Pololu Adjustable 9-30V Step-Up/Step-Down Voltage Regulator S18V20AHV Logic Analyzer Each phototransistor uses a capacitor

Each phototransistor uses a capacitor discharge circuit that allows a digital I/O line on a microcontroller to take an analog reading of reflected IR by measuring the discharge time of the capacitor

but it can be found in ST application note AN4545 (706k pdf) and design tip DT0037 (386k pdf)

which lets you use voltages above your stepper motor's rated voltage to achieve higher step rates

35-mm-Ausgangswelle des Schrittmotors befestigt werden

our 4-channel bidirectional logic level shifter can be used externally with those pins

Pololu Adjustable 9-30V Step-Up/Step-Down Voltage Regulator S18V20AHV Logic Analyzer Each phototransistor uses a capacitorThis powerful step up step down regulator efficiently produces an adjustable 9V to 30V output from input voltages between 3 V and 30 V while allowing a typical output current of up to 2 A when the input voltage is close to the output voltage and offering typical efficiencies of 80% to 90%. Its ability to convert both higher and lower input voltages makes it useful for applications where the power supply voltage can vary greatly, as with batteries that