playdate light

UPDATE: In the BOM I changed the 6mm to 8mm M2 screw as this is the correct variant! Sorry for the error.

A compact snap fit attachment using a standard AAA battery with a LED that swivels over the screen to provide a frontlight for the playdate console.

The swivel down motion actuates a cam and pushrod mechanism that pushes the battery away from the plus contact, acting as a switch. That same cam and pushrod mechanism acts with double duty to help fully close the swivel arm when close to the closing position, keeping it closed using the force of the AAA battery terminal spring.

The LED is mounted on a small custom DC to DC boost circuit board, allowing the use of low charge AAA batteries that may otherwise be discarded. The led circuit draws 100 mA, so a 750mAh AAA (e.G. LADDA) will last 7,5 hours.

This is a fairly involved project, please read through the description carefully.

Fabrication Instructions:

The pushrod.stl should be printed with FDM, all other parts either using SLS, MJF or SLA 3D printing. The parts in the photos were done using MJF. 

The included PCB gerber files are compatible with JLC PCB, the BOM for PCB is included in the downloads. The PCB has a 0.8mm thickness and has no other special manufacturing requirements.

BOM:

• M2 Nyloc nut
• M2x8mm Screw with 1.5mm hex socket
• Conical spring 0.4mm thickness, 6mm to 4mm; 8mm high (e.g. sourced from an old AAA battery remote contact) If you search at AliExpress “0.4mm conical spring” there should be suitable conical springs.
• sticky copper tape as a battery contact, alternatively any other piece of thin metal with double sided tape should also work as a contact
• thin flexible electrical wires - no single stranded wire, it must be flexible! I cut open an old USB cable and took the individual wires
• superglue, hot glue or thicker foamy double sided tape for mounting parts
• for the battery door: M1.6 nut and M1.6x4mm screw with flat top (laptop screw), one can also use a self tapping plastic screw sourced from some discarded electronics
• 5mm diameter 2mm high magnets (optional)

Order of assembly:

• assemble the PCB: Take care for the diode orientation: the anode is connected to R3, the cathode to GND. Add overly long wires, the postive termial is above U1, the negative above C1
• slot in the spring inside the base part, you may need to manually form the first turn with pliers to fit
• insert the pushrod in the base part, it may needs some force

• slot in the wires in the arm part, dont yet attach the PCB with glue/tape
• add the M2 nyloc nut in the arm part
• thread the wires through the opening of the base part
• mount the arm using the M2x6mm screw, take care to not clamp the pushrod
• slot in the PCB to the final position and make sure wires have some slight slop
• attach the copper tape (or alternative described above) for the + battery contact and solder the positive wire, solder the negative wire to the spring. Getting the right wire length is tricky, take your time.

• you now can glue the pcb into the recess
• mount the battery door with your preferred fastener, when using the M1.6 fasteners you may want to secure the m1.6 nut somehow from falling out of that slot.
• mount the magnets into the recesses 
• adjust the tension on the M2 screw so the arm is slightly sticky

Troubleshoot:

• on my unit I had to add a piece of thick tape to the end of the battery door to make sure the the AAA battery engaged the pushrod. The part touching the battery should not be sticky and allow the movement of the battery.