I have spend a two evenings to build a case and switches for a small autotransformer. I thought I share. The autotransformer itself is 3 amp unit I bought as a new. All other parts, except the 2.5A automatic fuse, are old 2nd hand stuff I had in my junk boxes.
Contains dangerous voltages and practices.
I did start by cutting a nice piece of 2.5mm white polycarbonate sheet to serve as a front face of the box.
![](https://www.eevblog.com/forum/projects/building-a-casing-for-a-small-autotransformer/?action=dlattach;attach=338670;image)
One might wonder why, well this box have seen 'some' PSU projects along the years.
![](https://www.eevblog.com/forum/projects/building-a-casing-for-a-small-autotransformer/?action=dlattach;attach=338672;image)
The autotransformer itself is a IP00 unit so it does need a box. Nice feature is the spare carbon, doesn't cost anything for the manufacturer, but certainly is nice bonus for the user.
![](https://www.eevblog.com/forum/projects/building-a-casing-for-a-small-autotransformer/?action=dlattach;attach=338674;image)
JOKARI is a nice tool for cutting power cables. Once you have used something similar the sidecutter method makes you.
![Rant :rant:](https://www.eevblog.com/forum/Smileys/default/rant.gif)
![](https://www.eevblog.com/forum/projects/building-a-casing-for-a-small-autotransformer/?action=dlattach;attach=338676;image)
The wiring is still not as It will be, even the circuit will be a bit different. I firts though I put the phase first through classic fuse and then to switch and there to automatic fuse, but I forgot to drill the hole for the fuse holder. I did want the unit to be usable next day (today) to test the indication light for the unit as it were old 220V and as a neon bulb I did want to know if the shunt resistor is on the right size for the specific bulb as the current mains voltage is now 230. What I did test it day before quickly with 230 volts it did seem so bright that I did wonder if it were already on the high edge in 220V setup. For the fusing I think I switch the thermal fuse to output line and see if it works and leave the classic fuse for the input line. Meratester is on the background measuring a stray voltages as usual.
![Confused :-//](https://www.eevblog.com/forum/Smileys/default/confused0024.gif)
Starting to look something.
![Smiley :)](https://www.eevblog.com/forum/Smileys/default/smiley.gif)
![](https://www.eevblog.com/forum/projects/building-a-casing-for-a-small-autotransformer/?action=dlattach;attach=338678;image)
Next day.
I made a test setup for the glimmer neon light. This is the dangerous practise part.
![Azn ^-^](https://www.eevblog.com/forum/Smileys/default/azn.gif)
Autotransformer powered IP00 test setup, without even safety isolation transformer.
Here is the picture of the setup. AVO8 is first for a voltage indication and only next it serve as a voltage measurement device here. The Unigor 6e is a current meter.
![](https://www.eevblog.com/forum/projects/building-a-casing-for-a-small-autotransformer/?action=dlattach;attach=338680;image)
220 Volts from the autotransformer. The old style screw binding posts are so nice with this type of stuff (while dangerous) and the weight of the test equipment is several kilograms so it serves as a anchor.
![Roll Eyes ::)](https://www.eevblog.com/forum/Smileys/default/rolleyes.gif)
![](https://www.eevblog.com/forum/projects/building-a-casing-for-a-small-autotransformer/?action=dlattach;attach=338682;image)
The old glimmer neon is running at 975 uA, isn't that nice scale in this. I think I replace the old 12k shunt with 24k shunt for compensate the nominal voltage increase an drive it a bit more low current.
![](https://www.eevblog.com/forum/projects/building-a-casing-for-a-small-autotransformer/?action=dlattach;attach=338684;image)
More picures and progress becoming days. Thx.