Published:2011/4/26 7:47:00 Author:Robert | Keyword: Gauge Head, Frequency Meter | From:SeekIC
As shown, 555 and R1, C1 etc. compose a monostable delay circuit, input square wave signal or the square wave signal after the shaping of Schmitt trigger, trigger 555.The circuitrequires the time constant R1C1<Tin, Tin is the cycle time of input pulse signal. Or, input signal can not trigger 555 every time, and flip it.
VT1, RP1 areconstant current source, by adjusting RP1 make the mA meter to be full scaleata frequency. The relationship between the gauge head and frequency is: when the frequency become higher, as the duty cycle increases, the average current increases too, the pointer deflectionis larger; otherwise, the deflection is smaller.
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