Hi Neville, You said ". . . I mounted a12V 1 watt 40mm brushless DC ball bearing fan, . . "
Damn, is that thing turbo charged ? Bill....WB6BNQ Neville Michie wrote: > Hi, > I have just commissioned a temperature control for my LPRO rubidium > oscillator. > When I read the specs I noticed that at 18V supply and about 40*C the > unit only requires about > 8 watts. That is getting close to what my stand-alone power source > can maintain. > Running at a higher temperature takes a little load off the ovens on > the lamp and the detector, > but it does have a penalty in MTBF. At 40*C I thought the trade-off > was worth it. > Now the local crystal oscillator is not temperature controlled and > its control voltage drifts widely. > So I bolted the LPRO to a plate of aluminium about 1/4 inch thick. On > the other side of the aluminium plate > I bolted heat sink fins about 3/4 long over the whole length. > The whole unit mounts inside a piece of about 3X4 aluminium > extrusion. At one end in a little plenum > chamber I mounted a12V 1 watt 40mm brushless DC ball bearing fan, in > the AL plate I drilled a > deep well in which a bead thermistor lives. > The whole thing is insulated in 1/2 inch plastic foam sheet. > When the fan running on 12V the temperature is held to 4 *C above > ambient. At 8 volts this rises to about 7*C. > The fan is quite unobtrusive on 8 V. > The thermistor is in a bridge circuit and switches the fan in a PWM > control mode with a 50 second cycle time. > The surface of the plate has less than 0.1*C variation over a day > with no sign of the temperature cycling. > The oscillator control voltage now rises on startup and then becomes > rock steady. > The next step is to get on with the building of the gear to measure > how well the LPRO now performs > at constant temperature. > Cheers, > Neville Michie > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.