Variable Voltage Control

O.K., So how can I measure the voltage at the end that gets the iron plugged in?. I have only an analog multimeter.

Voltage measure will be nonsense, you want to use the AC ammeter function. Beware, of course, the
wires you're connecting are live.
I've wired an outlet strip with (insulated banana plug) wires soldered to each side of the
power switch: with the switch ON, that outlet strip just powers sockets. With the switch OFF,
all current goes around the switch, through an AC ammeter plugged into those two wires...

That kind of rewired outlet strip is a convenient (safe) way to monitor AC current, but
there's also a nifty commercial gizmo, Kill-a-Watt, with suitable metering functions.
 
O.K. This is where I get lost. My meter has a section that is labled, ACV, with three settings, 10, 250, 500.
At the end of the wire where I would plug in the soldering iron I inserted the probes turned on the dimmer
and tried to see if it would show the volage increasing as I turned it more, but I got nothing, no readings at all the
needle never moved. Can someone explain how to do this and what I'm doing wrong.
 
Analog AC voltmeters are expecting a sinusoidal waveform. They actually measure peak voltage by converting the ac to dc with a rectifier and applying a scale factor to read out rms voltage. They are only accurate for the sinusoidal waveform.

AC dimmers use a triac which conducts partway through the cycle. As a result the output voltage is zero until the triac conducts and then it tracks the input voltage until the half cycle returns to zero when it turns off again. Triacs function on both positive and negative half cycles whereas scr's only conduct on the positive half of the cycle.

I haven't looked at digital voltmeter circuit but I would guess that they function in a similar fashion unless the meter is specifically rated as a true rms voltmeter.

For the uninitiated, rms means root mean s1quare and stems from the fact that power is the square of the voltage divided by the resistance. Since delivered power is usually of importance in electrical work, we would like to know what the power squared is. rms voltage is the square root of the voltage squared averaged over a period of time, usually one complete cycle. This may seem like some double talk but the rms voltage is actually different than the average voltage.

Bottom line, a voltmeter will not give an accurate picture of the power delivered to any device when using a dimmer unless the meter is a true 4rms reading meter. However, how important is it to know the actual voltage. All that is really necessary is to know that a particular reading givers good results when using the soldering iron.
 
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Voltage measure will be nonsense, you want to use the AC ammeter function.
For a resistive load. amperage is directly proportional to voltage at any given point in time. What you really want to measure is power.
 
O.K. This is where I get lost. My meter has a section that is labled, ACV, with three settings, 10, 250, 500.
At the end of the wire where I would plug in the soldering iron I inserted the probes turned on the dimmer
and tried to see if it would show the volage increasing as I turned it more, but I got nothing, no readings at all the
needle never moved. Can someone explain how to do this and what I'm doing wrong.
I expect that you need some loading to get a reading. The meter will not be a sufficient load. Connect some device like an incandescent light bulb and then measure.
 
All that is way above my head,but I think I just realized something.
Isn't the dimmer switch actually adding power to the outlet.
I have one in my dining room over head lights.
Sliding it upwards increases the brightness of the light . Therefore
it is not decreasing power but increasing it, ergo, this curcuit does not work for what I want.
Any ideas as how to do it, or is all this totaly incorrect?
 
Why not make it a fun project? Get a temperature controller with solid state relay and thermocouple. Mount it in a box and control temperature to with a couple of degrees. This project will get you to use CAD, Milling machine, lathe, and some hand tools. You will learn how the controller senses heat, self adjusts for accuracy, and controls using little blasts of power with the solid state relay.

I did the exact project for 3D printed parts needing precise control of the temperature when inserting threaded inserts into printed plastic parts using a soldering iron.








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Thats way too much work. I'm looking for simple easy DIY project.
 
Get a battery powered soldering iron and just keep taking the individual cells out until you get the right temperature.
 
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