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I've got a problem and it seems that there is an issue with understanding electronic's fundamentals.

I've got inspired by Jiri Praus video

I am trying to make this Rabbit-shape circuit to work. enter image description here

What I have:

  • 0.8mm brass wire,(black lines on a picture)
  • 1206 SMD LEDs, (tried to draw them in Photoshop, to show where exactly they are placed on a pic)
  • coin cell battery CR2032 (grey round thing which is held in place with a wire that should touch opposite pole of a battery)

What I do:

  1. I use multimeter to make sure that LED working (it lights up)
  2. Solder two wires to each LED's pads and check it with multimeter again (it works)
  3. Solder Led with two wires into the whole "circuit" - NOT working
  4. Solder a wire to the circut in a way that it would keep battery from both sides - NOT working

So I have an issue with step 3 and 4. I believe it's because I don't know how electricity flows.

Troubleshooting steps that I've already tried:

  • I've bought flux to make connection more solid
  • I tried all these steps with a wire that is used in USB cable
  • I tried to not to solder one of wires that goes to soldering pad - when one end is not soldered to circuit - it works. Once soldered - stops working.

What I would like to ask you for:

  1. Please advise what to read in order to have a better understanding in terms of electrictiy
  2. Please advise on how to fix the issue that I have faced (should all LEDs be pointing by the same pole toward the battery?)
  3. Any comments would be highly appreciated.
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    \$\begingroup\$ Your diagram doesn't show which wires are actually connected to which. They can't all be connected or it's just a short circuit. \$\endgroup\$
    – K H
    Apr 7, 2021 at 7:53
  • \$\begingroup\$ Sorry. They are all connected to each other, only the one that goes over the battery cell has two points of contact with the rest of circuit. Should I make draw large dots on my cirtuit in order to show which wires are connected? \$\endgroup\$ Apr 7, 2021 at 7:58
  • \$\begingroup\$ I don't feel like watching that video, but if they're all connected, it's just shorting the battery out, so no voltage gets applied to the LEDs. You need a set of wires that connect one side of the battery to one (correct) side of each LED and a set of wires that connects the other side of the battery to the other side of each LED for it to work. \$\endgroup\$
    – K H
    Apr 7, 2021 at 8:00
  • \$\begingroup\$ I wonder why my question got downvoted since I've did an effort and provided with all steps that I've performed and showed my research \$\endgroup\$ Apr 7, 2021 at 9:32
  • \$\begingroup\$ I didn't downvote, but I assume it's because while "why my LED bunny doesn't light up" won't get results from google, "how to wire LEDs" would have been an easy way to get results. If you want to get into electronics, you might want to play around with a solderless breadboard and some basic circuits and learn the fundamentals before you try to wire an electric sculpture. That said, based on the answers you have, you can connect the wires appropriately with insulation where necessary to prevent a short. Your question is well written, which is nice. \$\endgroup\$
    – K H
    Apr 7, 2021 at 9:37

4 Answers 4

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schematic

simulate this circuit – Schematic created using CircuitLab

Figure 1. (a) What you want. (b) What you've got.

All electronic components require some voltage across them to operate. You have short-circuits (the vertical wires in Figure 1b) that connect the top and bottom of each diode. This makes a zero volt difference between the top and bottom so the LEDs can't light.

Have a look at Battery and LED without resistor where I explain some other points about this circuit.

enter image description here

Figure 2. The circuit from the video with one of the two conductors overlayed in black.

In Figure 2 there are two isolated conductors.

  • The battery negative is connected to the conductor highlighted in black.
  • The battery positive is connected to the gold conductor around the outside of the device.
  • There is no direct connection between the black and gold conductors. Having one would create a short-circuit between the coin cell terminals and discharge the coin cell very quickly.
  • The battery is connected between the conductors.
  • The four LEDs are connected between the conductors. This is equivalent to Figure 1a.
  • Note that the gold circuit is touching the back of the battery and the black circuit is connecting the front.
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  • \$\begingroup\$ I am sorry, I cannot upvote since I am a new user, but the answer is really helpful and thanks for a link to your blog! Any advice on how to re-design my circuit? Do I understand correctly that it's better to use CircuitLab before actually soldering anything? \$\endgroup\$ Apr 7, 2021 at 8:20
  • \$\begingroup\$ You don't need CircuitLab. You just need a clear head. See the update. \$\endgroup\$
    – Transistor
    Apr 7, 2021 at 10:09
  • \$\begingroup\$ Thanks a lot! Those black lines explained everything! \$\endgroup\$ Apr 7, 2021 at 12:11
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The issue is likely that you are not constructing it as he does in the video.

The construction works because there is only two layers. A positive and a negative. With all the leds connected in the same way, from positive to negative. The positive section of the brass never touches the negative section of the brass.

In essence the ghost or heart or whatever video you look at has a an outside conductor and an inside conductor, which is simple. Your led placement makes it difficult to get a simple out positive and in negative separation.

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  • \$\begingroup\$ Thank you so much! You've gave me really important hints, now I see what's wrong \$\endgroup\$ Apr 7, 2021 at 8:20
  • \$\begingroup\$ I'll see if I can sketch out a possible solution tomorrow if you can't figure it out yourself. \$\endgroup\$
    – Passerby
    Apr 7, 2021 at 8:21
  • \$\begingroup\$ I would highly appreciate it. If I come up with a solution by myself - I will post it. I have few more geometric drawings that I would like to use as a circuit for soldering, so I would highly appreciate if you could share flow of your thought while designing the circuit. \$\endgroup\$ Apr 7, 2021 at 8:24
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there is an issue with understanding electronic's fundamentals

Yes. You can't route a trace directly from the battery + to battery -. That's a short circuit and with no current limitation, it will kill the battery in no time. All the current will take that route and none will go through the LEDs since they have a certain amount of resistance.

Furthermore, you can't just connect battery + to a LED anode then to battery -. Again there's no current limit but this time the LED will get fried instead.

Instead you need to achieve this basic circuit with a current limiting resistor:

schematic

simulate this circuit – Schematic created using CircuitLab

What value to pick for the resistor? Ohm's law. Most LEDs are rated at 20mA. You know the battery voltage, but there is a voltage drop across the diode. So now you have to research diode forward voltage. https://en.wikipedia.org/wiki/LED_circuit

Hint: R = (Vbat - Vfwd) / 20mA

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    \$\begingroup\$ 3.6V nominal led on a 3V coin cell with high esr. Resistor not needed. \$\endgroup\$
    – Passerby
    Apr 7, 2021 at 8:22
  • \$\begingroup\$ @Passerby Yeah I just realized. However, teaching newbies to connect LEDs without series resistor isn't friendly advice. Next up they'll use 9V battery and then there will be smoke. Also, it does depend on the LED used. \$\endgroup\$
    – Lundin
    Apr 7, 2021 at 8:24
  • \$\begingroup\$ @Lundin I am sorry, I am not sure that I fully understand this phrase: >"Furthermore, you can't just connect battery + to a LED anode then to battery -. Again there's no current limit but this time the LED will get fried instead." I've soldered two wires to LED pads and then touched these wires to + and - on battery, LED worked fine. Then I used 9V battery and fried LED right away :) (learn the hard way, right?) \$\endgroup\$ Apr 7, 2021 at 8:27
  • \$\begingroup\$ @Electronics, that's explained in the article linked in my answer. \$\endgroup\$
    – Transistor
    Apr 7, 2021 at 8:37
  • \$\begingroup\$ @ElectronicsNewbie Normal power supplies don't come with lots of built-in resistance. That just happened by chance in your case, since you used a coin cell battery which got enough internal resistance to actually skip the external resistor. That's a very specialized case. Supplying things straight out of a battery is primitive, normally you'd have a voltage regulator which guarantees a fixed voltage. \$\endgroup\$
    – Lundin
    Apr 7, 2021 at 8:43
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each LED needs a wire connection to a different side of the battery at each end and the wires from opposite sides aren't allowed to touch, tis means that you'll need to make some of the blobs out of sometthing non-conductive (like glass or epoxy glue)

here's one possible arrangement.

enter image description here

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