BSidesTLV 2026 · Tiny Badge

Soldering the BSidesTLV LED Badge

A beginner-friendly, through-hole soldering kit. No experience needed — the board literally tells you where each part goes. Follow along top to bottom.

Finished BSidesTLV badge with all components soldered

1What you're building

A round light-up badge. A 555 timer (U1) makes a steady tick. A CD4017 counter (U2) takes each tick and lights the LEDs one after another, so they chase around the board. The trimmer (RV1) sets the speed. Powered by a single CR2032 coin cell.

CR2032→555 clock (U1)→4017 counter (U2)→LEDs chase
The #1 rule: read the silkscreen. Every component has a white printed label and outline on the board — 1u, 470R, TLC555P, CD4017BE, and so on. Put each part on its matching label. For the parts that have a direction (chips, LEDs, the 1µF cap) the printed outline also shows which way round they go. When in doubt, trust the board.

2Tools & a 20-second soldering primer

You need

  • Soldering iron (~ 320–350 °C) + thin solder
  • Flush side-cutters (to trim leads)
  • Something to hold the board (helping hands / tape)
  • A CR2032 coin cell to test

How a joint is made

  1. Push the lead through from the printed side.
  2. Heat the pad and the lead together for ~1 second.
  3. Feed solder into the joint (not onto the tip) until it forms a small shiny cone.
  4. Remove solder, then iron. Snip the excess lead.
Heads up: the components mount on the side with the white labels. The pretty artwork (Alice & the rabbit) is the back of the badge — you solder from the plain/label side.

3The components

Photos below are of the exact parts (from LCSC). Match each to its silkscreen label. Note the two polarity tags: non-polar · any way has a direction

10k metal-film resistor
R1×110 kΩ
Sets the 555's tick rate. Metal-film resistor.
Bands: Brown · Black · Black · Red · Brown
non-polar · any way
LCSC C57436
470 ohm metal-film resistor
R2–R5×4470 Ω
Current limiters — one per LED. Same body as the 10k, different stripes.
Bands: Yellow · Violet · Black · Black · Brown
non-polar · any way
LCSC C1374787
500k trimmer potentiometer
RV1×1500 kΩ
Blue trimmer. Turn it later to set the chase speed. 3 legs — fits only one way.
3 pins · only fits one way
LCSC C48641852
TLC555 timer DIP-8 IC
U1×1TLC555P
8-pin timer chip — the oscillator. Has a notch / pin-1 dot.
notch must match board
LCSC C910886
CD4017 decade counter DIP-16 IC
U2×1CD4017BE
16-pin counter — sequences the LEDs. Has a notch / pin-1 dot.
notch must match board
LCSC C51898328
5mm LED
D1–D4×4LED 5 mm
The chasing lights. Long leg = +, flat side = –. Colour is cosmetic (kit may ship blue or red).
flat side / short leg = cathode
LCSC C2895496 (blue) / C473831 (red)
1uF electrolytic capacitor
C1×11 µF
Electrolytic (metal can) — the 555's timing cap. The one polarized capacitor.
stripe = – · long leg = +
LCSC C1579562
100nF ceramic capacitor
C2×110 n → 100 n
Substitution: board is marked 10n, but this build uses a 100 nF ceramic (part was out of stock). Circuit still works fine. Non-polar.
non-polar · any way
LCSC C1620210 · orig 10n was C51899417
100nF film capacitor
C3×1100 nF
Red box film capacitor — supply smoothing. Non-polar.
non-polar · any way
LCSC C506840
CR2032 coin cell holder
BAT1×1CR2032 holder
Coin-cell holder. Mounts on the printed side; the opening faces out so you can slide the cell in.
fits one way · + faces up
LCSC C5239862
About the 100 nF swap (C2): the silkscreen says 10n. This build intentionally uses a 100 nF ceramic there instead. It's a drop-in for this badge — don't let the label/value mismatch worry you. Everything else matches the board exactly.

4Direction matters — these 3 go only one way

Resistors, the 100 nF and 10 nF caps, and the trimmer don't care which way round they sit. The chips, the LEDs, and the 1 µF electrolytic do. Get these right and the badge works first try.

The two chips — U1 & U2

Each chip has a half-moon notch at one end (and often a dotted pin-1 corner). The board's printed outline has the same notch drawn on it. Rotate the chip so its notch lines up with the notch on the silkscreen, then press it in.

On this board: TLC555P (U1) notch points up toward the cap row; CD4017BE (U2) notch faces the trimmer (RV1) side. Always go by the printed outline.

The LEDs — D1 to D4

An LED has a long leg (+ / anode) and a short leg on the side where the plastic rim is flattened (– / cathode).

The silkscreen circle for each LED has one flat edge — line the LED's flat side up with the flat on the print. Short leg to the flat. All four LEDs face the same logic; just follow each printed outline.

The 1 µF electrolytic — C1

This metal-can cap is the only polarized capacitor. It has a printed stripe down one side marking the negative (–) lead, which is also the shorter leg. The other, longer leg is positive (+).

C1 is the left-most of the three top caps (marked 1u). Put the – stripe / short leg in the inner hole (the one nearest the 10n cap — that pad is ground) and the + long leg in the outer hole. Backwards, an electrolytic can bulge or fail.

Everything else

Resistors (R1, R2–R5), the 10n/100n and 100n ceramics/film (C2, C3) are symmetric — either orientation is fine. The trimmer (RV1) and battery holder (BAT1) have an odd leg pattern and physically fit only one way.

Component-side placement map showing every silkscreen label and outline
Placement map — the component side. Every part sits on its printed label: the cap row (1u / 10n / 100n), TLC555P & its 10k, the four 470R, the four LEDs, CD4017BE, the 500k trimmer, and the CR2032 holder.

5Soldering order — shortest parts first

Work from the flattest components up to the tallest. That way the board can lie face-down on the bench and each part stays pressed against it while you solder.

  1. Resistors — R1 (10k) and R2–R5 (470R). Bend the legs, drop each on its label, solder, snip. Double-check the 10k (Brown-Black-Black-Red-Brown) goes to the 10k spot and the four 470R to the 470R spots.
  2. The two chips — U1 (TLC555P) & U2 (CD4017BE). Match the notch to the printed notch. Solder one corner pin, check it sits flat, then do the rest. (No sockets in this kit — the chips solder straight in.)
  3. Ceramic / film caps — C2 (100n here) & C3 (100n). Non-polar, any way round.
  4. LEDs — D1–D4. Flat side / short leg to the flat on the silkscreen. Solder one leg, confirm the LED stands straight, then the other.
  5. 1 µF electrolytic — C1. Stripe / short leg (–) to the inner (10n-side) hole; long leg (+) to the outer hole.
  6. Trimmer — RV1 (500k). Press flat, solder its three legs.
  7. Battery holder — BAT1. Tallest part, last. Make sure it sits flush; solder its tabs well (they take mechanical stress when you insert the cell).

6Power up & adjust

  1. Inspect first. All joints shiny little cones, no blobs bridging two pads, every lead snipped. Re-check the chip notches, LED flats and the C1 stripe.
  2. Insert the CR2032 into BAT1, + (printed side) facing up, away from the board.
  3. Watch the LEDs chase. Then turn RV1 slowly with a small screwdriver to speed the chase up or slow it down.

If it doesn't light

Nothing at all
Check the coin cell orientation (+ up) and that the holder tabs are well soldered. Re-flow any dull joint on U1, U2 and the battery holder.
One LED never lights, others do
That LED is in backwards or has a cold joint — its flat/short leg must go to the flat on the print.
LEDs light but never move / chase
Suspect U1 (555) or its timing parts: C1 orientation (stripe to the inner/ground hole), the 10k (R1), and the 1 µF. Also confirm U2's notch is correct.
Chase speed won't change
Re-solder RV1's three legs and give the trimmer a full sweep.

7You're done 🎉

Finished badge, component side
Front — your finished work.
Badge back artwork
Back — the Alice-in-Wonderland artwork.

Wear it, trade it, and welcome to BSidesTLV. The whole trick was simple: every part belongs on its printed label, and the board shows you which way round the chips, LEDs and 1 µF cap go.