Greetings everyone! Apologies for the elementary inquiries. As a novice in PLC technology, I am curious about the feasibility of incorporating pulse-width modulation (PWM) with the CompactLogix L32E without the need for signal conditioning. Can this PLC support the implementation of 6 distinct PWMs with its available timers? Would it be prudent to utilize a board like the 1769-OB32 for this purpose? The desired frequency for the PWM signals is approximately 50Hz, with duty cycles ranging from 5% to 10%.
The majority of PWM outputs typically necessitate a higher frequency, but the CompactLogix lacks hardware-based PWM outputs. For instance, if you specify a 5% duty cycle at 50 Hz, your ON-pulse will equal 5% of 50/1000, resulting in 2.5 milliseconds. This is nearing the hardware's physical limitations (0.1 ms ON delay, 1.0 ms OFF delay) and the software's logical constraints (minimum RPI and Scantime considerations) for the controller. What devices are being controlled by the PWM signal?
Ken, you are correct. When I mention a 5% duty cycle at 50Hz, it translates to a 1ms ON-pulse within a 20ms cycle. This limitation seems to pose challenges for implementing PWM with CompactLogix. Is it feasible to drive a small servomotor using this controller, considering it will also be controlling other final elements in a MIMO plant?
By utilizing a third-party IO module like the Turck BL20 module along with the suitable gateway, you have the ability to obtain PWM outputs. Explore more about this functionality in the official Turck BL20 module datasheet.
Thank you for your response! In a discussion with Ken Roach, he mentioned that the hardware is nearing its physical limit with a 0.1 ms ON delay and 1.0 ms OFF delay, as well as the software reaching its logical limit with considerations such as minimum RPI and Scantime for the controller. What exactly does a 0.1 ms ON delay and 1.0 ms OFF delay refer to? Could it be related to commutation delay? And what is RPI? Any additional references on this topic would be greatly appreciated. In order to clarify, my goal is to adjust the duty cycle within a range of 1.5 - 2 milliseconds for the on-pulse/high level and between 18.5 - 18 milliseconds for the off-pulse/low level. Thank you once again!
Ken mentioned switching times of 0.1 and 1 milliseconds for the OB32 output card, which is equipped with protection components that limit the speed of switching. The RPI refers to the backplane communication speed. Achieving the necessary speed with multiple cards in your rack may be challenging. It's important to note that the OB32, like other output cards, can generate transient pulses of 1 millisecond if the output current is less than 1mA during start-up. Refer to the installation PDF for the 1769-OB32 for more information. Another option to consider is the ML1100 (Version 1763-L16BBB) micro PLC, which features 2 high-speed FET outputs (2 & 3) and a PWM instruction. It also includes Ethernet communication capabilities to communicate with your L32E. Additionally, it offers high-speed inputs for feedback if needed.
Hello there! No worries about the elementary nature of your queries, we all start somewhere. Now, to your question: The CompactLogix L32E indeed supports multiple PWM outputs, although achieving 6 distinct signals may be a smidge challenging because this PLC only has two Operational High-Speed Counters. Splitting these signals could potentially introduce a level of complexity as well as possibly judicial noise. For achieving PWM outputs at about 50Hz with duty cycles ranging from 5% to 10%, you may want to consider an add-on module like the 1769-OF8V or 1769-HSC High-Speed Counter module for a more optimized solution. Always remember to evaluate the trade-off between system complexity and your specific performance requirements when making such choices. Hope this helps!
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Answer: - Yes, the CompactLogix L32E PLC can support PWM without the need for signal conditioning.
Answer: - The CompactLogix L32E PLC can support the implementation of 6 distinct PWM signals with its available timers.
Answer: - It may be prudent to utilize a board like the 1769-OB32 for implementing PWM signals with the CompactLogix L32E PLC.
Answer: - The desired frequency for the PWM signals is approximately 50Hz.
Answer: - The duty cycles for the PWM signals mentioned range from 5% to 10%.
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