[sdiy] voltage regulator insulation

[Gordon JC Pearce]

On 15/07/12 19:02, ToAd wrote:
> Hello Guys,
>
> I'm currently building a +/-15V, 1A PSU for my  dual Mega Percussive
> Synth and some other drum voices.
> I use an LM317 and LM337. I want to use the metal case as heatsink.
> Now I read somewhere that you need to put an insulation plate between
> the metal case and the LM's.
> Is this really needed? What about the bolt that I'll use to hold the LM's?
> And where do I get this insulation plate? What kind of material is it?

For the positive rail, most LM78xx regulators have the centre tab 
connected to ground.  Unfortunately, the corresponding 79xx regulators 
have pin 1 as ground and the centre tab as the input.

So, you need the insulating washer on the negative one, at least.  This 
is usually a small rectangular rubber or mica sheet with a hole punched 
in one end.  You can either use nylon bolts, or you get a small 
insulating "top hat"-shaped bush that fits over the bolt and goes 
through the hole in the regulator tab.

-- 
Gordonjcp MM0YEQ