Step 2: Component placement on circuit board
Objective: Place circuit board components
This is a component planning step without soldering. Insert all components on the circuit
board without soldering. Pay attentions to the signal flow of the circuit. The
recommended placement is to arrange the ICs in 3 rows. U6, U7, U8 are on the top row,
with their outputs (pin 10 - 16) close to the top edge of the board where some 20 wires
will go to the LED ring. Place U4, U5 (CD4017) on the center row with pin 1 facing U6,
U7, U8 (ULN2003). U2 (LM556) and U3 (CD4013) are placed at the bottom row with
transistors, resistor and capacitors near them. Run wires from the circuit board to the
power jack, VR1, SW1, buzzer, LED0 – LED19. Try to arrange the components so that
these external wires access the circuit board near the sides.
Some components may have a different size than the placement plan given below and
therefore may not be possible to have identical placement. It is important to place all
components before soldering to avoid time-consuming rework after soldering. Use
Scotch Tape to secure IC sockets and components to the circuit board if necessary.
