Maker Badge
π Overview
Solder yourself a glowing maker badge: 100 LEDs laid out on a badge-shaped PCB that lights up as soon as you connect the battery. The author also sells a kit (PCB plus components), or you can source the parts yourself.
Soldering 100 LEDs is the perfect skills drill and very satisfying when it is done - wear it to a maker meetup and you will be the centre of attention.
π§° What you need
- Badge PCB (fabrication files provided, or buy the kit)
- 5mm LEDs x100 (2V / 20mA)
- 10 ohm resistors x6
- Slide switch x1 + assorted header pins
- Optional: USB socket for power
- Coin cell/5V supply + battery holder
π§ Step by step
Gather the parts
Buy all 100 LEDs at once and keep about 10 spares
The author's Tindie store sells a complete kit if you want an easy path
Schematic and circuit maths
Read the schematic first: LEDs in parallel groups, each group with a series resistor
Worked example: a 2V LED on a 5V supply with a 10 ohm resistor draws about 20mA
Decide the polarity layout before you solder anything
Solder the USB socket (optional)
If you want USB power, fit the socket first
Otherwise you can run it straight from a battery
Solder the resistors
Fit the six 10 ohm resistors according to the silkscreen
Resistors are not polarised, but the positions matter
Solder the 100 LEDs
One at a time, matching the LED polarity to the silkscreen
Work in groups and check every ten LEDs
Trim the legs
Trim all the legs once soldering is done to avoid shorts
Check for whiskers touching after trimming
Fit the switch and headers
Solder the slide switch and leave the header pins as an expansion or programming port
Check the switch direction: on means powered
Power it up
Fit the battery or plug in USB, flick the switch, and all 100 LEDs light
If one is dark, check its polarity and look for a cold joint
Wrap-up
Soldering 100 LEDs is training in patience and a steady hand
Pin the finished badge on or give it away as a gift
π‘ Tips
- When soldering LEDs, fix first then solder: tack one leg, check the orientation, then solder the other
- Telling 5mm LED polarity: the long leg is the anode, the bigger internal frame is the cathode (see the LED tutorial)
- Do not exceed 5V, and keep the current down or the LEDs will run hot, go dim, and eventually fail