BioSonic UC50D, UC50, UL2 and UL2E Technical Manual Rev 1.0 Jan 2003

BioSonic® UC50 and UL2 Ultrasonic Cleaning System

Table of Contents Section 1 Product Overview

1-1

Introduction ... 1-1 General Description ... 1-1 Models ... 1-2 Physical Description... 1-2 Accessories... 1-2 Controls and Indicators ... 1-3 Performance Specifications... 1-4 Declaration of Conformance... 1-6 Section 2 Preparation for Maintenance

2-1

Introduction ... 2-1 Safety Precautions ... 2-1 Section 3 Detailed Theory of Operation

3-1

Introduction ... 3-1 Block Diagram Discussion... 3-1 Detailed Theory of Operation: Overview ... 3-3 Section 4 Test Procedures

4-1

Introduction ... 4-1 Test Equipment ... 4-1 Test Results ... 4-2 Testing Procedures ... 4-3 Dielectric Voltage Withstand Test... 4-3 Ground Continuity Test... 4-5 Ground Current Leakage Test (Optional) ... 4-6 L1 & L2 Tuning Check ... 4-8 Power Input Test ... 4-10 Tank Capacitance and Load Resistance Test (Optional) ... 4-12 Cleaning Solution Activity Test ... 4-13 Visual & General Assembly Inspection... 4-14 Acceptance Test Data Sheet... 4-15 Maintenance Record ... 4-15

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BioSonic® UC50 and UL2 Ultrasonic Cleaning System

Section 5 Troubleshooting

5-1

Introduction ... 5-1 Troubleshooting Chart ... 5-2 Section 6 Disassembly and Assembly

6-1

Introduction ... 6-1 Disassembly ... 6-2 Housing Assembly ... 6-2 Electronic Timer ... 6-3 Mechanical Timer (Item 6)... 6-3 Printed Circuit Board (PCB) (Item 9) ... 6-3 Input Power Connector (Item 11) ... 6-4 Tuning Coil (L2) (Item 10) ... 6-4 Assembly ... 6-6 Housing Assembly ... 6-7 Electronic Timer ... 6-7 Mechanical Timer (Item 6)... 6-7 Printed Circuit Board (PCB) (Item 17) ... 6-8 Input Power Connector (Item 11) ... 6-8 Tuning Coil (L2) (Item 10) ... 6-9 Section 7 Adjustments

7-1

Introduction ... 7-1 L1 Tuning Coil Adjustment... 7-2 Using the L1 & L2 Tuning Check described in ... 7-2 Section 8 Parts Lists

8-1

Introduction ... 8-1 Ordering Parts... 8-1 Parts Information... 8-1 UC50D, UL2, and UL2E Main Assemblies with Electronic Timers... 8-2 UC50D, UL2, and UL2E PCB Assemblies with Electronic Timers ... 8-7 UC50, UL2, and UL2E Main Assemblies with Mechanical Timers ... 8-12 UC50, UL2, and UL2E PCB Assembly with Mechanical Timers ... 8-16 Section 9 Large Format Figures

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BioSonic® UC50 and UL2 Ultrasonic Cleaning System

List of Tables Table 1. UC50 and UL2 Available Models ... 1-2 Table 2. Accessories for BioSonic UC50 and UL2... 1-2 Table 3. Performance Specifications ... 1-4 Table 4. Model / Version Identification ... 3-3 Table 5. Troubleshooting Chart ... 5-2 Table 6. Electronic Timer LED States ... 5-3 Table 7. Disassembly Instructions ... 6-2 Table 8. Assembly Instructions ... 6-7 Table 9. L1 Tuning Coil Adjustment ... 7-2 Table 10. UC50D, UL2, and UL2E Main Assembly Parts List (Electronic Timer) ... 8-2 Table 11. UC50D, UL2, and UL2E PCB Assembly Parts List (Electronic Timer) ... 8-7 Table 12. UC50, UL2, and UL2E Main Assembly Parts List (Mechanical Timer)... 8-12 Table 13. UC50, UL2, and UL2E PCB Assembly Parts List A (Mechanical Timer) ... 8-16 Table 14. UC50, UL2, and UL2E PCB Assembly Parts List B (Mechanical Timer) ... 8-21

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BioSonic® UC50 and UL2 Ultrasonic Cleaning System

List of Figures Figure 1. BioSonic UC50D...1-1 Figure 2. UC50D/UL2/UL2E Electronic Power On/Off Timer Control ...1-3 Figure 3. UC50/UL2/UL2E Mechanical Power On/Off Timer Control ...1-3 Figure 4. Block Diagram ...3-1 Figure 5. UC50D/UL2/UL2E (Electronic Timer) Schematic – PCB 09900-[ ] – Sheet 1 of 2 ...3-8 Figure 6. UC50D/UL2/UL2E (Electronic Timer) Schematic – PCB 09900-[ ] – Sheet 2 of 2 ...3-9 Figure 7. UC50-100 (Mechanical Timer) Schematic Diagram – PCB 09799-04 ...3-10 Figure 8. UC50-115, UL2 (Mechanical Timer) Schematic Diagram – PCB 09799-01 ...3-11 Figure 9. UC50-115M (Mechanical Timer) Schematic Diagram – PCB 0979907 ...3-12 Figure 10. UC50-220 (Mechanical Timer) Schematic Diagram – PCB 09799-05 ...3-13 Figure 11. UC50-230 (Mechanical Timer) Schematic Diagram – PCB 09799-06 ...3-14 Figure 12. UC50-230CE, UL2E (Mechanical Timer) Schematic Diagram – PCB 09799-02 ...3-15 Figure 13. UC50-240 (Mechanical Timer) Schematic Diagram – PCB 09799-03 ...3-16 Figure 14. Dielectric Voltage Withstand Test Set-up Diagram...4-5 Figure 15. Ground Leakage Test Set-up Diagram...4-7 Figure 16. L1 Tuning Check Set-up Diagram ...4-9 Figure 17. Typical Oscillator Output Waveform ...4-9 Figure 18. Power Input Test Diagram for 115V Model from a 115V Source ...4-11 Figure 19. Power Input Test Diagram for 230V Model from a 115V Source ...4-11 Figure 20. Tank Simulator - Dummy Load Circuit Diagram ...4-12 Figure 21. UC50 and UL2 Assembly/Disassembly Diagram...6-5 Figure 22. Wiring Diagram for Electronic Timer UC50D/UL2...6-10 Figure 23. L1 Tuning Adjustment Set-up Diagram...7-3 Figure 24. Typical Oscillator Output Waveform ...7-3 Figure 25. UC50D, UL2, and UL2E Main Assembly (Sheet 1 of 2) ...8-5 Figure 26. UC50D, UL2, and UL2E Main Assembly (Sheet 2 of 2) ...8-6 Figure 27. UC50D, UL2, and UL2E PCB Layout ...8-11 Figure 28. UC50, UL2, and UL2E Main Assembly – 1 of 2...8-14 Figure 29. UC50, UL2, and UL2E Main Assembly – 2 of 2...8-15 Figure 30. UC50, UL2, and UL2E PCB Layout for -115M, -220, -230, -230CE, 230UK, -240, and UL2E ...8-20 Figure 31. UC50, UL2, and UL2E PCB Layout for -100 and -115 (04505 Rev. B)...8-23 Figure 32. UC50, UL2, and UL2E PCB Layout for -100 and -115 (04505 Rev. C)...8-24 Figure 33. UC50D Electronic Timer Schematic (PCB 09900)–Sheet 1/2 Large ...9-3 Figure 34. UC50D Electronic Timer Schematic (PCB 09900)–Sheet 2/2 Large ...9-5

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BioSonic® UC50 and UL2 Ultrasonic Cleaning System

Section 1 Product Overview Introduction This section briefly describes the BioSonic® UC50 and BioSonic UL2 Ultrasonic Cleaning Systems, including models UC50D, UC50, UL2, and UL2E. It describes the physical characteristics, including indicator functions and controls, and provides a table of performance specifications as well as the Declaration of Conformance. General Description The BioSonic UC50 and UL2 Ultrasonic Cleaning Systems are compact ultrasonic cleaning systems designed specifically for the dental industry to optimize time and safety in the office or laboratory. A typical unit is shown in Figure 1. The BioSonic UC50 and BioSonic UL2 provide timer-controlled operation for up to 30 minutes. The solid-state circuitry generates high-frequency sound waves that are carried through the specially formulated cleaning solution in the tank. These sound waves create vibration patterns of high and low pressure in the cleaning solution. The low pressure creates cavitation (millions of tiny bubbles or voids), and the high pressure causes these bubbles to collapse, creating enormous amounts of energy that are moving in all directions. The BioSonic UC50D and more recent versions of the UL2 and UL2E units are equipped with electronic timers as shown in Figure 2. The BioSonic UC50, and older versions of the UL2, and UL2E units are equipped with mechanical timers as shown in Figure 3.

Figure 1. BioSonic UC50D

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BioSonic® UC50 and UL2 Ultrasonic Cleaning System

Models Table 1 lists the available models of the BioSonic UC50 and UL2 Ultrasonic Cleaning Systems. The ‘dash’ numbers (-100, -115, -220, -230, 240) indicate the available power configurations (100V, 115V, 220V, 230V, and 240V respectively). As illustrated in the table below, some models include an EMI filter and each model has a designated line cord style. Table 1. UC50 and UL2 Available Models Catalog No.

Voltage

Filter

Line Cord Style

UC50D/UC50 -100

100V ± 10%

Yes

U.S.

UC50D/UC50-115, UL2

115V ± 10%

Yes

U.S.

UC50D/UC50 -115M

115V ± 10%

No

U.S.

UC50D/UC50-220

220V ± 10%

No

European

UC50D/UC50-230CE, UL2E

230V ± 10%

Yes

European

UC50D/UC50-230UK

230V ± 10%

Yes

Great Britain

UC50D/UC50-240

240V ± 10%

Yes

Australian

Physical Description The BioSonic UC50 and UL2 Ultrasonic Cleaning System is a lightweight, portable, counter-top unit with a 0.85 gallon (3.2 liters) tank capacity. The unit is activated by setting the timer on the front of the unit to the desired cleaning time (from 0 to 30 minutes).The fuse and AC input power connector are located at the rear of the unit. Accessories Table 2 lists the accessories available for the BioSonic UC50 and UL2 Ultrasonic Cleaning System. Table 2. Accessories for BioSonic UC50 and UL2 Catalog No.

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Description

UC-58

Plastic instrument basket

UC-153

Single-beaker positioning rack

UC-53

600ml beaker with cover

UC-55

Single-beaker positioning cover

BioSonic® UC50 and UL2 Ultrasonic Cleaning System

Controls and Indicators Power is applied to the electronic timer versions of the BioSonic UC50D, UL2 and UL2E units when the 5-, 15-, or 30-minute electronic timer button is pressed. Green “Power On” indicator lights illuminate on the electronic timer when the unit is operating. Refer to Table 6 for timer LED details. To turn the power off, press the “Off” button.

Figure 2. UC50D/UL2/UL2E Electronic Power On/Off Timer Control

Power is applied to the mechanical timer versions of the BioSonic UC50, UL2, and UL2E units when the mechanical timer knob is rotated clockwise to the desired cleaning time (30 minutes maximum). To turn power off, rotate the timer knob to the full counterclockwise position (“O”). A green “Power On” indicator light illuminates on the unit when the timer is set to any “On” position.

Figure 3. UC50/UL2/UL2E Mechanical Power On/Off Timer Control

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BioSonic® UC50 and UL2 Ultrasonic Cleaning System

Performance Specifications Table 3 shows the performance specifications for BioSonic UC50 and UL2 Ultrasonic Cleaning System. Table 3. Performance Specifications Electrical Safety and EMC Regulations CE Directives 73/23/EEC and 89/336/EEC UL Listed, USA and Canada FCC

IEC 1010-1 +A1 + A2, EN55011, EN50082 File 172299 CFR 47 part 18

Operating Frequency

53.4 KHz nominal

Power Consumption

60 watts max

Physical Characteristics Length

11.5 in (29.2 cm)

Width

9.0 in (22.9 cm)

Height

7.75 in (19.7 cm)

Empty Weight

6.375 Ib (2.9 kg)

Tank Capacity

0.85 gal (3.2 liters)

Tank Capacity at Waterline

0.53 gal (2 liters)

Tank Length

7.75 inches (19.7 cm)

Tank Width

5.75 inches (14.6 cm)

Tank Depth

4.125 inches (10.5 cm)

Input Power Requirements

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UC50D/UC50-100

100V±10%, 0.78 Amps, 50/60 Hz

UC50D/UC50-115, UL2

115V±10%, 0.68 Amps, 50/60 Hz

UC50D/UC50 -115M

115V±10%, 0.68 Amps, 50/60 Hz

UC50D/UC50-220

220V±10%, 0.35 Amps, 50/60 Hz

UC50D/UC50-230CE, UL2E

230V±10%, 0.34 Amps, 50/60 Hz

UC50D/UC50-230UK

230V±10%, 0.34 Amps, 50/60 Hz

UC50D/UC50-240

240V±10%, 0.32 Amps, 50/60 Hz

BioSonic® UC50 and UL2 Ultrasonic Cleaning System

Performance Specifications (continued) Fuse Type 100V units

5 x 20 mm, Two T 1.25A/250V

115V units

5 x 20 mm, Two T 1A/250V

220 – 240V units Environmental Conditions

5 x 20 mm, Two T500mA/250V Intended for indoor use Maximum altitude 6500 ft. / 2000m. Temperature range 41°F – 104°F (5°C – 40°C) Maximum relative humidity 80% for temperatures up to 88° (31°C), decreasing linearly to 50% relative humidity at 104°F (40°C) Mains supply voltage fluctuations, not to exceed ± 10% of the nominal voltage Transient over-voltages category II Pollution degree 2 Class 1 equipment

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BioSonic® UC50 and UL2 Ultrasonic Cleaning System

Declaration of Conformance European Community Council 73/23 EEC and 89/336 EEC

Manufacturer:

Coltène/Whaledent 750 Corporate Drive Mahwah, New Jersey 07430 USA

Date:

November 1998

Coltène/Whaledent, Inc. hereby declares that the product listed below has been tested according to the standards shown in this document. Coltène/Whaledent, Inc. further acknowledges that the product was found to be in compliance with these standards. Type of Equipment:

Ultrasonic Cleaning System

Types/Models:

UC50D-230CE UC50D-230UK UL2E

Brand Name:

BioSonic

Conforms To:

EN61010, EN 55011, EN 50082

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BioSonic® UC50 and UL2 Ultrasonic Cleaning System

Section 2 Preparation for Maintenance Introduction This section describes the precautions required for safe operation and maintenance of the BioSonic UC50 and UL2 Ultrasonic Cleaning System.

Safety Precautions

DANGER Exercise extreme caution when performing voltage and waveform observations. Use a suitable isolation transformer.

DANGER The unit contains hazardous electrical output and must be serviced by qualified personnel only.

DANGER Before assembly or disassembly and before servicing, disconnect the unit from the power supply.

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BioSonic® UC50 and UL2 Ultrasonic Cleaning System

DANGER To avoid risk of fire, replace fuses as marked.

DANGER To avoid electrical shock, do not immerse the unit in water.

DANGER Make sure that the unit is plugged into a three-wire grounded power source. Do not use plug adapters that eliminate ground.

DANGER Do not use flammable liquids with the unit.

WARNING Always wear gloves, safety glasses, and protective clothing when servicing the unit.

WARNING Do not place hand or fingers into ultrasonic tank while the unit is in operation. Always keep the cover closed during operation to reduce aerosols. 2-2

BioSonic® UC50 and UL2 Ultrasonic Cleaning System

CAUTION Do not operate the unit without sufficient solution in the tank. Operating a dry tank may result in permanent damage to the unit.

CAUTION Do not use water alone as the carrier bath. Water is not a satisfactory coupling agent unless a wetting agent is used.

CAUTION Do not place objects directly on the bottom of the tank. They may block cavitation, cause build-up of heat in the transducer(s), and result in premature failure. Always use proper accessory items (instrument basket, cassette rack, and beaker positioning cover) to hold items.

CAUTION Do not restrict airflow. Provide adequate ventilation.

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BioSonic® UC50 and UL2 Ultrasonic Cleaning System

Section 3 Detailed Theory of Operation Introduction This section provides both block diagram and detailed schematic descriptions of the BioSonic UC50 and UL2 Ultrasonic Cleaning System circuit operation.

Block Diagram Discussion The Block Diagram in Figure 4 shows the functional components of the BioSonic UC50 and UL2 Ultrasonic Cleaning System.

AC Input PCB Assembly

EMI Filter

NOTE: Some units for sale outside the EC, US and Canada do not have EMI Filtering. In units with mechanical timers, the Control/Timer is located in the main assembly housing rather than on the PCB assembly.

Control/ Timer

Rectifier Pulsing DC

Oscillation Start Network

Limiter

Load/Phase Network Oscillator Circuit

Tank Assembly

Isolation Transformer

Ultrasonic Transducer

Figure 4. Block Diagram

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BioSonic® UC50 and UL2 Ultrasonic Cleaning System

AC input power passes through the EMI Filter to the Control/Timer. The EMI filter has various configurations to comply with radio interference regulations in the region where the unit is marketed. The filter prevents any harmonics produced by the unit circuitry from being imposed on the AC line, where they could cause interference to other equipment connected to the same AC power source. The Control/Timer allows the operator to turn the unit on for a predetermined period of time, up to 30 minutes. When the unit is on, the Control/Timer allows AC power to flow to the Rectifier. The Rectifier converts AC to pulsing DC, which is supplied to the Oscillation Start Network and the Oscillator Circuit. The Oscillation Start Network generates a start pulse to initiate oscillations in the Oscillator Circuit. The Oscillator Circuit produces the signal that continuously drives the Ultrasonic Transducer. The Limiter circuit protects the components of the Oscillator Circuit from possible over-voltage damage. The Oscillator Circuit supplies current to the Ultrasonic Transducer via the Load/Phase Network and the Isolating Transformer. The Load/Phase Network stabilizes the power variations normally encountered with changes in fluid level and work load. The Isolating Transformer provides the proper impedance and drive level for the transducer and also increases safety by eliminating a direct path between the power circuit and the tank. The Ultrasonic Transducer converts electrical energy into mechanical energy (i.e. sound waves) which generates the cleaning action of the unit.

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BioSonic® UC50 and UL2 Ultrasonic Cleaning System

Detailed Theory of Operation: Overview The following paragraphs provide a detailed circuit description of the BioSonic UC50 and UL2 Ultrasonic Cleaning System. Table 4 should be used to identify the model/version and appropriate schematic figure for the applicable unit. The catalog number is printed on the back of the unit and the PCB assembly number is printed on the printed circuit board. Table 4. Model / Version Identification Catalog Number

PCB Assy P/N

Filter

Figure

UC50D-100

09900-01

Yes

UC50D-115

09900-02

Yes

UC50D-115M

09900-07

No

UC50D-220

09900-05

No

UC50D-230CE

09900-03

Yes

UC50D-230UK

09900-03

Yes

UC50D-240

09900-04

Yes

UL2

09900-02

Yes

UL2E

09900-03

Yes

UC50-100

09799-04

Yes

Figure 7, page 3-10

UC50-115

09799-01

Yes

Figure 8, page 3-11

UC50-115M

09799-07

No

Figure 9, page 3-12

UC50-220

09799-05

No

Figure 10, page 3-13

UC50-230

09799-06

No

Figure 11, page 3-14

UC50-230CE

09799-02

Yes

Figure 12, page 3-15

UC50-240

09799-03

Yes

Figure 13, page 3-16

UL2

09799-01

Yes

Figure 8, page 3-11

UL2E

09799-02

Yes

Figure 12, page 3-15

Electronic Timer

Figure 5, page 3-8 Figure 6, page 3-9

Mechanical Timer

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BioSonic® UC50 and UL2 Ultrasonic Cleaning System

Detailed Theory of Operation •

AC Input. AC power is supplied via a detachable cordset to an IEC connector (FH1) on the rear apron of the unit. The IEC connector contains two user accessible fuses. See Table 3 for specific fuse types.

•

EMI Filter. The EMI Filter design varies according to local radio interference regulations. The EMI Filter isolates the AC line so any harmonics produced by the unit circuitry are not imposed on the AC line. When the unit is on, the EMI Filter supplies filtered AC to the Rectifier. The EMI Filter resides between the IEC connector and the timer switch. In electronic timer units, it consists of R6, C8-1 (or C8-2), C9, C10, VAR1, T3 and in some models T5. The varistor VAR1 protects the unit from excessive voltage surges. In mechanical timer units it consists of R6, C8 through C10, T3 and in some models T4. Note: Some units do not have an EMI filter. UC50D, UL2 and UL2E units without filters are connected with zero-resistance jumpers ZR4 through ZR7 and have a direct connection from the IEC connector to the timer’s power switch.

•

Electronic Control/Timer. The UC50D and later versions of the UL2 and UL2E models are controlled by an Electronic Control/Timer. The Electronic Control/Timer consists of the electronic keypad, resistor networks RN1 and RN2, microcontroller IC1, oscillator XT1, resistor R8, capacitors C8 and C13, resistors R7 and R9, capacitor C14, transistor Q3, relay K1, and diode D11. The Electronic Control/Timer turns on the unit and shuts it off after a specified period of time. The microcontroller IC1 controls the operation of the entire unit via the output on lead 3. When the unit is off, resistors RN1 raise the voltage on IC1 leads 9, 11, 12, and 13 to 5V, With these leads “high,” the voltage on lead 3 is zero, keeping transistor Q3 in the “off” state. When a keypad button is pressed to turn the unit on, the keypad switch closes the circuit to ground and pulls the corresponding IC1 lead (9, 11, 12, or 13) to 0V, as marked. The circuitry in IC1 controls the lights on the keypad via IC1 leads 17, 18, and 1. Resistor network RN2 sets the proper current for the LEDs. Simultaneously, IC1 raises the voltage at lead 3 to 5 volts. This turns on transistor Q3 which closes relay K1, allowing AC power to pass into the rectifier and to start to operation of the unit. An oscillator XT1 (4 MHz) provides the timing signals for the microcontroller. Resistor R8 and capacitor C8 provide a master clear that resets the IC when the unit is plugged into an AC power source. Capacitor C13 filters and smoothes the 5V DC power signal. Resistor R7 provides a positive bias to the gate of transistor Q3. Resistor R9 and capacitor C14 provide approximately a one-second delay when the unit is plugged in, preventing it from cycling up and down if the power is rapidly switched on and off. Diode D11 eliminates negative spikes across relay K1 when the unit is powered off. Constant 5V DC power is supplied to the microcontroller by voltage regulator, VR1. Transformer T4 steps the voltage down from the AC input supply. Jumpers ZR2 and

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BioSonic® UC50 and UL2 Ultrasonic Cleaning System

ZR3 (100V/115V units) and ZR1 (220V/230V/240V units) connect the transformer appropriately for the incoming voltage. Bridge rectifier BR1 converts the incoming AC power signal to DC. Capacitor C11 smoothes the DC output of BR1. Capacitor C12 smoothes the output of VR1, and resistor R10 drains the charge on C12 when the unit is shut down. •

Mechanical Control/Timer. The UC50, and early versions of the UL2 and UL2E models are controlled by a mechanical timer. The mechanical timer is a rotary on/off timer switch mounted to the front panel of the unit that allows the operator to turn the unit on for up to 30 minutes. When the unit is on, power is supplied to the Rectifier through the timer switch. The timer switch shuts the unit off after the set time has expired.

•

Rectifier. When the unit is on, AC power is supplied to diode D1, which functions as a half wave rectifier, producing pulsing DC at the AC line frequency and approximately 63 percent of the peak AC line voltage. As the unit turns on, current limiter CL1(RT1 on mechanical timer units) limits rush current into diode D1. CL1 is a thermistor that provides high resistance when the unit is turned on and low resistance after 3-4 seconds as it warms, allowing the unit to begin operating. The varistor TVS1 protects diode D1 from transient voltage surges. The pulsing DC signal output from D1 is designed to set up and maintain the oscillation in the unit. The Rectifier output is filtered by series capacitors C5 and C6, which split the output voltage in half. Resistor R1 releases the charge on these capacitors once the unit is turned off.

•

Oscillator Start Network. The Oscillation Start Network consists of resistor R2, capacitor C1, diode D2, and diac D3. The Start Network triggers the Oscillator Circuit by charging capacitor C1 through resistor R2 when the unit is turned on. When the voltage across capacitor C1 exceeds about 27 volts, diac D3 conducts. This action applies a positive voltage pulse to the gate of Oscillator Circuit transistor Q2. Once transistor Q2 turns on, diode D2 conducts to allow capacitor C1 to discharge through transistor Q2 to ground. This process keeps the charge voltage of capacitor C1 below the threshold of diac D3 so that D3 is not triggered to produce start pulses when they are not required (while oscillation is sustained in the Oscillator Circuit). Should oscillation stop during use, the voltage on C1 can charge to the diac trigger level since Q2 and D2 are no longer discharging C1. Once the diac triggers, the oscillation is restarted and operation continues.

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BioSonic® UC50 and UL2 Ultrasonic Cleaning System

•

Oscillator Circuit. The Oscillator Circuit consists of transformer windings T1-A, T1B, and T1-D; MOSFET transistors Q1 and Q2; capacitors C2 and C3; resistors R3 and R4; and zener diodes D4 through D7. Transistor Q2 turns on when the Start Network applies a positive voltage to its gate, allowing current to flow from the positive rail of the Rectifier (via the voltage tap formed by C1 and C2), through the primary winding of Isolation Transformer T2, and through Q2 drain and source to the negative supply rail. Current is induced in the secondary T2 winding. It flows from T2 pin 10 through tuning coil L2, through crystals X1 and X2, and through transformer winding T1-D, returning to pin 9 of Isolation Transformer T2. This current flow through transformer winding T1-D simultaneously induces a negative voltage in transformer winding T1-B, turning Q2 off, and induces a positive voltage in transformer winding T1-A, turning Q1 on. With transistor Q1 on, the current flows from the positive rail of the rectifier through Q1, the primary winding of transformer T2, and capacitor C1. This induces current in the opposite direction in the secondary T2 winding, which flows from T2 pin 9 through transformer winding T1-D, through crystals X1 and X2, and through tuning coil L2, returning to pin 11 of transformer T2. Transformer winding T1-D will continue to induce a voltage in transformer winding T1-B and T1-A, alternating transistors Q1 and Q2 between “on” and “off” states. This action maintains oscillations in the tank assembly. Once oscillation has been initiated, capacitor C3 is shorted, and the start pulses are discontinued (as explained in the Oscillator Start Network description above). The Limiter functions as described below to prevent voltages of greater than ± 15 volts from appearing at the gates of the transistors. L1 is connected to T1-A to balance the transistor switching and produce optimum switching action. Transformer T1’s tertiary A winding serves to couple tunable inductance L1 to the transistor gates where it resonates at the operating frequency with the gate input capacitance. This balances the conduction cycle of each transistor.

•

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Limiter. Zener diodes D4 and D5 provide over-voltage protection for transistor Q1 by limiting the gate voltage to approximately 15 volts. In the same manner, zener diodes D6 and D7 provide over-voltage protection for the gate of transistor Q2. The zener diodes absorb energy that would damage the transistors if the diodes were not present. This potentially damaging energy is present during normal operation because of the large dynamic range that must be handled for efficient operation.