ATmega16 and 2X16 LCD to design a multimeter..............

Hi everyone
any ideal of how i can design a multimeter to measure voltage, resistance and capacitance using Atmega16 and an LCD. am using Stk500 board - Studio4 and WINAVR. any suggestion,direction is appreciated............thanks

hi tonire,
1. voltage: u will have to scale down the voltage to acceptable levels ( in the 0~5V range) before inputting it to the internal ADC of the mega16.
2. resistance: to measure this, u will ideally require a constant current source connected to the resistance to be measured so that the parameter can be converted to a proportional voltage which can be measured.
3. for the capacitance part, u need to measure the impedance of the capacitor under test by passing a high frequency signal through it or alternatively, use a 555 in astable configuration with the capacitor such that the frequency output is (inversely) proportional to the capacitance which can be measured by the uC.
:-)

[Topic moved to AVR Discussion Forum]

Thanks Pdi33 for the reply, can you please make the explanation a bit clearer maybe with a Circuit diagram.
Thanks.

well all he want to say is you need a signal conditioning circuit for scaling down the i/p full scale voltage to be measured, between the acceptable range of AVR internal ADC which is 0-5 V.

to make a conditioning circuit, you can use a resistance voltage divider + along with a zener diode to clamp voltage..

lets say you want to make a 0-15V voltmeter then circuit will be like this..