GB2336256A

GB2336256A - A motor controller

Info

Publication number: GB2336256A
Application number: GB9805784A
Authority: GB
Inventors: William Johnston; Graham Lowe
Original assignee: MICROFLOW UK Ltd
Current assignee: MICROFLOW UK Ltd
Priority date: 1998-03-19
Filing date: 1998-03-19
Publication date: 1999-10-13
Anticipated expiration: 2018-03-19
Also published as: GB9805784D0; GB2336256B

Abstract

A motor controller comprises a microcontroller 1 for controlling a plurality of functions, means for varying a voltage to be supplied to a motor to be controlled and means for supplying the motor to run at full power initially for a preset time and subsequently at a power level less than full power under control of the microcontroller. The motor controller may be used in a beer dispensing system comprising a beer supply line between a beer supply and a tap. A pump is disposed in the line to pump beer through the line from the supply to the tap. The pump is driven either by an induction motor or a series wound motor. Operation of the motor is controlled by the microcontroller in dependence upon signals received from a pressure switch 2 which monitors pressure in the line, a flow switch 3 which monitors flow in the line and a reset switch. The microcontroller operates to run the motor initially at a higher speed and then at a lower speed to overcome any tendency of an induction motor to stall thus enabling either an induction or a series wound motor to be used.

Description

2336256 A MOTOR CONTROLLER The present invention relates to an electric

motor controller. The controller is particularly, but not exclusively, intended for pump motors for use in beer lines.

The use of electric motor driven pumps in beer lines is well known. In driving such pumps both series wound and induction motors have been used. Differing supply voltage such as 240 volts or 110 volts have also been used. Currently, controllers for such pump motors are tailored to each individual application. This is. costly and inefficient. Apart from having to design and produce different controllers for different circumstances, a maintenance technician must carry a selection of controllers to be in a position to repair differing inadons.

According to the present invention, there is provided a motor controller comprising a microcontroller for controlling a plurality of functions, means for varying a voltage to be supplied to a motor to be controlled and means for suppl the motor to run the motor at full power initially for a preset time -and subsequently at a power level less than full power under the control of the microcontroller.

In a preferred embodiment of the invention the motor to be controlled is the pump motor of a fluid dispensing system, preferably a free flow beer or other beverage dispensing system. The dispensing system comprises a beer line leading from a beer keg to a dispense tap. The motor may be series wound or induction. The means for varying the reduced voltage to be supplied to the motor may be a potentiometer. A flow switch may be provided for monitoring the flow of beer in the beer line. A pressure switch is provided-for measuring the beer pressure in the beer line and a reset switch is provided for resetting the system. All these switches are monitored by the microcontroller. The supply circuit to the microprocessor comprises a capacitor, a bridge rectifier and voltage regulator. The capacitor is used to drop the voltage from the mains level. This reduced voltage is then rectified by the bridge rectifier, smoothed and clamped to a lower d.c. voltage and further reduced by the voltage regulator to provide the voltage supply for the microprocessor. The advantage of a capacitor over a resistor is that heat producing losses are reduced or eliminated as the impedance is totally reactive. In operation, when the dispense tap is opened the pressure in the beer line falls. This is sensed by the pressure switch and monitored by the microcontroller which acts to switch on the motor. The motor is run for a preset period at full power, thus overcoming any tendency to stall, and thereafter at reduced power. The flow switch indicates the flow of beer in the line. The absence of flow combined with a high pressure indicates that the tap has been shut. The motor is then set by the microcontroller to run on for a predetermined period after absence of flow to repressurise the line and then stop. The absence of flow combined with low pressure indicates an empty keg or a burst pipe. Under these conditions the motor is run for a predetermined period after which it will stop and not restart until the system is reset by operation of the reset switch.

In order that the invention may be more clearly understood, one embodiment thereof will now be described, by way of example, with reference to the accompanying drawings, in which:- Figure 1 is a circuit diagram of a universal motor controller according to the invention, and Figure 2 is a flow chart Mustrating the operation of the controller of Figure.l.

Referring to Figure 1, the controller comprises a microcontroller integrated circuit 1 for the control of all functions of the controller. A beer pressure switch 2 is provided to sense the pressure of beer in the line, a flow switch 3 is provided to ednse the presence or absence of beer in the line and a reset switch 4 is provWed for resetting the system. All of these switches 2, 3 and 4 are conno to appropriate pins of the integrated circuit 1. The power supply circuitry to the microcontroller is indicated generally by reference numeral 6. This comprises a bridge rectifier 7, zener diode 8, smoothing capacitor 15 and voltage regulator 16. The mains supply, usually 240 volts a.c., is connected to the circuit via terminals 13 and 14. Supply capacitor 9 is used to drop this voltage to a lower level which is then rectified by bridge rectifier 7 smoothed by capacitor 15 and clamped by zener diode 8 to 15 voltage d.c. and then voltage regulated by voltage requ-1ator 16 to 5 volts for the microcontroller. The supply capacitor 9 enables the supply voltage to be dropped without incurring significant heat producing losses. Terminals 10 and 11 are provided for connection of the controller to the chosen beer pumping motor. A potentiometer 5 is provided to enable the reduced voltage supplied to the motor and therefor motor speed to be varied as desired. Afl functions are timed to the phase reference of the mains supply. When the potentiometer resistance is low, a capacitor 13 in series therewith charges up and reaches a trigger level more quickly. When the trigger level is reached a pulse is sent, via an opto isolator 17, to a triac 18 earlier in the cycle which results in a higher voltage being supplied to the motor via terminals 10 and 11. As the potentiometer resistance is increased, capacitor 13 takes longer to charge and therefore reaches the trigger level later in the cycle. The pulse is sent to triac 18 via opto isolator 17 later resulting in a lower voltage being supplied to the motor thereby running the motor at a correspondingly lower power.

The operation of the above controller will now be described by reference to the flowchart of figure 2. The controller is connected to the beer pumping motor of the free flow beer supply system. The motor may be for a 110 volt or 240 volt supply and may be series wound or induction. The pressure switch 2 monitors the pressure of beer in the beer supply line to the barhead. When the pressure is greater than a specific preset level, for example, 321bs per square inch the switch gives an off signal to the microcontroller integrated circuit 1. This specific pressure may be adjusted electronically or by a mechanical adjustment on the pressure switch 2. Normally, at least three pre-set pressure levels are provided for. A bi-colour light emitting diode 12 is provided to indicate the status of the beer line. When the dispense tap at the barhead is operated, the pressure of beer in the supply line will fall below the specific preset level. This fail is detected by pressure switch 2 and a signal fed to the microcontroller integrated circuit 1 which in turn operates to supply current to the motor to run the motor via triac 18 for a presM time of two seconds at full speed. After that preset time, the speed of the motor drops to a preset lower running speed and therefor preset lower power. This lower speed is set by the potentiometer 5 as already described. This arrangement reduces any tendency for the motor to stall on start up but reduces power consumption by running at the lower speed during normal operation. The tendency to stall is greater with induction nx than with series wound motors in view of the lower start up torque produced with induction motors. Without this arrangement, therefore, the controller may not be able to cope automatically with both types of motor.

When the dispense tap is closed, pressure once again builds up in the supply line- and the flow switch 3 is monitored by the microcontroller integrated circuit 1 to detect when flow has ceased. The microcontroller integrated circuit 1 switches off the supply to the motor approximately two seconds later and the motor stops. By running the motor for a period of time after the dispense tap has been closed, the supply line can be repressurised. This reduces tendency to fob or froth when the dispenser tap is next opened. The final pressure in the supply line can be controlled by the speed of the motor or the over-run time.

Further safety features are provided as follows. If the motor runs continuously for more than a specific preset time for example five minutes, a fault such as a burst pipe is indicated and the microcontroller integrated circuit 1 operates to switch off the motor to prevent further beer supply. Conversely, if the pressure and flow switches 2 and 3 indicate no pressure and no flow, this indicates no beer in the supply line. The motor will then time out in twelve seconds after this condition is detected to reduce the possibility of damage to the motor. The LED 12 illustrates red to indicate that a time out has occurred and green to indicate that the lines have -7pressurised correctly after a beer dispense.

It will be appreciated that the above embodiment has been described by way of example only and that many variations are possible without departing from the scope of the invention.

Claims

1 A motor controller comprising a microcontroller for controlling a plurality of functions, means for varying a voltage to be supplied to a motor to be controlled and means for supplying the motor to run the motor at full power initially for a preset time and subsequently at a power level less than full power under the control of the microcontroller.

2. A motor controller as claimed in claim 1, in which the means for varying a voltage comprises a potentiometer.

3. A motor controller as claimed in claim 1 or 2, in which a supply circuit for the microcontroller comprises a capacitor, bridge rectifier and voltage regulator, the capacitor being used in operation to reduce mains voltage, the reduced voltage being rectified by the rectifier and further reduced by the voltage regulator.

4. A fluid dispensing system comprising a pump, a motor for driving the pump and a motor controller as claimed in claim 1, 2 or 3 for controlling the pump.

5. A fluid dispensing system as claimed in claim 4, in which the motor is an induction motor.

6. A fluid dispensing system as claimed in claim 4, in which the motor is a series wound motor.

7. A fluid dispensing system as claimed in claim 4, 5 or 6, in which a flow switch, which in operation is monitored by the microcontroller, is provided for monitoring fluid flow.

8. A fluid dispensing system as claimed in claim 4, 5, 6 or 7, in which a pressure switch, which in operation is monitored by the microcontroller is provided for monitoring fluid pressure.

9. A fluid dispensing system as claimed in any of claims 4 to 8, in which a reset switch, which in operation is monitored by the micro controller, is provided for resetting the system.

10. A fluid dispensing system substantially as hereinbefore described with reference to the accompanying drawing.

11. A motor controller substantially as hereinbefore described with reference to the accompanying drawings.