Preview. Preview. The board is real: REV A7, and everything described here is read off its silkscreen and its production files. It is not in the catalogue yet, so there is no price to quote. Register interest and we will tell you the day it lands.
DIY KIT own board · REV A7
LEARN TO SOLDER. 4 LEVELS.
Four levels from big through-holes down to 0.65 mm SMD and an SO-8 chip — 108 practice joints that connect to nothing, so nothing you do there can break anything. Then a finish line of 20 joints that has to work: hold the button and three LEDs and a buzzer tell you whether it does.
Coming soon
4
Levels, easy to hard
86+
Through-hole practice joints
12
SMD pairs, two sizes
1
Circuit that has to work
// The board, part by part
Read the board
Every part on the board, and what it is doing there. Point at a marker on the layout — or a row in the list — and the other side follows.
// The numbers
Specification
14 rows
Board
| Board size | 100.0 × 80.0 mm |
|---|---|
| Thickness | 1.6 mm |
| Layers | 2 |
| Material | FR-4, TG135 |
| Surface finish | ENIG (immersion gold) |
| Silkscreen | White, both sides |
| Weight | approx. 26 g Bare board |
| Mounting holes | 4 × 3.2 mm, 92 × 72 mm pattern 4 mm in from each corner |
Practice
| Solder joints | 128 108 practice + 20 on the finish line |
|---|---|
| Practice levels | 4, plus a working finish-line circuit |
| Finest practice pitch | 1.27 mm (SO-8) |
Power
| Power | CR2032, 3 V Zero standby current — the cell is only in circuit while the button is held |
|---|
Build
| Revision | REV A7 |
|---|---|
| Origin | Made in China · packed in UAE |
Four levels, in the order they are printed
Levels 1 to 4 are not connected to anything. Practise as many joints as you like, in any order — nothing you do there can break the circuit at the end. The board says so on the silkscreen.
| Level | What it is | Joints | Hole / pad |
|---|---|---|---|
| 1 | Big pads — your first joints | 12 | 1.00 mm |
| 2 | Medium pads | 24 | 0.80 mm |
| 3 | 2.54 mm pitch grid, 8 × 5 | 40 | 0.70 mm |
| 4 | SMD — 6 larger + 6 smaller pairs | 24 | 1206 and 0805 lands |
| 4 | SO-8 IC, 1.27 mm pitch | 8 | 0.60 × 2.00 mm pads |
| — | Finish-line circuit | 20 | mixed |
| Total | 128 |
The circuit that has to work
Hold the button: all three LEDs light and the buzzer sounds together. Release and everything stops.
Standby current is zero. The cell is only in circuit while the button is held, so it keeps for years instead of going flat in a fortnight.
3 × LED, 5 mm
Fit R upright, K to the marked pad. 2.54 mm lead pitch, 0.80 mm holes
3 × 1 kΩ resistor
1/4 W, fitted upright — pad spacing is 3.30 mm
1 × active buzzer, 3 V
BZ+ and BZ− marked on the silk. 7.60 mm lead pitch
1 × tact switch, 6 × 6 mm
Four pins, 6.50 × 4.50 mm pattern — press to test
1 × CR2032 holder
2-pin through-hole, ~20 mm pin pitch. Fit the cell last
Which parts work — and which will not
The board is drilled and marked for specific parts. Two of them are not interchangeable, and both failures look like bad soldering when they are not.
LEDs: red or yellow only
Blue, white and modern green LEDs have a forward voltage of 2.8–3.4 V. From a 3 V cell through 1 kΩ that gives essentially no current — and "all three light" is the board's entire pass signal.
Buzzer: active, not passive
There is no oscillator on the board. The button simply connects the buzzer across the cell, so a passive piezo makes no sound at all.
Buzzer current: ≤10 mA
A CR2032 cannot drive more than that alongside three LEDs.
Resistors: 1 kΩ, 1/4 W
Fitted upright. The pads are 3.30 mm apart, not the usual lying-down spacing.
What to solder into the practice levels
The levels need something to put in them. None of it is critical — these pads connect to nothing — so odd-value spares are ideal.
| Level | What to supply |
|---|---|
| 1 | Thick tinned wire, or spare component legs |
| 2 | 12 spare resistors, or wire links |
| 3 | 2 × 20-pin male header strips, 2.54 mm — snap into five 8-pin pieces |
| 4 upper | 6 × 1206 chip resistors, 0 Ω |
| 4 lower | 6 × 0805 chip resistors, 0 Ω |
| 4 IC | 1 × any SO-8 part |
Tools you will need
Not supplied with the board.
Soldering iron, 25–60 W
Anything temperature-controlled in that range is comfortable
Solder, 0.7 mm rosin core
Thinner than general-purpose solder — the SMD pads need it
Flush side cutters
Not optional. You cannot finish the board without trimming leads
Desoldering wick
For fixing mistakes, which is the entire point of a practice board
Everything is printed on the board itself
You should not need this page in front of you while you build.
Full instructions
Printed on the back silkscreen
QR code
On the back, linking to the build guide at diykit.ae
Component markings
R, LED, K, BZ+, BZ−, CR2032, SO-8 and DIP, on the front
The safety line
"FIT THE CELL LAST — NEVER SOLDER WITH IT IN", on the back
Fit the cell last
Cell last
Soldering with a coin cell in the holder risks shorting it through your iron and heating the cell. A hot lithium cell is not something you want on the bench.
Ventilate
Flux fumes. Open a window or run an extractor.
// Before you ask
Questions
8 questions
Do I need to know anything first?
No. Level 1 is deliberately forgiving — big pads, big holes — so the first joint you ever make is one that is hard to ruin. The levels tighten from there.
Why are the practice pads not connected?
So nothing you do on levels 1 to 4 can break the finish-line circuit. Practise as many joints as you like, in any order, then build the part that has to work.
How do I know if my soldering is good enough?
The board tells you. Build the finish line, hold the button: if all three LEDs light and the buzzer sounds, the joints conduct. That is a better answer than looking at them.
Which LEDs can I use?
Red or yellow, 5 mm. Blue, white and modern green will not work: their forward voltage is 2.8–3.4 V, and from a 3 V coin cell through a 1 kΩ resistor that leaves essentially no current. The LEDs stay dark and it looks like a bad joint when it is not.
Can I use any buzzer?
It has to be an active 3 V type drawing 10 mA or less. There is no oscillator on the board — the button just connects the buzzer across the cell — so a passive piezo makes no sound at all, however well you solder it.
Will the coin cell go flat sitting on a shelf?
No. Standby current is zero: the cell is only in circuit while you hold the button down. A built board keeps for years rather than going flat in a fortnight.
Why fit the cell last?
It is printed on the back for a reason. Soldering with a coin cell in the holder risks shorting it through your iron and heating the cell, and a hot lithium cell is not something you want on the bench.
Is it reusable?
The practice areas are, within reason — you can desolder and redo joints while learning. The finish line is meant to be built once and kept as the thing that proves you can.
// Register interest