Full Stack Electronics · The 555, from Transistors

The Parts

What to buy, how many, and when you'll need it.

You can buy the parts in stages. Start with the breadboard components for Stages One to Three. Choose the surface-mount parts when you reach PCB design in Stage Four. Each experiment shows you how to identify and connect the parts it introduces.

The tables separate the quantities you use from suggested purchases with spares. The supplier links are examples from Mouser. If you buy elsewhere, check the full part number, package and pinout against the experiment. A similar name or appearance does not guarantee a suitable replacement.

To start Experiment 1, you need one NE555 in an 8-pin DIP package, two 10 kΩ resistors, one 10 µF electrolytic capacitor and one 10 nF ceramic capacitor. You also need one red LED, one 220 Ω resistor, and the breadboard, wire and instruments listed in The Bench.

You can leave the rest until you need it. The schedule below shows when to have each new part ready.

When to buy

Before Experiment 1: the starter parts above. Buy spares now if you want to avoid a second order for the same values.
Before Experiment 2: the LM393, the CD4001B, two 2N3904 transistors, three 4.7 kΩ divider resistors, and four 10 kΩ resistors for the pull-ups and base resistors. Add a second set of timing parts (two 10 kΩ and a 10 µF), an LED and a 220 Ω resistor.
Before Experiments 3–6: 1 kΩ resistors for Experiment 3, and 4.7 kΩ resistors for the collector loads and the optional divider in Experiment 4. Add a 2.2 kΩ for Experiment 5 and 2N3906 transistors for Experiment 6.
Before Experiments 7 and 8: no new part types. Experiment 7 takes one 2N3906, one 4.7 kΩ and three 10 kΩ for the divider on the board. Experiment 8 takes four 2N3906, three 2N3904 and two 4.7 kΩ.
Before Experiments 9–13: a 1 µF ceramic capacitor for Experiment 9, the remaining breadboard parts for the complete timer in Experiment 12, and a 100 kΩ resistor for Experiment 13.
During Stage Four: choose components when you assign footprints in Experiment 17. Have samples ready for the printed layout check in Experiment 19, then order the PCBs after the design checks. Have the full assembly quantities ready for Experiment 20.

Breadboard components · Stages One to Three

The Needed column lets you keep the chip and IC timers assembled while you build the transistor timer on the third breadboard. You can reuse the parts that you remove as you improve that third build. The Suggested buy column includes spares, and extra transistors and divider resistors to measure and compare.

Semiconductors

Part and package	Needed	Suggested buy	First experiment	Example supplier
2N3904 (NPN, TO-92)	18	50	2	512-2N3904BU
2N3906 (PNP, TO-92)	7	20	6	512-2N3906BU
NE555 (8-pin DIP)	1	2	1	595-NE555P
LM393 (dual comparator, 8-pin DIP)	1	2	2	595-LM393P
CD4001B (quad NOR gate, 14-pin DIP)	1	2	2	595-CD4001BE
Red LED, 5 mm	3	10	1	604-WP7113ID

The complete transistor timer uses 16 NPN and 7 PNP transistors. Two more NPN transistors stay in the IC timer, so you need 18 in total.

Even transistors with the same part number vary slightly. Experiment 4 shows how much that matters when two of them share one current. Buy each transistor type from one manufacturer.

Resistors · ¼ W through-hole

Value	Needed	Suggested buy	First experiment	Example supplier
10 kΩ	20	50	1	603-CFR-25JB-52-10K
1 kΩ	2	10	3	603-CFR-25JB-1K0
4.7 kΩ	10	20	2	603-CFR-25JB-52-4K7
2.2 kΩ	1	5	5	603-CFR-25JB-52-2K2
100 kΩ	1	5	13	603-CFR-25JR-52100K
220 Ω	3	10	1	603-CFR-25JB-52-220R

The IC timer and the PCB each take their divider from three 4.7 kΩ resistors. The transistor breadboard build makes its divider from three 10 kΩ resistors in Experiment 7. The 4.7 kΩ breadboard quantity covers three for the IC divider, three for the optional divider in Experiment 4 and four for the transistor comparators.

A resistor assortment also works if it contains the listed values in enough quantity.

Capacitors

Part	Needed	Suggested buy	First experiment	Example supplier
10 µF electrolytic, rated at least 16 V	3	5	1	667-ECA-1EM100B (25 V)
10 nF (0.01 µF) ceramic, rated at least 16 V	1	5	1	Through-hole ceramic capacitor
1 µF ceramic, rated at least 16 V	1	5	9	80-C322C105K5R5TA

Each breadboard timer that you keep needs its own 10 µF timing capacitor. The 10 nF ceramic filters the NE555 control pin in Experiment 1. The 1 µF ceramic steadies the supply rail in Experiment 9. The remaining ceramics are spares.

Breadboards and wiring

These are the same supplies listed in The Bench, so count what you already have.

Item	Quantity	Example supplier
Full-size breadboard (I use the BusBoard BB830)	3	854-BB830
22 AWG solid-core hook-up wire	One set of reels in several colours	485-1311 (six 25 ft spools)
Jumper leads, pin to pin and pin to socket	One pack of each, with at least eight pin-to-socket leads for Experiment 21	854-ZW-MM-10, 854-ZW-MF-10

PCB components · Stage Four

The table below covers one PCB and matches the assembly list in Experiment 20. Buy spares for assembly. The suggested quantities allow for dropped or damaged parts. Order more if you plan to populate several boards.

The resistors and the ceramic capacitor use the 0805 size code: each part measures 0.08 by 0.05 inches, about 2.0 by 1.25 mm. The transistors use the SOT-23 package. Check both the value or model and the package when you order.

Part and package	On one PCB	Suggested buy	Example supplier
MMBT3904 (NPN, SOT-23)	16	25	863-MMBT3904LT1G
MMBT3906 (PNP, SOT-23)	7	15	863-MMBT3906LT1G
4.7 kΩ 0805	8	20	603-RC0805FR-074K7L
10 kΩ 0805	10	20	603-RC0805FR-0710KL
1 kΩ 0805	2	10	603-RC0805FR-071KL
100 kΩ 0805	1	5	603-RC0805FR-07100KL
0.1 µF 0805	1	5	80-C0805C104K5RAC

For the listed onsemi parts, the device codes are 1AM for the MMBT3904 and 2A for the MMBT3906. Other manufacturers can use other codes. Keep parts in their labelled packaging. Check the manufacturer's marking diagram and pinout before assembly.

Using a component sample book

I found this surface-mount (SMD) component sample book on eBay. It groups the parts by type and value in labelled plastic pockets. You can use a sample book like this, or buy the parts individually from the table above. Check the contents, packages and quantities before you buy. Some assortments contain only resistors or capacitors.

Front cover of an SMD component sample book found on eBay, listing 5435 surface-mount parts organised by type and value — The SMD component sample book I found on eBay. Its cover lists the parts inside.

Header and PCB

Item	Quantity	Notes
Vertical 1×8 pin header, 2.54 mm pitch	1 per board	J1, the module's eight pins. You can cut a longer strip to length. Example: 200-TSW10807GS
Fabricated PCB	1 to assemble, plus optional spares	Order after the checks in Experiment 19. Minimum order quantities, board prices and delivery charges depend on the manufacturer.

The timing resistors, the 10 µF capacitor, the LED and its 220 Ω resistor stay outside the module. In Experiment 21 you reuse Experiment 1's breadboard circuit and replace the NE555 with your PCB. You don't need another set of timing parts for that step.

The Bench lists the solder wire, no-clean flux gel, wick, isopropyl alcohol, swabs and tweezers. Include them in your assembly preparations if you haven't already.

Shopping checklist

These are the suggested purchase quantities from the tables, including spares. Tick an item when you have enough. This browser saves your ticks.

Start Experiment 1 →