I have an alarm device. It convert 12v to 4,3V to the phone. It's outputs are 4.7V, GND, and two output to the phone buttons
If the inputs loop of the alarm device is opened that means the wire have been cut, so it gives a signal to the buttons, so the mobile is start dialing a given phone number. Now because the something went wrong with the previously phone. It was needed to replace the phone so I am trying to interface a motorola t191 to the alarm curcuit. If I give 4.3V direct to the phone it doesnt accept and show an "invalid battery" message. The battery has 4 pin. I measured the battery curcuit to figure it out how to attach my supply.
The pins of battery are:
- pin1 B- Battery negative
- pin2 BATID Battery ID
- pin3 TBAT TemperatureBat(thermistor)
- pin4 B+ Battery positive
I found the the schematics of the battery. http://monitor.net.ru/forum/files/motorola_t191_-_dorabotka_v_cepi_raz_ema_akkumulyatora_546.png
I took apart the battery I have. http://imgur.com/W73Y7K5
R1 is the battery id resistor
R2 is the thermistor
It is different then the curcuit above.
Is there a way to power this phone with my 4.3V external power, or a simple way to solve this? Any help is appreciated.
Best Answer
Well it is obvious that when you have 4.7V V between pins 1 and 4 while the phone accepts 3.7V then you'll have problems.
The solution would be to step down the voltage to 3.7V using various different methods. A voltage regulator would do the job.