# Tag Info

54

Mains guy here. Nothing in LV electronics prepares you for mains. Don't be cheap Doing anything with mains electrical plays rather badly with "cheap". Or should I say "inexperienced people thinking cheap", as mains electrical equipment is very reasonably priced. Start at the end It sounds like you are just starting to work through the implementation ...

14

In the answers to this question is explained how you can do that complete zero-crossing detection circuit with just U1, R12 and 2 series resistors on the 220 V side. One solution uses a common optocoupler, the other one a Darlington optocoupler, which needs less current to drive the optocoupler's LED, so that's less power in the series resistors (less than ...

12

The first waveform looks fine for mains, it can get much worse. I suggest you use a rent a power corruptor, or use a lab with an operator, to see how vulnerable your dimmer is. And work with those results to improve the design of the phase angle dimmer.

11

It depends on the LED driver, but unless it's of a bad (or very specific need) design, a dimmed LED lamp will draw less power. Usually, dimming on LED lamps is done by PWM (Pulse Width Modulation). The LED will actually turn on and off faster than the eye can see. By modulating the ratio of the time the led is on and off, it simulates the dimming to the ...

11

To use a 9uF film Cap to match the impedance of a 60 W bulb drawing only 22W at 60Vrms/60Hz is actually more expensive than buying a dimmable LED bulb before they became fairly cheap. First of all a 60W bulb draws about 500W and up to 2.5kW cold for the 1st cycle. Second, the visible temperature of a 60W bulb is around 2800'K and Lava Red starts around ...

9

You should try wiring one of the fixtures as 2S2P. I'm betting that this will give you the nice warm glow you're looking for, and it's the easiest thing to implement.

8

I am going to assume it's an incandescent bulb of the "artistic" type with interesting filament structure. If it's an LED or CFL bulb, the below comments do not apply. It's possible to connect a silicon diode in series with the bulb to permanently dim it. The behavior is not linear because the light bulb proportionally sucks more juice (technically ...

8

PWM in this case is probably more about human perception than electronics. Your driver looks like it is simply designed to be a current source that can be turned ON and OFF as you see fit. And asking if $100\:\textrm{Hz}$ is different from $1000\:\textrm{Hz}$ is really more about asking how this impacts human perception than anything else. As you may ...

7

The network is there to prevent high speed/voltage transients from causing problems, such as spurious triggering of the triac. Triacs have a dv/dt rating (how quickly the voltage across them changes) above which they may trigger without a gate pulse. To show how this can cause issues, here is a rough approximation of the circuit without the capacitor: ...

7

What's Happening: Internal to the module, there are some diodes to protect the inputs. Typically these are ESD diodes, but they will conduct DC current if you reverse bias them. It's not a strong power source, and you have resistor limiting of it, so it's not very bright. The current flows from D1, into the driver VDD (weakly powering the module and LED), ...

7

The distortion is due to diode rectifiers, phase angle rectifiers. The distortion is not such big that should cause any malfunction. Possibly, the LED power supply misinterprets these false glitches with expected phase angle voltage from the dimmer.

7

One time event? 25 fixtures? For this do hire companies exist! While series strings and such are possible, the elephant in the room is most likely power distribution, specifically all that cable (Which then needs to be 'drunk uncle' proofed, not trivial). You can hire lighting fixtures designed for use as table centre pieces that are LED based and BATTERY ...

6

LED dimming is best achieved through Pulse Width Modulation of the power being supplied to the LEDs. A quick web search reveals several PWM dimmers available, specifically designed for LED strip light dimming, e.g. this one on Amazon for $8.50: Before buying and hooking up a dimmer, though, it might be useful to read a guide like this one, which will help ... 6 Basically what you are asking for is called a digital to analog converter, or D/A or DAC for short. In this case you want the full range to be 0-10 volts. From your description, it appears the receiving end passively pulls up the line, and is expecting the dimmer to put a variable resistance between it and ground. You want to outright control the voltage, ... 6 The question aroused my interest enough to set up an experiment. I changed the question's parameters in one key aspect: Instead of an LED strip with multiple LEDs in series, I hooked up 3 blue LEDs (Vf = ~2.8 Volts each) in parallel, with a single 100 Ohm resistor to limit current to all 3, to a 0.047 Farad, 5.5 Volt coin type "motherboard supercap". I ... 6 You can run LEBs (light emitting bulbs) with PWM. In fact, soft start actually increases their lifetime. It is possible to chop AC, but generally easier to rectify the AC then chop the resulting DC. Four diodes and a capacitor are good enough to make DC to run the bulb from. You also need to make a small low voltage supply to run the processor from. The ... 6 The common inrush limiters are just NTC (negative temperature coefficient) thermisters that are placed in series with the bulb. You just need one that has a longer thermal time constant. Pick one that has suitable voltage and current ratings, and also make sure that its steady-state power dissipation is at an acceptable level. You'll probably need a ... 5 This is simply not a do-it-yourself project. If you have to ask here, you shouldn't touch this. Get a professional with experience at this power level to do this, and of course be prepared to pay a real professional rate. This is not for amatuers. 5 First off if you are controlling a heating element you don't need a snubber. Second, safe is a relative term. If by safe you are asking if it will explode and catch fire then build it an find out. If by safe you mean can I or anyone here tell you that you have built a safe circuit, meaning that you won't hurt someone.... well good luck getting a commitment ... 5 The TRIAC driver that you chose (MOC3041) has a Zero Voltage Crossing detection circuit included. That means that you can't really control when to switch the TRIAC on. The Zero Voltage Crossing detection circuit will automatically turn your TRIAC on when the AC wave reaches a zero crossing point. If you want to do dimming, you'll have to use an triac driver ... 5 Looks workable. I doubt that you'd have major issues with the FET turning on substantially faster thahn the bipolar unless Q1 was a seriously low Ft part. If the LED current gets even say 20% above nominal then Vbe will be seriously high compared to normal (if 0.7V usually then = 0.84 V at 120%) and at +50% current Vbe = 1V+ and the transistor is trying ... 5 Well, a light bulb is a purely resistive device and if you think a series 2 kohms would fit the bill for reducing its brightness to the right level then it's worth considering using a capacitor instead. To get the same reduction in current you'll probably need between 2 kohms and 3 kohms and the capacitor value would be: - C = \$\dfrac{1}{2\pi f \cdot 2500}\...

5

Please look at page 8 of the datasheet under "Dimming Control". You can do either PWM or analog dimming. For analog, you vary the EN/DIM pin between 0.7V (0%) and 1.4V (100%). For PWM, you use a 1HKz signal with on > 1.4V and the duty cycle controls the brightness. You can do it either way. And to answer your question, putting 5V into EN should give you 1A ...

5

Relay Has low voltage drop when closed. Other than not exceeding the max current rating, you don't worry about dissipation. Inherently isolated. Can switch off at any time. Is relatively slow, ms to 10s of ms to respond either direction. Is a mechanical system, so eventually wears out from use. Consider each relay as capable of a finite number of ...

5

I would suggest that you try putting a single diode in series with the bulb(s). This will cut the rms current in half right away, then you can try various series/parallel combinations of bulbs to get the desired level of glow. If you used four 60W bulbs (240W total) we would expect the average diode current to be on the order of 1A (at 120V, half-wave ...

5

Go with LED bulbs You can get 12V filament-style LED bulbs for about \$5 apiece. At 12V/4W apiece, a four-bulb fixture will draw ~1.34 amps. Stick a 1.5 amp or higher power supply under the table, replace the fixture's plug with a female DC jack that matches your power supply, and you're off to the races. If you like to do your shopping on Amazon: A 4-pack ...

4

Yes, you can use PWM to dim LEDs with constant current power supply. Personally I would go with MOSFETs instead of NPN transistors. If nothing else MOSFET will dissipate less heat.

4

I'll add a few more things: 500 milliamps is a lot of current, and should be more than enough to drive the opto-isolator directly unless the uC runs at a different voltage. Even then, you can probably use it as a sink. If you still keep the transistor, you need a resistor between the GPIO and the base. B->E on a transistor operates like a diode, so it'll ...

4

I'm not aware of any IC that can replace a full zero-cross-detector, but I have been using this circuit and it works quite well and it has a very low power consumption. You can find more information here.

4

Lamp dimmers change the brightness of light bulbs by delaying the turn-on of the output till later on the AC cycle as shown below. This scheme works pretty good for resistive loads like incandescent light bulbs. It does not work very well with the cheap transformers found in the AC transformer type wall warts. If the transformer ends up being able to pass ...

Only top voted, non community-wiki answers of a minimum length are eligible