There are quite a few simple switching regulator chips for 12V --> 5V, requiring only a handful of parts to make a complete switching converter. For example, National Semiconductor (now TI after the recent purchase) LM2591HVT-5.0/NOPB. Stocked by Mouser and DigiKey at about $6. This series is available in a through hole 4-pin TO-220 style device so breadboarding up a one-off power supply isn't too difficult.
With careful attention to detail, bypassing and shielding it should be possible to build a quiet 5V, 1A supply around these parts. It can be small enough to fit into a 2"x2"x1" Hammond die cast enclosure, and you can use feedthrough caps for input and output, along with some internal LC filtering. Still, 5V at 700 mA with a switching regulator and a 12V battery (assuming 100% efficiency which isn't possible of course) the setup will require 300mA from the battery. For 100 hours of operation, you're looking at a 30 Ah battery requirement. While a battery will output more Ah with a 100 hour discharge cycle, it's not that much more. A 35Ah sealed 12V gel-cel type lead acid battery will run you about $100. For serious long duration battery operation, I would look for a more thrifty data logger. Jack K8ZOA On 1/6/2012 10:10 AM, John Gibson wrote: > Dear Elecraft list members, > > The recent thread on noisy switching power supplies leads me to a related > question. My son n8fyk, who teaches radio astronomy, has set up a project > with his students. They are using a 15m direct-conversion Radio Jove receiver > in the field to monitor radio emissions from Jupiter, the sun, and the > galaxy. The receiver operates from 12V, which is readily supplied by a > portable utility 12V battery pack. Their problem is powering their data > recorder, which needs about 5V at 0.7A. > > The data recorder is designed to operate from three internal AA alkaline > cells, but these give a limited run time. My son would like to be able to > leave the receiver and recorder for unattended operation for several days at > a time. > > One solution would be to use a 12V-to-5V power converter between the 12V > battery and the data recorder. For long battery life, it would be nice to > have the efficiency of a switching converter. Such a converter would have to > be RF-quiet, so as not to interfere with their weak-signal reception. > > I will be interested to hear what list members recommend. > > Thank you and 73, > > John, no8v > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
