(4) Variable AC Power Supply With a Twist:
Intro: (4) Variable AC Power Supply With a Twist:
One day I needed a 90 volt AC power source for a project I had in mind. I thought about it for a few days thinking of all kinds of things that I had no parts for. Then one day I was in Home Depot looking for PVC pipe for a plumbing job I needed to do in the house. As was my habit, I walked down the electrical isle and spotted the dimmer controls they had and thought maybe I could use a dimmer switch.
As it turns out, I have found that to get the variable voltage part out of it you need to plug in a window fan as a ballast to stabelize the dimmer circuitry. If you plug in some electronic thing and try to lower the voltage you will get wild voltage swings and damage the equipment. A running fan will stabilize the dimmer and you will get accurite voltage measurements.
Dims lights, controls fan speeds, and provides variable voltages. My computer runs cooler on 115v.
In Hawaii, the voltages are often as much as 128 volts so I plug the dimmer into a surge protector, a fan into the dimmer and turn it on low, measure the voltage to 115v, and plug in my computer.
The computer seems to like it because it runs cooler and so doed the computer power supply.
As it turns out, I have found that to get the variable voltage part out of it you need to plug in a window fan as a ballast to stabelize the dimmer circuitry. If you plug in some electronic thing and try to lower the voltage you will get wild voltage swings and damage the equipment. A running fan will stabilize the dimmer and you will get accurite voltage measurements.
Dims lights, controls fan speeds, and provides variable voltages. My computer runs cooler on 115v.
In Hawaii, the voltages are often as much as 128 volts so I plug the dimmer into a surge protector, a fan into the dimmer and turn it on low, measure the voltage to 115v, and plug in my computer.
The computer seems to like it because it runs cooler and so doed the computer power supply.
STEP 1: And Parts Is Parts:
See the photos below for the parts that were used.
Its pretty simple really.
Its pretty simple really.
STEP 2: Assembly:
The knockout can be hit with the claw of a hammer to bend it in and then grabbed with pliers and twisted around to break it off.
The restraining nut has got to be tight so the wires don't get twisted around inside. If they do, there will eventually be a short circuit.
The restraining nut has got to be tight so the wires don't get twisted around inside. If they do, there will eventually be a short circuit.
STEP 3: Electric Wireing:
Follow the photos closely.................
STEP 4: Dimmer & Outlet:
When the wireing is done tuck as much as you can in the box under the dimmer and the outlet so nothing is between the outlet and dimmer.
Test the outlet to see that it is wired properly by plugging it into the wall and plugging a serge protector into it. If the protected light comes on, its right. If not, re -wire it the right way. It has to be done right.
Test the outlet to see that it is wired properly by plugging it into the wall and plugging a serge protector into it. If the protected light comes on, its right. If not, re -wire it the right way. It has to be done right.
19 Comments
JoeTinkerer 7 years ago
Pretty neat, seems almost just like building a variac.
Dr.Bill 7 years ago
Yeah except the thing only clips the sine wave to lower the voltage. On induction motors it's death but if you need a temperature control for a soldering iron it works good.
Dr.Bill 8 years ago
This thing works best with incandescent lamps and motors that have Brushes...induction motors tend to just make noise and burn out.
redmarkonthewall 8 years ago
Myndbomb 9 years ago
I made this setup 4-5 years ago for a Dremel that was single speed. Since then I've been using it for a plastic welder to control how hot the tip gets and I've not had any issues. =)
TomShauley 10 years ago
Any suggestions?
Dr.Bill 10 years ago
granz 11 years ago
Dr.Bill 11 years ago
tylervitale 12 years ago
I'm trying to build a PSU with transformers in series, but they're gonna draw much more power than a light bulb.
Dr.Bill 11 years ago
buteman 11 years ago
buteman 11 years ago
This is important because if you try to connect something which is only meant for say 50 volts and not the full mains voltage it will be damaged by this.
Drillbert 12 years ago
bucklipe 12 years ago
You did a good job illustrating it.
However, the box above seems to be VERY unhappy about it...
(Look at the center yellow box in the first picture.)
EmptyE 12 years ago
error32 14 years ago
Dr.Bill 14 years ago
I have noticed the power supply runs cooler.
My point to all this was not so much for use on the computer as this type of supply creats a lot of RF noise.
W hat I did this project for was to supply old school equipment with low voltage. Restoring old AM Radios for instance. Sometimes the need arises to reform an old capacitor in a radio like this. The need for low voltage is there.
I work projects using old style neon bulbs that fire at 90v +/-. My supply needs to to be at 90v then. I really don't like to use voltage dividers.
Dr.Bill 14 years ago