Can modify a 120V LED to run on 12V?

Thread Starter

SethsVan

Joined Feb 26, 2024
4
I'm installing lights in a camper van and for aesthetic reasons, insist on my recessed ceiling lights having gold/brass trim. The problem is, they don't appear to make those for 12V systems (at least within my budget). Is it possible to run something like this on 12VDC? Important to note that it's not a traditional light bulb, so I can't just replace it with a 12V bulb. I'm assuming the in-line box reduces the voltage anyways, but I'm not sure. New to this, so any advice would be super helpful.
 

Ian0

Joined Aug 7, 2020
9,803
I'm installing lights in a camper van and for aesthetic reasons, insist on my recessed ceiling lights having gold/brass trim. The problem is, they don't appear to make those for 12V systems (at least within my budget). Is it possible to run something like this on 12VDC? Important to note that it's not a traditional light bulb, so I can't just replace it with a 12V bulb. I'm assuming the in-line box reduces the voltage anyways, but I'm not sure. New to this, so any advice would be super helpful.
Yes - definitely possible - what driver does it use? Switched mode or capacitive dropper?
 

MisterBill2

Joined Jan 23, 2018
18,461
OK, and an interesting challenge. The simple and safe way is a cheating trick, which is to add a 12 volt LED bulb inside the fixture next to the other bulb. The down side is then you need another power switch for the 12 volt portion. BUT it avoids having to fight with the drivers circuit for the LED element.
 

Ian0

Joined Aug 7, 2020
9,803
I'm familiar with the difference but not sure how to determine.
Look inside, if you find a large film capacitor with a voltage rating more than your mains voltage, a couple of diodes and no other semiconductors, then it's a capacitive dropper. If you find ICs, transistors and any inductive components, then it's a switched mode.
 

LesJones

Joined Jan 8, 2017
4,188
You don't say what the power ratings is for the LED lights. If you require about 5 watt rating then 12 volt MR16 may do what you require. Another posibility is to use 12 volt LED headlamp bulbs. (I have used one of these for a machine light on my lathe.)
Edit. I noticed that the link in post #1 gives the wattage rating as 3 watts. This is about the same as the MR16 bulbs. The link also say's that there are 5 LEDs in the unit. These are probably connected in series so would require about 15 to 17 volts. If this is the case then the small boost regulators sold on Ebay can be modified to be constant current sources. This is a link showing how to modify these boost regulators.

Les.
 
Last edited:

MisterBill2

Joined Jan 23, 2018
18,461
I have a serious concern about connecting any part of the RV system to the output side of the fixture power module. The reason is that because the module is a component in the fixture there is no requirement for the output to be isolated from the mains input. THAT could provide a sneak path for mains voltage to connect to the RV 12 volt DC system and cause problems, which could easily include some shocks and tripping circuit protection devices. And checking to see if there is such a connection, or serious leakage, is not quite as simple as you would think.
 

MisterBill2

Joined Jan 23, 2018
18,461
OK, and that appears to be the case, so converting the fixtures is the intent. In my RV the OEM lighting is all 12 volt, powered by either the RV battery or the power converter. I have installed some mains powered LED fixtures that do not appear to be simply changeable to either 12 volts or dual operation.
So it seems that the situation I commented is not involved in this project. A good catch indeed, but probably a useful caution for those wanting to create dual voltage fixtures.
 

Dodgydave

Joined Jun 22, 2012
11,301
I'm installing lights in a camper van and for aesthetic reasons, insist on my recessed ceiling lights having gold/brass trim. The problem is, they don't appear to make those for 12V systems (at least within my budget). Is it possible to run something like this on 12VDC? Important to note that it's not a traditional light bulb, so I can't just replace it with a 12V bulb. I'm assuming the in-line box reduces the voltage anyways, but I'm not sure. New to this, so any advice would be super helpful.
Those lights are 12V and use a 300mA constant current driver on mains, so if you want to run them on a 12V in your camper van, you just need a 300 mA driver on a 12V supply.
 

Ian0

Joined Aug 7, 2020
9,803
Those lights are 12V and use a 300mA constant current driver on mains, so if you want to run them on a 12V in your camper van, you just need a 300 mA driver on a 12V supply.
If you can place the driver externally (I.e. not inside the luminaire, I don’t mean outside the camper van) you will get better reliability of both luminaire and driver.
 

LadySpark

Joined Feb 7, 2024
124
I'm installing lights in a camper van and for aesthetic reasons, insist on my recessed ceiling lights having gold/brass trim. The problem is, they don't appear to make those for 12V systems (at least within my budget). Is it possible to run something like this on 12VDC? Important to note that it's not a traditional light bulb, so I can't just replace it with a 12V bulb. I'm assuming the in-line box reduces the voltage anyways, but I'm not sure. New to this, so any advice would be super helpful.
Interesting you picked out the correct ones to use with 12V directly by luck. Because those from that manufacturer are 12V and you don't need anything else to run them off 12V.
 

MisterBill2

Joined Jan 23, 2018
18,461
If it is a constant current driver why not try it directly on 12 volts. If it works you are all set. It may not work that way but itis worth a try.
 

Thread Starter

SethsVan

Joined Feb 26, 2024
4
If you can place the driver externally (I.e. not inside the luminaire, I don’t mean outside the camper van) you will get better reliability of both luminaire and driver.
I haven't bought the lights yet because I wasn't sure they were going to work, but I think I'm going to purchase them so I can identify the driver type (as well as what the adapter says). Are LEDs driver-specific, i.e. will they work with either driver type, provided I size it correctly?
 

Thread Starter

SethsVan

Joined Feb 26, 2024
4
OK, and an interesting challenge. The simple and safe way is a cheating trick, which is to add a 12 volt LED bulb inside the fixture next to the other bulb. The down side is then you need another power switch for the 12 volt portion. BUT it avoids having to fight with the drivers circuit for the LED element.
Interesting idea! My power switch is external so that's not a problem. However, there is only space inside the fixture for a small LED strip, which would still (to my understanding) require an external driver. So I'm not sure that would eliminate the problem of finding a 12V driver.
 

Jon Chandler

Joined Jun 12, 2008
1,048
Are LEDs driver-specific, i.e. will they work with either driver type, provided I size it correctly?
It depends on the LEDs and how they are wired together. The forward voltage (Vf) of white LEDs is around 3.4 volts. To light up a series string of LEDs, the voltage of the supply must be greater than the sum of Vfs in the string plus some margin. Three white LEDs in a string would have a total Vf of a little over 10 volts, so a 12 volt supply could illuminate a string of 3 LEDs (with a series current limiter resistor or constant current supply). The sum of Vfs for 4 series white LEDs exceeds 12 volts, so that can't work.

The LEDs in this lamp could all be in series to get the Vf sum close to line voltage, or they may be in a series/parallel arrangement that can volt on 12 volts. The specs on the driver will provide a good clue.
 
Top