[Boatanchors] OT : TVS DIODES

[W2HX]

I ask because you cannot use a 7812 regulator on a 12V (or 13.8V source).  According to the spec sheet, the 7812 requires 14.5V to maintain line regulation. Basically the 7812 was not meant for use in an application like yours.  It was meant to regulate an input of 15 to 35V down to 12.

 
73 Eugene W2HX
 

-----Original Message-----
From: boatanchors-bounces at mailman.qth.net [mailto:boatanchors-bounces at mailman.qth.net] On Behalf Of W2HX
Sent: Monday, September 10, 2012 6:24 PM
To: boatanchors at mailman.qth.net; kf4nsradio at verizon.net
Subject: Re: [Boatanchors] OT : TVS DIODES

Is the application to eliminate a small battery on the radio for use with an ac mains source or a dc 12v of the vehicle?

73 Eugene W2HX

-----Original Message-----
From: Dick KF4NS [kf4nsradio at verizon.net]
Received: Monday, 10 Sep 2012, 6:11pm
To: boatanchors at mailman.qth.net [boatanchors at mailman.qth.net]
Subject: [Boatanchors] OT : TVS DIODES

I know this is a bit off topic but with all the knowledgeable guys here when it comes to some of  the new stuff, I hope someone can help.

I have put together a battery eliminator for use of my HT in the car, built into a gutted battery pack. I have all the components selected including ferrite beads for the + - leads from the cigar lighter which is fused at 2A, fed to a 7812 regulator having in and out capacitors as recommended in the applications page from the spec sheet.

It has come to my attention that I could protect the input from EMI RFI and surge by adding a TVS diode in the power leads. After studying the wealth of information available on the INET, I am so confused about how to choose the appropriate diode. The filters that Mouser lists for selection of a diode have left me totally in doubt. I am referring  to the INFINEON brand of  diodes.

Anyone with any experience and advice to share would be greatly appreciated.

73, Dick KF4NS
St Petersburg, FL 33714 USA
Keep The Glow!

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