High Speed Outputs
Pulse-Width Modulation (PWM) Output The pulse output of the Micro PLC can also serve as a PWM output port. Pulse-Width Modulation (PWM) is a highly efficient and convenient way of controlling output voltage to devices with large time constant, such as controlling the speed of a DC motor, the power to a heating element, light brightness control or the position of a proportional valve. PWM works by first turning the output to full voltage for a short while and then shutting it off for another short while and then turning it on again and so on in accurate time intervals. The advantage of using PWM is that you can easily amplify the drive current to a larger load such as larger permanent magnet DC motor by using low cost DC Solid-State Relays (SSR) to boost the current switching capability. Using SSR has the added advantage of isolating the CPU from the high current load.
PWM as Analog Voltage Output
Inverter
Rievtech Micro PLC
Low-cost analog output
R1
DC 12-24V
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C1
+
PWM Output
Com
Vin
GND
Width of pulse (a)
Width of pause (b)
V full
a + b x V full a
Avarage voltage
Modulation period
The speed can be controlled by changing the pulse width of the PWM output.
ter
Cut
r
ode
Enc
The output can also serve as an analog voltage output when a smoothing capacitor is inserted in the circuit. One of the application examples such an analog voltage output is an inverter speed control.
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Mo
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Inve
PL C
icro
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ut
vtec
utp
Rie
M O
PW
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