What kind of output drives do US Digital encoders have?
The HEDS transmissive optical encoder module does a good job of sinking current (3.2 mA or 3.86 mA to ground), but they dont pull up to +5V as well (40 μA or 200 μA to +5V). The encoder module outputs are open collector with a 65 kΩ internal pull-up resistor. When driving a cable, they will provide good high-to-low transition times. But low-to-high times will stretch out in proportion to the cable length and capacitance. If a cable driver is not used, you can add a pull-up resistor (2.7 kΩ to 3.3 kΩ) to +5V on each output to improve these rise times. The EM1 transmissive optical encoder module will source and sink 8 mA at TTL levels.
