PLC wiring diagram by relay control solenoid valve -

The principle of PLC control solenoid valve

PLC control solenoid valve, principle is, the switch output module of PLC, connected to the solenoid valve coil. When the module of the corresponding points, output voltage, electric solenoid coil, contact us. No voltage output, coil, losing electricity off contact.

PLC wiring diagram by relay control solenoid

there is a place to note that if your PLC is transistor output, the output of dot COM to 0 v, so pick the transistor output and relay output can do it.

the negative terminals of the PLC (COM) by relay

PLC/Y0 meet relay is end

a solenoid connect relay contact public end

solenoid valve normally closed relay contact head side by common

PLC control electromagnetic valve drive circuit 1, for light emitting diode ( Including light coupling device) Its current limiting resistors selection shall ensure that the diode current in 8 ~ 10 ma as well, such as low current is too small the luminous intensity ( Not bright) , optical coupling device for the luminescence brightness low optical coupling effect becomes poor. So the figure of 10 k resistor should be 2 ~ 3 k Ω.

2. If the 24 v supply to the PLC and the electromagnetic valve power supply is to use the same power, saves the light coupling device, drawing imaging I circuit, which can greatly simplify the circuit and it can reduce the point of failure.

from the picture, you use the PLC controller can be mitsubishi, the output circuit is negative logic, namely: the positive answer the COM common point of the 24 v power supply, the output switch ( Relay contact or transistor switch) In the outlet ( Yn） Negative extreme with 24 v power supply, so used shall be the PNP transistor, can form the minimalist output circuit, see below:

scheme used in the optical coupling isolation is main or to protect the PLC, the solenoid valve short break, insurance resistance Ω 22 May not be reliable, but the worst outcome is burning switch tube TIP. Scheme used in the optical coupling isolation is main or to protect the PLC, the electromagnetic valve short break, insurance resistance Ω 22 May not be reliable, but the worst outcome is burning switch tube TIP.

a: will I draw to the amplifier circuit form above, when the solenoid coil short-circuit, will not burned the PLC, the output reason: short circuit when R2 into still for PLC output load ( 10 k) ( The current is only 2. 4mA） 。 At this time due to the large coil short circuit to produce the short circuit current will harm of 24 v power supply, therefore can adopt the following two kinds of circuit power overcurrent protection role:

1, will fuse RD in the series circuit ( See XiaZuoTu) Too much, if produce coil short circuit, current will lead to RD to cut off the power supply is disconnected.

2, between G1 tube emitter and 24 v power supply through a resistor R4, R4 value = 1/10 ~ 1/20 of electromagnetic valve coil resistance, then use a 24 v relay and R4 in parallel, R4 then concatenated J0 relay the normally closed contact of ( See XiaYouTu) 。 Under normal circumstances, Y0 = 1 ( Output = 0 v) , G1 tube conduction, R4 = 1 ~ 2 v voltage, voltage solenoid = 22 ~ 23 v, so the electromagnetic valve can be normal. J0 by voltage is too small will not suck. Such as solenoid valve coil short circuit, the circuit becomes emitter follower circuit: the J2 = 24 v voltage and suck, the normally closed contact disconnect, cut off the R4, make the circuit won't produce too much current. Then use the normally open contact closure, a short circuit alarm signals. Here with relay protection, is considering coil short-circuit phenomenon is not often happened frequently, so don't have to consider the service life of the relay.

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