# Constant Value in Micro Logix 1000 PLC

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#### Jamie G

I am trying to implement a simple position control of a pneumatic actuator with a PLC USING ONLY A PROXIMITY SENSOR. The problem is I don't know how to input a constant for my desired distance. I have the basic instruction sets of:
ADD, AND, BSL, BSR, CTU, CTD, COP, CLR, DCD, DIV, DDV, ENC, EQU, FFL, FLL, FRD, FFU, GEQ, GRT, HSC, HSE, HSD, HSL, INT, IIM, IOM, JMP, JSR, LBLB, LES, LEQ, LFL, LFU, LIM, MCR, MSG, MEQ, MOV, MUL, MVM, NEG, NEQ, NOT, OSR, OR, RAC, RES, RET, RTO, SBR, SCL, SQC, SQO, SQR, STE, STS, STD, SUB, SUS, TND, TOD, TOF, TOM, XOR. The PLC is a simple Micro Logix 1000. Any help would be greatly appreciated.

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#### Steve Myres, PE

You can either use an integer register (like N7:0), or most math and number manipulation instructions (MOV, FLL, etc.), will accept a hard coded value typed in for "Source A", etc. If you use the integer register you will have to load the value manually at program or run time, or have your program write to the register with a MOV instruction.

File protection is not available in the MicroLogix, so you can't create a "constant" in the way we normally think of it.

Steve Myres, PE
Automation Solutions
[email protected]

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#### Alan Rimmington

Use the MOV instruction. Source = Your constant value. Dest = N7:0 (or word you wish to use)

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#### Vince Dooley

Three ways:
1. Use your programming facilities to write a number directly into a data register.
2. Use the MOV command in a rung to move the desired constant into a register if you don't need to change it again.
3. Use an operator interface such as the Microview panel or DTAM if you want to change it regularly. (You need programming capability for the Microview)

Vince Dooley

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#### Rajesh Agravat

Use the MOV instruction and move the hardcoded integer value to the destination register. if you have any MMI/HMI interface attached with micrologix 1000 then you can use that to move the value inside the register.

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#### Jeff

Just select an address to hold your constant like N7:0, then just use that address in all your instructions that need the constant. Are you wanting to occasionally change the constant? If so, how? by a switch position, thumbwheels, database....etc...