110v in digital input in MD2424 ?

[thomas3333]

Hello,
We have recently bought a T100MD2424 and two EXP1616.
But now, we need to read 110v DC (some mA) from digital input ?
Do these cards support it because in the documentation, it is written 24V maximum.
Do you have better product for our project ?
Thanks

[support]

The EXP1616R support 24V AC input so the best way is to use a small transformer to convert 110V to 24V AC to feed to EXP1616R.

The other possible method may be to use a resistor or a series RC circuit to the EXP1616R's inputs. The EXP1616R has input impedance of approximately 5.6K ohm so you have to add a resistor or RC circuit that can has impedance of approximately 15K ohm at 60Hz. Three quarter of the 110V will then be dropped across the RC circuit and 1/4 across the EXP1616R input.

Please note that you must exercise all precautions and put up warning label on the control panel if you are connecting live inputs to the PLC via series RC circuit, in order to prevent possible electric shock to the users or maintenance personnel.

[thomas3333]

Thanks for your answer. We found a solution and finally don't need 110V, 24V is better  

I've got another problem (perhaps may I create a new topic ?)
I want to write 16 outputs at the same time (like function 15 of Modbus protocol) but MD2424 only support function 16.
So I have created a simple custom function : OUTPUT[1] = DM[1]
clocked on 100ms.
It seems to work but when I used Modbus function 16 to write to DM, data memory is not persistent. So I need to send Modbus command every 100ms which not very efficient !
Do you have any solutions to simulate correctly Modbus function 16 ?
Thanks in advance for your help.

[support]

Are you refering the PLC acting as modbus slave? You can use MODBUS function 16 to write a single 16 bit data or mulitple 16-bit words to the PLC in a single modbus command. The PLC's digital outputs are mapped to holding register 40017 to 40032 (binary offset address is 16 to 31) so if you send a MODBUS function 16 to this address range you can immediately change 16-bits of outputs.

Your solution of OUTPUT[1] = DM[1] will also work if you write the data to DM[1] frequently. The DM[1] data should be persistent unless your PLC's program changes the data all the time. (Do you mean volatile? DMs are indeed volatile memory in the sense that the content are lost when power down.)