Making an Illuminated Wooden Name Plate Using Flexible Filament LEDs, a Microcontroller and a Constant Current Circuit

This article shows how a rectangular thin piece of wood can be made into an illuminated name plate using flexible filament LEDs and a programmable LED driver circuit board. Instructables: Constant Current Circuit for Flexible Filament LEDs Using Cytron Maker Nano RP2040 With PWM Brightness Control shows how to make the LED driver circuit board which can control and vary the brightness of the filament LEDs.

American black walnut was used for this as some leftover veneers were available. Aircraft grade or "laser" thin plywood would also be suitable. An easier alternative with a more "electronic" look would be a large piece of stripboard or protoboard.

The flexible filament LEDs were arranged and affixed to resemble some handwriting. Elegant fonts are achievable with more fixing points.

• Something flat to mount the flexible filament LEDs on, this could be:
• a thin piece of seasoned wood (used here);
• thin aircraft grade plywood;
• stripboard (normally used for electronics);
• protoboard (normally used for electronics).
• Something to attach the circuit board to the name plate, this could be
• nylon or metal standoffs (one end would need to be bonded to name plate),
• small wooden blocks - used here with self-adhesive velcro and PVA wood glue.
• Red and at least one other colour solid core wire to connect the circuit board to the filament LEDs.
• And solder, soldering iron, wire strippers for that task.
• A drill and drill bits to make 1mm, 2mm and 3mm holes. A cordless drill with variable speed was used.
• Thin (nylon) monofilament fishing line to tie down the filament LEDs and a hot glue gun to hold the line on the reverse side. Drennan carp and silverfish mono 2.9lb 1.31kg 0.14mm was used.
• 3/32" and 1/8" heatshrink and a hot air gun (a hairdryer on hot and low-speed setting may suffice) to hold the ends of the filament LED in place.
• For a wooden veneer.
• Something to cut the veneer into a reasonable rectangular - a Japanese pull saw (nokogiri) was used with two clamps, low-tack double-sided tape and two pieces of medium-densify fibreboard (MDF) to hold the veneer in place. A try square or similar will be needed to check right angles.
• Coarse sand paper and fine sand paper.
• A surface finish - Rustin's Danish oil was used.
• The LED driver circuit board and 5 flexible filament LEDs from Instructables: Constant Current Circuit for Flexible Filament LEDs Using Cytron Maker Nano RP2040 With PWM Brightness Control.
• Something soft like bubble wrap is useful for when the half-complete veneer with filament LEDs on needs to be placed face down.

The 3.5mm (9/64") American black walnut veneers were left over from a previous project and were approximately the right size at 275x102mm. The veneer had one good edge, three other rough edges and needed to be trimmed to size.

The design featured three letters. The letter size was based on the dimensions from making each letter from a single 300mm flexible filament LED. The maximum height for the capital letter A was 80mm.

The image above shows the veneer clamped between two pieces of medium-density fibreboard (MDF) which provided a partial guide for the Japanese pull saw (nokogiri). The veneer was also held in place with some double-sided tape. This was low-tack tape but it can still damage the surface and is best used only on the reverse side. Some coarse sand paper is visible on top of the MDF. It's attached using the double-sided tape. It was used to make the veneer rectangular and clean up the edges to make them smooth.

After trimming and sanding it was 250x100mm. The 100mm side isn't quite long enough to completely hide the longer side of the circuit board behind the name plate when viewed from an angle - 250x125mm would have been better.

The flexible filament LEDs are just under 2mm wide but bulge at the ends. A 3mm hole is practical to allow them to easily pass through the name plate and avoid forcing sharps bends. A 1mm hole is suitable for the fishing line fixing points as the hole will be hidden by the wider filament LED on top.

The holes were marked on the wood with pencil and then a 2mm drill bit was spun slowly in reverse to mark all of the holes. The 3mm and 1mm holes were then drilled. This was practised on a scrap piece of hardwood with similar thickness first.

The layout of the holes loosely followed the template in the photograph above. The letter A was created by following the long sides of the A and then going around the back of the veneer for the A's crossbar. The intention was only to get a reasonably close rendition - more fixing points and experimentation would be required to follow a template or font precisely and there will always be limits on the bend radius.

Minimising the length of the drill bit protruding from the chuck and reseating the bit in the chuck until it can be seen to spin with minimal lateral movement (runout) will help to drill precise holes. The chuck will leave a mark if it goes too far and presses against the veneer - this is easy to do accidentally with the short, fast-penetrating 1mm drill bit.

If stripboard had been used instead of a wood veneer then the holes could have been enlarged with the 3mm drill bit.

Small drill bits are fragile and can easily break during drilling. Eye protection and spare drill bits are wise precautions.

Danish oil is easy to apply evenly and provides a pleasant satin finish. Only the front and sides were oiled (see photograph above on the left). The back is left unoiled as it won't be visible and the unfinished surface is better for gluing items to.

The second photograph shows the oiled piece alongside an unfinished piece of walnut.

Rustin's warning (due to linseed oil content): "IMPORTANT: Rags used for oiling must be laid out flat to dry or destroyed otherwise they may catch fire due to spontaneous combustion."

Some cherry offcuts (featuring heartwood and sapwood) were used to make the standoffs for the circuit board. These were oiled on the sides only and when dry were scored and glued to the name plate in a place which would not obstruct any of the holes. Glue bonds for wood are stronger if clamped/weighted, therefore it made sense to do this before the filament LEDs were mounted.

Self-adhesive velcro was attached to the underside of the circuit board (see above) and to the wooden standoffs after the glue had set.

A multimeter was used to check the adhesive on the velcro wasn't conductive. The copper tracks under the smaller piece of velcro were cut as a precaution.

The vertical placement of the standoffs was chosen to allow the lower edge of the circuit board to act as a support to allow the veneer to rest on a desk.

The first stage per letter/figure is:

1. feed the filament LED through and check the length is good for the whole letter/figure;
2. add two overlapping pieces of heatshrink to one end (terminal) to hold it in place on the reverse side of the veneer.

Two layers/sizes of heatshrink were used to get a thicker "collar" to hold the filament's terminal in place, 3/32" and 1/8".

The letters/figures can now be completed by:

1. using the fishing line to hold each part of the filament LED and hot gluing the line on the reverse side;
2. fixing the other end of the filament LED using heatshrink.

It's very useful to power the LEDs during construction to help orient the filaments. The filaments produce more light in one direction, hence in most cases it makes more sense to orient them towards the observer rather than the name plate. For tight bends like the top of the A the filament LED needs to go on its side.

Hot glue works well for holding the filament LEDs in place. A piece of fishing line was looped around the filament LED poking the ends through the 1mm hole. The lines were then gently pulled taught and pressed against the reverse side of the veneer to glue them at the hole and along the line for about 15mm (1/2") of the line. The line should be held for about 30 seconds to allow the glue to start solidifying. Blowing on the glue will help to cool it.

The hot air gun for the heatshrink needs to be kept away from the hot glue spots as it can remelt them.

This was a lengthy, fiddly task!

Three black wire loops were hot glued to the board to keep the longer filament LED ends more or less flat against the veneer.

The solid core 22AWG wires were cut to length and shaped and then soldered to the circuit board. The circuit board was then attached using the velcro and the wires were soldered to the filament LEDs in the order below.

1. 5V power using red wires to the LED anodes (marked with a tiny hole in the connector).
2. Short one under the board (not visible in photograph) to the middle letter D.
3. Left one to the right letter A.
4. Right one to the left letter A and then onto the two lines. This gauge of wire is easily capable of carrying the current for three LEDs over this short distance.
5. Transistor collector lines to the LED cathodes.
6. pwm0 (white) - top line.
7. pwm1 (yellow) - bottom line.
8. pwm2 (green) - right A
9. pwm3 (blue) - middle D.
10. pwm4 (white again) - left A.
11. pwm5 is not used here and left unconnected.

Solid core wire was used to allow it to be shaped for the route. The length on the first white wire was unfortunately short - an extra length of wire was soldered on to it.

If the circuit board needs to be removeable then some sort of connector or terminal block would be needed.

Note: the wire colours used here do not match the filament LED colours.

The name plate looks nice with the coloured LED light on the moderately dark walnut. The fishing line works well for invisible attachment.

The fine sanding could be improved with more sanding and finer sandpaper and there are a few barely-visible small indentations from the drill chuck on some of the 1mm holes. The veneer isn't tall enough to obscure the attached LED driver circuit board when viewed from above but this was due to what was easily available.