Soldered Refill 2.0 Kit - Components
This page goes through every part in the kit: what it is, the numbers that matter when you wire it, and the mistake that most often kills it.
Resistors
The kit holds 50 × 330 Ω and 50 × 10 kΩ, both through-hole with 5% tolerance. Those two values cover the two jobs a beginner circuit almost always needs.
330 Ω is the LED series resistor. At 3.3 V it lets roughly 4 mA through a red LED, at 5 V roughly 9 mA. Both are bright enough to read across a room and both stay well inside what a GPIO pin can source.
10 kΩ is the pull-up and pull-down value. Put one between a button pin and 3.3 V and the pin reads HIGH until the button pulls it to ground. It is also the value to reach for in a voltage divider with a photoresistor, since the two are then in the same order of magnitude.
Read the value off the colour bands: orange-orange-brown-gold is 330 Ω, brown-black-orange-gold is 10 kΩ.
Capacitors
10 × 100 nF 50 V ceramic. These are the decoupling capacitors. One across the supply pins of an IC, as close to the chip as the breadboard allows, smooths out the current spikes the chip draws when it switches. The NE556 in particular behaves much better with one fitted. They also set the timing on the control pin of a 555 or 556 circuit.
5 × 10 µF 25 V electrolytic. These are the bulk capacitors, roughly a hundred times larger than the ceramics. They hold up the supply rail when something with a real appetite for current switches on, such as a motor through a MOSFET. In an RC timing circuit a 10 µF capacitor is what stretches a delay out to seconds instead of milliseconds.
1N4148 signal diode
Ten of them, in a small glass body with a black band at one end. The band marks the cathode, the leg current flows out of.
The 1N4148 blocks up to 100 V in reverse and passes a couple of hundred milliamps forward, and it switches fast enough for logic-speed signals. In this kit it has two jobs. As a flyback diode it sits across a relay coil or a motor, band toward the positive supply, and absorbs the voltage spike the coil throws out when the current stops. As a steering diode it lets you OR two signals together or protect an input against reverse polarity.
NPN transistor, TO-92
Ten general-purpose NPN transistors in the flat black TO-92 package. A small current into the base lets a much larger current flow from collector to emitter, so a GPIO pin that can only manage a few milliamps can switch a load drawing a hundred or so.
Use one to drive a relay coil, a small buzzer, or a string of LEDs that would otherwise overload a pin. Always put a base resistor between the GPIO pin and the base; 10 kΩ from this kit is a sensible starting point.
The three legs are emitter, base and collector, and the order depends on the exact part. Read the marking on the flat face and check the pinout before you wire it.
IRLZ44N logic-level N-channel MOSFET
Three of them, in the large TO-220 package with a metal tab and a mounting hole. Rated 55 V drain-to-source and 47 A continuous drain current, with an on-resistance of about 0.022 Ω specified at a gate drive of 5 V.
The word that matters is logic-level. An ordinary MOSFET needs around 10 V on its gate before it turns fully on, which a microcontroller pin cannot supply. The IRLZ44N is designed to turn on from logic voltages, so a 5 V pin drives it directly.
This is the part that lets the kit switch things the beginner kits cannot: 12 V LED strips, DC motors, pumps, heaters, solenoids. The load goes between the positive supply and the drain, the source goes to ground, and the gate goes to the GPIO pin through a small series resistor. Add a 10 kΩ pull-down from gate to ground so the MOSFET stays off while the board is booting.
Photoresistor, 10 kΩ
Five light-dependent resistors with the familiar zigzag track on the face. Bright light drops the resistance to a few kilohms; darkness pushes it up into the hundreds of kilohms.
On its own a photoresistor tells a microcontroller nothing, because an analog pin measures voltage, not resistance. Wire it in a voltage divider with one of the 10 kΩ resistors and the junction between them becomes a voltage that tracks the light level, which analogRead() can then measure.
The 2.3 Photoresistor Analog Read example walks through that divider step by step.
Small THT pushbutton
Five 4-legged tactile buttons that straddle the centre channel of a breadboard.
The catch with these is that only two of the four legs are useful. The two legs on the same side of the button are joined together inside it, permanently. Pressing the button connects one side to the other. So the two wires must come from opposite sides, diagonally across the centre channel. Take both from the same side and the circuit behaves as if the button is held down forever.
A pressed button also does not settle cleanly. The contacts bounce for a few milliseconds and a fast microcontroller reads that as several presses. 2.2 Button Debounce shows how to filter it in software.
SPST panel switch, 17 × 13 mm
Three square panel-mount switches, single pole single throw: one circuit, on or off, and it stays where you put it. Unlike the pushbuttons, these latch, so they suit a main power switch or a mode selector on a finished project.
They mount through a rectangular cutout in an enclosure panel and terminate in solder lugs rather than breadboard-friendly pins, so solder a short wire to each lug before trying to use one on a breadboard.
Potentiometers, 10 kΩ and 100 kΩ
Three of each, both through-hole with three legs. Turning the shaft moves a wiper along a resistive track, so the resistance between the wiper and each end pin changes while the total between the two end pins stays fixed.
Wire the two outer legs to 3.3 V and ground and the middle leg becomes an adjustable voltage that analogRead() reads as a value from 0 to the top of the ADC range. That is the standard way to add a volume knob, a brightness dial or a threshold adjustment to a project.
Which value to use. The 10 kΩ is the one for voltage dividers feeding an analog pin: low enough that the ADC input impedance does not skew the reading, high enough that it does not waste current. The 100 kΩ is for RC timing, where a larger resistance stretches the same capacitor over a much longer period. Pair a 100 kΩ potentiometer with a 10 µF capacitor on an NE556 and you get an adjustable delay running into seconds.
5 mm LED pack
One pack of 13 LEDs in assorted colours.
The longer leg is the anode and goes toward the positive side; the shorter leg is the cathode and goes to ground. There is also a flat spot on the rim of the case next to the cathode, which is easier to find once the legs have been trimmed.
Passive buzzer QMB-09B-03
One passive buzzer. Passive means it has no oscillator inside: it makes a sound only when you feed it a changing signal, and the pitch is whatever frequency you send. That is what makes it able to play melodies rather than just beep.
On a microcontroller, tone() generates the square wave and noTone() stops it. The buzzer goes straight between a GPIO pin and ground with no resistor, since the pin only ever swings between 0 V and the supply voltage. Look for the + marked on the top of the case; that leg is the positive one.
The NE556 in this kit can drive it too, with no code involved at all: wired as an astable oscillator with a 100 nF capacitor, its output lands in the audible range and drives the buzzer directly.
NE556 dual timer IC
One NE556 in a 14-pin DIP package. It holds two complete and independent 555 timers, sharing only the supply pins. Each half triggers at about one third of the supply voltage and its threshold sits at about two thirds, and each output can sink or source up to 200 mA, which is enough to drive an LED or the buzzer directly.
Two resistors and a capacitor around one half give you an astable oscillator: a square wave whose frequency is set entirely by those component values. Swap the capacitor for a larger one and the same circuit becomes a slow blinker; make it small and the output moves into the audio range. Wired as a monostable instead, one half produces a single pulse of a fixed length each time it is triggered.
With two timers in one chip you can chain them, using one to gate or trigger the other, which is how a single NE556 produces a warbling siren or a blinking tone.
NE556 datasheet
Texas Instruments, dual precision timer
Large breadboard and jumper wire set
One large breadboard and one set of jumper wires, so the kit works standing on its own without borrowing parts from another project.
The breadboard inner rows are connected in groups of five across the centre channel, and the two long rails down each edge carry power and ground. If that layout is new to you, 0.1 Breadboard Fundamentals explains it before you build anything.