3. Assembly and Reflow

99 decimal counter: Assembly

Assembly Time!

Now that you have deposited solder paste on your circuit, all that is left to do is place your components and reflow the solder on the board.

Surface mount components

The circuit requires the following components that have been included with the 99 decimal counter kit:

• SN74LS08 IC × 1

• SN74LS47 IC × 2

• SN74LS93 IC × 2

• Push button tactile switch × 1

• Diode × 1

• 150Ω resistors × 14

• Seven segment display × 2

• 0Ω jumper resistors × 3

• 10kΩ resistors × 1

• Wire connector × 3

Carefully place your components onto the corresponding pads, as shown in the board layout below.

Use the tweezers included with V-One to place components precisely.

Do not smear the solder paste when placing components. Once they are placed, press down gently so the components rest evenly on the pads.

Both the LED and the electrolytic capacitors have a polarity. Remember to double-check that they are placed in the correct orientation before you solder them to the board. When in doubt, reference the circuit schematic shown above.

The decimal in the corner indicates the orientation of the seven-segment display.

The solid paint stripe indicates the component's pin 1 location for proper orientation.

The dot indicates this component's pin 1 location for proper orientation.

The solid stripe on this component indicates the cathode side.

Once all of the surface mount device (SMD) components are placed, proceed to the HEAT step.

Even though diodes are typically marked where the cathode is, there are, of course, exceptions to this rule. Because of this, it is very important to carefully review the datasheet of every diode/LED that you plan to use in your future designs.

Reflow

Now that all of the surface mount components are placed, the circuit is ready to be reflow soldered.

1. From the Start menu, select the HEAT workflow.

2. Click the REFLOW tile.

3. Select the solder paste you're using, based on the lot name printed on the cartridge label.

4. Click REFLOW to start the process.

V-One gets hot while reflowing. Do not touch! Do not leave unattended while heating!

When the heating cycle finishes, V-One will start glowing blue. This means the soldered PCB is safe to remove.

The result

Power and connect the pulse generator board to the 99 decimal counter board, and watch your circuit come alive. If everything is working, the seven segment display LEDs will be lit and count up at a steady rate, and you can control the counting speed by adjusting the trimmer on the pulse generator board. You can also reset the counter to zero at any time by pressing the button on the 99 decimal counter board. You should also be able to measure oscillation from the middle signal connector on the output side of the board.

The top connector should be a steady 5V, the middle signal connector should change in rhythm with the flashing LED, and the bottom connector is ground.

If you have an oscilloscope, you should also be able to measure the square wave. First, connect the probe to the oscilloscope and then to the circuit's ground and signal output. Adjust the probe's compensation for a sharp waveform. Next, adjust the Volts/Div and Time/Div settings until the square wave is clearly visible and stable on the grid. Finally, use the grid, the oscilloscope's built-in measurement tools, or cursors to find the peak-to-peak voltage, period, frequency, and duty cycle of the signal.

Congratulations! You have completed the 99 decimal counter circuit board.

That concludes the tutorial. If you ran into any hiccups along the way, let us know at [email protected].

As a reminder, this decimal counter circuit is part of a set of circuits designed to work together in a series. You’ll need to complete the voltage regulator circuit and the pulse generator circuit for this board to operate properly.

Voltage Regulator Project

Pulse Generator Project