This circuit is from an old Mullard (Philips) manual with applications using the 555. Choosing appropriately the resistors and the timing capacitors, the ranges obtained can exceed days.
The traditional circuit was taken from a French magazine Radio Plans that no longer exists but can...
This circuit was found in an 80's Radio Electronics. The circuit multiplies the frequency of a low...
This circuit makes use of a 741 single source operational amplifier to measure resistors on a...