Wittern 3589 Brake Mechanism Diagnostic and Testing -... | terminalfaults.org

Technical Background:

The brake mechanism utilizes a 24V DC solenoid to engage/disengage a mechanical brake on the motor shaft. The solenoid coil resistance should measure within +/- 10% of its nominal value (typically 50-100 ohms). PWM (Pulse Width Modulation) control signals may be used to modulate braking force. Signal attenuation or voltage drops along the wiring harness can impact brake performance. The motor controller utilizes hall-effect sensors to monitor motor speed and position, feeding back to the brake control logic.

Symptoms:

Observed brake mechanism failure in the Wittern 3589 coin/bill handling system. Symptoms include uncontrolled motor overrun after dispensing, audible grinding noises during brake engagement/disengagement, and failure to hold position against gravity.

Possible Causes:

Defective 24V DC solenoid (open circuit or short circuit).
Mechanical binding or obstruction within the brake linkage.
Worn or contaminated brake friction material.
Failure of the motor controller to send the correct PWM signal to the brake solenoid.
Wiring harness damage or loose connections leading to voltage drop to the brake solenoid.
Environmental factors (extreme temperatures, -40C) causing lubricant stiffening, affecting mechanical operation.

Solution:

1

Visually inspect the brake mechanism for any obvious damage, debris, or obstructions.
2

Using a calibrated multimeter, measure the voltage supplied to the brake solenoid during engagement/disengagement. Verify it is within the specified range (24V DC +/- 10%).
3

Measure the resistance of the brake solenoid coil. Compare to the manufacturer's specifications. An open or short circuit indicates solenoid failure.
4

Inspect the wiring harness and connectors for corrosion, damage, or loose connections. Repair or replace as needed.
5

Actuate the brake mechanism manually. Check for smooth, uninhibited movement. Lubricate moving parts with appropriate low-temperature grease (silicone-based).
6

Verify the functionality of the hall-effect sensors using an oscilloscope. Check for correct output signals proportional to motor speed.
7

If the motor controller is accessible, check for any error codes related to the brake mechanism.

Safety Warning:

The Wittern 3589 operates with 24V DC, which poses a shock hazard. Disconnect power before performing any maintenance or testing. Ensure the area around the kiosk is dry and free from obstructions. Due to the unattended public environment, take precautions against vandalism. Ensure all replacement parts are properly grounded.

Prevention:

Regularly inspect and clean the brake mechanism. Lubricate moving parts with low-temperature grease every 6 months. Ensure wiring harnesses are properly secured to prevent strain and vibration damage. Monitor the system for unusual noises or performance degradation, addressing issues promptly.

Expert Tip:

A common failure point is corrosion on the solenoid connector pins. Apply dielectric grease to the connector after cleaning to prevent recurrence. Also, check the condition of the return spring on the brake linkage, as fatigue can reduce its effectiveness.

Frequently Asked Questions

•What is the typical lifespan of the brake solenoid?

The solenoid lifespan is typically 5-7 years, or 500,000 cycles, but can be significantly reduced by environmental factors.

•What type of grease is recommended for the brake mechanism?

A silicone-based low-temperature grease is recommended to maintain lubrication in cold environments. Avoid petroleum-based lubricants, which can stiffen at low temperatures.

•Where can I find the manufacturer's specifications for the solenoid coil resistance?

The specifications are usually found in the Wittern 3589 service manual, or printed on the solenoid itself. Check the Wittern website for documentation.

Technical Background:

Symptoms:

Possible Causes:

Solution:

Safety Warning:

Prevention:

Expert Tip:

Frequently Asked Questions

•What is the typical lifespan of the brake solenoid?

•What type of grease is recommended for the brake mechanism?

•Where can I find the manufacturer's specifications for the solenoid coil resistance?

Related questions

Technical Background:

Symptoms:

Possible Causes:

Solution:

Safety Warning:

Prevention:

Expert Tip: