Timers in Fanuc PLC used to delay the process. For example, we will have to switch ON and switch OFF lubrication motor periodically in the machine, for this we use a timer so that we can switch ON lubrication motor ON for some period of time and OFF for some period of time. We need to set time in timer address T and these addresses are non-volatile memory addresses.
There are total five types of timer instructions available in Fanuc PLC as explained below:
On-delay timer (TMR) / Sub number 3:
To use this timer you will have to set time in timer address T and you can do same on CNC screen.
For example, see picture 1, when the status of address bit X1.5 becomes ‘1’, timer instruction actuated and starts counting time, after completion of time, the status of output coil R100.0 becomes 1, due to this, the status of input normally open address R100.0 becomes ‘1’ and output coil address Y2.3 gets ON.
We used timer number 1 in the below instruction, so we need to set time in Timer address T0000 refer to picture 2.
Fixed on-delay timer (TMR) / Sub number 24:
The time set in this timer is fixed. You cannot change time once set, however, if you want to change time, you will have to change or edit in sequence program (ladder program).
For example, see picture 3, when the status of address bit X7.4 becomes ‘1’, timer instruction actuated and starts counting time, after completion of time, the status of output coil R10.5 becomes 1, due to this status of input normally open address R10.5 becomes ‘1’ and output coil address Y6.5 gets ON.
We used timer number 1 in the below instruction, so we need to set time in PLC instruction (in ladder program) only as shown in picture 3. In below we time value 8000, its means 8000 milliseconds and that equals to 8 seconds
Fixed off-delay timer (TMRBF) / Sub number 77:
This is also a fixed timer. But this timer will work opposite of TMRB. You cannot change time once set, however, if you want to change time, you will have to change or edit in sequence program (ladder program).
For example, as shown in picture 4, when the status of address bit X3.4 becomes ‘1’, the status of timer output coil address R20.0 immediately gets ON and the same time, the timer gets reset. Now when the status of address X3.4 becomes ‘0’, the timer starts counting time and after time completes, the timer output becomes ‘0’.
If the address bit X3.4 is turned on again before the time-up, the timer will be reset.
On delay-delay timer (TMRC) / Sub number 54:
This is works like On – delay timer, but here the operator can change the time value any time in timer address. Also, you need to set the timer accuracy number and timer register address.
Let’s take below example, as shown in picture 5 when the status of address bit X1.5 becomes ‘1’, timer instruction actuated and starts counting time, after completion of time, the status of output coil R60.0 becomes 1, due to this status of input normally open address R60.0 becomes ‘1’ and output coil address Y60.0 gets ON.
But here we set time value in address T0000 as used in below timer instruction; we set to value ‘2’ as a timer accuracy and timer register address R200.
Table no. (a) for timer accuracy:
|Timer Accuracy Value||Setting Number in PLC Instruction||Range of time setting|
|8 milliseconds||0||8 milliseconds to 262.1 seconds|
|48 milliseconds||1||48 milliseconds to 26.2 minutes|
|1 second||2||1 seconds to 546 minutes|
|10 seconds||3||10 seconds to 91 hours|
|1 minute||4||1 minutes to 546 hours|
|1 milliseconds||5||1 milliseconds to 32.7 seconds|
|10 milliseconds||6||10 milliseconds to 327.7 seconds|
|100 milliseconds||7||100 milliseconds|
How accuracy will work in Timers?
Let’s take an example, as shown in below picture 6, we use timer address T0000 for setting time value, the timing value we set here is 4992 and accuracy is set to value‘48’ automatically because, in PLC timer instruction, we used timer accuracy number as 0001 as shown in Picture7.
Now the total timer value becomes set value X accuracy value
= Set value X accuracy value
= 4992 X 48 milliseconds
= 4992 X 48 X
= 239.616 seconds
It’s very important to refer Table (a) to set proper accuracy for timer address
We can set timer accuracy from CNC screen also, refer below steps and picture;
- Open timer setting page.
- Press [OPRT]
- Press [ACCRCY]
- Select 1MS or 10MS or 100MS or 1SEC or 1MIN
Stop watch timer (TMRST/TMRSS) / Sub number 221/222:
It will accumulate timer value when we make input status ON and preserve the cumulative value as an integrated time. This timer is rarely used in the Fanuc plc ladder.
Applications of Timers in Fanuc PLC ladder program:
- Lubrication motor logic
- Chuck alarm logic
- Turret finish signal
- Tailstock logic