date 10/06/2021

│ page 6 of 7

CUI Devices

│ SERIES: CFM-40C │ DESCRIPTION: DC AXIAL FAN

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APPLICATION NOTES

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

Figure 1: Tachometer

Output Circuit

Figure 2: Tachometer

Output Waveform

Polarity Protection

Able to withstand 10 minutes of reverse polarity connection between the positive and negative wires without causing

damage.

Output Type: Open Collector

5 V fan: 3.3~5 V

All others: 3.3~15 V

Ic≤5 mA

R≥Vs/Ic

4 Pole Motor

N=RPM

T=60/N (sec)

FG=1/T*2 (Hz)

N=FG*30

Additional Resources: Product Page | 3D Model