# Rotary Encoder Question

#### nmateik

Joined Dec 10, 2019
20
I'm trying to figure out what components and the logic I need to understand in order for a rotary encoder to be able to physically control the power output of a capacitor. I know there is a micro controller or processor in the chain of command that the rotary encoder would run through. I imagine that there is some sort of harness that is attached to the PCB which would connect itself to some device that would control the power output of the capacitor. I imagine that its a pretty simple concept, but I haven't found the answer online.

Regards

#### Papabravo

Joined Feb 24, 2006
15,019
I'm trying to figure out what components and the logic I need to understand in order for a rotary encoder to be able to physically control the power output of a capacitor. I know there is a micro controller or processor in the chain of command that the rotary encoder would run through. I imagine that there is some sort of harness that is attached to the PCB which would connect itself to some device that would control the power output of the capacitor. I imagine that its a pretty simple concept, but I haven't found the answer online.

Regards
I've never heard of anybody controlling the power output of a capacitor. This is a totally new concept. Could you possibly elaborate on this point? On the other hand the rotary encoder is pretty simple by comparison.

#### KeepItSimpleStupid

Joined Mar 4, 2014
4,466
I've never hear of anybody controlling the power output of a capacitor. This is a totally new concept. Could you possibly elaborate on this point? On the other hand the rotary encoder is pretty simple by comparison.
The only application, I can think of is:

Are you talking about a Capacitive Discharge Spot Welder? Used one at work. Actually had tubes in it.

Way out on a limb: CDI https://en.wikipedia.org/wiki/Capacitor_discharge_ignition

#### drc_567

Joined Dec 29, 2008
1,060
In the usual sense, capacitors do not supply or consume real power, as in the unit of watts. Capacitors are designated in terms of VARs, volt-amps reactive. On the real-imaginary rectangular coordinate system, the capacitive VARS would be plotted on the imaginary axis, at right angles to the real watts axis, and opposite in sign to inductive VARS. Controlling the magnitude would usually require adjusting the magnitude of the capacitance, similar to adjusting a potentiometer in order to adjust a real axis resistor.

#### Papabravo

Joined Feb 24, 2006
15,019
In the usual sense, capacitors do not supply or consume real power, as in the unit of watts. Capacitors are designated in terms of VARs, volt-amps reactive. On the real-imaginary rectangular coordinate system, the capacitive VARS would be plotted on the imaginary axis, at right angles to the real watts axis, and opposite in sign to inductive VARS. Controlling the magnitude would usually require adjusting the magnitude of the capacitance, similar to adjusting a potentiometer in order to adjust a real axis resistor.
Only similar concept I can think of is trimmer capacitors that adjust plate separation to adjust capacitance, or air-gap capacitors that adjust by rotating the plates. Trimmers and air-gap capacitors are not used in power applications AFAIK. What is usually plotted in the complex plane has nothing to do with power it is either impedance or admittance. If it is admittance the sign is reversed, so capacitors have positive admittance and inductors have negative admittance. I suppose you could plot watts on the real axis but to get VARs do you just multiply a real voltage and a real current by j (the imaginary unit) to get reactive power. So how does one interpret such a plot? Does the vector sum of three values (for an R, an L, and a C) produce anything meaningful?

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#### drc_567

Joined Dec 29, 2008
1,060
... @Papabravo
You are surely correct at commercial power levels. Capacitor var adjustment typically would involve addition or subtraction of parallel capacitors.
... At the circuit board level, trimming may or may not be practical.
... If the application is for minimal power levels, determine an increment of capacitance that gives a significant change, and devise some method of putting them in the circuit, in parallel, one at a time.

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#### Papabravo

Joined Feb 24, 2006
15,019
Only similar concept I can think of is trimmer capacitors that adjust plate separation to adjust capacitance, or air-gap capacitors that adjust by rotating the plates. Trimmers and air-gap capacitors are not used in power applications AFAIK. What is usually plotted in the complex plane has nothing to do with power it is either impedance or admittance. If it is admittance the sign is reversed, so capacitors have positive admittance and inductors have negative admittance. I suppose you could plot watts on the real axis but to get VARs do you just multiply a real voltage and a real current by j (the imaginary unit) to get reactive power. So how does one interpret such a plot? Does the vector sum of three values (for an R, an L, and a C) produce anything meaningful?
No that's not right. To do it correctly you express the voltage and current as complex exponentials and then you multiply them together to get a time varying power function with the proper magnitude and phase.
$P_0\;=\;V_0 e^{(j\omega t\;+\;\phi)}\cdot I_0 e^{(j\omega t\;+\;\psi)}\;=\;V_0 I_0 e^{(j2\omega t\;+\;\phi\;+\;\psi)}\;=\;V_0I_0cos(2\omega t+\phi+\psi)\;+\; jsin(2\omega t+\phi+\psi)$

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#### SamR

Joined Mar 19, 2019
3,049
Quite a bit of confusion about what you are trying to control but rotary encoders are typically used to input a signal to a uC. Depending on which way it is turned one switch makes before the other to send "up/down" to the controller.

#### Papabravo

Joined Feb 24, 2006
15,019
Quite a bit of confusion about what you are trying to control but rotary encoders are typically used to input a signal to a uC. Depending on which way it is turned one switch makes before the other to send "up/down" to the controller.
Right -- that is the simple part of the question. The hard part of the question is "...which would connect itself to some device that would control the power output of the capacitor." I'm really struggling to figure out what the TS is talking about here.

#### SamR

Joined Mar 19, 2019
3,049
control the power output of the capacitor.
I wouldn't even begin to get into that foolishness...

Joined Jul 18, 2013
22,308
Rotary encoder can take a few forms, one most popular is the dual signal 'Quadrature' type.
Max.

#### nmateik

Joined Dec 10, 2019
20
It's for an inverter welder so I know its possible, because when I turn the rotary encoder clockwise it increases the power output of the welder. the capacitors are connected to the positive terminal there's 4 of them in series, so there's a physical change going on.

#### Papabravo

Joined Feb 24, 2006
15,019
It's for an inverter welder so I know its possible, because when I turn the rotary encoder clockwise it increases the power output of the welder. the capacitors are connected to the positive terminal there's 4 of them in series, so there's a physical change going on.
So I guess there is some magic going on under the hood.

#### Sensacell

Joined Jun 19, 2012
2,718

Save us from a silly guessing game.

#### nmateik

Joined Dec 10, 2019
20
Save us from a silly guessing game.
Why should it matter? They both work on the same principal a rotary encoder in-fact is adjusting the power output of the capacitor which was clearly stated in my original post.

#### Sensacell

Joined Jun 19, 2012
2,718
Why should it matter? They both work on the same principal a rotary encoder in-fact is adjusting the power output of the capacitor which was clearly stated in my original post.
It's always helpful to establish context when asking questions, this helps others to understand what you are doing.

#### jpanhalt

Joined Jan 18, 2008
11,088

#### SamR

Joined Mar 19, 2019
3,049
Yes, most encoders have a push switch but require a uC to interpret their "up/down" signals.

#### Papabravo

Joined Feb 24, 2006
15,019
Here's a link the the manual. The wiring diagram is on page 28/29: https://www.lincolnelectric.com/assets/servicenavigator-public/lincoln3/imt10164.pdf

There is no magic. The control appears to be a typical rotary encoder with press to select. One can adjust inductance to control the arc. The only mention of capacitance was a safety note about discharging the capacitors before servicing.
So how is the inductance adjusted in response to the movements, forward or backward, of the rotary encoder??