I usually like to build my projects before I blog about them. This is probably due to the number of times the initial plans do not lead me down the envisioned path. The simplicity of this build along with a good pile of solid resources and the fact that I must wait for my panel meters to arrive has made me decide to blog a preview.


In my shop almost never a week goes by with out the need of an AC voltage source. I use the AC source to test motors, lights, power supplies, and circuit boards as well as a substitute for transformers. Since I have built several DC bench supplies and blogged about them over the recent years I decided that it was about time to build an AC power supply suited to my needs. I am currently using a Variac that is plugged into an isolation transformer for my applications but it doesn't monitor the voltage or the current so there is always a lot of patch wires and a couple meters to clutter the bench.


Here is my wish list for the new bench AC power supply:


0 to 160 volts no load output

2 to 3 Amps capable

Isolated from the mains

Binding post and AC receptacle Output

High Voltage warning light

Meters for indication of Output Volts and Current


Initially I found the following items in my parts grave yard:


This will be the isolation transformer. I can put 115 volts on the primary and it will have 130 volts on the secondary. This will drive the small Variac pictured below.



The case will be from an old Dental Cavitron Scaler. I have used this same style case before to build a Bench Power Supply and a DC Electronic Load.



The Plexiglas blank control panel was cut a couple years ago in anticipation of an application for this case. The case as seen in this picture it still needs a cleaning and a coat of paint.



The case has been painted and I have the tentative control panel layout on the sheet of paper next to the case.



The chassis has had some modifications. The metal that the variac is mounted to was originally part of the chassis deck but it has been cut and folded up to provide additional support for the relatively heavy variac. The cut out on the right side of the chassis came with the original piece of equipment. Anomalies like this often dictate where components and controls need to be placed. In this case it will be the recess needed to allow the mounting of an AC line Output jack on the front panel.


I have also produced a tentative Schematic for the power supply. I say tentative as I do not yet have the digital AC panel meters and so I am guessing at their requirements. Nothing ever runs true to plans so I will very likely have to take back a few of the things I told you here when I blog about the completion of the build.  Here is the tentative schematic.



One advantage to giving a preview of what I am building is that I can welcome any advice that anyone is willing to send my way. In the past ideas and advice from my many friends here on element 14 have resulted in renovations and improvements in subsequent builds.


Sorry about the title but sometimes it helps to get people in the door when I leave them asking what the heck is he talking about now.


Thanks John