Road Rage Regulator Orientation Revisited

[stevewire]

I don't think I understand Brian's description in the original thread, or possibley I have the wrong part.

http://www.madbeanpedals.com/forum/index.php?topic=5170.0



I ordered two: NCP7815TG from Mouser.
http://www.mouser.com/Search/ProductDetail.aspx?R=NCP7815TGvirtualkey58410000virtualkey863-NCP7815TG
I want 12 through 15 volts.

[RobA]

If you look at the traces on the bottom of the board, the hole to the outside and just below the 15V lead hole is connected to the 15V output. So, it's the output pin from the regulator. The center hole is connected straight to ground, so it's the ground (or common) on the regulator.


Edit: Looking at the spec sheet for the one you linked to, that aligns with the idea of having the regulator face up if you were to bend it over like usual. (But, you can't do that if you have the sag in and you don't really want to without insulating the board because that metal tab is ground.

[stevewire]

RobA,
Thank you very much.  I had wondered if Brian's description in the original post was bending the regulator, but I did not see anything about bending.  Correct me if I am wrong, I could bend it in either direction (and multiple degrees - space allowing) and a bit of electrical tape would suffice insulating the metal tab? 

I went to the data sheet link.  I see what you are saying about the pinout.  There is a code on the bottom of the label face that ends with the letter "G".  I had thought this meant that pin three was ground. 

[RobA]

I see what you mean about the G. As far as I know, they never mark the pinouts on these types of packages. That would make things too easy . That's probably a date/location/lot code.

I would guess that electrical tape would be OK for the job. I would put it on the board though since that plate on the regulator helps to dissipate heat. Not that there is a whole bunch of heat involved here because you are only dropping about 3 volts at less than 20mA. Actually, I hadn't thought about it before, but it would seem that it should be possible to use one of the TO-92 package regulators here at that current level. Maybe someone else could comment on this. Anyway, it certainly won't hurt to use the big regulator -- overkill is always good.

[RobA]

Oh yeah, forgot to answer this, as far as I know, you could bend them anyway you want. Typically they are bent with the metal tab down and screwed to a ground plane to get better heat dissipation. Sometimes though they are hooked to heat sinks with fins and kept off of ground if they are going to produce more heat. I don't think either thing is really needed for this use. The charge pump here can't really draw enough current to cause that much heat -- not even an LT1054 would.

[stevewire]

Thank you once again, RobA.  I had never used a regulator or seen one before this.

[RobA]

You're welcome. There's always something new in electronics. There are so many devices that do so many different things. It's amazing really.

Edit:
I mentioned this in another thread, but it's good here too. I learned all about voltage regulator pin outs just a bit ago when I had one in wired wrong. They kinda pop and blow pieces everywhere. I was sure I had it in the right way and put in another only to get another explosion and shrapnel flying. Then I looked at the spec sheet a bit more carefully and figured out I had it wired wrong. My breadboard still has some black dust stuck in it as a visual warning for me to be a bit more careful .