ER20-LCD and other parts always turn ON with 5V USB connection

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Dawood
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ER20-LCD and other parts always turn ON with 5V USB connection

Post by Dawood » Mon Mar 22, 2021 11:06 am

If you are using Raspberry PI or something similar for 24 hours with Er20 but the LCD, Erysensor, hotend fans don’t go off due to the 5V coming through the USB connection and it is frustrating, don’t worry we got your back. Before going to sort out this let me clear one thing here, the stock ER20 motherboard is designed the way which is frustrating for some users because they are using the Raspberry Pi and don’t want to unplug the USB cable or press the reset button to restart the printer each time in order to have a successful boot. There are a lot of things to discuss, hope you guys will share your opinions or queries below, I will answer each one of them, Now let’s jump directly to the solution.
Let me show you the different lines in the board of ER20 board, also the line in the screenshot which we need to cut.
ER USB Port Schematic Diagram.png
ER USB Port Schematic Diagram.png (92.63 KiB) Viewed 138 times
USB 5V line-1.png
USB 5V line-1.png (1.79 MiB) Viewed 138 times
In the schematic diagram, 6 lines can be seen coming from the USB port. 3 out of 6 are GND, 2 are data lines and the one which is highlighted as 1(5V) is the line we need to cut. Kindly use a tool having a sharp tip in order to cut the line without damaging the lines near to that.
USB 5V line 1.png
USB 5V line 1.png (1.95 MiB) Viewed 138 times
Kindly cut(scratch) the line with much care, making sure the surrounding area is not damaged. This procedure will cut the 5V from the USB port permanently.
If you are thinking this may have some adverse effects on the board or the USB port itself, you are wrong, why? Let me explain to you. The Fuse near to the USB port function is to isolate and protect the USB connection, How? Let me share a full picture of the motherboard so that I can explain it clearly.
ER20 Board.png
ER20 Board.png (1.41 MiB) Viewed 138 times
I will explain the MCU, SWD and Power in. The MCU is directly connected with SWD pins(5V), if the MCU gets damage, it will affect the 5V of the SWD and due to this the PSU voltage will fluctuate, which in turn will have an effect on the 5V of line 1, so the Fuse on this line function is to isolate the USB port if there are any fluctuations, it works like a protector. If we don’t use the Fuse here the 5V line will directly go to the USB port, so in case of voltage fluctuations, there is a high probability that the disturbance can damage the USB port in the computer if connected via USB cable. What will happen if we cut the 5V line? Mmmmmm, Nothing will happen, why? Because after cutting the line (isolate the USB port from any damage) will have the same role like there will no 5V goes to the USB port so any fluctuation in 5V will not damage any USB port. Will it affect the function of the USB port? The answer is no, why? Because the 5V gives power to the USB port in order to work properly but there is 5V also coming from the computer through USB wire, so cutting this line will have no effect on the function of the USB port, as the data and other lines working properly.
After this procedure, you can plug the USB cable for 24 hours (Raspberry Pi). The LCD will turn Off after Powering off the PSU. When you turn ON the PSU, LCD will start with a complete boot without any need to press the reset button or First turn ON the printer then plug the USB cable.

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