Recently in a limit move slowly into the motor control design, need to use the photoelectric switch, online check found that Taiwan's light ITR9606 and omron of EE - SX498, but the price difference is too big, too, a light at 1.5 yuan, omron $27, BBS of the warrior guidance about how to choose, the output of the omron detection side is 3 feet need 5 v power supply, but the measurement result is higher transmission ratio, if is light pull-up resistor set a larger can also tell the level of high and low,