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55 Threads found on Dimming Led
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
PWM dimming frequency is 200Hz. I change duty cycle from 10% to 1% with 10 steps equally separated, such as 10%, 9%, 8%,.....1%, within 3s. It looks flickering in the run, maybe especially at the middle of this run. What may happen? jitter of duty cycle, or overshoot of current in led?
Ordinary CFL bulbs cannot be used with dimmers unless the ballast is compatible with dimming.
Hi, do you have access to google? Then do a serach "led dimming PIC". Loads of schematics, descriptions, programs... Klaus
Hi All, I am using High Power led for my project. To Dim the brightness of leds I have bought IRF450N(TO-220) Package. I am using 15V SMPS. 5 led are connected in series. I gave +15V to one end of seriesly connected leds(say Anode). Cathode of Fifth led is connected to Gate of IRF540N. Source is (...)
Hello, I'm working on a project (theoretical stage right now) and I need some suggestions. I plan to use 6 led chains of different colors - that's multiple 5mm high brightness led's wired serially in a single chain (all led's in a given chain are the same color). Normally they draw about 20mA of current when fully lit, but the voltage (...)
hi friends i want to use micro. pic 16f676 for dimming purpose of 20w cob led with 12v dc, is it possible with this micro? please help me. i have proton plus compiler. thanks in advance,
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 (...)
The color shift of white leds isn't a myth, it's specified by manufacturers, see e.g. , diagram 8 and 9. It's however small, and I believe that you may have missed it when the test setup isn't sensitive. But there are surely led applications where the color shift m
Hello, Have just been running switch mode led driver demo boards from and I usually do Analog dimming, so am not used to listening out for ?whining? during PWM dimming. However, all of these boards ?whine? when PWM dimmed?.the whining sound varies as the PWM dimming frequency is varied (kind of as you?d (...)
Hello, The MAX16834 led driver IC obviously performs disconnection of its error amplifier output from the feedback compensation components during PWM dimming ?OFF? intervals. (this can be seen from the block diagram on page 8 of the max16834 datasheet, where a switch can be seen at the output of the error amplifier). This feature vastly improv
Hello, Has anybody experienced problems when sending "PWM dimming style" current pulses down wires to leds (wires of length up to 2 metres long)?....I am referring to sending PWM dimming pulses to a 42V, 2.5A led module. Presumably the current pulses should not have too steep sides or else radiated emissions will result?
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
Do you think 1mA is enought to open this transistor? It's a darlingtion with B > 1000, so Ic/Ib=70/1 would indicate saturation. The applied dimming method is unclear though.
The clue as to why a standard dimmer doesn't work is printed on the lamp itself, "85-265V". The electronics inside the lamp are able to maintain constant current through the led over that voltage range so phase control, whether leading or trailing edge are unlikely to work. You might get some limited control using a trailing edge dimmer but it wo
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
Dear all, I am using dimmer circuits designed with TRIAC (BTA16-600B) which is shorted. What could be the reasons. Connected incandescent lamps/led drivers. When i replaced the TRIAC the incandecent lamp is flickering. What is the purpose of choke in dimmer output? Please suggest. Regards, Sundar.A
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 (...)
Why discrete components? That just makes things more complicated... Do you need isolation? dimming?
"Yes" the 'comp' pin voltage will be frozen during pwm dimming off cycles?
Hello, Page 14 of the LM3421 led driver IC datasheet gives a solution circuit for implementing analog dimming of the leds. Unfortunately that circuit allows the analog dimming, but does not allow one to know exactly what dimming level one is dimming to (it just allows one to dim to more (...)
led lightbulbs for use with triac dimmers have to be made with certain features which prevent the triac's sudden switching from exciting damaging resonances in the led lightbulbs EMI filter. led lightbulbs which are not meant for triac dimming do not have these features, and so they may be destroyed by being accidentally (...)
Offline led drivers use primary side control (via the bias winding) in order to regulate the output led current when triac dimming is used. eg the linkswitch ph family.... Surely one cannot achieve tight regulation of output via the bias winding?, since after all, it is separated from the secondary (ou
You don't need a buck converter, or ANY kind of converter. As I said, you just need a variable pulse width signal which you would use to drive a mosfet. And what do you mean by "dimming and control". dimming I understand but "control" of what? If this is a stand-alone circuit, i.e., no microprocessor, you can just use a 555 and mosfet.
I need to slowly DIM and slowly make a led brighter. The leds are ceiling lights may be in the range of 6W-12W. it is having a SMPS already there. So I plan to introduce a MOSFET between the SMPS and led which in turn will PWM'ed from a Microcontroller. This is my plan and I tried it, but the dimming is not smooth (...)
I need to slowly DIM and slowly make a led brighter. The leds are ceiling lights may be in the range of 6W-12W. it is having a SMPS already there. So I plan to introduce a MOSFET between the SMPS and led which in turn will PWM'ed from a Microcontroller. This is my plan and I tried it, but the dimming is not smooth (...)
I wonder why it's necessary to use 200 or even 500 kHz for led dimming? Apart form the many right things that have been already said about MOSFET's versus BJT for fast switching, there's another rather simple point. BJT need to be operated with sufficient base current to achieve low saturation voltage. Do you know where you get the base current
You don't need a MCU to make an led driver unless you want dimming control. Furthermore the MCU will be low voltage drive @ 30mA +/-5. If this current is intended to drive 32 leds @ 3.2V you need to convert 3.7 to 100V at 3Watts average load. We call this a 32 Series or 32S string. Often when voltages exceed 50 Voltages they are put (...)
i'm building a digitally based, analog display clock using led's for the display. also, a microcontroller is used ( ATmaga168). i need the led's to be Auto dimming (reduces the intensity of the led display when the environment is darkened and restores brightness in normal light). actually im kinda lost at designing such (...)
Hello, We are doing a buckboost led driver using LM3429. (15W) We want to flash the leds on and off at ~2Hz. We intend to use the nDIM pin to do this. ... though can we use a BJT instead of a FET to take nDIM low and turn the leds off? (example shown on page 14, figure 13 of datasheet)
Hi, I am troubled of how can I make my tri-color led dim. I have a 595 shift register where my tri-color RGB led was connected. My goal is to dim it so I can have a different color. How should I do it in Keil C51 code? Should I use Timer interrupt? Hardware pwm? BTW, I successfully light/blink those tri-color led but (...)
Yes, you can increase the led current to compensate for the dimming. Check the maximum peak led current (and time it is allowed), maximum average current, and the maximum current through your drivers, then calculate the series resistors to give the maximum current without exceeding any of these. The average led forward (...)
hello, what is the suitable frequency range for the PWM control of a: 1)motor 2) dimming of led?
When you use CCP, you're using the hardware PWM. So, for PWM without CCP module, use software PWM. One way would be to use a timer. Have the timer interrupt at the end of each period. Depending on the time required, keep output on and off as required. Check this out: AN1074 - Software PWM Generation for led dimming and RGB Color Applications [u
Try BAM (Binary Angle Modulation) instead of PWM. Batsocks - led dimming using Binary Code Modulation - Binary Code Modulation It is most effective way to control brightness of led's. You can use it with shiftPWM. There is a shiftPWM examlple for controlling of 768 led?s at 32 brightn
I have a series of leds I am going to dim them using a PWM signal coming in here at point A to a transistor. However I dont want the load on the circuit to change as there would be multiple of these in parallel. Is this the correct way to do this with 2 transistors and a not gate in the middle. So either the current is going through the leds when P
I have a strobing led that is controlled by a microcontroller via an N MOSFET. The strobing led is carrying a modulated signal. The microcontroller will pulse the gate voltage of the MOSFET to turn the led on and off. (see picture) 60972 A new design requires this led to have adjustable intensity. Since (...)
Hello, I have a small circuit based around an LM3409 led driver. I need to control the analog dimming using 2 inputs. Inputs are 0 or 5v. I will be using logic level FETs. The LM3409's analog input pin is a 1.24V 50uA supply that can either be varied using an external analog voltage, or reduced by tying it to ground through resistors. Attached is
First the most important is the led that you will use. And second is the heating of the led, you must control. Third, the source mut be a voltage controlled, current controlled source. ANd does'nt mather if it is a linear or switching source. Fourth is the dimming control.
Hello, We are driving leds for TV backlights. We are doing Analog dimming, and the led current maximum is 500mA. We can change the led current at a speed of 25mA per millisecond. Do you think this will be quick enough? We cannot change the current any faster, as the offline led driver (...)
Hi, I would like to make a simple light level sensor circuit which is used to as input to control the light output of an automated light dimming system. I can only think of using an LDR with a resistor in a voltage divider circuit and connected to the ADC of a microcontroller to get varied voltage readings with changing ambient light. Are there
I have a controller board that I'm using to turn led circuits on and off via SSRs. I like the programatic control I have, but the SSRs aren't suitable for dimming. My question is, is there a plug replaceable part for the SSRs that will give me the voltage control I need for led dimming? My controller is: Sensoray 2653 (...)
hi guys! i have knowledge in understanding PIC16f877,but im not familiar with pic12f615,, as my title stated i have to built a led dimming circuit,building the circuit is ok,but its the code,as u can see the code is in assembly language which i have no knowledge of, here are my objectives initilaise pwm on (...)
Can anyone give me a good reference for a Angle Detector, dimming Decoder and Controller for led Driver? The only reference I have is the National Semiconductor DataSHeet which is . It is in figure 1 page 7 and the explanations are in page 10 and 11 respectively. I already finished my design for the co
Hello jason, Just go through the link you will get some information for dimming & Lighting control. Please let me know how's going? Regards Chanchal
Driving 4 high power leds RGBW using a microcontroller (4-chnl PWMs) with a 4 channel built-in high-current driver. I can use the PWMs for dimming and also to provide different flashing sequences for each channel separately. But what about color mixing? What is it? Where can I get an algorithm and software example to produce color mixing?
I think u can also use pulse dimming.
HI, I built this led driver,and it's very good.But I have a problem.I would like to build a PWM dimming with microcontroller(AVR or PIC), but I don't know plan is two pushbutton- up and down. Please put in schematic. Many thanks Added after 5 minutes: The link: