Obviously, when the switch is opened, dimmer #4 goes to zero, then dimmer #3 ramps down to zero, then #2, and finally #1 circuit. Help please.” I only had the Arduino UNO board and a couple of LEDs so ...

Similarly, one BS170 mosfet was used in my prototype to drive the 3 x White LEDs strip. This part number (and ofcourse the LED type) is not very critical. If you want to use a bi-polar transistor, don ...