HP Classic Calculators Emulator

PX Series Calculator Assembly

Let me start by saying that this is not a soldering tutorial.
There are plenty of great tutorials online like:

Sparkfun has an excellent one: Through-Hole Soldering.
And so does Adafruit: Guide To Excellent Soldering.

Everyone has his style for building/soldering things. This is just my way of building/assembling the calculator.

Tips:

Take your time, don't rush it.
Make sure all solder joints are well soldered.
All components should sit completely flush against the pc board.
It might help bending the leads of the parts slightly to keep them in place.
Start by soldering the shortest components.

For old assembly instructions click here.

Let's begin:

Step 1.0

Start by soldering the shortest components.

Resistors R1 and R2
Capacitors C1, C2, C3 and C4
Serial header
32.768KH Crystal XTAL
It is good practice to solder the crystal can to the PCB.

Step 2.0

Set the microcontroller completely flush against the board.
Make sure the microcontroller notch or dot (pin 1) is aligned with the pcb markings.

Step 3.0

Continue to solder:

CR2032 Battery holder.
Rest switch.
ISP Programming header
Speaker

The battery holder is designed for both CR2016 and CR2032 batteries, so the spring may feel a bit tight when you use the thicker CR2032. To fix this, gently bend the springs so the CR2032 fits more comfortably.

Step 4.0

Solder the 9-pin female header onto the display module.

Step 5.0

Mount the four 4mm brass spacers using 3mm bolts.

Step 6.0

Mount the display header.

Insert the 9 pin male header from the bottom.

From the front side of the PCB push the pcb so that the pins protrude more.

Mount the display module with the 3mm bolts and insert the header.

Solder the 9 pin header.

Remove the plastic holder from the 9 pin header and cut the leads short.

Remove the display module.

This is how it should look.

Step 7.0

Adding the 39 buttons.

Take the 3d printed case and flip is over.

Place the PCB on the back side of the 3d printed case.

Mount all 39 buttons.

Attach the 7mm brass posts with the 5mm bolts to the top plate.

Place the top cover to help align the buttons.

Remove the 3D-printed case and flip the PCB to solder all the buttons. Keep the top panel in place to prevent the buttons from shifting. Start by soldering only two diagonal pins on each button. Verify that all buttons are properly aligned, then proceed to solder the remaining pins.

Step 7.0

Mount display module.

Mount the display moudle using the four 3mm bolts.

Now it's time to test the calculator. Insert a 3V CR2032 coin battery and the display should show "Pr Error".

Step 9.0

Assemble the 3D case.

Take the 3d printed case and place the bottom panel on the back.

Place the PCB on the top of the case.

Place the top panel with the 7mm brass bolts on top.

Flip the calculator and screw the bottom plate with the 8mm bolts.

This is how it should look.

Schematic

Part List

Part	Value	Description
C1, C2	0.1µf	Decoupling Capacitor
C3	0.1µf	Speaker impedance
U1	ATMEGA328P	Microcontroller
J1	6 pin female headers	PI Programing header
BAT	Battery Holder	CR2032 Battery Holder
SPK	BUZZER	Speaker
XTAL	Clock Crystal 32.768kHz	Clock
R1	10KΩ	Reset pullup resistor
R2	10Ω	LCD backlight resistor
BTN's	6x6mm tactile switch 7mm height	Key buttons
RST	6x3.5 mm tactile button	Reset button
DISP	Display 192X64 LCD	Display