Fong LED 01

 Introduction Notes: 1. LED turns from dark to dim at around 2.5V, 1mA, dim to bright around 3.0V, 100mA, and very bright, dazzlingly blinding at 3.5V and max current of 350mA. 2. So for status/indicating light, 3mA should be enough, for near distance, 3.0V should be OK. For building/home lighting, 3.5V 350mA should be the limit.

Introduction Pico Scroll Pack A sparkly 7 x 17 grid of snugly packed, individually controllable white LEDs to bling up your Raspberry Pi Pico, accompanied by a quartet of useful buttons. Take a moment to appreciate the simplicity and elegance of a bright white LED, so often overlooked next to its  flashy RGB cousins . Pico Scroll Pack incorporates 119 white LEDs in a tidy 7 x 17 matrix, along with four tactile buttons for interacting with your Pico-based contraption.  The brightness of each LED is individually controllable, and it's very nice for displaying graphs, scrolling messages, soothing snowfall animations or for visualising cellular automata. Shiny. Features 17x7 matrix of white LEDs (119 total) Individual PWM brightness control of each LED IS31FL3731 LED matrix driver chip , I2C address: 0x74 4x tactile buttons Pre-soldered female headers for attaching to Pico Compatible with Raspberry Pi Pico. Fully assembled No soldering required (as long as your Pico has header pins att

Introduction Board Spec

Introduction I found LM334  CCS's performance in high current mode not very satisfactory for current higher than 100mA.  So I am thinking of exploring other circuit designs. I quickly read the follow articles to get a rough idea of different CCC circuit designs. [1]  Active Transistor Constant Current Source - electronics-notes.com [2]  The Basic MOSFET Constant-Current Source June 06, 2016 by Robert Keim - aac [3]  Current Mirror BJTs - aac [4]  Simple constant-current driver - lednique [5]  Simple variable current source for approx 2A, constant load - EESE, 2017jun06 [6]  Current Limiting - Wikpedia   [7]  Current Source - Wikipedia After comparing and contrasting all these designs, weighing pros an cons, I am thinking of exploring the following circuit as described below: 1. One power MOSFET  2. One DAC 3. One current sensing amplifier. / to continue, ... 

Introduction The performance of LM334 High Current circuit is poor. I think the main reason is that the PNP BJT current amplification is difficult to design, because  (1) The transistor needs to be in saturation mode, but static current gain is not well defined, and therefore bias current also not easy to specify. (2) I could not any design/application notes on this high current circuit. However, I found the following two references explaing very well the theory behind the LM334 device.  I am thinking of DIYing a similar CCS using power MOSFET, to achive high current. Next post will not be talking on LM334.  In other words.  This is the last post of LM334.

Introduction I put the LM334 high current circuit and instead just test the one series, no CCS case with RGWYW LEDs, with and without heat sink. I found the results disappointing: The CCS cicrcuit does not seem to perform better than the 24R single resistor circuit.  I also tried different values for the bias resistor, from 560R to 3k. I found that smaller the resistor, the larg the LED current in the ranch of 78mA (for 1k) to 56mA (for 3k). I also don't know how to better control the LED current beside change the values of Rset and R1.  So I need to google again for more design ideas. .END