There are many uses for a good current source, in particular, to drive a noise generator, Noise Source TWS-N15. Not much to write home about, but because of frequent requests, I am publishing the circuit here. It will work for small current from 2 or 3 mA up to 10 or 20 mA with no problem, and very little drift over temperature and time. For R, uses a good resistor. Input voltage can be up to 35 V, or even higher.
This blog is hosted by a professional provider, but the manuals archive (which needs quite a bit of storage), and other webpages, and my fileserver, is running on two machines, a Dell OptiPlex FX160 as the main, eco-efficient system (in Germany), and a Dell PowerEdge SC1425 with a Raid 1, 3 TB hard drive system as the backup, and currently my main system in Japan (where I am living on a temporary business assignment). Recently, the SC1425 failed, it just would not start up anymore. Power supply seems OK – likely, a severe issue. Checked all the memory and everything, but to no avail.
After fiddling around for about 2 hours, and still no success, I decided to order a new server – a new old server, Dell PowerEdge 850. Just about 35 Dollars used. Rather than 2x XEON processors, it has a Pentium D, 3.2 GHz Dual-Core. Plenty of power for a web- and fileserver.
A couple of days later, the unit arrived – removed the SATA Raid controller (running on Ubuntu with software Raid), and some BIOS settings (activate SATA, disable Keyboard error, enable boot from USB, default power up status is ON) plus BIOS Update. Also, reconfigured the router to make sure this machine will get all the HTTP requests.
A few tests – the harddrive is working fine, about 100 MB/s (sure there is a cache). The Raid 1 is up with no repairs or anything.
A quick check – also the web server is reachable.
I wouldn’t recommend a single PowerEdge for your super critical applications, but they are pretty good for the current cost, as long as you don’t mind the fan noise.