DERULER - Components

List of included components

Box 2 – Mechanical

Reference	Marking	Value	Package	Description	Quantity
BZ1		FUET-7525-3.6V	SMD	Magnetic Buzzer	1
BUTTON1, BUTTON2		UK-B0228-G4.3-250	SMD 6x6x4.3	Tactile Button	2
J1	–	–	SMD	Rectangular pin header 2×5-pin 2.54mm pitch	1
J2	–	–	SMD	Rectangular pin header 1×3-pin 2.54mm pitch	1
–	–	–	–	9V battery cable	1

Box 3 – Semiconductors

Reference	Marking	Value	Package	Description	Quantity
U1	AMS1117	AMS1117-3.3	SOT-223	Voltage regulator 3.3V	2
U2	STM32L 051K6T6	STM32L051K6T6	LQFP-32	Microcontroller	1
Q1	1AM	MMBT3904	SOT-23	Transistor BJT NPN	2
D1	–	TC5050RGBF08-3CJH-AF53A	5050-6P	RGB LED	2
D2	T4	1N4148W	SOD-123	Silicon Diode	2

Box 4 – Resistors

Reference	Marking	Value	Package	Description	Quantity
R1	104 or 1003	100kohm	0805	Microcontroller boot mode pull-down resistor	10
R2, R4	15R0	15ohm	0805	Current limiting resistor (Green & Blue LED)	10
R3	560	56ohm	0805	Current limiting resistor (Red LED)	10
R5	132 or 1301	1.3kohm	0805	Current limiting resistor (BJT base)	10

Box 5 – Capacitors

Reference	Marking	Value	Package	Description	Quantity	Picture
C1, C2, C3		10uF	0805	Decoupling capacitor	3
C4, C5, C6, C7, C8		0.1uF	0603	Decoupling capacitor	10

Box 6 – Soldering challenge

Reference	Marking	Value	Package	Description	Quantity
–	–	0ohm	0201	Soldering challenge resistor	10
–	–	0ohm	0402	Soldering challenge resistor	10
–	0	0ohm	0603	Soldering challenge resistor	10
–	000	0ohm	0805	Soldering challenge resistor	10
–	000	0ohm	1206	Soldering challenge resistor	10
–	000	0ohm	2512	Soldering challenge resistor	1

Reference designators

When drawing a circuit schematic each component is annotated with a unique reference designator. Most commonly they consist of a letter indicating the component type and succeeding digits incremented in sequence for each unique part starting from one. For example if the circuit has three resistors, they may be assigned designators R1, R2, and R3.

List of component types

Letter	Component type
C	Capacitor
D	Diode
J	Jack (pin header or connector)
L	Inductor
Q	Transistor
R	Resistor
U	Integrated circuit
Y	Crystal or oscillator

References

https://en.wikipedia.org/wiki/Reference_designator

Unit of values

Units

Symbol	Name	Description	Derivation
Ω / ohm	Ohm	resistance	1 Ω = 1 V / 1 A
C	Coulomb	charge	1 C = 1 A / 1 s
F	Farad	capacitance	1 F = 1 C / 1 V
A	Ampere	current	1 A = 1 C / s = 1 V / 1 Ω
J	Joule	energy	1 J = 1 C * 1 V = 1 W × 1 s
V	Volt	voltage	1 V = 1 J / C = 1 A × 1 Ω
W	Watt	power	1 W = 1 J / s = 1 V × 1 A

Unit prefixes

Symbol	Name	Value (exponential)	Value (decimal)
p	pico	10^-12	0.000 000 000 001
n	nano	10^-9	0.000 000 001
µ / u	micro	10^-6	0.000 001
m	milli	10^-3	0.001
k	kilo	10³	1 000
M	mega	10⁶	1 000 000
G	giga	10⁹	1 000 000 000

References

Identifying resistor values

Three- and four-digit marking

R = m × 10ⁿ

The most common method for marking a 5% tolerance resistor value is using three digits representing an exponential number in scientific notation. Four digits can also be used. The first two or three digits are the mantissa (m) and the last digit is the exponent (n) with a base of 10.

Small values containing R

There’s a special case for small values where the letter R is added to notate the decimal point. Digits preceding the R represent the integer and the succeeding digits are the decimals.

Examples

A resistor marked 132 means the mantissa (two first digits) is 13. The exponent is the last digit which is 2. The resistor value would be 13 × 10² = 1300 or 1.3 kohm.

A resistor marked 1003 means the mantissa (three first digits) is 100. The exponent is the last digit which is 3. The resistor value would be 100 × 10³ = 100 000 or 100 kohm.

A resistor marked 56R0 means the integer is 56. The decimals are 0. The resistor value would be 56.0 ohm.

A resistor marked R005 means the integer is 0. The decimals are 005. The resistor value would be 0.005 = 5 mohm.

References

Footprints

A footprint is the layout pattern on a circuit board for soldering a component. The simplest type consists of two square pads of exposed copper for soldering the component at both ends. The exposed copper is usually coated with soldering tin from the factory to prevent oxidation and easier soldering. This process is called HASL (hot air solder leveling). The DERULER project uses a different process called ENIG (electroless nickel immersion gold) that plates the copper with a nickel and gold layer to achieve the same result. In the past most components were of THT (hole-through technology) which relies on plated holes in the PCB for soldering. Today THT is usually only used for connectors and components that require improved mechanical support. Instead most components are now of SMD/SMT (surface-mount device/technology) type which is the only type used in this project.

Resistors and capacitors

Both chip resistors and capacitors (ceramic/MLCC/multi-layer chip capacitor) come in standardized sizes that are coded with their length and width in imperial units. There are metric equivalent codes but they’re not commonly used and has overlapping values which can be confusing. The component height can vary depending on the manufacturer and part number. Typically resistors are black and thin while capacitors are taller and brownish.

Code (Imperial)	Size (L × W, imperial)	Code (metric)	Size (L × W, metric)
0201	0.024 × 0.012 inch	0603	0.6 × 0.3 mm
0402	0.04 × 0.02 inch	1005	1.0 × 0.5 mm
0603	0.06 × 0.03 inch	1608	1.55 × 0.85 mm
0805	0.08 × 0.05 inch	2012	2.0 × 1.2 mm
1206	0.12 × 0.06 inch	3216	3.2 × 1.6 mm
2512	0.25 × 0.12 inch	6332	6.3 × 3.2 mm

Semiconductors

Many SMD semiconductors components follow standard footprints according to SO (small-outline) standards such as SOT (small-outline transistor), SOD (small-outline diode) or SOIC (small-outline integrated circuit) which are available in various sizes with different number of pins. Higher pin count ICs such as microcontrollers commonly use QFP (quad flat package) and more recently QFN (quad-flat no-leads package). In this project we’ve picked packages which are relatively simple to solder with a regular soldering iron and doesn’t require special tools such as a hot air soldering station.