I appreciate any help as I try to figure this lightbox project. I need to wire up to 144 3V (built-in resistor) LEDs from flickering tea lights (normally battery powered).

Not sure how many to wire in parallel for a 120V outlet, and what power adapter to get. Suggestions welcome. LEDs-diagram

  • 13
    \$\begingroup\$ No...... this will end badly. \$\endgroup\$ – Spehro Pefhany Sep 8 '14 at 22:05
  • 4
    \$\begingroup\$ I like best that the wires appear to be shorted at the end of the chain. \$\endgroup\$ – George Herold Sep 9 '14 at 1:21
  • 2
    \$\begingroup\$ Why would someone vote to close this? It appears very clear what OP is asking plus leaving him/her without help can result in serious injuries. \$\endgroup\$ – Vladimir Cravero Sep 9 '14 at 7:07
  • 1
    \$\begingroup\$ A holy smoke show project? \$\endgroup\$ – hkBattousai Sep 9 '14 at 13:01
  • \$\begingroup\$ You should not attempt to design anyting connected to 120V mains before having learned a fair bit about electronics and electricity. Start with low voltage circuits. For example every appliance must have a fuse. How will you handle isolation. \$\endgroup\$ – TEMLIB May 2 '20 at 9:31

3V LEDs can't be wired in parallel and plugged into 120V AC socket.

They will all be destroyed.

They can only be wired in parallel and powered from (approximately) 3V DC

This article "Hacking a Candleflicker LED" suggest that it might not be practical to wire a few in series either as they appear to modulate their power supply.

You could drive them in parallel with a 3-5V power supply.

Assuming each LED is no more than 30mA (0.03A), 33 LEDs would be 1A. A 'wall-wart' would be cheap. (The LEDs might be even less power.)

While we haven't got a datasheet for your tea light LEDs, you might want to compare them to this range of Candle Flicker LEDs to get their current rating.

For example, these Yellow 5 mm Clear Candle Flicker LED are rated at forward current of 30mA. They need a current limiting resistor on each LED. Some have quite significant forward current (abut 3x nominal), so decoupling capacitors would help. Also the power supply should be increased significantly to ensure it has some headroom.

I would build the chain in sections and test them using a multi-meter to measure current, to ensure it stays within the capabilities of a power source. Be careful when measuring current because the LEDs are not on all the time, so the reading might be wrong. Give yourself some headroom.

  • \$\begingroup\$ If I get a 3V power supply can I wire all 100+ of them though? \$\endgroup\$ – Emiliest Sep 8 '14 at 22:15
  • \$\begingroup\$ @Emiliest - we can't say whether a 3V power supply will power 100 LEDs or not, without knowing the current used by each LED, and the maximum current the supply can deliver. If the total current demanded by the LEDs is less than the maximum rated current of the power supply, then it should work. \$\endgroup\$ – Peter Bennett Sep 8 '14 at 22:42
  • 3
    \$\begingroup\$ @Emiliest - Just don't have a short circuit at the end of the chain (as shown in your diagram), that might destroy the wires or the power supply or start a fire. For 100 parallel LEDs (with built-in current-limiting resistors), your 3V supply needs to be rated for a current at least 100 x the rated current of each LED. \$\endgroup\$ – RedGrittyBrick Sep 8 '14 at 22:43

Also, you should account for voltage drop if this is going to be a long run of any sort. 40 ft of 22 guage wire would cost you 2 Volts for instance so you should consider running a 5V power supply to compensate if you are running any lenght. Here is a voltage drop calculator. http://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=52.96&voltage=5&phase=dc&noofconductor=1&distance=40&distanceunit=feet&amperes=1&x=64&y=21

  • 1
    \$\begingroup\$ Its better if you provide answers that don't contain links, links break and then the answer is worthless. Also provide some equations on how to calculate \$\endgroup\$ – Voltage Spike Sep 20 '17 at 20:24

You have shorted all LEDs. This is not a parallel connection of the LEDs yet. enter image description here Again 3V LED can't tolerate 120V. If you want to connect those LEDs in parallel then you have to use voltages near 3V and some resistances in series to fix the current. One more thing is that you have to keep in mind the current rating of the supply. If you want to connect too many LEDs in parallel then it requires more current.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.