Industrial 0V to +10V Digital
abstract: ac and dc motors in modern industrial systems are often controlled via programmable logic controllers (plcs) where an industrial mechanical potentiometer controls the motor speed. the wiper of these potentiometers can become worn over a period of time. this article discusses a simple circuit using few solid-state surface mount devices. it uses a digital potentiometer to achieve the same performance, eliminates problems with wiper contacts wearing out, and saves money in the long run.
dc and ac motors in modern industrial systems are often controlled by programmable logic controllers (plcs) located in a control room safely away from the process. if an operator must set the motor speed manually while observing the process, the component of choice is usually an industrial-grade potentiometer, whose wiper produces a 0v to 10v signal that feeds back to a motor controller in the control room. such potentiometers are expensive and prone to wear. with wear they can open the control loop, allowing the motor speed to ramp up and out of control.
with a few components, a reliable, low-cost, all-surface-mount, solid-state digital potentiometer can be implemented for industrial applications (figure 1). the result is a direct drop-in replacement for the wear-prone mechanical potentiometer, and it occupies the same space within an electrical enclosure. it takes power from the +10v formerly supplied to the mechanical pot from the motor controller. the solid-state pot provides a similar 0v to 10v output, and delivers as much as 15ma to the controller.
figure 1. this solid-state industrial potentiometer simulates an equivalent mechanical potentiometer, and fits in the same space.
the key to this circuit is a low-power digital potentiometer ic, 100kω version (u3). configured as a voltage divider, this ic provides an output of 32 discrete voltage steps between its minimum and maximum settings (0v and 5v). a low-power linear regulator (u1) provides a +5v supply rail for u2, u3, and a resistor ladder internal to u3 (whose maximum rating is +5v).
pb1 and pb2 constitute a double-pushbutton industrial switch. each high-to-low transition produced by pb1 increments the digital potentiometer's wiper by one step (depressing pb2 while toggling pb1 decrements the wiper by one step). u2 is a switch debouncer that provides (in addition to the debouncing) a 40ms fixed delay between its outputs and the switch action.
to provide 0v to +10v outputs as required by the motor controller, a single-supply, rail-to-rail op amp (u4) amplifies the u3 output by a factor of two. the input common-mode range for this op amp, (250mv beyond either supply rail), allows it to generate 0v to +10v outputs like a mechanical potentiometer. the 1% resistors r1 and r2 set the op amp gain to 2v/v.
the circuit's low quiescent current ranges from 86µa for a 0v output to 186µa at +10v. to lower this quiescent current, choose the 200kω version of u3. because the op amp is stable for any capacitive load, it easily drives long, shielded, multi-conductor cable runs back to the control room. another benefit of the all-surface-mount solid-state construction is important for class 2 enclosures: its lower power dissipation produces less heat within the electrical enclosure.
a similar version of this article appeared in the september 20, 2001 issue of edn magazine.
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dc and ac motors in modern industrial systems are often controlled by programmable logic controllers (plcs) located in a control room safely away from the process. if an operator must set the motor speed manually while observing the process, the component of choice is usually an industrial-grade potentiometer, whose wiper produces a 0v to 10v signal that feeds back to a motor controller in the control room. such potentiometers are expensive and prone to wear. with wear they can open the control loop, allowing the motor speed to ramp up and out of control.
with a few components, a reliable, low-cost, all-surface-mount, solid-state digital potentiometer can be implemented for industrial applications (figure 1). the result is a direct drop-in replacement for the wear-prone mechanical potentiometer, and it occupies the same space within an electrical enclosure. it takes power from the +10v formerly supplied to the mechanical pot from the motor controller. the solid-state pot provides a similar 0v to 10v output, and delivers as much as 15ma to the controller.
figure 1. this solid-state industrial potentiometer simulates an equivalent mechanical potentiometer, and fits in the same space.
the key to this circuit is a low-power digital potentiometer ic, 100kω version (u3). configured as a voltage divider, this ic provides an output of 32 discrete voltage steps between its minimum and maximum settings (0v and 5v). a low-power linear regulator (u1) provides a +5v supply rail for u2, u3, and a resistor ladder internal to u3 (whose maximum rating is +5v).
pb1 and pb2 constitute a double-pushbutton industrial switch. each high-to-low transition produced by pb1 increments the digital potentiometer's wiper by one step (depressing pb2 while toggling pb1 decrements the wiper by one step). u2 is a switch debouncer that provides (in addition to the debouncing) a 40ms fixed delay between its outputs and the switch action.
to provide 0v to +10v outputs as required by the motor controller, a single-supply, rail-to-rail op amp (u4) amplifies the u3 output by a factor of two. the input common-mode range for this op amp, (250mv beyond either supply rail), allows it to generate 0v to +10v outputs like a mechanical potentiometer. the 1% resistors r1 and r2 set the op amp gain to 2v/v.
the circuit's low quiescent current ranges from 86µa for a 0v output to 186µa at +10v. to lower this quiescent current, choose the 200kω version of u3. because the op amp is stable for any capacitive load, it easily drives long, shielded, multi-conductor cable runs back to the control room. another benefit of the all-surface-mount solid-state construction is important for class 2 enclosures: its lower power dissipation produces less heat within the electrical enclosure.
a similar version of this article appeared in the september 20, 2001 issue of edn magazine.
安科瑞Acrel-1000变电站综合自动化系统
电磁干扰的来源及抑制措施解析
浅析我国电子垃圾处理行业政策及现状
奥拓电子智能一体机解决方案已应用于众多知名高校
88E1518-A0-NNB2C000以太网收发器Marvell
Industrial 0V to +10V Digital
智能IC卡水表的结构原理及采用LSD4F8108 MCU的设计方案
对石化行业储罐如何进行安全监测
Vishay宣布将缩短MLCC供货周期
一加手机怎么样_和华为哪个好
为什么Eplan经过培训以后依然很难用起来
晶优光伏首次亮相Intersolar Europe 创新组件定制模式吸睛无数
会议室监控中心指挥中心P1.875小间距全彩LED大屏价格
灰尘传感器的应用，在扫地机器人上的作用分析
电子元器件口碑之选 松腾电工实至名归
Littelfuse推首款277V保险丝 专为危险区域高压应用而设计
深化汽车电子赛道布局，国民技术发力车规芯片
西门子博途S71500通过PROFINET组态HMI连接
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高合HiPhi X是华人运通旗下首款量产可进化超跑SUV