So now the case is printed and all the parts are ready for assembly. What else do I need?
Three things: signal jack, power jack and encoder knob.
The signal jack is an output connector for the generated signal. Typically, BNC bulkhead connectors are found on test equipment. This is a standard. I have lots of adapters for other types of cables. Normally, the ground of the BNC connector is just tightened against a metal case. This provides proper bond for the ground side of the connection. Since my case is plastic, I needed to wrap a wire around the connector base and tighten it in place. This ground wire then completes the circuit board. It’s easy run two wires from the BNC connector to terminal block on the PCB.
Next, I need to attach power. Most small 5V power supplies use barrel connectors, typically 2.1 mm. Almost all small electronic devices use this type of connector. I have a bunch of barrel connectors that break out to screw terminals. (See upper right. These connectors are used for powering CCTV equipment. They are available on E-Bay in bulk. They come in handy for a variety of projects. The screw terminals make it easy to connect power to you PCB.) The plug fits snugly through the hole in the back of box.
Signal Generator Assembly – Plastic Nuts and Knobs
To complete the signal generator assembly, I needed a nut to tighten the rotary encoder to the top cover. There is a wonderful parametric tool on Thingiverse for creating custom screws, nuts and threaded rods. In my case, I made a 1/4 inch 32 TPI nut for the KY-040 encoder.
Finding a model for a knob was easy. This knob fits a 6 mm D shaft to turn the encoder. If you find the fit is too tight, just scale the model up by 1-2% and this will make the hole wider.