| 摘要 |
<p>PURPOSE:To unnecessitate an expensive A/D converter and to enable A/D converting even with a microcomputer without a dedicated terminal such as a serial input, etc., by using a general purpose input port and an easy V-F converting circuit. CONSTITUTION:A system consists of a V-F converter 1 converting an analog signal Vin into a pulse having a frequency corresponding to an input voltage and the microcomputer 2 which measures pulse width outputted from the V-F converter 1 and also converts it into digital data so as to execute an processing. The V-F converter 1 is provided with a integrator 3, a comparator 4, resistors R1-R5, a capacitor C and a transistor TR. The integrator 3 outputs the triangle wave of the frequency being proportional to the Vin voltage and the comparator 4 reshapes it to be a square wave. The output of the comparator 4 inverts a polarity by the transistor TR so as to feed it back to the integrator 3. The microcomputer 2 can obtain the input voltage of Vin by measuring pulse width outputted from the V-F converter 1.</p> |
