Enclosure Printing

The individual elements for the enclosure were 3D printed with the following settings.

Layer Height: 0.15mm

Infill Density: 25%

Infill Pattern: Tri Hexagon

Base Adhesion: Brim

PCB Assembly

For ease of assembly mount the components with the lowest profile first progressing to those with the highest profile last.

As this enables you to solder the components in on a flat surface which helps to hold them in place.

Resistors.

Bend the leads of the resistors at both ends with pointed nose pliers and insert the correct value between the holes in the board. The values are printed on the board to reduce errors in assembly.

Solder the wires to hold in place.

Sockets

Insert the IC sockets paying attention to the pin 1 identification and solder in place.

Ceramic Capacitors

Bend the wires with pointed nose pliers if applicable to fit between the holes and prevent excessive stress on the component body and solder in place.

Electrolytic Capacitors

Bend the wires with pointed nose pliers if applicable to fit between the holes and prevent excessive stress on the component body and solder in place.

Terminal Blocks

Insert the pins through the board and solder in place.

Before inserting the IC's visually check the board to ensure all the connections are soldered and that no solder bridges exist and/or with a DMM (on diode or resistance), check between + and - on the power terminal to ensure there are no short circuits.

Once you are confident that no shorts or opens exist and that all the passive components are correctly placed its time to insert the IC's again making sure that they are correctly orientated and inserted into the correct socket.

The names are printed on the board to reduce errors in assembly.

Ensure ESD protective precautions are followed to prevent damage to the IC's during handling and insertion.

Box Assembly

There are a number of elements involved in the box assembly.

Starting with the base the Breakout board is screwed to the shortest pillars. These are already printed with through holes allowing self tapping screws (M3 x 8mm max.), to be inserted from the top or bolts (M3 x 9mm min), to be inserted from the bottom and a nut fitted on the top.

M/F 115mm jumper wires connect the Breakout board to the PCB terminal block and Display board.

The connections from the Breakout board to the PCB are:

P0 to CLK IP

P1 to FCTRL IP

3V to + & 0V to -

Prior to fitting the PCB the OLED display needs to be connected.

However, for this project the main edge connector is bypassed and right angle terminal pins are soldered to the I2C expansion port.

The connections from the Breakout board to the Display board are:

SCL (19) to SCL

SDA (20) to SDA

3V to 3V

0V to 0V

The connections to the switches are:

Enable (Button A- P5)

Range (Button B -P11)

With the remaining connections for these two switches connected together at 0V.

The PCB is fitted to the 27mm pillars with self tapping screws (M3 x 8mm) or bolts (M3 x 30mm).

Proceed to connect the terminal posts, switches and potentiometers to the front panel.

The pre-existing holes may need deburring or adjusting in size if different elements are used this can be accomplished with a file or drill as required.

The front terminal posts are connected to the PCB at the terminal blocks.

The potentiometers are connected to the terminal pins on the PCB and an anti turn hole may need to be drilled at the rear of the front panel panel as this is not pre-printed.

Fit knobs appropriate to the potentiometers.

Once the front panel elements are fitted the display needs to be set in place.

Included within the box elements are two display slots these attach to the back of the front panel and hold the display in place.

The upper holes in the slots only sit over the protruding edge of an M3 x 8mm nut and bolt whilst the lower holes are held in place by a nut and bolt that passes all the way through the front panel and the slot.

However, due to the position of the connector across the top of the display board the display is set back from the opening in the front panel creating a gap. This gap is taken up by a transparent piece of Perspex 52mm x 52mm x 5mm in size.

At 26mm x 5mm along the bottom of the Perspex block a 3mm hole both in the Perspex and coincident with the front panel is made and held together with an M3 x 10mm bolt.

The right hand side panel has a 8mm hole to accommodate the USB plug but this may required widening subject to the size of the plug body.

The box can be fully assembled using the pre-printed holes which align with their neighbouring edges and fixed with M3 x 8mm self tapping screws.

Text Inlay

The text is included as part of the 3D printing process for permanency and with the intention that each character will be filled in to create an inlay.

Prior to filing in the characters some preparation may be required to remove excess material as a result of over extrusion which may create islands or barriers in the character. Use a scalpel or picking tool to remove these.

The characters could be filled in with a variety of materials, paint, correction fluid, nail varnish or liquid epoxy resin. In this case epoxy resin will be used which will be a 2 part 1:1 mix.

Epoxy resin pigment is added once the resin is mixed which for this project is a white pigment.

Depending on the viscosity, the area and level of detail, drying time and ease of cleaning surfaces and material different application techniques can be employed.

These may range from syringe, paint brush, spreader or dropper.

The dropper technique using a skewer or cocktail stick will be employed were the stick is dipped into the resin and small drops of resin are transferred to the depression which will hold the resin in place once dry.

Apply the drops in small quantities and build up the filling, if you over fill; the excess can be removed with a tissue, cotton bud paint brush or skewer.

The greater the percentage of infill the smaller any bleed through around the character due to the reduction in voids. This bleed through my result in the resin being sucked out of the character being filled.

You could repeatedly fill the character(s), or refill once the resin has set filled in local voids which my prevent further bleed.

Once all the letters are filled in leave horizontally until the resin has cured.

Another example of this technique can be found in a previous project: Micro Binary Clock