I am very satisfied with this mod and I now have a laptop with a very useful feature – a keyboard with backlight.
The keyboard works perfectly, you can switch the backlight ON/OFF by pressing Fn-F9. After some time, when you don’t use the keyboard, the backlight switches off.
I truly recommend you try this yourselves. It is easy to implement and at a very reasonable price.
My laptop is Acer Aspire E5-575G – 50JT model N16Q2 that came with the standard keyboard without backlight.
I broke the keyboard and I started to look up on the Internet for a new one. I then saw that there is a backlit keyboard for my laptop, only 5EUR more expensive than mine! I bought it and started thinking how to manage the backlight power supply of the keyboard. The model printed on the keyboard is LV5P_A51BWL.
The keyboard has a separate cable for the backlight with 2 wires ending with four pins – 1 for negative, 2 for positive power supply and 1 that is not used.
I tried to put the backlight cable in the right position and started looking if there is a place on my motherboard for connecting the backlight cable.
I discovered there is one indeed, but the elements that must be soldered there were missing.
I made some measurements and found out that there is a power supply +5V and a control signal on the motherboard.
I soldered the missing elements following this scheme, made based only on my experience and the motherboard PCB layout.
And with the soldered elements.
The necessary element are:
R1 – 680 ohms
C1 – 470 nF
T1 – standard NPN low power transistor, I used BCW66
T2 – MOSFET P-channel , I suggest with Id >1A, I used IRLML6402
And that’s all. Now your Acer E5-575G has backlit keyboard.
If I could help you saving time by reusing my ideas, consider contributing this project.