So I've ordered a few prototype parts about a week and a half ago, got them in last week and hopefully ordered a PCB last Thursday. The main goal of this intermediate prototype step is to realize functionality of the daughter board, allow of some flexibility with the final design in seeing the prototype and possibly making changes, and finalize the sensors/actuators used.
Parts List
| Ref | Desc | PN | Supplier | Price | QTY | Total | Explanation | ||
| RN1B | RES ARRAY 10K OHM 10TRM 8RES SMD | MNR35103CT-ND | Digikey | 0.336 | 10 | 3.36 | Pullups or pulldowns for the sensors or outputs | ||
| RN1 | RES NET BUSSED 10K OHM 8-SIP | 4608X-1-103LF-ND | Digikey | 0.32 | 10 | 3.2 | Alternate through-hole package for pullups or pulldowns | ||
| CABLE ASSY R/A 2.5MM MONO 6' | CP-2202-ND | Digikey | 2.61 | 5 | 13.05 | Connection to sensors, board side | |||
| CABLE ASSY R/A 2.5MM STEREO 6' | CP-2204-ND | Digikey | 2.64 | 5 | 13.2 | Alternate sensor connection, 3 pin | |||
| CN7-CN20 | CONN JACK MONO RT ANG 2.5MM | CP1-2503AM-ND | Digikey | 0.39 | 5 | 1.95 | Cable to solder sensor to, 2-wire | ||
| CN1-CN6 | CONN JACK STEREO RTANG 2.5MM | SPC21360 |
| 0.694 | 6 | 4.164 | Alternate sensor cable, 3 wire | ||
| CAP CER .1UF 50V Y5V 0603 | 490-1568-1-ND | Digikey | 0.027 | 10 | 0.27 | Analog input decouple cap, boardside | |||
| RN2, RN3 | RES ARRAY 100OHM 16TERM 8RES SMD | MNR18101CT-ND | Digikey | 0.095 | 10 | 0.95 | Digital I/O current limit (series) resistors | ||
| Total | 40.144 |
I had to replace the 2.5mm stereo jack with one from Newark because it was out of stock at Digikey. It wasn't the same part at all, so I had to redesign the Eagle library part. I chose not to include the analog input filter caps for now on the board layout (so no reference), but will try out the board with and without and see if I need them in the final design. I have a feeling they won't do much either way.
Proto Board Circuit and Layout
Below is my prototype circuit and layout. I'm not sure where I could post the Eagle files, as these pictures are not going to be that great for anyone wanting to make their own.
The layout.
The layout above has the ground planes "ripped up" for easier viewing, but the actual board has a top and bottom ground plane filling in most of the white space. This helps reduce noise and reduce power supply impedance (usually a bad thing in embedded projects).
The layout above has the ground planes "ripped up" for easier viewing, but the actual board has a top and bottom ground plane filling in most of the white space. This helps reduce noise and reduce power supply impedance (usually a bad thing in embedded projects).An annotated, explained version of the board layout is shown below in fashionable colors.
Next post will be about the details of soldering up the connectors to the actual sensors/actuators. Stay tuned.
~JWilly
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