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Actuators
Published in Volker Ziemann, A Hands-On Course in Sensors Using the Arduino and Raspberry Pi, 2018
In the example shown in Figure 3.3, the 1 kΩ resistor on the base limits the input current across the base-emitter link to 5 mA, provided the control voltage is 5 V. If the transistor has an amplification of 100, which is typical for many small signal transistors, it can switch up to 500 mA, which is more than is actually needed in this case. The actual current flowing through the collector-emitter link is determined by the 12 V supply voltage to the LED and the 680Ω resistor limiting the current. Note that using the transistor also decouples the voltage level of the controlling circuitry and the supply voltage, here 12 V, of the consumer, the LED. This way of operating a transistor is called open collector, because we can think of the collector terminal as a generic connection point for an (almost) arbitrary load that is connected to its own supply voltage. If the emitter-collector link is in the nonconducting state, no current flows, and the load is turned off. If a positive current flows into the base terminal, the emitter-collector link becomes conducting, the lower terminal of the load is shorted to ground, and a current flows from the load’s power supply through the load and turns it on.
Sequentially automated extraction of nucleic acids with magnetophoresis in microfluidic chips
Published in Instrumentation Science & Technology, 2023
M. Kashif Siddique, Ruizhi Lee, Songjing Li, Lin Sun
Accurate determination of the system’s initial position is crucial for fluid injection into the microcavities of the microfluidic chips. An MITG PM-F45 optical sensor, based on an NPN open-collector transistor, is utilized for this purpose, with a response time of less than 80 microseconds. The voltage value from the sensor is monitored to calculate the start position, and when the optical sensor detects the start pointer, it halts the stepper motor rotation. The system then calibrates the position based on the maximum voltage value detected by the optical sensor. Six microfluidic vacuum pumps, Skoocom SC3701PM, are responsible for precisely loading and unloading biomedical samples, reagents, and elution solutions into the microfluidic chips. These pumps create suction to transfer the desired fluids into the microfluidic channels, ensuring accurate and controlled delivery of the necessary substances for the experimental process.
Retrofitment of a CNC machine for omni-directional tungsten inert gas cladding
Published in Virtual and Physical Prototyping, 2019
Sajan Kapil, Pravin Kulkarni, Prathamesh Joshi, Seema Negi, K. P. Karunakaran
While moving on a trajectory, the desired angle of rotation of wire has to be calculated. The encoders are sampled during constant time intervals and the pulses are accumulated in the registers of X and Y encoders. The angle of orientation () at any sampling count is given by the following expression.A proximity sensor is used to preserve the reference/home position of the wire feeding nozzle. This sensor also makes sure that the wire feeding nozzle should not cross the home position and avoids winding of wire around the torch. Figure 10(b) shows the mounting of an encoder with a fixture and housing on a leadscrew of a 3-axis CNC machine. These are incremental encoders (Resolution: 1024 PPR; Voltage: 24 VDC; Output: Open collector NPN 24 VDC; Number of channels: 2 quadrature output). The encoders will give output in pulses (each pulse will correspond to leadscrew motion) those are input to the PLC. This PLC has 14 I/O configuration with 8 inputs and 6 outputs. Figure 10(c) shows the different components of the PLC. By using the above discussed logic in PLC one can get the incremental angle of rotation of the wire feeding nozzle (see Figure 11). This angle of rotation will be then transferred to the stepper motor through its drive. The complete process of omni-directional TIG cladding operation is summarised in a flowchart shown in Figure 11. The entire cladding system has been integrated with the existing CNC machine and experiments have been performed using the HLM process.
Development of Data Acquisition and Protection System of Infrared Thermometer for EAST NBI
Published in Fusion Science and Technology, 2018
C. D. Hu, W. Liu, C. C. Jiang, L. Z. Liang, S. Liu, S. H. Song, J. X. Wang, L. Tao
The AD650 used in V/F and F/V circuit contains advantages of high-frequency operation and low nonlinearity previously unavailable in monolithic form.8 A wide range of input voltage used by a flexible input configuration and simple interfacing to either standard logic families or optocouplers is allowed by open-collector output with separate digital ground.