Decoding Mitsubishi FX3 Programming: Understanding K9999999 Value, C251 Assignments, and Press Position Transfer

When it comes to the M8000 counter, it's important to understand that these are hardware counters linked to the physical inputs X0-7. To utilize the high-speed counting function, the counters must be enabled by setting them to true. Essentially, M8000 must be constantly on from the initial scan to activate it. The actual inputs, such as X0 and X1 (two-phase), connected to the counter are what increase or decrease the count. Each scan updates the counter value to the 32-bit word D200 and D201. On the first scan, the counter's maximum value is typically set to 99999, assuming the encoder doesn't exceed this count. The PLC is then put into run mode from a stop or power down state, transferring the counter value to D200 and D201 on each subsequent scan. In the event of an up/down counter reaching its max set value, it will pause counting until the count is reduced below the limit. However, this delay could potentially result in damage to the equipment being controlled. Failure to enable the high-speed counters on every scan may cause the inputs tied to them to function as regular inputs instead. It's common for the inputs connected to encoders to remain unused in the program and cannot be cross-referenced, even though they are active.

• 13-09-2024
• parky

It's important to note that while the ladder rung may resemble a typical counter, hardware/software counters function differently. The compiler recognizes that these counters are meant for high-speed operations. When active under continuous enablement, the input count pin is linked to the relevant input. Without enablement, the high-speed mode behaves like a standard input, with parameters such as a 10ms transition from true to false based on processor I/O updates. Enabling HSC or interrupt bypasses the input filter, allowing for instant access in either mode.

• 14-09-2024
• parky

Parky explained that while the ladder rung may appear similar to a regular counter, hardware/software counters function differently. The compiler recognizes these counters as being for high-speed purposes. When enabled under continuous enablement, the input count pin is linked directly to the relevant input, operating at high speeds. Without enablement, the high-speed mode acts as a normal input with a 10ms true to false transition based on I/O updates. Enabling for High-Speed Counter (HSC) or interrupt bypasses the input filter for instant access. Thank you for clarifying, I understand now. I am still figuring out the specifics of the first rung (where is K99999999?), but it is set up and X0/X1 trigger the count.

• 15-09-2024
• drbitboy

While it may seem unusual at first, the approach to programming in south east Asia differs from other PLC systems. In Japan, they typically use the Timer number as a contact instead of the done bit or Counter.Q. For instance, calling a counter like [C 200, K300] sets the limit before the count contact becomes true. Conversely, calling a counter like [C200, D200] loads the current count into a D register. You can also load a Counter in a comparison, such as [CMP > C200, 150]. In the newer IEC format, they have introduced IEC timers with additional bits like IN, PT, Q, ET, and Preset variables, similar to other PLCs like AB.

• 15-09-2024
• parky

In the context of hardware counters, Parky pointed out that M8000 in the Mitsubishi M8002 PLC is crucial for enabling high-speed counters to work effectively. These counters are directly linked to physical inputs X0-7, and to ensure accurate counting, M8000 must be activated from the first scan. The inputs X0 and X1 play a key role in incrementing or decrementing the count, with the counter value being transferred to D200 and D201 each scan. This up/down counter is set to a maximum value of 99999 on the first scan, and M8002 is activated to run the system. It is important to enable the high-speed counters on every scan to prevent the inputs from reverting to normal inputs. Any values above 360 in the encoder counts may cause issues, as the system is designed to only count up to 360 during regular operations. The resetting of the counter value on startup is done as a precautionary measure, but in some cases, retaining the numbers may be necessary to avoid losing the machine's position. In a specific case involving a Chinese machine used in an American small business, the lack of proper support and language barriers have led to confusion about certain functions, such as the "Position" button acting as an origin/home offset. By not resetting the encoder counts on startup, the machine can maintain its position and avoid timing issues in subsequent operations.

• 15-09-2024
• arpus4KM

Having a homing position in place is crucial for ensuring the machine resets correctly in case of power failures. Instead of automatically resuming from where it left off, the operator should be prompted to reset the machine in the correct sequence before starting the system. This process involves checking for normal start conditions and if needed, performing a homing or return sequence to ensure drives and cylinders are in the correct position. Servo drives often rely on a homing sensor to return to a home position before moving to the correct position, typically 0 counts. This precision is especially important for critical tasks like picking up items. Some systems may also periodically recalibrate in creep mode to maintain accuracy.

• 15-09-2024
• parky