Hello forum members In my spare time I make lighting fixtures as a hobby and am currently working on a fixture that should incorporate both a halogen lighting bulb and some sort of small led lighting. This is a picture of the fixture that I'm currently producing. This would act as a standard for a cap that I have not made yet, in this cap will be placed the halogen light bulb. There are holes in every piece of the standard big enough to fit a normal cable for household electronics through. I want to illuminate the third piece from the bottom (the blue flat ring) with a led as shown in the next picture. It is not certain that I will light it from above but I have already glued the bottom four pieces together so that's why I did it this way to show it to you. Lighting it from below should be a better option because then I can leave the bottom fourth piece see-through. In this case I used a torn apart module from a small ikea reading lamp. This module however is too big to use as it has the module itself, a small on/off button and a plug to put it in the power circuit. Here is a photo of the led module used and a photo of the halogen bulb that will be used. The problem is that my knowledge of electronics is not very broad and so I'm only stuck with the idea for now and have no idea where to buy or how to put together small leds in a lighting fixture. My question is if anyone knows of a sollution to use both the halogen and led or maybe knows of a way to buy a smaller led or multiple leds and maybe produce a module myself that I can incorporate in the fixture. There is space in the bottom piece of the standard to put in a transformator and maybe a small circuit for a couple of leds but I only want one cable coming out of the fixture to plug in the power circuit with an optional on/off switch for both the halogen and led(s) at the same time. Thanks for the reading and all help is welcome!
First of all you shold resize picture to some 2MP (1600x1200) before posting them with the (img)-tags. This reduces laoding-times and usually it's large enough, when you think about screen-sizes (1920x1080). Anyways. You can build a small circuitry to connect a LED directly to 230V. Be aware that the resistors can get very warm in such a circuitry, as you need to heavily reduce the current. Therfore I'd go with a small GU9-socket 230V halogen-bulb, which aswell gets pretty warm. Another option would be to use a 230V LED ofc.
Driving LEDs from Mains Voltage First of all, usual warnings about lethal voltages, need for good insulation, etc. That said, the simple way to do this without lots of heat is to use a capacitor as a voltage dropper - there will be a phase shift, but this doesn't matter in this case. A 0.1uF capacitor has an impedance of around 32K at 50Hz; naturally, it needs to be rated at 400V. The next point is that LEDs need DC, so you need a bridge rectifier again rated at 400V for safety, and then just put the LEDs in series across the + and - pins. This gives a mean current of around 6mA, which may be adequate with high brightness white LEDs; if not, doubling the capacitor size doubles the current, and so on. So - two low cost components plus the LEDs. How much easier can it get?
No offence, but for an LED that is an absolutely terrible idea! The correct way to deal with this would be to use a small 240/12v transformer, rated at 1 or 2 amps for a few leds. A bridge rectifier, a large smoothing capacitor to reduce the ripple, and finally a voltage regulator to output a smooth 10v dc or there abouts, the entire circuit could be built on a small piece of PCB about an inch square. Then it would be a simple case of using an LED calculator to work out the size of the resistor needed to limit the current depending on how many leds you want and if you're going to wire them in parallel or series. If you connect an LED directly across the terminals of a bridge rectifier in your design you WILL blow it instantly.
