Getting good contrast with 1602 display

[keble6]

Great extension, thank you. Not related to your code, but I wonder if you managed to get good contrast on the 1602 LCD at 3.3V. Did you find a way? My 1602 with the PCF8475 I2C backpack gives very low contrast.

[shaoziyang]

Hi, The voltage level will affect the contrast of the LCD. If the voltage is low, it is not easy to obtain good results.Therefore, it is necessary to increase the power supply voltage of the LCD. The voltage of SDA/SCL cannot be lower than 0.7VDD, so the maximum voltage of the LCD power supply is 3.3/0.7=4.7V. You can try to provide about 4V power to the LCD separately, or connect 1 or 2 1N4001 diodes in series to the USB 5V to power the LCD, which can reduce the voltage by 0.6-1.2V. Note that the power supply limit voltage of the microbit is 3.9V, and exceeding the chip may permanently damage it. And remove the I2C pull-up resistor on the LCD first.

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-- Best regard! Shao ziyang ***@***.*** 2023年11月24日 At 2023-11-23 18:19:59, "Rob Wilson" ***@***.***> wrote: Great extension, thank you. Not related to your code, but I wonder if you managed to get good contrast on the 1602 LCD at 3.3V. Did you find a way? My 1602 with the PCF8475 I2C backpack gives very low contrast. — Reply to this email directly, view it on GitHub, or unsubscribe. You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[keble6]

Thank you, that's a very clear explanation!

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On Fri, 24 Nov 2023, 02:51 shaoziyang, ***@***.***> wrote: Hi, The voltage level will affect the contrast of the LCD. If the voltage is low, it is not easy to obtain good results.Therefore, it is necessary to increase the power supply voltage of the LCD. The voltage of SDA/SCL cannot be lower than 0.7VDD, so the maximum voltage of the LCD power supply is 3.3/0.7=4.7V. You can try to provide about 4V power to the LCD separately, or connect 1 or 2 1N4001 diodes in series to the USB 5V to power the LCD, which can reduce the voltage by 0.6-1.2V. Note that the power supply limit voltage of the microbit is 3.9V, and exceeding the chip may permanently damage it. And remove the I2C pull-up resistor on the LCD first. -- Best regard! Shao ziyang ***@***.*** 2023年11月24日 At 2023-11-23 18:19:59, "Rob Wilson" ***@***.***> wrote: Great extension, thank you. Not related to your code, but I wonder if you managed to get good contrast on the 1602 LCD at 3.3V. Did you find a way? My 1602 with the PCF8475 I2C backpack gives very low contrast. — Reply to this email directly, view it on GitHub, or unsubscribe. You are receiving this because you are subscribed to this thread.Message ID: ***@***.***> — Reply to this email directly, view it on GitHub <#7 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AE6VELN35TDX7BXY4WYLG73YGADTZAVCNFSM6AAAAAA7XQYOIKVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMYTQMRVGA4DMNRUHA> . You are receiving this because you authored the thread.Message ID: ***@***.***>