March break has found me a project! Here is a little background. My friend’s dad gave me an old Uninterruptable Power Supply (UPS) he had at home, but that the battery was no good. I have plenty of batteries, so this was a non-issue. The UPS was a godsend because that same day I had gone shopping for one, but not found one suitable for the server.

When I took this used UPS home, and hooked up all the batteries in my arsenal, I discovered that it was too weak to power the server for more than 2 seconds. Bummer. Even for power flickers that was not suitable, as there is a 5 second delay after the power returns before it switches back to mains power. What to do, what to do…

Oh, I know. Make my own!

Update: My testing proceedures blocked me from finding one critical fault with the design. As you will notice, I am using a resistor in order to short the capacitor from the AC-DC adapter, in order to more quickly de-energize the relays. Unfortunately, it still isn’t fast enough. My testing involved simply unplugging the adapter, and checking for any flickering in the devices. However, this testing does not remove mains power. Thus, the slight lag time for switch over does not affect the device, as it is has power on both relay positions. However, in a real situation, the power fails, both on input power and the adapter, and I’ve tested that my switch over time in this case is too great for most devices.

Fix to come…

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Thursday, March 4th, 2010 electronics, projects 8 Comments