AU2021200033B2

AU2021200033B2 - Radiator fan heater

Info

Publication number: AU2021200033B2
Application number: AU2021200033A
Authority: AU
Inventors: Peter Denison Clarke
Original assignee: Individual
Current assignee: Individual
Priority date: 2020-01-09
Filing date: 2021-01-05
Publication date: 2022-01-06
Anticipated expiration: 2041-01-05
Also published as: AU2021200033A1

Abstract

Provided is a radiator fan heater 10 comprising a fluid-filled radiator 12, a fan 14 arranged proximate the radiator 12, an electric heating element 16 configured to heat a fluid within said radiator 12, and a controller 18. The controller 18 includes a user-selectable temperature setting 20, an ambient temperature sensor 22 for sensing an ambient temperature, and power control circuitry 24. The circuitry 24 comprises a bidirectional triode thyristor or 'triac' 26 connected to the heating element 16, a zero-voltage crossing bilateral triac driver 28 for driving the triac 26 from a mains AC supply 30, and a triangular wave generator 32 configured to generate a triangular wave from said mains AC supply 30. Circuitry 24 also includes a dual comparator 34 which compares the ambient and user temperatures in order to adjust a firing angle of the triac 26, via the driver 28, as referenced to a zero crossing of the AC waveform via the triangular wave. In this manner, the power control circuitry 24 modulates the mains AC supply 30 to the heating element 16 to regulate the heater 10 at the user-selectable temperature. Also provided is an associated electronic thermostat implemented via analogue discrete components or via a microcontroller. 1/3 10 14 12 18 24 16 20 22 30i 1 Figure 1.

Description

1/3

14 12

18

24 16

20 22

30i 1

Figure 1.

RADIATOR FAN HEATER TECHNICAL FIELD

[0001] This invention relates broadly to the field of

electric heating, and more specifically to a radiator fan

heater and an associated electronic thermostat for heating

appliances.

BACKGROUND ART

[0002] The following discussion of the background art is

intended to facilitate an understanding of the present

invention only. The discussion is not an acknowledgement or

admission that any of the material referred to is or was part

of the common general knowledge as at the priority date of the

application.

[0003] Conventional fan heaters typically comprise a

heating element with a fan for forcing air across said heating

element and the heating element regulated by a bimetallic strip

thermostat. Such bimetallic thermostats are known and one end

of the bimetallic strip is generally mechanically fixed and

attached to an electrical power source, while the other

(moving) end carries an electrical contact. In adjustable

thermostats, the moving end of the bimetallic thermostat is

positioned with a regulating knob or lever, with the position

set to control the temperature.

[0004] Such conventional thermostats often deteriorate over

time and is often a failing point for a heating appliance, as

the contacts move or become fouled which leads to the appliance

no longer being able to regulate temperature accurately.

[0005] In addition, conventional thermostats for heating

appliances, such as electric frying pan thermostats, do not

produce even heating, as the heating element is either 'on' or

'off'. This can lead to burnt food due to such uneven heating,

or other undesirable cooking conditions.

[0006] The current invention was conceived in order to

ameliorate some of the shortcomings in the field of electrical

heating appliances.

SUMMARY OF THE INVENTION

[0007] According to a first aspect of the invention there

is provided a radiator fan heater comprising:

a fluid-filled radiator;

a fan arranged proximate the radiator;

an electric heating element configured to heat a fluid

within said radiator; and

a controller including:

a) a user-selectable temperature setting;

b) an ambient temperature sensor for sensing an

ambient temperature; and

c) power control circuitry comprising:

i) a bidirectional triode thyristor or 'triac'

connected to the heating element;

ii) a zero-voltage crossing bilateral triac

driver for driving said triac from a mains AC

supply;

iii) a triangular wave generator configured to

generate a triangular wave from said mains AC

supply; and iv) a dual comparator which compares the ambient and user temperatures in order to adjust a firing angle of the triac, via the driver, as referenced to a zero crossing of the

AC waveform via the triangular wave;

wherein the power control circuitry modulates the mains

AC supply to the heating element to regulate the heater at the

user-selectable temperature.

[0008] The skilled addressee is to appreciate that by

adjusting the firing angle of the triac, i.e. the point in the

mains AC voltage waveform where the triac turns on, the mains

voltage applied to the heating element can be modulated and

the temperature can be effectively regulated according to the

comparison between sensed and desired temperatures.

[0009] Typically, the radiator fluid is water with or

without additives.

[0010] Typically, heating element comprises a cartridge

heater.

[0011] Typically, the user-selectable temperature setting

includes a potentiometer.

[0012] Typically, the ambient temperature sensor includes

a thermistor.

[0013] Typically, the triac driver includes an optocoupler

to decouple the mains AC supply from the power control

circuitry.

[0014] Typically, the triangular wave generator comprises

a diode-bridge rectifier, fixed voltage regulator and

associated resistive and capacitive components for producing

the triangular wave to the comparator as derived from the mains

AC supply.

[0015] Typically, the fan is supplied from the mains AC

supply.

[0016] Typically, the power control circuitry is configured

to control the fan according to the sensed ambient and/or user

selectable temperature setting.

[0017] According to a second aspect of the invention there

is provided an electronic thermostat for an electrical heating

appliance having a heating element, said thermostat

comprising:

a user-selectable temperature setting;

an ambient temperature sensor for sensing an ambient

temperature; and

power control circuitry comprising:

i) a bidirectional triode thyristor or 'triac'

connectable to the heating element;

ii) a zero-voltage crossing bilateral triac driver

for driving said triac from a mains AC supply;

iii) a triangular wave generator configured to

generate a triangular wave from said mains AC supply;

and

iv) a dual comparator which compares the ambient and

user temperatures in order to adjust a firing angle

of the triac, via the driver, as referenced to a

zero crossing of the AC waveform via the triangular

wave; wherein the power control circuitry modulates the mains

AC supply to the heating element to regulate the heating

element at the user-selectable temperature.

[0018] Typically, the user-selectable temperature setting

includes a potentiometer.

[0019] Typically, the ambient temperature sensor includes

a thermistor.

[0020] Typically, the triac driver includes an optocoupler

to decouple the mains AC supply from the power control

circuitry.

[0021] Typically, the triangular wave generator comprises

a diode-bridge rectifier, fixed voltage regulator and

associated resistive and capacitive components for producing

the triangular wave to the comparator as derived from the mains

AC supply.

[0022] According to a further aspect of the present

invention there is provided a radiator fan heater and an

electronic thermostat for an electrical heating appliance

substantially as herein described and/or illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

The description will be made with reference to the accompanying

drawings in which:

Figure 1 is a diagrammatic representation of an example

radiator fan heater, in accordance with one aspect of the

present invention;

Figure 2 is a diagrammatic representation of a circuit

diagram shown in LTspice, a well-known 'Simulation Program

with Integrated Circuit Emphasis' (SPICE) simulation software

package, of an example of the controller of Figure 1; and

Figure 3 is a diagrammatic representation of a circuit

diagram shown in LTspice of a further example of the

controller of Figure 1 implemented by means of a suitable

microcontroller.

DETAILED DESCRIPTION OF EMBODIMENTS

[0023] Further features of the present invention are more

fully described in the following description of several non

limiting embodiments thereof. This description is included

solely for the purposes of exemplifying the present invention

to the skilled addressee. It should not be understood as a

restriction on the broad summary, disclosure or description of

the invention as set out above.

[0024] In the figures, incorporated to illustrate features

of the example embodiment or embodiments, like reference

numerals are used to identify like parts throughout.

Additionally, features, mechanisms and aspects well-known and

understood in the art will not be described in detail, as such

features, mechanisms and aspects will be within the

understanding of the skilled addressee.

[0025] With reference now to the accompanying figures,

there is shown one possible embodiment of a radiator fan heater

10. In the exemplified embodiment, the fan heater 10 comprises

a fluid-filled radiator 12 and a fan 14 arranged proximate the radiator 12. In Figure 1, the fan 14 is shown distal from the radiator 12, but this is only for ease of explanation.

[0026] The radiator 12 is typically filled with water which

may include additives, such as corrosion inhibitors, additives

to improve heat capacity, or the like. The heater 10 also

includes an electric heating element 16 which is arranged and

configured to heat the fluid within the radiator 12. In a

typical example, the heating element 16 comprises a cartridge

heater, or the like.

[0027] The heater 10 also includes a controller 18 which

has a user-selectable temperature setting 20, an ambient

temperature sensor 22 for sensing an ambient temperature, and

power control circuitry 24. In one embodiment, the user

selectable temperature setting 20 includes a potentiometer and

the ambient temperature sensor 22 includes a thermistor.

Variations hereon are possible and within the scope of the

present invention.

[0028] As more clearly shown in Figure 2, one example of

the power control circuitry 24 comprises a bidirectional triode

thyristor or 'triac' 26 connected to the heating element 16,

and a zero-voltage crossing bilateral triac driver 28 for

driving the triac from a mains AC supply 30. The triac driver

28 also includes an optocoupler to decouple the mains AC supply

from the power control circuitry 24. An example of such a

traic driver is the ON Semiconductor' MOC3043 triac driver and optocoupler.

[0029] The power control circuitry 24 also includes a

triangular wave generator 32 which configured to generate a

triangular wave from the mains AC supply 30. In the present example, the triangular wave generator 32 comprises a diode bridge rectifier, fixed voltage regulator and associated resistive and capacitive components for producing the triangular wave from the mains AC supply 30. An example of the voltage regulator is the Linear TechnologyTM LT1021 fixed voltage regulator.

[0030] The power control circuitry 24 further includes a m dual comparator 34, such as the Linear Technology LT1018

comparator, which compares the ambient and user temperatures

in order to adjust a firing angle of the triac 26, via the

driver 28, as referenced to a zero crossing of the AC waveform

via the triangular wave from the wave generator 32. In this

manner, the power control circuitry 24 is able to modulate the

mains AC supply 30 to the heating element 16 to regulate the

heater at the user-selectable temperature.

[0031] With reference to the circuit of Figure 2, the wave

generator 32 comprises resistors R2, R3, and R4 as supplied

from the voltage regulator U3. Input B+ to the comparator 34

and capacitor Cl produces a triangle wave. When capacitor Cl

is charging and comparator Ul output is at 24V, the B+

reference is at 12.385V. When capacitor Cl reaches this

voltage, the B+ reference changes to 11.615V. The output

voltage of comparator Ul changes to zero.

[0032] The capacitor Cl discharges through R1 to 11.615V

and the output voltage of comparator Ul changes to 24V and the 'new' B+ reference becomes 12.385V again. This repeats over

and over to produce the triangular wave. For the values shown

in Figure 2, 12V is applied to comparator U2+ or 1/2 power to

the controlled device. If the ambient temperature drops, as sensed by thermistor R5, full power is applied to the heating device via the driver 28 and triac 26.

[0033] If the ambient temperature rises, the triac is

switched off and no power is supplied to the heating element

16 shown as resistive element R10. The power to the power

circuitry 24 and heating element 16 is supplied directly from

the mains AC supply 30, as shown.

[0034] As part of the wave generator 32.1, the mains supply

live wire is connected to a diode bridge, as shown, through

a 15k 5-watt resistor R8. Mains supply 30 neutral is connected

to the other side of the diode bridge, as shown. Using a 24

volt fixed regulator U3 to comparator U2's positive input, the

output of U2 is connected to the cathode of the triad driver

28, as shown, which turns on the triac at zero crossing of the

AC waveform when the output is low.

[0035] In this manner, one cycle of the triangle wave takes

0.133s. One half-cycle of the AC mains supply takes 0.01s.

This means that for 1 cycle of the triangle wave the mains

have run 13.3 half cycles. The duty cycle is determined by the

+ input of comparator U2, which determines the power applied

to the heater element 16. Variations on the elements described

in this example are, of course, possible and within the scope

of the present invention.

[0036] The skilled addressee is further to appreciate that

the fan 14 is also typically supplied from the mains AC supply

30. Accordingly, the power control circuitry 24 may be

configured, in one embodiment, to control the fan 14 according

to the sensed ambient and/or user-selectable temperature

setting, as per the triac, or via another methodology. In one example, the fan may be controlled by a user via a manual setting, or the like.

[0037] The skilled addressee is further to appreciate that,

while the example shown in Figure 1 comprises a radiator fan

heater 10, the invention also comprises an associated

electronic thermostat for any suitable electrical heating

appliance having a heating element. For example, the invention

may find similar application in regulating a temperature of a

kettle, an electric frying pan, a toaster, or the like.

[0038] In such an embodiment, the invention comprises an

electronic thermostat for an electrical heating appliance

having a heating element 16, with the thermostat comprising

the user-selectable temperature setting 20, the ambient

temperature sensor 22 for sensing an ambient temperature, and

the power control circuitry 24.

[0039] As above, the power control circuitry 24 generally

includes the triac 26 connectable to the heating element 16,

the triac driver 28 for driving said triac from a mains AC

supply 30, and the triangular wave generator 32 which is

configured to generate a triangular wave from the mains AC

supply 30 as described above.

[0040] The power control circuitry 24 also includes the

dual comparator 34 which compares the ambient and user

temperatures in order to adjust a firing angle of the triac

26, via the driver 28, as referenced to a zero crossing of the

AC waveform via the triangular wave, so that the power control

circuitry 24 is able to modulate the mains AC supply to the

heating element to regulate the heating element at the user

selectable temperature.

[0041] It is also to be appreciated that the invention, in

particular the electronic thermostat, may also be implemented

via a suitable microcontroller, an example of which is shown

in Figure 3. For example, the wave generator and comparator

(and even driver) may be comprised in a single microcontroller

package, or the like. In the example of Figure 3, an Atmega m

328P microcontroller is used to perform similar functions as

the analogue circuit of Figure 2. Such a controlling circuit

performs "temperature-controlled power" and can be used for

controlling the power output of a heating device, represented

by heating element 16.

[0042] With conventional thermostats, supposing a

controller sets a desired temperature of 22C. If the ambient

is less than this, the conventional controller applies full

power to the heater 16 and when 22C is reached no power is

applied. At a certain lower temp full power is applied again

and thus the heater or other appliance cycles on and off. The

controller of the present invention is configured and adapted

to apply temperature-controlled power, where if the desired

temp is set at 22C, the controller applies full power at 21C.

At 21.5C, half power is applied and at 22C no power is applied.

In this manner, the applied power is proportional to the

temperature. Because of this the ambient temp will lie between

21C and 22C. An advantage of such a control scheme, is the

application of even heating, rather than uneven heating

resulting from conventional cycled heating approaches, i.e. 'on' or 'off' heating.

[0043] The following provides an example of temperature

controlled power supplied to a mains-operated device, using a

microcontroller program in the Arduinom program language on an

Atmega m 328 microcontroller for a PWM control method with an

output to a zero-voltage crossing triac optocoupler:

int a=AO; // this reads the analog input port AO

int pwm = 12; assignss pin 12 to variable pwm

double t2; thiss sets the timing for pwm

void setup() /7 setup loop

{

pinMode(pwm, OUTPUT); declaress pin 12 as output

Serial.begin(9600);

}

void loop()

{

a = analogRead(AO); /7 reads the analog voltage at the AO port

if (a <506){ /7 if the temperature is more than .5c below the set temp apply full power

t2=0; // set temp is value of resistance connected in series to thermister

} // thermister connected to 5v, resistance to ground

if (a>518){ /7if temp more than .5c above set temp apply no power

t2=1023;

}

if (a>=506 && a<=518){

t2 = ((a-505)*85.25)-85.25; /7 covers values of a between 497 and 524. avoids negative values

}

digitalWrite(pwm, HIGH); /7 sets pin 12 HIGH

delay((1023-t2)/5); /7 waits for (1023-t2)/5 ms (high time)

digitalWrite(pwm, LOW); /7 sets pin 12 LOW(t2);

delay(t2/5); // waits for t2/5 ms (low time)

Serial.println(a);

Serial.println(t2);

Serial.println(1023-t2);

}

[0044] The following provides an example of temperature

controlled power supplied to a mains-operated device, using a

microcontroller program in the Arduinom program language on an Atmega T 328 microcontroller for a phase control method with an output to a zero-voltage crossing triac optocoupler:

int a; thiss reads the analog input port AO

/7 for zero crossing

int t; thiss is the temperature read on port Al

double d; thiss variable sets the delay in turning on the triac

void setup() /7 setup loop

{pinMode(11, OUTPUT);

Serial.begin(9600);

}

void loop()

{ a = analogRead(AO); /7 reads the analog voltage at the AO port if (a==1023){ pinMode(10, INPUT);// sets anode of opto led to hiZ opto off

} // pin 10 connected to anode of opto led

else{

pinMode(10,OUTPUT);

digitalWrite(10, LOW); //sets anode to low after zero crossing

}

t = analogRead(A1); readss temperature at Al

if (t< 506){

d=0.1; turnss on triac at .lms

}

if(t>518){

d=9.5; turnss off triac at 9.5ms

}

if (t>=506 && t<=518){

d=(t-505.87)/1.2766;}

Serial.println(t);

Serial.println(d);

digitalWrite(11,LOW); turnss off opto for delay time

delayMicroseconds(d*1000); /7pin 11 connected to cathode of opto led

digitalWrite(11, HIGH); turnss on opto after delay

}

[0045] The skilled addressee will appreciate that

variations on the above programming language are possible and

within the scope of the present invention.

[0046] Applicant believes is particularly advantageous that

the present invention provides for a radiator fan heater and

associated electronic thermostat which allows for precise

temperature control in an elegant and efficient manner. The

heating element and controller are supplied directly from an

AC mains supply without requiring transformers or other

conventional methods, thereby improving power efficiency.

[0047] Optional embodiments of the present invention may

also be said to broadly consist in the parts, elements and

features referred to or indicated herein, individually or

collectively, in any or all combinations of two or more of the

parts, elements or features, and wherein specific integers are

mentioned herein which have known equivalents in the art to

which the invention relates, such known equivalents are deemed

to be incorporated herein as if individually set forth. In the

example embodiments, well-known processes, well-known device

structures, and well-known technologies are not described in

detail, as such will be readily understood by the skilled

addressee.

[0048] The use of the terms "a", "an", "said", "the", and/or

similar referents in the context of describing various

embodiments (especially in the context of the claimed subject

matter) are to be construed to cover both the singular and the

plural, unless otherwise indicated herein or clearly

contradicted by context. The terms "comprising, " "having, "

"including, " and "containing" are to be construed as open

ended terms (i.e., meaning "including, but not limited to,") unless otherwise noted. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items. No language in the specification should be construed as indicating any non-claimed subject matter as essential to the practice of the claimed subject matter.

[0049] It is to be appreciated that reference to "one

example" or "an example" of the invention, or similar exemplary

language (e.g., "such as") herein, is not made in an exclusive

sense. Various substantially and specifically practical and

useful exemplary embodiments of the claimed subject matter are

described herein, textually and/or graphically, for carrying

out the claimed subject matter.

[0050] Accordingly, one example may exemplify certain

aspects of the invention, whilst other aspects are exemplified

in a different example. Variations (e.g. modifications and/or

enhancements) of one or more embodiments described herein might

become apparent to those of ordinary skill in the art upon

reading this application. The inventor(s) expects skilled

artisans to employ such variations as appropriate, and the

inventor(s) intends for the claimed subject matter to be

practiced other than as specifically described herein.

[0051] Any method steps, processes, and operations

described herein are not to be construed as necessarily

requiring their performance in the particular order discussed

or illustrated, unless specifically identified as an order of

performance. It is also to be understood that additional or

alternative steps may be employed.

Claims

1. A radiator fan heater comprising:

a fluid-filled radiator;

a fan arranged proximate the radiator;

an electric heating element configured to heat a fluid

within said radiator; and

a controller including:

a) a user-selectable temperature setting;

b) an ambient temperature sensor for sensing an

ambient temperature; and

c) power control circuitry comprising:

i) a bidirectional triode thyristor or 'triac'

connected to the heating element;

ii) a zero-voltage crossing bilateral triac

driver for driving said triac from a mains AC

supply;

iii) a triangular wave generator configured to

generate a triangular wave from said mains AC

supply; and

iv) a dual comparator which compares the

ambient and user temperatures in order to

adjust a firing angle of the triac, via the

driver, as referenced to a zero crossing of the

AC waveform via the triangular wave;

wherein the power control circuitry modulates the mains

AC supply to the heating element to regulate the heater at the

user-selectable temperature.

2. The heater of claims 1, wherein the radiator fluid is water

with or without additives.

3. The heater of claim 1, wherein the heating element comprises

a cartridge heater.

4. The heater of claim 1, wherein the user-selectable

temperature setting includes a potentiometer.

5. The heater of claim 1, wherein the ambient temperature

sensor includes a thermistor.

6. The heater of claim 1, wherein the triac driver includes an

optocoupler to decouple the mains AC supply from the power

control circuitry.

7. The heater of claim 1, wherein the triangular wave generator

comprises a diode-bridge rectifier, fixed voltage regulator

and associated resistive and capacitive components for

producing the triangular wave to the comparator as derived

from the mains AC supply.

8. The heater of claim 1, wherein the fan is supplied from the

mains AC supply.

9. The heater of claim 1, wherein the power control circuitry

is configured to control the fan according to the sensed

ambient and/or user-selectable temperature setting.