CUI DEVICES | SERIES: CFM-40V | DESCRIPTION: DC AXIAL FAN

date 08/12/2022 | page 9 of 11

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APPLICATION NOTES

Figure 1: Auto Start Protection

Auto Restart Protection

When the fan motor is locked by an external force, the device will temporarily turn off electrical power to the motor and restart

automatically when the locked rotor condition is released.

Tachometer Signal (Yellow Wire)

The tachometer signal is for detecting the rotational speed of the fan motor. The output will be a square wave when fan is operating and

logical high (Vcc) when fan motor is locked (See Figures 4~5 below). The relationship between RPM & output pulses from the signal wire is

as follows.

1 RPM = 2 Pulses

1 Pulse

1 RPM

Run

Locked

Vsig

t

VL

Vcc

Figure 5: Tachometer

Output Circuit

DC Fan

Red (+)

Yellow

Black (-)

Customer Circuit

Vcc

Ic

RL

Vcc ≤ max input voltage

Ic ≤ 4 mA

RL ≥ Vcc/Ic

VL ≤ 0.5 V

Vsig

Figure 4: Tachometer

Output Waveform

Rotation Detector Signal (White Wire)

The rotation detector signal is used to detect if the fan motor is operating or stopped. The output will be logical low (VL) when fan is

operating and be logical high (Vcc) when fan motor is locked. (See Figures 2~3 below).

Figure 2: Rotation Detector

Output Waveform

Figure 3: Rotation Detector

Output Circuit

Run

Locked

Vsig

t

VL

Vcc

DC Fan

Red (+)

White

Black (-)

Customer Circuit

Vcc

Ic

RL

Vcc ≤ max input voltage

Ic ≤ 4 mA

RL ≥ Vcc/Ic

VL ≤ 0.5 V

Vsig

Run

t

Locked

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