Hi Everyone,
I finally decided to try to cram it all into a Hammond 1598J enclosure, so here is a picture of what I'm planning on doing.
I've had a another couple of threads with some info:
https://www.eevblog.com/forum/projects/chassis-recommendation/msg786191/#msg786191https://www.eevblog.com/forum/projects/what-would-you-use-relay-ssr-etc/msg784297/#msg784297What I've done is taken the RFTG apart and shed its outer metal case - I finally gave up on trying to cool it using a secondary box or outside fan and just want a single GPSDO box with everything inside. Most of the heat from the rubidium module is generated in its base plate so I flipped the LPRO-101 and the RFTG pcb over and am going to mount them upside down. I found some standoffs to facilitate this for the RFTG pcb.
The LPRO-101 base plate had 6 nice threaded holes in it already so I mounted some heat sinks to it and I'm going to position the fan to pull air across them. I'm using a TC74 i2c temperature sensor to detect the base plate temperature and plan to vary the fan RPM to attempt to keep the temperature decently consistent - I'll probably try to implement a slow changing PID loop on it that changes the fan RPM very little - I don't want to notice/hear it changing speeds all the time. This case is a split style so I plan on getting the bottom half on my CNC and am going to cut enough 1/4" diameter holes in a grid on the underside for incoming air.
I've been managing the RFTG (you can see its status, rubidium lock state, time and frequency corrections, etc.) using really old Windows 3.1 software on a notebook, but my goal is to create a UI with the Noritake display sample I have (24x6 characters) and some input buttons in the front panel. I will have to emulate the software, but I've had my Saleae 16 on it to decode most of how it works. The goal is to be able to do almost everything the windows software can do, but again inside this box with its own UI.
I'm using the ublox GPS board from iteadstudio and already have an AVR program that converts its output to the motorola oncore GPS data stream that the RFTG expects. I still need to design a new main control board to run the fan pid, control the RFTG/GPS power, and run the UI. I am thinking of using a dedicated tiny841 AVR for the GPS data conversion and an atmega324 for the main AVR. There are two mounting points on the upside down RFTG pcb towards the front and I'm going to mount the custom PCB to them and then plug the GPS shield on top of that. The custom board will also generate 5V (control board, gps board, and display 1A) and 12V (fan, 500mA) using some CUI dc dc converters from the 24V DC input voltage.
Is there any good reason to have a 15 MHz or 1PPS output? The only one that has really been important to me is the 10 MHz reference, but the RFTG board does have these other two outputs.
Any other ideas or thoughts? I'm tired of having this project in pieces hanging over itself, my goal is to get it in one box where I can just flip it on and let it discipline itself with the GPS.