5v 2a ldo regulator trouble. HELP

[Matt79jd]

I am having trouble with my new mod and posting threads but any how i have a problem. I just wired up a new 5v mod using a fairchild KA278RA05C

It tested good and everything worked great until i wired it to the board. (MadVapes PCB) Testing the leads to the atty I get no voltage. I am getting full voltage between pin 1 and 4. The Regulator slowly gets hotter and hotter so I just take the batteries out. The switch works fine according to a continuity test.

My Wiring

Pin 4: 470 ohm resistor, Switch
Pin 3: other side of resistor, negative battery, Ground for Atty, LED
Pin 2: Center of atty, LED
Pin 1: Switch, Positive Battery

Pin 4: ADJ
Pin 3: Grd
Pin 2: Vo
Pin 1: Vin

Pics to guide

http:
//i654.photobucket.
com/albums/uu270/matt79jd/
PCBWiring.jpg


Please I need some expertise to help me.

 

[Scubabatdan]

I am having trouble with my new mod and posting threads but any how i have a problem. I just wired up a new 5v mod using a fairchild KA278RA05C

It tested good and everything worked great until i wired it to the board. (MadVapes PCB) Testing the leads to the atty I get no voltage. I am getting full voltage between pin 1 and 4. The Regulator slowly gets hotter and hotter so I just take the batteries out. The switch works fine according to a continuity test.

My Wiring

Pin 4: 470 ohm resistor, Switch
Pin 3: other side of resistor, negative battery, Ground for Atty, LED
Pin 2: Center of atty, LED
Pin 1: Switch, Positive Battery

Pin 4: ADJ
Pin 3: Grd
Pin 2: Vo
Pin 1: Vin

Pics to guide

http:
//i654.photobucket.
com/albums/uu270/matt79jd/
PCBWiring.jpg


Please I need some expertise to help me.

Well everything looks right, ensure pin one on the LDO is actually not 180 degrees out. Double check the soldering for bleed over and shorting between pads, Double check the switch to ensure it is working not open. Test for continuity on all wires, and output voltage between 1 & 3 and 2 & 3. It sounds like a short or faulty LDO.

Attached is a pic on pin one for your LDO from the KA278RA05C datasheet.
Hope this helps
Dan

 

[cpcp68]

I am having trouble with my new mod and posting threads but any how i have a problem. I just wired up a new 5v mod using a fairchild KA278RA05C

It tested good and everything worked great until i wired it to the board. (MadVapes PCB) Testing the leads to the atty I get no voltage. I am getting full voltage between pin 1 and 4. The Regulator slowly gets hotter and hotter so I just take the batteries out. The switch works fine according to a continuity test.

My Wiring

Pin 4: 470 ohm resistor, Switch
Pin 3: other side of resistor, negative battery, Ground for Atty, LED
Pin 2: Center of atty, LED
Pin 1: Switch, Positive Battery

Pin 4: ADJ
Pin 3: Grd
Pin 2: Vo
Pin 1: Vin

Pics to guide

http:
//i654.photobucket.
com/albums/uu270/matt79jd/
PCBWiring.jpg


Please I need some expertise to help me.

If you use pin 4 with a switch in the model you mentioned (RA05C), it will not work. pin 4 is the adjust pin (A is for adjustable). If you leave it floating you will have a fixed 5V output, for other values you need to connect two resistors as indicated on the datasheet.
If your intent was to use pin 4 as enable/disable (with a switch), you need the other part, KA278R05C (without the 'A'). If you are using this type already, well, I do not know what is going on, sorry. Maybe a picture of the reverse side of your board will help.

Good luck.

 

[Scubabatdan]

If you use pin 4 with a switch in the model you mentioned (RA05C), it will not work. pin 4 is the adjust pin (A is for adjustable). If you leave it floating you will have a fixed 5V output, for other values you need to connect two resistors as indicated on the datasheet.
If your intent was to use pin 4 as enable/disable (with a switch), you need the other part, KA278R05C (without the 'A'). If you are using this type already, well, I do not know what is going on, sorry. Maybe a picture of the reverse side of your board will help.

Good luck.

It is interesting that the pics from madvapes does show pin 1 and 4 connected with a switch, and he did say that it worked before soldering it to the board. That is why I am leaning toward a short somewhere.
Of course in their (madvapes) diagram they show a 4 pin LDO but tell you to use a 5 pin LDO.
MadVapes e-Cig 'How To' Tutorials • View topic - 5 Volt 3xAAA Box Mod by Ez Duzit

And he has mimiced what madvapes has posted:
http://i654.photobucket.com/albums/uu270/matt79jd/PCBWiring.jpg
http://i654.photobucket.com/albums/uu270/matt79jd/IMG_0268.jpg

And he did say it worked, so there must be a cross of solder or wires to produce the problem IMHO.

ADDED##############

The only thing I see different is that on your pic, the switch wire on pin 4 is after the resistor, an on the madvapes tutorial it is colocated next to pin 4 before the resistor.
I would move that wire before the resistor next to pin 4 and try again (should not matter) but that is the only thing I see different with out looking at the bottom..

Dan

 

[cpcp68]

Dan,

I agree, the schematic is correct. What I am pointing out is that the component Matt used may not be.

Lorenzo.

 

[5cardstud]

I have to agree with both of you. If he has the right reg. then it has to be a short or bad reg. The first one I made the trouble I had was the tutorial calls for a different polarity than the pics. I was trying to follow both until I finally caught it and, Boy, did I have problems. Finally ended up eliminating post 4. Was on different box mod.

 

[Scubabatdan]

If you use pin 4 with a switch in the model you mentioned (RA05C), it will not work. pin 4 is the adjust pin (A is for adjustable). If you leave it floating you will have a fixed 5V output, for other values you need to connect two resistors as indicated on the datasheet.
If your intent was to use pin 4 as enable/disable (with a switch), you need the other part, KA278R05C (without the 'A'). If you are using this type already, well, I do not know what is going on, sorry. Maybe a picture of the reverse side of your board will help.

Good luck.

I just saw what your talking about the "A", yes if he desoldered the POS wire from the battery on pin 1 and desoldered the switch wire from pin 4 and ran the POS wire to the switch where the wire was running to pin 4 then it should work. So when he hits the switch voltage energizes the LDO and the regulated 5vdc would go out pin 2 VO. And he will probably need to remove the resistor as it is fixed for 5vdc without any "External" resistors. Of course the switch probably wont last very long with that amount of voltage. Better to get the KA278R05C instead as you suggested.

Sorry for the confusion,
Dan

ADDED###########

KA278RA05C
• Nominal 5V output without adjusting
• Output adjustable between 1.25V and 32V
• 2A output low dropout voltage regulator
• TO-220 full-mold package (4pin)
• Overcurrent protection, thermal shutdown
• Overvoltage protection, short circuit protection

 

[cpcp68]

Dan, you are right. It is entirely possible that the switch is not rated for this much power.

 

[WillyB]

Well to double check the actual part number on the chip itself, as cpcp68 mentioned, seems like a good idea.

But assuming MadVapes diagram to be correct things should work as wired per the OP's pics, which do in fact match up with the guide also.

And he did say:

It tested good and everything worked great until i wired it to the board...

Those thick clumsy wires can be a pain to work with, and we didn't see the back soldered side.

So after soldering/assembling we now get:

The Regulator slowly gets hotter and hotter so I just take the batteries out...

Scubabatdan's original assessment of "sounds like a short or faulty LDO" sounds correct to me.

FWIW it also seems like a lot of work for an under rated LDO. There are better choices.

 

[Matt79jd]

thank you for all your replies. I did in fact remove the resistor and eliminated pin 4. It was a no go but now I believe the switch will not handle the power. The switch is rated at 12v 50ma. The regulator did not get hot and was alright just no voltage from pins 2 & 3. The regulator was bought some where else and I didn't realize it was adjustable I thought it was a control. But anyways I am going to run some test and try different things. I will keep you posted.

 

[Matt79jd]

What type of wire do you guys recommend?

 

[Matt79jd]

If you use pin 4 with a switch in the model you mentioned (RA05C), it will not work. pin 4 is the adjust pin (A is for adjustable). If you leave it floating you will have a fixed 5V output, for other values you need to connect two resistors as indicated on the datasheet.
If your intent was to use pin 4 as enable/disable (with a switch), you need the other part, KA278R05C (without the 'A'). If you are using this type already, well, I do not know what is going on, sorry. Maybe a picture of the reverse side of your board will help.

Good luck.

Thank you I realized that after I put up the post and reread the data sheet. I eliminated pin 4 and re soldered the pins because of a bad connection and what do you know I got it to work. Thank you again.

 

[cpcp68]

you are very welcome

 

[cpcp68]

What type of wire do you guys recommend?

I think anything below (meaning larger than) 26AWG will work just fine.

Here is a nice table:

http://www.powerstream.com/Wire_Size.htm

 

[breaktru]

Regulator Question.
Okay,, here I go.....
I read a LITTLE, notice I said a little, on Linear regulators. They mention that depending on the load, they can add to battery drain. The better choice would be a switched regulator where current is over say 50ma. What I noticed is that switched regulators take up more room and cost more.
So with that being said. Why would a 5v mod be better than a 6v mod using a HV attys. Can't you find the right ohmage of atties for a 6v mod? And by not using a regulator on a 6v to bring it down to 5v the batteries should last a little longer.