Finally putting variac together

terryblulite

terryblulite

RIP 1954-2019
Spent some time today making a knob coupling and brass extension shaft,and welding holes shut in a box a neighbor gave me.Then boring and punchin' holes.I need to get another fuse holder,and some rubber feet. I have some heavy industrial receptacles and 20A light switches, so thought this would be the project to use a couple of 'em.Simpson meter I've had around forever,and the 7.5 A vari-ac courtesy of Endspec.You can barely see it,but I had to weld 2 lock collars together to raise the knob and pointer up to where the "scale" will be.I have good strain reliefs.So should only be a couple bucks to get it runnin'.So- Switch and fuse on the line in,fuse on output.

Is there any reason to switch the output?
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If anything I'd put a GFCI on the output to be extra safe, but I guess that's what the fuse is for.

Sometime it's good to have a manual switch, too, because sometimes gear goes to sleep rather than off completely when it's switched off.

Looks like a great project you've got going!
 
Good point on the modern stuff going into standby:yes: well ,now's the time to consider all this.The only thing that's for sure is the unit location and feet.I can still change the panel layout.
 
Looking good, since you are building is it possible to add a ammeter as well? This way you could see the current rise before anything trips or smokes.

I really need to learn how to weld.
 
:yes:sure like to have an ammeter- all I have layin' around is a 100ma model of a different style -haha-This could easily go from a 75 dollar project to 300 real quick!......:scratch2:...this box could get crowded...maybe if I leave room for an ammeter the same size and style...awright,I'll leave a spot for one!:D
 
One thing I might suggest is to get a "Kill a watt" meter ( http://www.p3international.com/products/special/P4400/P4400-CE.html ) and incorporate it into your front panel. I got mine from Harbor Freight, they are available many other places including the net. It is a digital volt, ammeter, watt, kilowatt/hr and power factor meter all in one. I got mine for about $25.00.

In order to use it in a Variac you will need to supply straight 120VAC to the measuring circuitry. Otherwise the meter will quit working as you reduce the voltage. A quick look at the circuit board will show how to do this (PM me if you need more specifics).

I still use my analog meters since I like the swinging needle (easier to see out of the corner of your eye when you are adjusting something) but the digital meter is much more accurate and trustworthy than the old analog meters.
 
The kill-a-watt at HF is 99 bucks! Oh well.I have a plan:yes:Burned a day or so(groceries,hose for the truck,laundry,sleep)
I burned up a few cheap rubber feet for the metal box trying to bore them out for bolts-the washers in them just spin and melt the feet.In the future,I'd go with real rubber feet with 1/4 20 studs or holes already big enough for bolts.Waste of time and money otherwise.I'm using some plastic/rubber feet I found in my junkpile(s) until I can get some in.
I made a 1/8" AL plate to cover 1/2 of the bottom of the box,mostly under the variac unit.All the holes are bored for feet and the unit.Volt meter on the top left,room for an ammeter top right,outlet/switch/fuse on the bottom right.
On the front right of the box - I'm going to put on two small angle iron "guards",and between them will be a Hubbell 20A toggle main power SW,fuse holder below that,the cord strain relief below that. A fl. indicator lamp will be above the main power SW. I have 2 metal spring loaded handles to mount to either side. well,guess I better get something done!:yes:
 
This is pretty much the layout.Made some progress today,added two vents and grills.One is low on the side,the other is high on the rear.I used pop-rivets to hold the screen(I cut up a closeout wastebasket from Staples:yes:...got plenty of steel vent cover material now!) I sprayed the inside of the box and switch plate silver,and used truck bed spray to coat and texture the outside.Then a coat of red on the outside.The spring loaded handles I left alone.A little touch-up during final assembly,and it'll be OK.
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Finally put this thing in his new home.No more cardboard boxes! I'll pull it one more time after I have all the wiring ready to hook up.I put in a piece of 1/8"AL because the bottom warped a bit because I used my gas torch to weld all the holes shut.If you use a TIG or wirefeed,that won't happen.Also,the box has corner seams that might contribute to a flimsy or uneven bottom.So the plate should even out the stresses of mounting it,There are only 3 mounting ears,and the base is cast-hopefully I'm not stressing the base too much. Still need to get some better quality screws.I'll make some labels for fuse ratings and such.Then make a scale for the pointer after I get it powered up.
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