Continuation of "TOKO Inductors Needed for EM Theremin"

Posted: 2/11/2008 5:48:53 PM

Joined: 9/25/2007

oops..double post
Posted: 2/22/2008 3:36:51 PM

From: Escondido, CA

Joined: 2/6/2008

Regarding 3-terminal regulators ...

For our purposes:
LM320T-12 = LM7912 = UA7912 = a negative 12V regulator.

LM340T-12 - LM7812 = UA7812 = a positive 12V regulator.

These are all interchangeable numbers. National Semiconductor made both a "78xx" series and a "340" series. I am not sure of the differences, but you won't see any difference in your regulator circuits.

Also, the "12" in the numbering scheme is the output voltage. So a LM320T-5 or a UA7905 are negative 5 volt regulators.

You should also check out the 3-terminal adjustable regulators ... LM317T is a positive one that can be programmed via a resistor value to a wide range of values. LM337T is the negative one.

It's hard to find any LM7808s anymore, but you can use a LM317T and 2 resistors to get 8V output. I built a +/-9V power supply using adjustable regulators.

RoHS is causing a lot of grief for availability and part numbering. The good news is that you can still use lead-bearing solder to solder a RoHS-compliant part to a board that is not prepared for lead-free soldering. This is true for just about everything except parts in BGA packages. If any one is capable of soldering these by hand, I lay down my soldering iron to them! Even machines have a tough time correctly soldering BGA parts!

Posted: 2/22/2008 3:51:02 PM

Joined: 9/25/2007

Thanks for the info on regulators...I ended up using and MC78L12 and MC79L12 for the positive and negatives. They worked great for me.

In the schematic, there is a power supply circuit that gives us a +/-12VDC, but why wouldn't it be better to just use a 12VDC adapter and completely skip the power supply circuit? Just wondering...

I've now solved all of my Theremin problems, and it works great...thanks everyone for all the help.

I got one of those atlas mic stand mounting flanges, but its base covers a very small surface area- it doesn't seem like the theremin would be very safe mounted that way...? Are there any thoughts on this?


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