Monday, April 26, 2010

Faraday Cage - Studio Control Room - EMP Fallout Shelter

My most recent project that I am working on is my studio control room.

My long term plan is to use this small room as both the sound-isolated audio recording control room, and my base of operations for my HAM radio equipment.

The room is about 5' x 40" x 6' 3" tall. The amps and computers will be located in the utility room in the basement, isolated both from the control room and the studio. (So as to avoid fan noise and unwanted heat.) The lines will be run into the control room for the speakers, monitor, and USB for the keyboard, mouse, and other devices.

One of the things I'd like to do with this room is to make it a Faraday cage. I'd like to completely shield it electronically. I am looking for inexpensive metal for the cage, but for now it seems that the materials are too expensive for me to buy at the moment.

I'd love copper sheets on the walls, ceiling, and floor, but I think I'll have to settle for aluminum.

If you know of anywhere I can get inexpensive aluminum rolls... Please tell me. :)

My wall stud structure is built, and I am about to put the wooden outer walls up in the near future. I'll try to post updates as I go.

Thursday, February 18, 2010

Manual Battery Bank Selector with Bank to Bank Trickle Charge

The following circuit is pretty simple. I just finished building it, and it seems to work great.
There is basically a DPDT toggle switch that selects the power source from Main to Reserve battery. Center position is off. The secondary toggle switch enables bank to bank trickle charging.
The max current is 6A for charging, and due to the diodes, the secondary bank should never reach the full charge level of the source bank. (Example... source bank = 13.3V, destination bank = 12.4V)
Assuming the source bank is large, and stays at 13.3 despite the outgoing current... The destination will likely stop charging when the voltage reaches 12.95 Volts. (I believe my diodes to have a .35v drop. I need to actually verify the "lab" voltage in the real world.)

The max voltage difference between 2 "good" battery banks that I can see would be 12.0v vs 14.1v. (I've never had my battery above 13.3Volts...)
This is 2.1V, but the voltage difference would decrease very quickly as current begins to flow. The current is limited by the battery internal resistance, and the resistance of the power lines as well. Obviously this leads to power loss during the transfer, but it is small in the grand scheme of things.

Important note - Make sure both battery sources are fused near the battery! Shorts can cause fires or explosions. These lead to acid burns, loss of property, and suffering.

What would you use this for?

I am using it to put a small 12v battery bank in my office to run laptops, AA battery chargers, cell phone chargers, radio equipment... ETC.

This allows me to use the power line coming from my solar power setup, or to use the local bank.
The local bank will be connected to a trickle charger, and can be maintained at full. If the solar bank gets low, I can boost it from my local bank. Likewise, in the Summer... If my solar bank is full, I can leave the float charger off, and charge the local bank via the solar power bank.

See the schematic above. Note that SWA is 2 sides to the same switch.