The previous iteration of GPS+voice interface boxes came from the Sherline CNC mill, with a considerable amount of huffing & puffing. I got the Thing-O-Matic to simplify that process…
The general idea is to build a box that clips onto the radio in place of the standard battery pack. External power comes into the box and goes directly to the radio’s battery contacts; this will pose a problem with the Wouxun KG-UV3D, because it wants 7.2 V rather than the stepped-up 9 V from the Li-Ion packs I’ve been using. I think a three-wire power cord is in order: +9 V for the interface, +7.2 V for the radio, and common.
The box also interfaces with the radio’s mic and speaker jacks. Last time around, I made a gluing fixture to keep the plugs in alignment while the epoxy cured around the plugs in the plate, but maybe I can simplify that with 3D printing. Plastic will be better in one respect: the shells of the two plugs must be electrically isolated.
This first-pass (*) approximation shows the three tabs on the pack that engage the radio’s base:
A detail of those tabs, as seen from the bottom:
The ICOM IC-Z1A battery pack had a set of slip-in alignment features that held the pack on the radio, so two strips of tape sufficed to hold the interface box in place. Each Wouxun battery pack includes a spring-loaded latching mechanism that engages a pair of ramped tabs on the radio body that hold the pack against the spring-loaded battery contacts. That means I must come up with an actual latch of some sort to oppose the contact springs, but I haven’t figured that out yet.
The solid model, with the plug mounting plate floating beside it, looks like this:
Tomorrow, the solid modeling…
* It’s actually the third printing of the bottom plate with the three tabs and the base plate with the battery contacts. That’s how I figured out the 0. 5% shrinkage thing.
[Update: The sketch with the dimensions emerged from beneath a pile o’ stuff…]