Power supply for small filament bulbs.

[Chrisr40]

Hi everybody - thanks for looking in on this post.  I would be very grateful for some advice please. I have about 10 of the lamp posts below which originate from I know not where but most likely an impulse purchase at a show many years ago. They are small filament bulbs and not LED.

I wanted to make sure that running them off the 12v auxiliary point on a Duette would be safe and not risk overloading the controller. I don't know the rating for the bulbs hence my request for advice. Many thanks. Chris. 

[DCB]

My Duette 12 volt DC output is about 14.5 volts off load but some other units are around 20 volts on light load.

I would use a 9 volt power unit to prolong the bulb life, a 1/4 amp or 1/2 amp  fuse or polyswitch would be good to protect the wiring.

[sharris]

The first thing I'd check is whether they are 12V bulbs. Grain of wheat bulbs, which I assume are in these lamps, can come in 3V and 6V (possibly even 1.5V) versions too.

[Chrisr40]

Hi Sharris. Thanks for your reply.  Please excuse my ignorance but how would I go about doing that ?

I have a recollection that they are 12v and do have one that got broken so ended up being used by me to test that track was live without any ill effects so far. 

Many thanks Chris

[royaloak]

Easiest way is probably to connect the (bare) wires to a 1.5V battery and see if they light up, if not then try 2 batteries (to give 3V) etc etc until you get the brightness you are after, then work out how to get that voltage on a permanent basis.

[cliff park]

If they are 12v lamps run them on 9v or 10v. Filament lamps supplied with a volt or 3 under their rated voltage look a more realistic colour and last forever. The rated voltages tend to be for use in , say, a torch, where you want a bright, white light.

[Brober]

My understanding is that assuming they are indeed 12v lamps the limitation on your power source is the amp rating.  Say that each lamp uses 100mA each and your power source is rated at 1Amp them you can have 10 lamps on the supply.   If you can change them to LEDs then they would each be rated more likely around 3-5 mA each. Well within the capacity of the power supply allowing upto 200 lamps.

 

Hope this helps

[kevinlms]

41 minutes ago, Brober said:

My understanding is that assuming they are indeed 12v lamps the limitation on your power source is the amp rating.  Say that each lamp uses 100mA each and your power source is rated at 1Amp them you can have 10 lamps on the supply.   If you can change them to LEDs then they would each be rated more likely around 3-5 mA each. Well within the capacity of the power supply allowing upto 200 lamps.

 

Hope this helps

Better to look in the junk box, at the power packs which came from long forgotten equipment.

 

With any luck there will be one with a rating of about 9V and 1 Amp minimum. The current rating is the important one to look for, too low and it might overheat.