PT#9 LED Cube RGB Charliecube Ghosting Fix

Hello, we meet again in this video, I will not talk about the software yet but I want to talk about the glitch of this cube I found a little problem in this cube so these LEDs, when we turned it on as you can see here hope you can see it clearly at the camera those LEDs which supposed to be off some are showing a little dimmed red light they are very dimmed, but we can see them so in this video, I want to share how to fix those ghosting problem ok so.



these RGB LEDs, are having different forward voltage for each of the colors forward voltage is the voltage needed to turned on the LED for each colors, and they are different and the red one is the one having the lowest forward voltage may be around 1 volt so, when there is a little leakage to the LEDs, the red one can easily turned on we will fix this problem with a little modification I will try by using a component I will try to add a diode and there will be a component to be replaced so I am looking for a way to add the diode without changing the board so, this switch, when we slide it on, the circuit won't turned on directly because we have the soft latch circuit onboard so we need to press the soft latch button, then the circuit will be on so, I will choose to remove the switch and replaced it with the diode the purpose is to drop the voltage a little since this is 5V being used here and in the kit I prepared, I gave the USB to DC jack cable and usually we have 5V for USB power source so, hopefully the diode would drop the voltage low enough so it won't light the Red LEDs OK, now it is turned on as you can see, the red ghosting is now gone since the voltage already dropped by the diode the dropped voltage may be around 0.

7V not so big, but low enough so it won't light the red LEDs ok, seems there is a problem, definitely need a fixed so after I tested it 1 whole night the diode solution is not works well I am not sure why, but the diode causing problem to the soft latch circuit so the soft latch circuit can not be controlled by the microcontroller and the power can not be turned off and this cube is on until morning, because the micro always failed to turned it off I even tried to change the diode's position to the Fet's drain leg and it still not working right the circuit still won't turned off so finally I decide to change the solution instead of using the diode, I am using an LDO a Linear Drop Out it is 3.

3V regulator LM1117T fortunately, the pin for this regulator can fit perfectly to the PCB it have Ground Output Input pins, which position is at the right place for this pcb so from the 3 hole here, the output is at the middle, and input at the right one and the first pin at the left, must be connected to Ground at this pcb, that first hole is not connected to anywhere so, here I soldered it like this and for the first pin, connected to Ground through the Ground Plane at the back for the PCB so most of the back part at this PCB is Ground plane so I removed the masking a little, and soldered that pin to it and this is works perfectly let me put them back together first so after I use the regulator first I was planning to drop the voltage to 4 V, but since I don't have regulator with that output value, I use a 3.

3V regulator it is to removed the ghosting, so the LEDs that supposed to be off, really stays off this is the result functioning perfectly so, the soft latch circuit also working as it should now the micro can turned off the circuit again so it must using a linear regulator, instead of diode so can not use diode, I don't know why, may be need another capacitors but I don't want to add too many additional components so I only add this regulator to replace the switch maybe next time if I found a regulator with 4 V output, I will use that instead but for now, this works well ok, thats it thank you for watching.

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