Construction

Soldering: Should you be lucky enough to have a soldering iron with an adjustable bit temperature set it to around 350 to 370 °C for classic rosin-cored, lead/tin solder which produces reliable joints on DIY projects. Leadfree solder will need a temperature of around 380 to 400 °C.

1. Insert the components into the PCB from the component side. See the placement plan near the parts list.
2. Make good contact with the soldering tip onto the solder pad and the component lead.
3. After about half a second introduce the solder so that it contacts the pad and lead.
4. When the solder melts and flows (should take around one second) remove the solder and then the iron from the joint.
5. Check the joint is good.
6. Clip off protruding component lead.

Component mounting sequence: Component leads can be bent using flat nose pliers. Always grip the lead on the component side of the bend. Don’t make the bend too close to the component body.

1. Resistors (arrange them so that the color rings indicating their value can be read from left to right).
2. Capacitors (check their values).
3. Pushbutton.
4. The IC socket (line up pin one with position 1 on the layout).
5. The seven segment display (check orientation of the decimal point lead).
6. IC 2 (make sure it’s correctly orientated). Don’t mount this too close to the board. Leave a gap of about 5 mm between the component base and the board surface. A component mounted close to the board can be subjected to relatively large levels of mechanical stress which may cause internal damage to the IC.
7. The battery clip (feed the wires through the strain relief holes first. Black wire to the GND pad and red wire the 9 V pad).