Analog input - Mitsubishi FX3G PLC / GX Developer

Good Evening,

I am an under graduate engineering student presently working on a project involving the Mitsubishi FX3G PLC.

I plan to programme the PLC using GX developer.

At present I only have one Analogue input I wish to input to the PLC and I will be doing this through the use of a Special Function Block (Mitsubishi FX2N-4AD)

The input will be a simple voltage input of -10 to +10 Volts.

I have referred to the relevant manuals and so far I have came up with the following ladder logic:

----|M1|------[TO K0 K0 H3330 K2]--------
|
|
--[FROM K0 K10 D10 K2]-------

Can anyone advise as to their thoughts on what I have so far produced.

The idea behind the system is to obtain a value from the A/D converter and then put together a HMI design that could then utilise the information.

Any help would be greatly appreciated.
Thank You in advance.
Joe

Just a brief update on this thread. Today I managed to get onto GX developer and input the ladder logic from the above post, I noticed on GX developer that my ladder logic takes up 20 steps.
Once I ran the programme on GX Developer I noted that a blue '0' appeared below the from command, I can only assume that this is the programme representing no voltage input? Please correct me if I am wrong.
I am planning on downloading the programme to the PLC on Thursday and hooking up a power supply to the FX2n-4AD under the hope that I can simulate a voltage input, and hopefully get a value appearing in the place of the blue '0'.
I shall keep this updated as I go, however I would appreciate any information or guidance.

Thanks in advance.

Hello,

The blue '0' is the digital value returned from the A/D converter. You can very easily simulate a voltage input with regular batteries. Off the top of my head the digital values returned will be 0-4000 so using a 9 volt battery should return a value of ~3600.

Hope this helps,
Dave

if you want read voltage you should set[k0 k0 hff00 k2].
That meansnly channel 1 and 2 you can use channel 3&4 is off.
In my project i measure volts in truck car by 4A/D mitsubishi and i use potentiometer to calibrate volts.After that set up you hmi the minimum and maximum value for display(meter). Your second command is good.But remember about channels.
for read you can also use that command:
BMOV U0\G10 D2

Thank you for the responses.
Today I managed to carry out a functional test and after a few alterations I was able to get the programme working as desired.
My errors were that I had used the table of BFM# values in the latest FX3G user guide, however, referring to the FX2N manual the BFM values were quoted differently.
I also had to set an initial pulse M8002 at the beginning to set M1.
Once this was complete I got the programme running and from my 0 - 10V input I received a value in monitor mode of 0-2000.

dploof23 - you were correct about the blue '0' thank you for your help.

artmierz - reading the voltage worked fine with H3330, I referred to the FX2N manual and it says the channel selection is made by the 4 hex number in BFM#0. The least significant bit represents channel 1 and the 4th bit controls channel 4. The parameters are as follows: 0= pre-set -10-+10Volts, 1= pre-set 4-20mA, 2 = pre-set -20-+20mA and 3 = channel off. I will look into what you have said and I will also look at the BMOV U0\G10 D2 command. Thank you for your time and advice.

Once I had ran the programme today, I began to look at how I will make the PLC communicate with DAQ factory (the software I will be using to configure my HMI). I couldn't manage to get the PLC to communicate with DAQ factory successfully, although I have read online that the FX3G will not communicate with DAQ factory on an FX Direct protocol?
This made me begin to look at a FX3G-485-BD add on for the PLC in order to make it communicate via an RS485 connection. Has anybody had any experience of using this?

Once again thank you for the help so far.

Regards.

Its been a while, so I thought I would post an update on this thread.

I have now managed to obtain a 4-20mA D.C. Current supply so I can now simulate a 4-20mA signal as opposed to using the 10V power supply.

An issue I have now encountered within GX Developer, is that when the FX2N is receiving no current (signal) it displays -250, which I understand is because to display zero 4mA is required, however, rather than just display the -250 statically, it flashes between -250 and 0 on the GX monitor mode screen.

This takes me onto my next problem which is now I am linking the PLC to DAQ factory, when I operate the signal between the range of 4 and 20mA the HMI works fine, however, when I disconnect the current loop the HMI Variable Value displays 32517. I have found a relationship between the value and that is because it is a 16 bit system (32768) if I minus the -250 that is displayed on the GX screen this will give me roughly 32517, the number I am being displayed with. Can anyone suggest what the issue is and how I can correct this so that the HMI does not present this value.

Thank you in advance,

Hello,
I am not sure if I understand what you are asking, but if you would like to stabilize the display when your current drops to below 4ma, you could write into the logic a compare so when ever the value is <0 you move a zero into the data register you are monitoring. Once the value is >0 the normal reading would take back over.

Hope this helps,
Dave

The display on GX Developer has now been resolved, I have re-produced the programme and after converting it appears to now present the value in a much more stable state.

As for the DAQFactory side, I was receiving the 32k number as opposed to the negative 250 I was being displayed with on the PLC software. This has now been rectified by implementing the following sequence:

private fred
while (1)
fred = Device.FX3G.ReadS16("D10",1)
if (Private.fred[0][0] > 32255)
ANA_10.AddValue(Private.fred[0][0]-32767)
else
ANA_10.AddValue(Private.fred[0][0])
endif
delay(1)
endwhile

After implementing the sequence, a stable negative number has now been produced.

I have now specified a new command that when the number drops below zero it initiates a comms fail alarm, this is due to the use of a 4-20mA signal.

Once again thank you for your input.

Regards.