# Walter R07: power choice and first-print strategy

The NOCO is not the selected battery. It has been removed from the current physical assembly. The generic slotted tray and power allowance preserve options; they are not a promise that any battery or charger will fit.

## Power needs measurement before choosing the pack

The purchased USB TO AUDIO adapter is a5V USB device that drives the passive speakers. Waveshare specifies2.6W per channel into4Ω. The purchased speakers are8Ω/5W; that marking is not a constant5W draw per speaker and does not establish the adapter's output into8Ω. Separate speaker batteries are not inherently required. A separate regulated supply or appropriately powered USB hub may still be necessary after testing the total load and data/power topology.

The Pi5 documentation recommends the27W supply and distinguishes5V/5A-capable power from5V/3A operation. Its downstream USB allowance is1.6A with an appropriate5A supply and600mA with a3A supply; the fan shares the peripheral budget. The main screen, USB audio, microphone, radar, added modules and transient loads must be assessed together. Do not infer5V/5A support from a battery's headline wattage or capacity.

For the first mechanical prototype, use a verified external supply and the intended actual cables. Decide on the portable battery, regulation, protection, charging access and safe shutdown after the bench load is known. No electrical wiring redesign, GPIO change, battery alteration or hardware purchase was performed in this revision.

Sources checked for this revision:
- https://www.waveshare.com/wiki/USB_TO_AUDIO
- https://www.waveshare.net/wiki/USB_TO_AUDIO
- https://www.raspberrypi.com/documentation/computers/raspberry-pi.html#power-supply

## What to print first

Use the separate Walter_First_Fit_Kit_R07 folder. These are small nominal interface/material coupons, not a full-body order. A maker should use the intended process and actual hardware to record:

- main-screen and speaker hole alignment, screw diameter and safe engagement;
- Pi mounting alignment and board/cooler revision;
- small-display depth, plug exits and removable retention;
- USB/HDMI molding size, straight strain-relief length, cable diameter and minimum bend radius;
- camera ribbon connector orientation, latch access and minimum bend constraints;
- printed seam/clearance and M3 nut-pocket compensation;
- body-touch electrode/controller response through the proposed material and finish.

Then assemble an open rack with the real parts and cables. Confirm access, disconnection sequence and power under the intended workload. Print an unfinished shell after the interfaces pass, test it closed, then apply the cosmetic finish. The current model is not a guaranteed-fit print release.

## Future additions

IMU and touch-controller volumes are explicit empty allowances, not models of purchased boards. The touch cartridge is replaceable;1.2mm is a nominal radial skin allowance, not a proven capacitive-touch stack. Keep the main touchscreen glass exposed.

A thermal printer is deferred. It needs a selected mechanism, paper roll, loading path, outlet and measured power demand. No claim is made that a printer fits inside this head. The rear service interface is meant to make a later external module or base revision possible.

## Cable allowances

The new curved cable volumes show local straight-entry and bend space, not fully connected harnesses.30mm straight allowance and20/25mm centre-line bends are design targets to test against the actual cables. They are not manufacturer minimum bend specifications. The Check space calculation reports intersections between the current rigid components and reserved volumes. It cannot certify unmeasured plugs, flexible-wire behavior or hands/tool access merely because no intersection is found.