Re: Morse tutor
On my displays, there is a driver transistor, Q1, a J3Y = S8050, with a 1k resistor at the base, and the other end of the resistor to the LED pin. So that must be the componenets you refer to.
I haven’t downloaded you new BP program yet, so I don’t know the PWM pin number. But that, I’m sure, could be seen in the program or in another of the GitHub files.
OZ1QZ / John
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Nice to hear from you again!
I have all of the software on GitHub. I updated the software for the 'old' tutor, which is here:
The display updates will work on your old STM32 device, except for backlight control. I have not updated the ESP32 code yet.
For backlight control, the old tutor requires a hardware change. The first step in the procedure is to look at the back of the display pcb, where the components are mounted, and determine if there is a driver transistor for the backlight circuit. It will consist of a 3-pin transistor (SOT23 package) and adjacent 1K resistor. I have discovered that some displays have this driver. Other displays connect the backlight LEDs directly to the backlight pin. If you need help locating this transistor I can send you a photo of it.
The new code controls the backlight by varying the duty cycle of a PWM signal. If there is a transistor driver, we can solder a single wire from the PWM signal to the backlight pin and we are done. If there is no transistor driver on-board, the backlight current (about 90mA) is too much for the.microcontroller to handle. In that case we would need to add our own transistor driver. The pocket tutor pcb has a transistor driver, which can be bypassed if not needed.
Does that help at all?
On Sun, Jul 19, 2020 at 5:37 AM John Kristiansen <john.k@...> wrote: