Sensor for heart monitor (CB21075E)

We found this heart rate sensor circuit in a Popular Electronics from the 90s. The placement of the emitter and the receiver is important.

| Clique na imagem para ampliar |

Interface SCR and Relay (CB12106E)
This interface was found in a Modern Electronics magazine from 1990. Although the circuit is...
Audio Priority Switch (CB12434E)
We found this circuit in a 1981 publication. We applied an audio signal, for example, a music...
Voltage Follower with the CA3140 (CB12304E)
In a voltage follower, the voltage gain is unitary, the input impedance is very high, and the...