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Found 7 results

  1. Hi, all I'm using a PCA9685 with a pinout board like Adafruit's. I'm trying to run a bunch of LEDs at 20 mA, and the chip is supposed to be able to source 10 mA and sink 25 mA. I understand that to have it Source, you connect the LED between the PWM and GND pins and to Sink you connect it between V+ and PWM. I've tried both ways and using a multimeter and a red LED I get 12.5 mA. Why is it not 25 in Sink? Also, why do I get 12.5 on Source mode as well? Is there anyone have ideas of it? if possible a simple explanation would be nice. Many thanks.☺️
  2. Good day, all 🙂 Recently, I have a system running at 62V max, 54V nominal based on voltage divider rule formula. I wanted to have a little alert LED, so I was thinking about using 10, 1kohm resistors, and adding the LED bewteen the 9th and 10th (or 1st and 2nd, if it matters), to get at most 6V and just a few mA. Is a better/easier way? Is this a really crappy way? Or is this a perfectly fine way? 😶 Voltage Divider Basic and Rule.pdf
  3. Hi everyone. Can you help me with this circuit I am working on, please?. (Image 1) It consists of a TP4056 charger/controller connected to a 3.7v/1.4Ah Li-Ion battery to supply a low battery indicator and a load (3 leds + 2 fans) through a MT3608 Step Up to raise voltage from 3.7v to 9v. When the TP4056 is charging the battery through the USB port, the load is disconnected by the P-Mosfet. PROBLEM: Voltage drops significantly when the load is connected. Test1: Circuit without Debouncing/Load connected: Voltage drops from 3.68v to 3.46v (image 2). Low Battery Indicator: Blinks. Test2: Circuit with Debouncing/Load connected: 1) Debouncing Circuit: The voltage drops to 2.19v at the output of the Smichtt Trigger, therefore it isn't possible to energize the Step Up and the rest of the circuit. 2) Low Battery Indicator: Blinks when switch is pressed. Test3: Circuit with Debouncing/Load disconnected: 1) Debouncing Circuit: Works fine (image 3). 2) Low Battery Indicator: Doesn't blink when the switch is turned ON/OFF. Is there something that I am forgetting to put in the circuit so the voltage is dropping? I would suppose that the problem is at the DC/DC conversion of the Step Up, but everything is meeting its requirements (Vin:2v-24v/Imax: 2A). My system details: Power consumption: 1.702W Low Bat Indicator: (0.037W, 3.7v/0.01A) Load: 2 Fans (1.44W, 9v/0.16A), 3 Leds (0.059W, 2.92v/0.02A). Debouncing Circuit based on a Schmitt Trigger 74HC14 (Vin:2-6v/Vout:2-VCC, VCC and GND connected to battery line).
  4. Hi everyone, newbie here! Trying to find a power supply for LED backlight strips off of an LCD television. I've stripped it down but can't see it marked clearly anywhere. There are 2 strips with 6 LEDs on each. Printed on the light strips is the following: GJ-2k17 CSP-315 Pitch 109 (614x12) -v2.1 O1T38-1 RJ94V-0 E349376 HY-AI YK 1825 Attached are photos Cheers for any help!
  5. Hello, I am trying to modify an FM radio such that it blinks an LED according to the data I transmit from my FM transmitter. I am following the circuit attached below. Is it possible to connect LED to speaker terminals to obtain such result? or any other suggestions? Thanks
  6. I want to charge a LiPo battery via the ballance plugs. So it's a ballanced charge, and I don't run into any problems, day in and day out.The light can be very small, but I want it to be bright. So even using a couple LEDs would make a really nice and bright mailbox light.I want the light to last all night long. So that means I need to know the current draw of the LEDs to the capacity of the LiPo batteries.etc.I need help on this. I need help with the fact how to use an Op Amp to shut the light off when it's daylight out.. or a specific amount of light is sensed.Light Sensed : Start charging, and turn off the LED lights.Light Sensed : Set the Op Amp to detect 4.2vdc. When it does, shut down the charging, &LED's stay off until darkness is detected.That's my idea of a mailbox light, with very long battery life, and high current solar charging abilities.Can anyone help me with this kind of circuit? Here is where my LED come from http://www.kynix.com/Search/led.html
  7. How do I measure how many watt LED diode is on. Have some different that I do not know the value of.
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