![]() For instance, the button required to flash the chip during programming also functions as the battery test button and the button to save the current light output setting to EEPROM.Ĭomponents required only for programming were moved off to a separate board. We saved space by having controls play multiple roles. We had to create a custom ESP8266 Eagle SMD package to fit the narrow confines, and all of the ESP traces had to be routed beneath the module. This posed a particular challenge in finding a way to route all of the traces using just 2 layers. In particular, the board is only 0.83" high, with a large notch in the bottom. ![]() This highly constrained set of requirements made layout of the PCB difficult. While the ESP-12F is relatively small for what it does, it occupies a lot of our very limited PCB real estate. Unfortunately, there was not much space to work with and we also wanted to design a single PCB that could be used in each of the 3 panels with the existing mounting hole patterns. The ESP8266 ESP-12F manages the PWM pulses, input controls, and LED battery level indicator. The power required meant some large TO-220 packages for the voltage regulator and MOSFET power transistor plus a 2W resistor. Each of the three panels had unique characteristics that had to be handled through component selection. We had to make sure to select components that would support the full power draw. Working out the circuit proved straightforward. We discarded all of the existing electronics and controls, keeping only the enclosure, LED panel, and battery. The software is composed of three main elements: PWM control of the LED panel, the HTTP WiFi server, and the HTML code for the user interface. The ESP8266 used as a standalone microcontroller/SoC met all these requirements as well as providing the WiFi access point we needed for remote control. ![]() 5 candela per square meter! We needed a microcontroller with a 10 to 12 bit PWM resolution to achieve this low a light level. Measurements indicated that we needed to be able to dim any panel down to about. A friend pointed us to an article on PWM control for high power LED circuits, and a prototype based on an ATTiny provided our proof of concept.įrom the prototype, we learned that the dimming provided by typical PWM using 8 bits, as available on the ATTiny or Arduino Uno, did not dim these panels sufficiently for night sky photography settings. We took them apart and analyzed the circuitry, concluding that the only way to meet our goals of would be to design a new circuit from scratch using a microcontroller. ![]() (This project will describe how to modify the Neewer panels only, but the board and firmware will support the Yongnuo also.) We had three different panels available: a Neewer CN-216, a Neewer CN-160, and a Yongnuo YN 1410. Moreover, the lights were located fairly far away from the shooting location, with a lot of cacti and brush in the way as well, making exposure adjustments time consuming and tedious. We compensated for this by using filters and multiple sheets of vellum paper, but we agreed there must be a way to electronically limit the light output and simultaneously gain more precise control. The problem we quickly ran into was that the panels put our far too much light. We were leading a night sky photography workshop, and the goal was to light foreground objects while getting a dramatic shot of the night sky in a remote area. This project came about for a very practical reason.
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