Omron FQM1-MMA21 Output Wiring Precautions, Output Short-circuit Protection, Transistor Output

Wiring Precautions Section 3-6

3.Relation between FQM1 OFF current and sensor leakage current:

IOFF ≥ Ileak

Connect a bleeder resistor R if Ileak is greater than IOFF. Use the following equation to calculate the bleeder resistance constant.

R ≤ (RIN ⋅ VOFF)/(Ileak ⋅ RIN – VOFF)

Power W ≥ (VCC – VR)2/R ⋅ 4 [allowable margin]

Two-wire sensor

VR R

VCC

DC input

RIN

VCC: Power voltage

VON: FQM1 ON voltage

VOFF: FQM1 OFF voltage

ION: FQM1 ON current

IOFF: FQM1 OFF current

RIN: FQM1 input impedance

VR: Sensor output residual voltage

IOUT: Sensor control current (load current)

Ileak: Sensor leakage current

R:Bleeder resistance

4.Precautions on Sensor Surge Current

An incorrect input may occur if a sensor is turned ON after the FQM1 has started up to the point where inputs are possible. Determine the time re- quired for sensor operation to stabilize after the sensor is turned ON and take appropriate measures, such as inserting into the program a timer de- lay after turning ON the sensor.

Programming Example In this example, the sensor’s power supply voltage is used as the input to CIO 0000.00 and a 100-ms timer delay (the time required for an OMRON Proximity Sensor to stabilize) is created in the program. After the Completion Flag for the timer turns ON, the sensor input on CIO 0000.01 will cause output bit CIO 0001.00 to turn ON.

0000.00

TIM

0000

#0001

TIM0000 0000.01

0001.00

Output Wiring Precautions

Output Short-circuit Protection

If a load connected to the output terminals is short-circuited, output compo- nents and printed circuit boards may be damaged. To guard against this, incorporate a fuse in the external circuit. Use a fuse with a capacity of about twice the rated output.

Transistor Output	A TTL circuit cannot be connected directly to a transistor output because of
Residual Voltage	the transistor’s residual voltage. It is necessary to connect a pull-up resistor
	and a CMOS IC between the two.

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