The use of microcontroller is in every field even we can use it in the design and fabrication of biomedical equipments. A little example is here. The microcontroller at89s51 (8051) is here used to develop a heart beat monitoring system. By placing your finger in between a LED and photo resistance, we can detect the pulses of heart, the analog voltages are further processed with an operational amplifier LM 358, this chip has two built in OPAMPs. The TTL pulses or digital pulse are then feed to the external interrupt of microcontroler 8051. By using a software counter in the code , we can count the pulses, and the result the process is displayed on an LCD (2 line 16 characters).