Column: Optical isolation


Figure 5: Module 2 circuit


Figure 6: Module 2 connections


with the output path adds isolation and decoupling from high-frequency transient noises. A transient voltage suppressor (TVS) is used to filter out any transients entering from VOUT


. In this design, the circuit’s input is


powered by +12V, whereas its output is powered by +5.00V, +12V and −12V, isolated from the +12V at the input. Te circuit can supply up to 20mA. We have assumed that VIN


comes


from the DAC output of a 5V micro- controller with 0.00V ≤ VIN


≤ 5.00V.


When 0.00V ≤ VIN VOUT


= 2VIN ≤ 5.00V, − 5. Te input voltage range VIN = 0.00-5.00V, hence VOUT = −5.00V


to +5.00V; see Figure 3. Table 1 shows examples for input and


output voltages for the two modules, with the prototype circuit boards shown in Figures 4 and 7. To calibrate with S1 open: Set VIN


to


+5.00V, and by adjusting P1 make VOUT


= +5.00V. With S1 closed, the calibration


steps are: 1. Set VIN


to +5.00V and then by adjusting P1 make VTP1 = 0.00V, VOUT = +5.00V.


2. By adjusting P2, make sure that when VIN


= −5.00V and, also, 14 December/January 2023 www.electronicsworld.co.uk when VIN = +5.00V, VOUT = +5.00V.


Module 2 Figures 5, 6 and 7 show the optically- isolated analogue output Module 2, with its connections to the DAC output of a 5V microcontroller. As with Module 1, the circuit is also PUPIA3 based, with a high-linearity analogue optocoupler (HCNR201) providing photovoltaic isolation. Module 2 operates exactly the same


way as Module 1, and it contains all the same components as Module 1, but with R6, D3 (10V Zener diode) and C5


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