GX developer: Forcing a Digital Input ON

[Mas01]

In GX developer, is there a way of forcing a digital input to ON (e.g. X070 to TRUE/On). I've just installed a QX10 module and I want to check that the PLC recognises X070=TRUE by displaying the LED for the appropriate channel on the front of the module.
Thanks

 

[Mas01]

Edit....
I just tried Online/Debug/Device test...
Then I set X070 to FORCE ON
but no LED lit up on the front of the module.
For info, there are no devices connected to this module yet. The wires just go to a terminal strip and finish there.

 

[Ronnie Sullivan]

Quick answer = No (maybe for 1 scan)

 

[tdoa]

The led is wired in such a way that it needs 24v on the input to light up, forcing the input ON wont put 24V on the input.

If its all cabled up, grab a piece of wire and connect the input to 24V.

 

[Mas01]

The led is wired in such a way that it needs 24v on the input to light up, forcing the input ON wont put 24V on the input.

If its all cabled up, grab a piece of wire and connect the input to 24V.

The QX10 module has printed on the front panel "100VAC". Also the module specification says "Rated input voltage 100-120VAC.". What makes you say 24V?

 

[Steve Bailey]

The QX10 module has printed on the front panel "100VAC". Also the module specification says "Rated input voltage 100-120VAC.". What makes you say 24V?

The AC voltage rating is for the input signal. It will be true when the valtage at the terminal exceeds 100 VAC. The indicator LED is on an internal 24 VDC circuit.

The PLC CPU only requests data from the input module about whether the input points are on or off. It does not send any information to the input module about whether or not the points are forced.

 

[Mas01]

The AC voltage rating is for the input signal. It will be true when the valtage at the terminal exceeds 100 VAC. The indicator LED is on an internal 24 VDC circuit.

The PLC CPU only requests data from the input module about whether the input points are on or off. It does not send any information to the input module about whether or not the points are forced.

Thanks for this.
So if I get my hands on a 24VDC power supply, how do I connect it to the channel to test it out?
Do I connect the power supply +ve to the terminal block and the -ve to COM ?

 

[Steve Bailey]

What are you trying to test? Forcing the input on in GXDeveloper does not apply voltage to the input terminal on the module. It only makes the PLC program behave as if the input were actually on.

 

[Mas01]

What are you trying to test? Forcing the input on in GXDeveloper does not apply voltage to the input terminal on the module. It only makes the PLC program behave as if the input were actually on.

I'm trying to test the channels into the module. My understanding is that the little LEDs on the front of the module only light up when it sees 24VDC as an input. So I want to use a power supply (only for test purpose), connect it to say the first channel and the appropriate LED should come on.
This is the first time I've installed a QX10, so all a bit new to me.

 

[tdoa]

The QX10 module has printed on the front panel "100VAC". Also the module specification says "Rated input voltage 100-120VAC.". What makes you say 24V?

Sorry, its very rare for me to use IO at anything besides 24V DC..

The same concept applies, grab a 120V AC and connect it to your input, take a bit more care handling the wire.

 

[parky]

The QX10 is 100-120VAC so will not work on 24V, you need to connect 110v AC you need to use the QX80 for 24V DC

 

[Steve Bailey]

You can't test the physical wiring of an input circuit by forcing that input in GXDeveloper. That's not what forcing does. Forcing only makes the program in the PLC behave as if the input point was in the on/off state dictated by the force.

 

[Mas01]

The QX10 is 100-120VAC so will not work on 24V, you need to connect 110v AC you need to use the QX80 for 24V DC

Ok thanks for this. There are no QX80 modules in our PLC, they're all QX10.
So do I connect the power supply + to the terminal block (this goes to channel 0 on the module), and the power supply -ve terminal to COM (this goes to the terminal labelled COM on the module)?

 

[parky]

It depends on the circuitry in the card, some may Drive the LED from the internal 5V bus, some will drive it directly (via a resistor before the opto isolator i.e. on the input side. so as it is a QX10 then you cannot drive the LED with 24v or 5V (as some are) to test the input then you must apply the correct voltage for the card in the case of QX10 then it must be between 100-120v AC.
Forcing an input on will only force the image bits, the PLC copies the real inputs to an internal image before the main program scan (there are exceptions like forcing the real inputs to update the input image during scan).
likewise, the output image is copied to the real output image at the end of the main program scan (well in Mitsubishi anyway). This is common on many PLC's in other words the update of the I/O image is synchronous, there are some that use asynchronous, and most will allow forcing of I/O update by interrupt or during program scan.
Many in PLC's, forcing an input will cause it to be on for only one scan as the inputs are updated synchronously, however, there are some that have an enable bit associated with each input (or output) so that it can be forced on in the program regardless of the state of the real I/O or program controlling it.

 

[Mas01]

It depends on the circuitry in the card, some may Drive the LED from the internal 5V bus, some will drive it directly (via a resistor before the opto isolator i.e. on the input side. so as it is a QX10 then you cannot drive the LED with 24v or 5V (as some are) to test the input then you must apply the correct voltage for the card in the case of QX10 then it must be between 100-120v AC.
Forcing an input on will only force the image bits, the PLC copies the real inputs to an internal image before the main program scan (there are exceptions like forcing the real inputs to update the input image during scan).
likewise, the output image is copied to the real output image at the end of the main program scan (well in Mitsubishi anyway). This is common on many PLC's in other words the update of the I/O image is synchronous, there are some that use asynchronous, and most will allow forcing of I/O update by interrupt or during program scan.
Many in PLC's, forcing an input will cause it to be on for only one scan as the inputs are updated synchronously, however, there are some that have an enable bit associated with each input (or output) so that it can be forced on in the program regardless of the state of the real I/O or program controlling it.

Thanks for the reply. My only objective was to "exercise" a few of the input channels, just to get some confidence that I had installed it correctly. To this end, I have installed my QX10 in the same manner as the existing 4 x QX10 already in the PLC.
All I was trying to achieve was to see the LEDs illuminate.