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I have a 12v DC input that I am stepping down to 2v with 610 ohm resistor. When power is removed the light is staying on for a period of time and slowly dims.

Would the resistor be acting like a battery?

Any ideas if not the resistor?

Thanks

EDIT: My circuit is a resistor wired to the positive arm of the LED and the negative wire off of the negative arm. I am connecting it to a car battery in this case. When I take the leads off the battery the light stays on and dims over time

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  • \$\begingroup\$ We definitively need a circuit to answer your question. Or a thousands words of description, but a picture is worth... [sic]. Oh, and please edit your question, don't place additional information in some comments. \$\endgroup\$ – the busybee Feb 24 at 13:09
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I have a 12 V DC input that I am stepping down to 2 V with 610 ohm resistor. When power is removed the light is staying on for a period of time and slowly dims.

I suspect that you mean when you switch off the mains power that the LED fades out.

schematic

simulate this circuit – Schematic created using CircuitLab

Figure 1. An old-fashioned power supply driving an LED.

How it works:

  • SW1 switches the power on and off.
  • XFMR1 is a transformer and steps the voltage down from mains to the low voltage required - probably about 9 V AC in your case.
  • BR1 is a bridge rectifier consisting of four diodes. No matter what the polarity of the input voltage on the ~ ~ terminals the voltage is "rectified" and current always comes out on the + terminal. The bridge rectifier will output pulses of current at the peaks of the alternating voltage.
  • C1 is the smoothing capacitor which stores some charge between pulses from BR1.
  • R1 limits the current to the LED to a safe value.
  • D1, the LED, will have a certain "forward voltage", Vf, at the current set by R1.

Would the resistor be acting like a battery?

Definitely not. The fading effect is caused by the charge stored in C1 slowly bleeding out through R1 - D1.

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  • \$\begingroup\$ Hmm my circuit is a resistor wired to the positive arm of the LED and the negative wire off of the negative arm and I am connecting it to a car battery in this case. When I take the leads off the battery the light stays on and dims over time. \$\endgroup\$ – markblue777 Feb 22 at 23:52
  • \$\begingroup\$ @markblue777 - Is that a "bare" LED? Or some kind of packaged "LED flashlight-type of device"? Please can you edit the question and add a photo or two showing the battery, wiring and the LED you are using? Thanks. \$\endgroup\$ – SamGibson Feb 22 at 23:58
  • \$\begingroup\$ Hmm, those details and the details of the LED still haven't been edited into to your question. \$\endgroup\$ – Transistor Feb 23 at 0:14
  • \$\begingroup\$ Yeah because I was asleep. \$\endgroup\$ – markblue777 Feb 23 at 7:58

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