How can I decrease 150w to 20w?

[joshboe]

Hello,

Firstly, I'd like to apologise for my question if it is basic or impossible, I know next to nothing about electronics.

I am trying to make a moth trap and am stuck on the electronics part.

I have a 12v 20ah rechargeable LiFePO4 battery and a 20w 240v Sylvania blacklight bulb. I found out I need an inverter to run the 240v AC bulb off the 12v DC battery, and so have a 12v to 240v 150w inverter.

The question is, how can I decrease the wattage of the inverter to a lower amount as to not fry the bulb?

Thank you for reading and I hope you can help.
-Josh

 

[KlausST]

Hi,

the bulb draws 20W
the inverter can deliver up to 150W.

If the bulb just drwas 20W then everything is O.K.

Mind that an european AC outlet can deliver more than 3000W ... but you still can connect a 20W bulb to it without problems.

***
The other way round is problematic: You can´t run a 150W bulb on an inverter that is made to deliver 20W max.

 

[joshboe]

Hi,

the bulb draws 20W
the inverter can deliver up to 150W.

If the bulb just drwas 20W then everything is O.K.

Mind that an european AC outlet can deliver more than 3000W ... but you still can connect a 20W bulb to it without problems.

***
The other way round is problematic: You can´t run a 150W bulb on an inverter that is made to deliver 20W max.

Oh my goodness I never even thought about that. Thank you so much, I wish I had asked earlier to save me hours of searching for very expensive Australian inverters and dubious calculations. Many thanks

 

[Audioguru]

An old fashioned incandescent light bulb draws up to 10 times its hot power when it is cool. Then the 150W inverter might not work with the bulb.

Can't you use a car 12V light bulb? An LED one uses much less current but is the same brightness.

 

[c_mitra]

An old fashioned incandescent light bulb draws up to 10 times its hot power when it is cool. Then the 150W inverter might not work with the bulb.

Can't you use a car 12V light bulb? An LED one uses much less current but is the same brightness.

Blacklight bulbs are fluorescent lamps and they have high resistance when cold (not operating) and low resistance when on (operating). In fact, they should be run from a current driver (a series resistor will do) for a reliable operation.

 

[Audioguru]

I see these incandescent blacklight bulbs every halloween:

 

[Externet]

Those incandescent bulbs coating filter out every light wavelength except the tiny percentage of UV the filament may emit; so their emission is waaay overrated and may not meet expectations for other than party/decoration use. There is violet and near-ultravioled LED if of any interest :
----> https://www.ecosia.org/images?q=ultraviolet led bulb

--- Updated Jul 26, 2022 ---

12VDC ultraviolet bulbs and emitters exist; you will not need to use any inverter nor complications by connecting it directly to your battery.
----> https://www.ebay.com/sch/i.html?cam...&mkcid=1&mkrid=711-53200-19255-0&toolid=20004