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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
Ok your dimming period is 5ms The on time for 5% is 250us. Is your led driver capable of getting back up to regulation level in 250us? Is it a hysteretic led driver. Does it have a frequency compensated feedback loop?……if so it might be slower unless you have a controller which “freezes” the error voltage during the (...)
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?
Hi, I am trying to design a led Driver of 12W(24v/0.5A) output , where I can keep the voltage constant and vary the current. i.e. I would like to understand if we can vary the current by introducing the current control loop in the SMPS /Driver itself... i.e. Inner control loop which would supply the desired current to the leds (Thus enabling dim
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
At 70mA the saturation voltage is only about 0.75V so it should only dissipate about (0.75 * 0.07) = 0.05W. That would barely heat it. Is this a linear dimming circuit or are you using PWM? Please show your schematic. Brian.
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 (...)