This circuit has a sensitivity of 2uW. We found it in documentation from the 1980s. The integrated circuit is from that time. Equivalents can be tried.
This circuit was found in a 1970 Philips documentation. The components are from the time, and...
This circuit uses two sensors that are placed at the intersection of a miniature railway, causing...
This application is not modern since few computers have parallel ports. But you can use this...