Thursday, 16 February 2017

Power Supply - NLC - Build notes

Building a Nonlinearcircuits PSU.
This just supplies +/- 12V for Eurorack modulars.

Andrew's build notes are here:
http://www.sdiy.org/pinky/data/WAMOD3%20%20psu.pdf


The virgin PCBs

 Ok, lets twerk
Keeping Miley happy.

The PCB receives 12VAC from a plugpack/ wallwart
. The 1N4004 diodes split this into positive and negative waveforms.
 
The 4700uF capacitors then smooth out these waves
. The 7812 and 7912 regulators then convert the rectified & smoothed
signals to +12V DC and -12V DC and these are fed to the connectors to be distributed to your lovely modules.
I'm using 250v TDK film caps for the four small 100nf caps
Probably a bit overkill, but it's what i had in stock at the time.


Some pics of the 7812 & L7912 voltage regulators attached to various heatsinks.


 In the NLC build notes, Andrew stresses the importance of isolating the regulators from the heat sinks.

The smaller heatsinks came with grommets and mica insulators, so I think I'll use those.
He also recommended using heatsink paste.

Andrew F recommended I use these - http://www.taydaelectronics.com/capacitors/electrolytic-capacitors/4700uf-50v-105c-radial-electrolytic-capacitor-19x40mm.html

25V caps are okay but better to get 35V or 50V rating. just to keep the action well clear of the edge.

Always bigger is better with heatsinks, smaller ones cant soak off so much heat so will limit the current output of the regs. With a small one you will only get 3-400mA, a big one will get you double that (roughly...very)

The other thing to watch is the proximity of the heatsinks to the caps.
They do appear to be pretty close in the pics.
My sinks don't appear to get hot but they could cause problems if the temp exceeds the cap ratings.
These caps have a rating of 105 degrees celsius.

------------------
This PSU also has space for a 78L05 regulator.
Most of these are rated at 100mA

However, a standard LM7805 can be as high as 1A
A LM7805 might be a good substitution
If you are substituting remember:

1. the pinout is different so the 7805 goes in backwards

2. the 7805 can suck a lot more current than the 78L05 (10x more) and can take as much as the 7812, so keep it in mind and dont try to overwork it.


No need to change caps.

I'm using 1K resistors for the LEDs



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