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55 Threads found on Led Dimming
Hi, I'm fairly new to microcontroller design and have been asked to implement an led delay for a display piece. It needs to sense when someone walks close and fade leds to maximum brightness and stay on for a period of time. I am thinking of using some form of motion sensor to trigger a microcontroller input pin. I'm considering either usin
Undervoltage lockout being tickled by weak mains, poor socket connection or a PFC front end problem? Thermal protection toggling due to a die or board level heat issue? Control loop instability? Noise issue w/ current mode control at low duty cycles is often a problem, with the turnoff edge coming close to turnon the switch "ringing tail" ma
Hi everyone, I need some Ideas for my project. I am doing a project called Digital Home. Means everything can be controlled by Wifi( Smartphone) How can I Dim one CFL or led-100W ( replacement of Incandescent Bulb). Which(Voltage or current) one should I control In order to make the led/CFL to Dim
I can't give you the code because as far as I'm aware, you will be the first person to use it and I'm not prepared to spend hours writing it for you. I will help you to write your own program though. You need to make decisions: What PWM rate do you want to use? How much current does the led need? TSOP devices will decode any IR protocol, are you
Reduce the 1k resistor to around 270 Ohm. That should give you near the 20mA you need through the leds for full brightness.
hi, To keep the cost down I would use a 555 timer as a PWM generator for each chain. For only 20mA per led chain, from a 24Vdc source, a BJT or a 2N7000 MOSFET would be suitable. The frame frequency of the 555 PWM generator could be selected for each led colour chain. Lots of simple circuits on the web.
The best choice is a dimmable driver with 0-5V control or PWM control. I suggest any MOSFET with logic gate drive and low RdsOn will do. I assume you know Ohm's Law. You also need a good heatsink for led and wiser to buy than
Hello, We are doing PWM dimming of led drivers. We need to set up an Arduino board so that the Arduino can deliver the PWM dimming signal. The PWM dimming signal has to be a variable duty cycle square wave at any frequency between 500Hz and 30KHz. We would like the PWM dimming duty cycles to be smoothly (...)
As far as I know, each led is designed using specific components to bright a very small range on the light spectrum, actually defined by a discrete transition of the electron between two energy levels of the atom, so that, assuming a high enough PWM frequency, should not make any difference in the human perception of the color shift.
Besides piezoelectric behaviour of high Er capacitors, you should also consider magnetostrictive properties of ferrites. Both will sound. I can't follow the idea that you really need to use special capacitors and inductors for a run-of-the-mill led driver. If your application is sensitive in this regard, e.g. home led lighting, you preferably fi
So if I have your question right, you want to know why Marketing has no idea of what matters to Applications or what Design thought was a great feature? Sounds like a technical problem to me. Yeppers. I think the answer lies with what kind of person goes into marketing. This is either a failed engineer, or a non-engineer, in my observation. Eit
If you are getting EMI from SMPS and current loop to leds the noise will be radiated proportional to the area of the loop and the current pulse I.p-p and radiation loss according to Friis Equation. Obvious not having twisted pairs and feed each end with a single is a worst case design or best case noise generator. The only way to avoid it now is
You just have to check for the output current only. The voltage doesn't care, as the led will self adjust the voltage across its terminals. By using a PWM signal and using the output current as feedback signal you could accomplish your task (led dimming). Think about led as a simple diode - you don't have to set the (...)
I doubt the led/transistor current is only 20mA because they are multiplexed. Multiplexing causes PWM dimming so the peak current must be pretty high to make enough average current. As you can see from the specification for saturation, beta is not used when a transistor is used as a switch. Beta is used when a transistor is a linear amplifier with
Hello, I got a problem that I dim power led 4-7W/50V, but I wonder why my Transistor TIP122 is over heating. I measure the current Ic = 70mA and Ib = 1mA only. I also try change to other transistor but I still got this problem....:sad:
led bulb have small circuit inside which makes DC voltage for powering led. This circuit is power supply for led which is usually done using one "big" capacitor ~1uF, 275VAC or similar for step down voltage to small DC value. This is reason why it is not possible to dim led. Regards, Mr.Cube
Dear All, I'm planning to build some intelligence in my car lights and I need your advice on recognizing ambient light intensity. I've already build DLR control in my car using PIC12F683 which is Mercedes style dimming for the DRL led's when turn signal is activated. Now I'm planning to make another version which would automatically switch from
If an incandescent lamp burns out, a high short circuit current might flow. Triac dimmers that are not protected by a built-in fuse can be damaged in this situation. Flickering of incandescent lamp can indicate a defective triac control circuit. led drivers aren't necessarily suited for dimmer operation. - - - Updated
Constant peak pulse current yes, but variable pulse frequency or duty cycle or PWM means variable average current and thus dimming. Constant DC current through led means constant brightness for that current and different for different current. There is too much commercial names for circuits that can cause confusion.
I am building a led panel for my aquarium and need to control the dimmer which requires the following criteria : Power ON with dimming: DIM ~ -Vin >2.5 ~ 6VDC or open circuit Power OFF : DIM ~ -Vin < 0.8VDC or short 100 ~ 1KHz 1mA at PWM dimming OFF and 24VDC input can someone guide me on where to start in order to design this using (...)