5v Voltage Regulators

depends on the manufacturer, so what is printed on it?

Here is an example of a 7805 voltage regulator

http://electronics.howstuffworks.com/digital-electronics4.htm

Thanks, that is exactly what I was looking for. I got my reg at good ole Radio Shack and while trying to figure out how to install it, I broke off the center terminal...go figure.

Hello again, kbrtom

Often it is possible to carefully scratch away enough of the encapsulating plastic around a broken semiconductor package to get a soldered joint onto a broken terminal.

In the situation of your low voltage regulator, the centre connection does not carry appreciable current.

Have a try at repairing the connection, with a thin flexible wire soldered directly to the broken part where is comes out of the plastic package.

If you succeed, you have learned a new skill, saved a trip to Radio Shack, saved a dollar also.

Kind Regards....

Sounds like a challenge. I will give it a shot. Thanks for all your help.

Hello kbrtom

Advise if you succeed, or otherwise, with .

Kind Regards....

I will let you know. Thanks for all your help.

So why then do you not give me a good answer vote?

Sorry, my friend. I just kinda got excited to finally get some answers. I tried this same question with a couple of other forums and they just made smart ass remarks. But, I just gave you the vote. Thanks again for your help !!!!!!!!!!!!

If its a standard LM7805, you'll find that the center leg is also the Heatsink mounting tab.

The best place I go to to find out how devices should be connected is the manufacturers web site

National Semi Cond.. www.nsc.com

LM7805 = Linear Monolithic +ve 5.0 voltage regulator (NSC)

LM7905 is the -5.0V equivalent (78 = +ve, 79 = -ve) then the following digits are the voltage

LM317 is your adjustable reg, where the centre pin (TO-220) is your "ADJ" input (calc your output with 1.2 V from ADJ-OUT, then lift your ADJ pin to suit (zeners help here))

Then go have a look at the "Linear" section (havn't been there for a while, have the books at home for the Linear components, and a few others)

Thank you. I will check it out.

"LM317 is your adjustable reg, where the centre pin (TO-220) is your "ADJ" input (calc your output with 1.2 V from ADJ-OUT, then lift your ADJ pin to suit (zeners help here))"

I have to correct you here - pinout on the lm317 is A,O,I - Adj, Out, In The Out is actually connected to the tab, as the chip has no direct ground connection in typical configurations.

I use the LM317 as current regulators for LEDs like this:

pin 1 = output to LED(1 or several in series) anode

a 10 ohm 1/2 watt resistor from pin 1 to pin 2

pin 3 = input V+ anywhere from 4 to 35 volts

the beauty of this is the voltage doesn't matter as long as it's a little more than required by the number of LEDs you have in series and the number of LEDs you use doesn't matter as long as you don't exceed your supply voltage. I typically use 24 volt transformers with a full wave bridge and a disc cap, usually around .047 or .1uf and a decent sized electrolytic, about 1,000uf or whatever's handy in the junk pile soldered right to the diodes (the dc output part, obviously) It's very forgivable - short circuit and thermal runaway protection built into the 317 makes it worry-free.

Disc caps, man I havn't heard that term in many years, they still sell them?

thought everyone had upgraded to the mono cap by now

Yeh, guess I had got a little ahead of myself during lunch time ...

the LM317 can be found in many packages, I usually used the TO-3 style (long ago) but lately seen them on the surface mount side.

On 7805s and many other 3-terminal regulators, the center terminal is connected to the heat sink tab, so just connect a wire to a screw in the hole in the heat sink. (Not true on the 78L05)

Guessing cause the 78L05 (and 79L05) are the TO-92 style packages with no heatsink ?

if you look at the front of it, the leads are In, Ground, Out. The middle pin (gnd) and the tab/heat sink are connected internally - you're good.

Center terminal broken? use the metal tab.

IF the regulator is in a plastic pack with a big metal tab on it (TO220 package) you might find that the metal tab is the same as the lead which you broke off (center lead). You might be able to check this with an ohm meter if there is any of the center lead left.

Bill

Hello kbrtom

You really need to advise the Maker's markings on the regulator.

You may have a Negative Voltage regulator = 7905 which is installed in the Negative line, unlike the 7805 which is a positive regulator.

If you connect a regulator improperly, it is very sudden and also means you then must buy a new regulator, somewhat sadder and wiser.

Kind Regards....

Ok, thanks. The only markings on the reg are "7805A"

Lie the reg down, heatsink on the table, pins towards you

L-R

Input - Common - Output

As mentioned before the heat sink tends (although is not always) to be linked to the Common pin

Either way, you will often find more components like thse that you can find datasheets on the web - Pinouts are common for most of these generalist parts (this is one thing analog electronics has over more powerful micros - I wish they could just pick a standard pinout on a micro!

yeah, standardizing would be a big help - especially for people like me that are trying to learn this stuff. Some of the concepts of electronics are confusing enough without being item specific. Thanks for the input though

The above is not true (unfortunately) for the -ve series of regs ;o(

It's quite possible that you will fry your regulator if you get it wrong.

Two options; Purchase three and try each option or get a data sheet and get it right first time. You've given no information that'd enable anyone here to help you but you ought to be able to track down a data sheet via google fairly easily.

Dude, never, never, never, never buy parts from Radio shack. Period, no debate allowed. Back in the day when ships were wood, men were iron etc. I used to teach electronics at a small community college. We found that when you buy parts from Radio rip off, that the leads could be anything. One bag of transistors all marked 2N3904 could have transistors with leads that were ebc others that were ecb others that were ceb, you name it the leads could be in that order. This was all in one bag. Buy your parts on line from a reputable source such as Newark, or Allied or even Digi-key. Better yet find a reliable local source. We were lucky to have Shields Electronics right there in town (Knoxville Tn) They had every IC known to man and most other parts available right over the counter all for reasonable prices. If you asked, they even had data sheets free for the asking.

I had a friend of mine tell me the same thing. He also suggested Digi-key so that's who I've been using. Thanks

I guess not quite every IC... but I guess they had a quite a range of the common stocks.

I want to thank everybody that responded to my question. I learned a lot just from your statements.

Hello kbrtom

Did you manage to repair the damaged regulator?

Kind Regards....

yes I did. I took a high speed power carver with a tiny 1/16 dia grinder bit to carefully grind back the case to expose a small amount of the broken tab. I then soldered a single strand wire (about 3 inches long ) to the terminal, then clipped it to about the same size as the other terminals. I have not tested it yet, but it looks good.

You could have just attach a wire to the heatsink, if you are not sure just use a multi meter set in Ohm setting (or diode setting with sound) to check if what is left of the middle terminal is connected to the heatsink

If your after any grider bits, the next time your at the dentist, ask for some they are chucking

works great on PCB's