Hi One consideration is weather / when the FE writes the DDS setting to internal EPROM. You can easily wear out an EPROM if it's writing every time the DDS is updated. On the flip side, having the EPROM save the last correct value might make the "unplug and walk around" part a bit easier.
Bob -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Chris Albertson Sent: Thursday, January 12, 2012 12:03 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] FE-5680A Mechanical Question I plan to lock my FE5380 to a GPS also. But I want to mine to "unplug able". The idea is to connect the GPS and let it sync for some period of time. Perhaps hours or maybe weeks, the longer the better and then you can disconnect the GPS and the FE5680 free runs at that frequency. Plug it back in to sync it. I think it's clear that a small micro processor is required or a desktop computer could be used. The FE5680 uses the RS232 port for frequency adjustment you are going to need a computer. I think a Tiny AVR would do fine. It is a $2, 8-pin chip. It has a 10-bit A/D converter to read the phase offset and you can use another pin for serial output to the FE5680. If you used a digital phase detector you'd not need the A/D. The controller would work like the typical GPSDO controller except the DAC is physically inside the FE5680. This make it easier. Physically, It will be mounted inside a steel box about the size of a shoebox (The box once held a pair of large sized disk drives, from back in the days when drives where about 3" thick) There is a thick aluminum plate the divides the box vertically. the FE5680 sits on top of the plate, a heat sink is bonded to the underside of the plate. A low speed fan moves air through the box slowly. The fan is controlled by a temperature sensor bonded to the plate the FE5680 is mounted on. This is a crude type of "oven" using the FE5680 is a heating element. I hope to stabilize temperature to about 2C. I'll start with a simple comparator chip as a on/off fan controller and eventually use another 8-pin uP to do a full PID controller with a three wire fan Chris Albertson Redondo Beach, California _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
