# Tag Info

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You want to find $\alpha$ in the following equation: $$V_{rms} = V_{pk}\sqrt{\frac{2\pi - 2\alpha + sin(2\alpha)}{4\pi}}$$ In other words, you want to find out when: $$V_{pk}\sqrt{\frac{2\pi - 2\alpha + sin(2\alpha)}{4\pi}}-V_{rms} = 0$$ Then you have an entire wikipage dedicated to Root-finding algorithms for solving these kinds of problems. As the ...

3

Given R3, R4 & C1 that diode is doing mostly diddly squat. Generally you add a diode in parallel with the driving resistor at a gate of a Mosfet to accelerate turn-on or turn-off by providing more drive to the Miller-multiplied Drain-Gate capacitance. In this particular case the diode seems to be there to bypass the resistive divider and provide more ...

3

The root cause of the hysteresis (aka "snap-on" effect) in simple triac/diac dimmers is the capacitor not being discharged by the diac in the previous half-cycle and entering the subsequent half-cycle with the opposite voltage across it. Consider just the positive case where the capacitor is negatively charged from the previous half cycle. The negative ...

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That's not a polarized cap you're seeing on the schematic The universal sign of a polarized capacitor, regardless of whether it is using straight-plates-with-hatching, straight-plate/bent-plate, or plate-in-plate symbology, is the + sign that marks the actual polarity of the capacitor on the schematic. From the lack of that plus sign here and the fact this ...

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Your question is very broad, so the answer will be pretty generic as well. In general terms, and considering your electronics knowledge and software requirements, I would suggest to use a RasberryPi, which will allow you to do the dimming by controlling a PWM GPIO. The big question is if the lamp you have chosen is dimmable. The most likely answer is no, ...

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Using the super-dumb lookup table method, and using a dumb binary search to find values, I get: double angle_lut[101] ={ 0.00000, 0.02478, 0.03936, 0.05161, 0.06258, 0.07268, 0.08215, 0.09114, 0.09973, 0.10800, 0.11600, 0.12376, 0.13132, 0.13870, 0.14592, 0.15300, 0.15996, 0.16680, 0.17354, 0.18019, 0.18675, 0.19324, 0.19966, 0.20602, 0.21231, 0.21856, 0....

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Why is it that in every triac analog dimming circuit I find that the triac triggering circuit is fed through the load and not straight from the mains? In most countries there is no neutral available in the wall switchbox where the dimmer is mounted. Arranging the circuit to find a neutral path through the load avoids having to rewire the switchboxes with ...

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That's a high quality LED (if genuine) - depending on volume then an Asian sourced semi-equivalent would be much cheaper. Battery life is very very dependant on operating current. For a battery of adequate voltage across the operating time Operating life = Battery_mAh_capacity / LED-mA. If you operate the LED at 700 mA then 3 x AA Alkaline ...

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Now average RMS current is only 10A even though peak RMS is still 20A No, it's 14.14 amps and quite close to the breaker's limit. If the current taken is normally 20 amps RMS for a full AC scenario, you can project this to power by squaring. So 20 amps becomes 400 amps squared. It is the power that is halved by introducing a half wave rectifier so, 400 ...

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Both turn on when the gate voltage is high, one is shunting the body diode so neither body diode conducts (therefore the drop is proportional to Rds(on)*2). When blocking, one body diode cannot block so almost all the voltage appears across the other MOSFET. The circuit driving the gates does not see much voltage relative to the “ground” at the junction, ...

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In situations where something has worked for a long time (days) and has suddenly stopped, it can be difficult to tell exactly what happened. As far as flaws with your circuit (that would make it suddenly stop working after a month), the photodiode is the biggest thing that looks weird to me. Not to mention (from a terminology standpoint) "Comm" or Common ...

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I cannot exclude that the circuit can principally work (as per PCB layout; your schematic is currently wrong, at the time of this writing). The IRF740 should have plenty enough heat dissipation capability for 3W of continuous power (its abs max is given at 125W continuous), so I wouldn't be very concerned about RdsON, as long as the IRF740 FET is genuine (...

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This answer is just to help you with your schematic. Figure 0. OP's schematic. It is badly laid out making it difficult to follow the schema of the circuit. There are numerous unnecessary kinks and cross-overs. BR1 is installed incorrectly. When V1 goes negative BR1 will short-circuit the mains supply and will be destroyed (as there is no fuse). Q1's ...

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You need a transistor with much lower Ron. 1000W at 400V is 2.5A. Your transistor's Ron is .55 Ohm. That implies ~3W dissipated power, which is too much for a TO-220 package without a major heatsink. You should use a transistor with an Ron in the 10-20mOhm range.

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I have used some electret microphone (with amplifier) to localize the source of that buzzing. Thanks to Sunnyskyguy EE75 for the this tip. Well, I found not one but several parts that were making the buzz :( inductor L1 ceramic capacitor C3 trimmer RV1 trimmer RV2 (the main trimmer for brightness) Possibly some others, but these were the loudest. ...

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When you use Quadrant IV, it requires much more Ig which with 1k series requires more line voltage and thus switches with more transient loss. A 60W appears as a 600W load when cold. To reduce Pd in Triac Thus I suggest you verify ZCS is ok then swap pins on U5-4,6. You can remove the snubber for this snubberless Triac part. Ref This fix should also ...

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Furthermore I remember that current vs light given by a LED is heavily non-linear. That means that if I manage to cut the current in half the light will not be half but probably 1/4 or even 1/5. If I'm not wrong again. It is actually directly linear to the current (once you factor heat variation), but what is not linear is the eye response to light ...

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That diode will make the FETs turn on faster and turn off more slowly. It's probably done to achieve some advantageous compromise between switching losses and reduced RF interference.

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The front page of the STD7NM60N data sheet states clearly that it is intended for: - They are therefore suitable for the most demanding high-efficiency converters. This means that they ARE susceptible (almost certainly) to situations where the gate-source voltage isn't as robust as it could be. To verify this, the best place to look is the graph for ID ...

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The main issue here is ( no pun intended) the lower main line injection of 0.5kV with a 1us rise time and Miller capacitance coupling of impulse voltage back to the gate drive is probably exceeding the Vgs levels. This rise time equates to a the driving spectral energy band of $f_{-3dB}=0.35/t_R= 350kHz$ You have a CM choke on 1 side but not the other. It ...

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I think this might work. $θ = {Arccos (1 - 2P )}$ for per unit power (0 to 1) Using Conduction angle from right to left to match direction as it appears on time scale for x = P Well I can curve fit to your results.

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You don't give any info about the LED strip, so I'll assume 12V and less than 2Amps. The simplest solution would be to use a power supply which supports dimming by resistor, for example this one. Check out page 4. You need to order the correct version which is dimmable by connecting a potentiometer or a fixed resistor between the two DIM wires. It's really ...

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A 2-wire overhead fan controller would work. You can keep the 3-speed switch and put the speed controller in series with the lowest speed tap. That way you have all the higher speeds, and the LOW becomes a LOW-LOW. In your photo, the heat sink seems small. If it gets too warm, add some metal or put the dimmer into the airstream. Remember, don't go too low on ...

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Here is how a traditional switch is wired. Note the switch is in series with the load. Black is supply hot; red is switched hot; white is return (neutral). A dimmer is a type of powered switch. That would include dimmers, PIRs, lighted switches, smart switches, any case where the switch needs power for its own onboard electronics. Here's how an ideal ...

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Your UPS likely has a square (non-sinewave) output. The square output likely exceeds the dv/dt rating of the triac, causing it to turn on. You might want to consider a snubbing network to reduce the dv/dt transients.

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