Project: Time delay switch for mobile chargers:

Dear All

Here is useful project.
Time delay switch for mobile chargers:

Most of the mobile phone batteries can be fully charged within 2 Hours of time. This circuit is useful especially night time. Before going for sleep, we can put the charger on and go for sleep. Don t worry about over charging, this circuit will switch off the charger after 2 Hour. This is a simple monostable multi vibrator, which will switch on the circuit for a particular time period. When the circuit is in standby mode, transistor Q1 does not conduct, since its base is floating. When the switch( SW1 ) is pressed and current flows through R5 and the switch to provide positive bias to transistor Q1. Transistor Q1 conducts and its collector voltage drops, which acts as a negative trigger input for the monostable. Here a pulse will be generated 7200 second duration ( 2 hour ). See the attachment.

Hi,

Current cell phones can be left on charge without detriment, since they contain a complete charge control system.

Not having an automatic system in the phones would be dangerous, as most use lithium batteries.

This would be useful though for some dumb chargers such as those used on some commercial hand held radios.