Re: Morse tutor

John Kristiansen

Thanks Bruce.

Good information.

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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Fra: Bruce Hall
Sendt: 19. juli 2020 14:18
Emne: Re: [w8bhMorseTutor] Morse tutor


Hello John,


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:

Hello Bruce


You did it again! Nice work with the portable tutor and the documentation. Top class!

I hope to get the new software implemented to my 'old' tutor, and need a hint for the display improvement. Can I find it in your Githup account?


BR OZ1QZ / John


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