Remote Control Emitter Stop Button Circuit Safety
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Solution Overview
Problem
Remote control transmitters for hoisting machines face challenges in meeting the safety requirements of the Machinery Directive for the stop function, specifically category 3 compliance, as they struggle to ensure safe stopping and prevent restarts during electrical faults.
Innovation Solution
A remote control transmitter with a double circuit stop button using normally open contacts and a combined transmitter-receiver strategy, where the stop button generates three signals, and a stop circuit that ensures safe shutdown through active and passive commands, utilizing a Flip-Flop circuit to manage power and signal integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a stop button with double circuit and normally open contacts is used to achieve category 3 safety compliance, then the safety and reliability of the stop function is improved, but the device complexity increases
Solution Approach 1:
The stop button is divided into two independent normally open contacts (ST1 and ST2) that must both be closed for normal operation. This segmentation ensures that a single contact failure cannot compromise the stop function, directly addressing the safety requirement while managing complexity through functional decomposition
Solution Approach 2:
The permanently closed contact KBP serves as a pre-prepared safety mechanism that immediately triggers shutdown if opened. This beforehand cushioning ensures that even if the normal stop contacts fail, a backup safety path exists, enhancing reliability without requiring complex real-time monitoring systems
2Reliability
If the stop button generates three signals (ST1, ST2, KBP) for the stop circuit to ensure safe shutdown, then the reliability and fault detection capability is improved, but the device complexity increases
Solution Approach 1:
The three signals from the stop button create a feedback system where the circuit continuously monitors the state of ST1, ST2, and KBP contacts. The stop circuit uses this feedback to detect faults and trigger appropriate shutdown sequences, improving reliability through continuous status verification
Solution Approach 2:
The stop circuit acts as an intermediary between the mechanical stop button and the final shutdown action. It processes the three signals, determines fault conditions, and coordinates the shutdown sequence, thereby managing the complexity of signal interpretation while ensuring reliable safety response
3Reliability
If the transmitter uses a combined transmitter-receiver strategy with active and passive stop commands, then the safety and reliability of the stop function is improved, but the power consumption increases
Solution Approach 1:
The transmitter uses periodic radio communication to send encoded stop commands to the receiver. This periodic action ensures reliable command transmission while allowing the system to enter low-power states between communications, balancing safety requirements with power consumption concerns
Solution Approach 2:
The patent replaces direct mechanical or continuous electrical control with radio frequency communication for transmitting stop commands. This substitution reduces continuous power consumption while maintaining reliable command transmission through periodic encoded messages, addressing both safety and energy efficiency requirements
Data Source
Figure 1
Figure 2
AI summary
The transmitter has a stop button (13) provided with two contacts (C1, C2) which respectively are normally open and which respectively are closed when the stop button is pressed in stop demand of a hoisting machine, where the contacts respectively originate two signals (ST1, ST2). A contact (C3) permanently closed originates a signal (KBP), and is interpreted during the stop demand of the machine, where accidental opening of the contact (C3) indicates absence of the stop button. A power supply input (+VBAT) is common to the contacts (C1-C3).