Phone Charging

ian field

Joined Oct 27, 2012
6,539
i want to do it in the cable. so that the phone will fell disconnected
Many phones flash up a battery full indication - a photo cell could detect that and trip a breaker circuit.

It would be unwise to tamper with the battery circuitry in any way - most phones use lithium cells, and those can catch fire if the charge control goes wrong.
 

KMoffett

Joined Dec 19, 2007
2,772
Sounds like a microprocessor (powered continuously by the USB) monitoring an inline current-sensing resistor and a MOSFET to disconnect the power when the charge current level drops.

Ken
 

AnalogKid

Joined Aug 1, 2013
8,157
Sounds like a microprocessor (powered continuously by the USB) monitoring an inline current-sensing resistor and a MOSFET to disconnect the power when the charge current level drops.
Or a comparator (no microcode).

Or the standard current shunt plus transistor base-emitter junction current sensor driving the series pass transistor. Two transistors, 3 resistors, and one cap, but 0.6 V drop across the sensor. Germanium?

ak
 
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