insure they wired in series.

I have a bunch of 1.5V lamps I want to use eventually and I was thinking of buying a few of these:

http://www.ebay.com/itm/1-5-27...&hash=item2c61786fc7

You couldn't build these yourself any cheaper even if you had the parts considering your time as $$. There are some other variations under $20 if you search. These could be installed in buildings too or located strategically around the layout.

here is my step down pole to use 1.5 bulbs.
cheap and easy.

AG.

Very nice. Could you describe the parts list, diagram, etc.?

Thanks,

George

Tried the lights in series off the 3VAC tap of the PowerChief.

Worked fine.

I'm now looking at mounting the billboard, the terminal strip, and the lights over the billboard.

Thanks everyone.

George

George!
I don't know to who is the question, but thinking it was for me here is the answer.
if you have 1.5 volts bulb 15mA X 2
the total will be 3.0 volts 30 ma.
so, feeding them with 12volts you need to subtract 3 volts and the total in this case 9, you divide by 0.03 total 300 ohms resistor.
is you have different resistor you need to put them on series to reach 300 ohms.
I install them on a pole like a pole fuses.
Andre.

quote:

if you have 1.5 volts bulb 15mA X 2
the total will be 3.0 volts 30 ma.

Not so. You will have 3.0 volts and 15mA for a series connection, or 1.5 volts and 30mA for a parallel connection. Your 300 ohm resistor is incorrect. It should be 600 ohms - 600 x .015 = 9V of drop for a series connection.

For a parallel connection, 350 x .030 = 10.5V of drop.

You right..
my bad.
I get confused a little, anyway I took this for one buld 1.5v 15mA= 700 ohms
AG

OK, now I'm a little confused.

Going back to the original configuration:

3 Volts AC tap on the PowerChief 120F is the power supply.
Lights are wired in series:

+ _O_ _O_ -

This should be OK, right?

George

Yep, George, you're fine. They're talking about connecting to 12 volts, just a little thread drift going on.

quote:

Originally posted by gunrunnerjohn:
Yep, George, you're fine. They're talking about connecting to 12 volts, just a little thread drift going on.

Cripe, I can do that on my own without any external help.

If I decide to do what AG and Dale Manquen are discussing, then I would:
1) Run a 12 VAC buss around the layout
2) At the billboard with the lights, install a 600 Ohm resistor.
3) Wire the lights in parallel.

By the way, how many Watts for this resistor? The Digi-Key catalog lists about 20 of these 600 Ohm resistors.

George

George, 1/4 watts is fine.
I did it on my layout because most the building are 12 volts so, I just run a 12 volts wire and step down as I needed.
Andre.

Are these really 15 milli-amp bulbs? That's a mighty small bulb! Even my grain of wheat bulbs take more power than that.

Are you sure it's not .15 amps or 150 MA?

quote:

Originally posted by gunrunnerjohn:
Are these really 15 milli-amp bulbs? That's a mighty small bulb! Even my grain of wheat bulbs take more power than that.

Are you sure it's not .15 amps or 150 MA?

Miniatronics
http://www.miniatronics.com/Me...=1_1&Product_Count=2
AG.

quote:

2) At the billboard with the lights, install a 600 Ohm resistor.
3) Wire the lights in parallel.

See my calculations above:
600 ohms for series connection, or
350 ohms for parallel connection.

For the series connection a 1/4 watt resistor will be fine (620 ohms or 560 ohms are standard values), but for the parallel connection a 1/2 watt resistor will be required (330 ohms is the common standard value.) You could parallel two 680 ohm 1/4 watt resistors to get 340 ohms with 1/2 watt capacity.

(600 and 360 ohm resistors are available, but they are from the less-available 5% sequence of values.)

OK, I believe. That's a tiny light bulb!

Guys,

You can check out the completed billboard at: Blooming Mill Billboard.

Thank you for all the help.

George