Let the whole circuit operate at 9V and put a resistor (calculated above) in series with each led.
Go to the following page to see how to do the calculations for the resistor:
I also want to know if there is any benefit of using a constant current driver IC on the output side before the LED rather than directly connecting output to the LED? They use the same parts, more or less, but theirs has pin 3 outputting to the LED and yours uses pin 7. I'm just trying to understand, and that one I found before yours.
I have a 12V 2A - Power supply, but would maybe upgrade to higher Ampere. I plan to use one of the circuits above for each colour. That would make about 100 to 120 RGB-LED's (so 300 to 360 LED's). I would estimate that the LED-tube has a length of roughly 4m. I would like to use that circuit to control the LED like this: One ic can control well up to 4 Mosfets in paralel. Tape was 24V so we put one additional 12V adapter for the oscillator. We changed transistor with mosfet IRFP140n and built 2pcs with 4 channel to control each channel 14 peaces o 3m long tape. But if you have questions please use the forum instead to post it. Resistor 4.7 KOhm 1/4 Watt 5% Carbon FilmīEFORE you post a comment:You are welcome to comment for corrections and suggestions on this page. More info about th above connections can be found here. For example, when powering with 15 volts, the transistor can control up to 26 rows of 4 LEDs each, that makes 26 x 4 = 104 LEDs in total. The last number, indicates how many LEDs in total can be controlled with each connection. Remember that the transistor may need heat-sink if it gets hot. If you think of pushing the transistor to the edges, then you should first measure the real current that your LED array draws, and do not exceed the maximum 800mA that the transistor can handle. For example, when powering with 12 volts, the transistor is capable to drive up to 26 lines of 3 LEDs each (and of course a protective resistor on each line) and that is the current limit of the 2N2222. The next number shows exactly this: the number of rows for each connection that the 2N2222 can handle. Each row composed by a number of LEDs and a protective resistor (RP) can be multiplied in parallel, as many times as the 2N2222 permits. LEDs should always be connected in series with resistors. Although multiple LEDs connected in parallel can use just one resistor, this must be avoided. Each LED row must have its own protective resistor. The RP is the protective resistor for each row. As i told you before, only the LED array will change with the power supply. This is the power supply that the controller operates with. As always, click to enlarge if an image is too small.įor each LED connection above, i give some characteristics. You can use whichever LED or connection you like, as long as you do not exceed the current limit of the transistor (for the 2N2222 this is 800mA). For these connections, i used high brightness 30 mA 3.6 Volts 3mm and 5mm LEDs. I will suggest some connections that i have already tried and took some measurements myself. The LEDs are connected to the "LEDS" pad on the right. R1 pulls up the discharging transistor (inside the 555). In other words, the R2 controls the brightness of the LEDs. The potentiometer R2 controls the charge and discharge times, and thus the duty cycle of the PWM. Here is the controller circuit, able to operate from 4 to 15 volts as is: The circuit can operate at a wide operation voltage, from 4 to 15 volts, and the only thing that changes is the LED array. Similar to the LED Off Delay with dimming effect circuit, i will break the circuit into 2 pieces, the controller and the LEDs. Again i will use as output the discharging capacitor from pin 7, which will control the base of the power transistor. The circuit is based on the 555 timer, connected as a PWM generator. I then suggested that he would better use a PWM circuit to control them. He had a schematic with a potentiometer that would control a batch of LEDs. I use 5 volts for power supplyĪ few days ago, someone posted a question to the forum about dimming LEDs.