I design microscopes and need to build and move optical devices using stepper motors and servos. I was helped by the experts in this workshop a few years ago and have since become more able to write code for Arduino. I was surprised to find that a cheap servo could be used to set the opening of a photographic iris without any need for a homing device, and I have posted the code and the details here for doing this and getting a display of the absolute angle of the servo rotor, which I previously thought could only be done with a stepper with a homing switch. I hope someone finds this useful. It was also my first foray into using an OLED display, which is very useful because microscopy has to be done in a darkened room.