L7805CV 5V Voltage Regulator 1.5A

[StealthRT]

I seem to be having some problems with hooking up the L7805CV Regulator. When i provide it 12v @2A i seem to be getting an output value of 10.xxV???

What could i be doing incorrectly? Does it matter that the power supply is 2A and the Regulator is 1.5A?

Schematic: https://www.electro-tech-online.com/custompdfs/2012/08/A-179.pdf

(TOP VIEW)
--------|====== Output
|       |====== Ground
--------|====== Input

I have my photo below hooked up looking at it from the back.

**broken link removed**

What would i be doing incorrectly?

 

[StealthRT]

Crap.. had it hooked up wordsback... :/

 

[ronsimpson]

I think you have the input and output reversed.

 

[ronv]

Looks like you have input and output reversed.

 

[unclejed613]

dyslexic pin connections...... yes the data sheet pictures the device from the front.......

 

[ronsimpson]

Crap.. had it hooked up wordsback... :/

Every one of us have done that. The one that has not, lies.

 

[tvtech]

Crap.. had it hooked up wordsback... :/

LOL, at least you are honest. You figured out your mistake by yourself and corrected it. .

Regards,
tvtech

 

[WTP Pepper]

Not forgeting that most linear regulators have high gain amplifiers inside and need stabilizing by external caps mounted close to the device.
In the picture you posted, the device could be completely unstable and your DVM could be measuring anything.
Voltage regulators are rarely stand alone devices.

 

[tvtech]

Not forgeting that most linear regulators have high gain amplifiers inside and need stabilizing by external caps mounted close to the device.
In the picture you posted, the device could be completely unstable and your DVM could be measuring anything.
Voltage regulators are rarely stand alone devices.

Stealth had not even got to that stage yet when the regulator was actually working.......

So posts about showing how clever you are don't solve problems

I really enjoy posters like Stealth.

Regards,
tvtech

 

[atferrari]

That has a name

LOL, at least you are honest. You figured out your mistake by yourself and corrected it. .

Regards,
tvtech

Call it experience and be happy!

Sorry, but I have never connected a regulator backwards. (*)

Believe it!

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[tvtech]

Call it experience and be happy!

Sorry, but I have never connected a regulator backwards. (*)

Believe it!

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(*) Since the start of 2012.

It can happen my friend.

I deal a lot with the little LM317T. Also three legs. Also a regulator...

Put a 7805.....in my hand and I have to rethink.

Regards,
tvtech

 

[unclejed613]

79xx (negative) regulators are easier to hook up wrong because their pinout is different and harder to remember...... yes, we've all fried a few regulators in our time...as well as a few electrolytic caps....

 

[tvtech]

79xx (negative) regulators are easier to hook up wrong because their pinout is different and harder to remember...... yes, we've all fried a few regulators in our time...as well as a few electrolytic caps....

Hi Uncle Jed

I know you know a lot. The worst though is a Main Smoothing cap put in the the wrong way round...

I only did it once. Good lesson for me. A long time ago

I never made the same mistake again

Regards,
tvtech

 

[unclejed613]

i worked as an amp test tech for a manufacturer, and the amp had these 15000uf/75V caps in the power supply. one time we had a "newbie" working in assembly, and he was getting 50% of the caps backwards. the first one of these amps i got at my test station, failed the power up test on the variac, where i slowly turned up the variac and watched the ammeter. this amp pegged the ammeter at 10V. i checked all the usual stuff, and couldn't find a shorted rectifier, output transistors, wiring, etc... so after about an hour of checking stuff, i did the "show me where it hurts" test (power it up with no variac and see where the smoke comes from)..... both of the big caps went off spewing smoke like smoke grenades. after checking the day's production from the assembler, i found about half the caps in backwards, and the assembler didn't know they were polarized (or had been shown and forgot).

 

[tvtech]

Hi Uncle Jed

Funny stuff...only us old buggers will get it though.....heck I am only 49...though.
But a proper 49 though.

You know, and I am digresssing now: it is so totally cool for me to learn from you all. Seriously.

Sure, I can walk the walk and talk the talk....but the whole thing here is to pull as a team.

Every post you make teaches me something I did not know before. This is a great Forum. Love this place.

Best regards,
tvtech

 

[WTP Pepper]

Stealth had not even got to that stage yet when the regulator was actually working.......

So posts about showing how clever you are don't solve problems

I really enjoy posters like Stealth.

Regards,
tvtech

What is your problem? My post was nothing to do with how clever I am. I was just passing on experience. Instabiltiy on long pieces of wire happens.

 

[tvtech]

What is your problem? My post was nothing to do with how clever I am. I was just passing on experience. Instabiltiy on long pieces of wire happens.

Hi WTP

Sure, if the regulator was actually working...and there were instability issues, your post would have helped

Never mind, no problems

Cheers,
tvtech

 

[()blivion]

View attachment 66351

 

[WTP Pepper]

View attachment 66351

These devices are used by the millions every day. At which point do you think the datasheet is wrong?

 

[tvtech]

These devices are used by the millions every day. At which point do you think the datasheet is wrong?

Hi WTP..rather let it go.

The OP had the regulator in backwards....and posted here asking for help.
And then realized what he had done. And clarified and fixed his own mistake. And reported back here for us to see.

I like people like that

If he has instability issues after the Regulator was actually working...yes then we would all help..

So, it's not about Datasheets or anything else. Its about the correct advise for solving THAT particular problem.

Think about it,
tvtech