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I am building a light bulb with an integrated neodymium magnet for an art piece. I have successfully integrated the magnet into a LED bulb model that suited my needs so it works but now I want to lower the brightness and it does not support dimming.

I have therefor decided to try to lower the brightness with a resistor but I don't want to break it so I want to ask about the best place to position it and what strength/type of resistor to use for it to not overheat or otherwise damage the circuit.

I tried doing this with an earlier model of the same kind and it worked but the next morning when I switched it back on it burnt out a LED diode. That time I put a 10K Ohm (or 1M Ohm resistor.. one of them gave me a good dampening of the light) between the LED circuit and the power going in (the gray cable marked B in the image). I am not sure if this was because I accidentally short circuited it or if current had been building up over the night and then it released it all at once.

So I would like to ask for some advice on the questions marked in bold above (placement and recommended resistor) or perhaps you will get back to me telling me not to do it that way, any valuable input is welcome. Below is an image of the finished bulb and the LED driver inside.

All help or advice is greatly appreciated, many thanks in advance

enter image description here

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  • \$\begingroup\$ +1 for good job with the photo montage. What will the magnet do? \$\endgroup\$
    – Transistor
    Commented Aug 5, 2017 at 11:52
  • \$\begingroup\$ Add a circuit digram and don't forget to label all the components R1, C1 etc so we can advise better. Also how are you powering this? \$\endgroup\$
    – Warren Hill
    Commented Aug 5, 2017 at 12:38
  • \$\begingroup\$ Why not use an led with the brightness that you want? \$\endgroup\$
    – Jason Han
    Commented Aug 5, 2017 at 12:52
  • \$\begingroup\$ @oldsea .What is the function of the magnet ? \$\endgroup\$
    – Autistic
    Commented Aug 5, 2017 at 13:09
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    \$\begingroup\$ @Autistic It keeps a knife balanced on a wine glass (victornyberg.com/img/…) \$\endgroup\$
    – oldsea
    Commented Aug 5, 2017 at 16:02

1 Answer 1

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Your big metal film cap is is the main part that sets up led current and hence brightness . If you increase the series resistor value you will waste power to dim the lamp .Halving C will halve the led current Try some lower values to get your desired level of brightness .Remember that this cap is a mains part and should be safety rated like X2 .If you do not have an assortment of caps on hand you can use your existing caps in series to ascertain your desired value for purchasing .

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  • \$\begingroup\$ Thank you for your response. I will consider replacing the film cap as you suggested but I am inclined to take an easier route since power consumption is not an issue. If I decide to insert a resistor into the circuit, does it matter where I place it? And is there anything I need to consider regarding strength of the resistor in relation to where I place it? Thank you \$\endgroup\$
    – oldsea
    Commented Aug 5, 2017 at 16:09
  • \$\begingroup\$ Sorry to bump this with you, your answer is more than valid but it doesn't answer my primary question: Is inserting a resistor into the circuit an ok way to solve the issue? \$\endgroup\$
    – oldsea
    Commented Aug 6, 2017 at 10:43

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