EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: TViT on January 01, 2025, 10:01:35 pm
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Good afternoon everyone! I want to make a controlled dimmer so as not to twist the wheel, but to set the desired voltage at the output and, accordingly, the power and brightness of the incandescent lamps.
I did everything, I consider the voltage on the network and on the load after controlling the TRIAC as RMS (the root of the sum of the squares of the samples, divided by the number of samples. For half-period 180-185 of the counts at the moment)
But somehow it doesn’t work out. If when the TRIAC is turned on in the middle of the half-wave, and need in setting 100V at the load, I get half the power of the multimeter at the load and shows 99-101V, but then at 10V or 20V, not accurate values of the output voltage are obtained. Roughly speaking, I install 20V at the load, and multimeter displayed is 5-8V. I measure with a not true rms multimeter, of course it also distorts the testimony. But not very big error measurements.
How can I as much as possible as much as possible to calculate the current voltage in the network and the active voltage at the load. The brightness of the lamp as a need power? Or other load for example simply heater. And accordingly, understand when to include the TRIAC if i need 10V on a load. And how I should calculate Voltage max accuracity on a load ?
Please help :(
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I did not get all of your statements but the relation between voltage and brightness is unlinear for a lightbulb.
Why would you need a precise measurement?
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Triac dimmers are not very accurate. Changes in the mains waveform can effect the output. The output waveform is quite a bit different from a sine wave. A DMM that is not true RMS can be quite a bit bit off, especially at the low end. One could still see if the voltage is about stable or variable.
There are few very special dimmers (may not be available in the normal form factor) that actually measure the RMS value and regulate the power, but this is the absolute exception.
Old style incandecent lamps are anyway a thing of the past. Modern LED lamps may not react to the RMS value, but a somewhat different metric and many types don't like dimmers at all or require different FET or IGBT based dimmers that control the turn off part.
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I did not get all of your statements but the relation between voltage and brightness is unlinear for a lightbulb.
Why would you need a precise measurement?
I know what lamp not linear, she is just as example. I need simple equal between set output voltage settings in smart dimmer and voltage on a load. As example I connect a simple heater. And I want see or I expect to see the same voltage on a load. Naturally, as much as possible.
Why would you need a precise measurement?
And I want see or I expect to see the same voltage on a load. Naturally, as much as possible.
To set the desired voltage at the load. As much as possible.
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Triac dimmers are not very accurate. Changes in the mains waveform can effect the output. The output waveform is quite a bit different from a sine wave. A DMM that is not true RMS can be quite a bit bit off, especially at the low end. One could still see if the voltage is about stable or variable.
There are few very special dimmers (may not be available in the normal form factor) that actually measure the RMS value and regulate the power, but this is the absolute exception.
Old style incandecent lamps are anyway a thing of the past. Modern LED lamps may not react to the RMS value, but a somewhat different metric and many types don't like dimmers at all or require different FET or IGBT based dimmers that control the turn off part.
I know all this. The only question is how to consider samples from ADC and know when to include a TRIAC. Now my algorithm is dynamically adjusted to set output voltage. If on out voltage more set in smart dimmer, I increase offset value from start half wave. If voltage less than set, I reduces offset value.
And the question is essentially how to properly consider samples from ADC and when turn on TRIAC.
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You can use a bridge rectifier and a MOSFET to get PWM control of a resistive load.
Recall that the RMS AC power is equivalent to the DC power.[attachimg=1]
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You can use a bridge rectifier and a MOSFET to get PWM control of a resistive load.
Recall that the RMS AC power is equivalent to the DC power. (Attachment Link)
Not can. Because neede control power up to 10kW. If more elements in shem more losses and the larger dissipates power.
I will try to more accurately measure the voltage on a load, I can have great distortions when measuring. I hope so ... Otherwise, why such discrepancies at 100V on load is also 100V, but at 20V required at the load I have 5-8V no thoughts.