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Articles BRX Do-More Counters Do-More Do-More Designer Inputs Outputs PLC PLC Basics PLC Learning Scan Timers

Timing Diagram NOT Just Used for a Timer

Logic circuits in a PLC ladder logic program are either on or off. The inputs change, which will affect the outputs. This can be expressed in a timing diagram. The timing diagram or chart will show you how the ladder logic program will respond to the changing states of the inputs and outputs.
Timing Diagram NOT Just Used for a Timer
This visual method is an excellent way of understanding how the PLC ladder logic functions. We will discuss a timing diagram and how it is used for timers, counters, and ladder logic. This will help in understanding or troubleshooting your PLC programs. Let’s get started.

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PLC PLC Basics PLC Learning Productivity 1000 Productivity 2000 Productivity 3000 Productivity Suite Timers

Productivity 2000 PLC Ladder Logic Timers

Timers are one of the first things you learn about programmable logic controllers. (PLC) Just about every PLC program will include timer instructions. The Productivity 2000 Series PLC has several different timer instructions for your program. We discussed the timed coil (TMC) and flasher coil (FLS) last time as part of the ladder logic output discussion. (Ladder Logic Output InstructionVideo)
Productivity 2000 PLC Ladder Logic TimersWe will now look at using the Simple Timer (STMR) and the Timer (TMR) instructions in the productivity suite software. Let’s get started.

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BRX Do-More Counters Do-More Do-More Designer PLC PLC Basics PLC Learning Timers

BRX Do-More PLC High-Speed Input Timer


The High-Speed discrete inputs can be configured to measure the amount of time between pulses. When you want a scaled value representing a speed or rate, the high-speed input timer is a better option for pulse rates below 5 kHz. This is compared to using the high-speed input pulse counting selection.
BRX Do-More PLC High-Speed Input TimerThe BRX Do-More series of programmable logic controllers have built-in high-speed inputs. These inputs can function in Counter, Timer, or Pulse Catch modes. Every CPU will have either 6 or 10 high-speed inputs (HSI) available depending on the model. These inputs can be used for input frequencies from 0 to 250Khz. 250Khz represents 250000 input counts per second that can be coming from devices connected to your PLC like an encoder. Due to the speed of the inputs, they function on the BRX Do-More PLC asynchronous with the PLC scan time.
We will continue looking at the high-speed inputs on our BRX Do-More PLC, by looking at the pulse timer mode. Previously we looked at the high-speed count mode of the PLC. We scaled the count to display RPM (Revolutions per Minute). Scaling the edge trigger timer from our incremental encoder, we will scale and compare the RPM from last time. Let’s get started.