NE555定時器的制作的電壓頻率轉(zhuǎn)換器,NE555 V-F CONVERTER

關(guān)鍵字：基于NE555定時器的低價格電壓頻率轉(zhuǎn)換器

　　NE555定時器和Miller積分器結(jié)合組成電壓到頻率轉(zhuǎn)換器，價格低于50美分。

　　1971年，Signetics——Philips的前身——生產(chǎn)了NE555定時器，目前制造商每年仍生產(chǎn)超過十億件產(chǎn)品。通過給NE555增加一些器件，可以構(gòu)造價格低于50美分的簡單電壓頻率轉(zhuǎn)換器。電路包括NE555定時器和基于TL071的Miller積分器（圖1）。應(yīng)用中輸入電壓為0到-10V，產(chǎn)生0到1000Hz的輸出頻率范圍。C₁的電流為輸入電壓的函數(shù)：IC=–VIN/(P1+R1)。

　　C₁的電壓達到V_CC的2/3時，定時器的內(nèi)部放電晶體管打開，C₁的電壓回到V_CC的1/3，比較器的低閾值。到電壓的1/3處，放電晶體管關(guān)閉，C₁再次開始充電。C₁充電時，NE555的輸出為高，而C₁放電時，NE555的輸出為低。輸入電壓和C₁充電時間的乘積為常數(shù)。因為放電時間小于充電時間，下面的公式計算了輸出頻率f_OUT~V_IN/(P₁+R₁)×C₁×1/3V_CC。

　　P₁校準了輸出頻率和輸入電壓的關(guān)系。因為放電時間約為30µs，電壓頻率轉(zhuǎn)換的精度隨頻率的增加而降低。如果設(shè)定100H

　　英文原文：

　　NE555 timer sparks low-cost voltage-to-frequency converter

　　The combination of an NE555 timer and a Miller integrator yields a voltage-to-frequency converter that costs less than 50 cents.

　　Gyula Diószegi and János Nagy, Divelex Ltd, Budapest, Hungary; Edited by Charles H Small and Fran Granville -- EDN, 2/21/2008

　　In 1971, Signetics—later Philips—introduced the NE555 timer, and manufacturers are still producing more than 1 billion of them a year. By adding a few components to the NE555, you can build a simple voltage-to-frequency converter for less than 50 cents. The circuit contains a Miller integrator based on a TL071 along with an NE555 timer (Figure 1). The input voltage in this application ranges from 0 to –10V, yielding an output-frequency range of 0 to 1000 Hz. The current of C1 is the function of input voltage: IC=–VIN/(P1+R1).