Power supply + and -

[colum]

I want to make a Power supply using A 7812 + Volt and a 7912 - Volt for a dual supply but several of my books show different wiring for the 7912 -V so if someone would just tell me the simple wiring for the Transformer Center Tap (ground) and the -V in and the -V out , there are 3 legs left to right with #1 3 2 facing the front on both...Thanks...Jeff

 

[davenn]

I want to make a Power supply using A 7812 + Volt and a 7912 - Volt for a dual supply but several of my books show different wiring for the 7912 -V so if someone would just tell me the simple wiring for the Transformer Center Tap (ground) and the -V in and the -V out , there are 3 legs left to right with #1 3 2 facing the front on both...Thanks...Jeff

The pin connections of the 7912 are indeed different to the 7812

use the datasheet for accurate info

here's a + and - 12V supply from my collection .....
use appropriate transformer for the mains voltage in your country



Dave

 

[colum]

Thanks Dave for that excellent diagram...Live long and prosper" -Spock
Jeff

 

[davenn]

Thanks Dave for that excellent diagram...Live long and prosper" -Spock
Jeff

no probs

add the usual mains power switch and also a fuse ~ 1A in the hot (P) lead of the mains input

 

[colum]

Hi Dave, I checked the diagram again and it seems they mislabled Capacitors 4 and 5 instead of 3 and 4 so I wonder if you know anyone that actually built this circuit...I have found a circuit and built it and it was photocopied but the pin numbers were reversed and this was a well known publication or I think thats what happened
anyway if I blow it I will not blame you I will just go on to the next Windmill...Thanks...Jeff

 

[davenn]

Hi Dave, I checked the diagram again and it seems they mislabled Capacitors 4 and 5 instead of 3 and 4

probably was a typo on my part that I didn't pick up ... I will have to do an edit

C1, C2 are the 1000uF the labelled C4 and C5 are the 0.1uF, they should be C5 and C6
I may have been leaving room to add C3 and C4 on the input to the regulators, they would also be 0.1 uF

am editing the image as we speak, will post it soon

 

[davenn]

here we go ......




just a note ... C3,4,5,6 should be mounted as close as possible ( practical) to the pins of the reg chips

 

[colum]

Thanks again davenn, just one last thing is your ICs Pin layout 1-3-2 facing the front and i do appreciate all of the trouble you are going through ....colum (jeff)

 

[colum]

All my books show the pins as #1 #3 #2 which is incorrect your diagram is correct and thanks for your efforts
Be well....colum...and thanks

 

[Herschel Peeler]

I want to make a Power supply using A 7812 + Volt and a 7912 - Volt for a dual supply but several of my books show different wiring for the 7912 -V so if someone would just tell me the simple wiring for the Transformer Center Tap (ground) and the -V in and the -V out , there are 3 legs left to right with #1 3 2 facing the front on both...Thanks...Jeff

Pinout can vary with the case style, too.

 

[Colin Mitchell]

Don't forget the ripple will be 10v for 1 amp and the margin you have is less than 7v.

 

[colum]

Thanks Colin for that information 10 Volt is alot. I hope the capacitors will smooth things over but luckily this is not going to power any ICs just an old Synchronous motor and antique tuned reed meter...colum (jeff)