CA1156743A - Relative humidity/temperature sensing control - Google Patents
Relative humidity/temperature sensing controlInfo
- Publication number
- CA1156743A CA1156743A CA000359475A CA359475A CA1156743A CA 1156743 A CA1156743 A CA 1156743A CA 000359475 A CA000359475 A CA 000359475A CA 359475 A CA359475 A CA 359475A CA 1156743 A CA1156743 A CA 1156743A
- Authority
- CA
- Canada
- Prior art keywords
- relative humidity
- output signal
- temperature
- comparator
- digital
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D22/00—Control of humidity
- G05D22/02—Control of humidity characterised by the use of electric means
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Engineering & Computer Science (AREA)
- Automation & Control Theory (AREA)
- Ventilation (AREA)
- Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
- Control Of Temperature (AREA)
Abstract
ABSTRACT
A device for controlling electrical equipment associated with a building in response to selected pairs of exterior temperature and interior relative humidity signals derived from temperature and humidity sensors, the pairs of signals being preselected such that the electrical equipment is activated only for those combinations of temperature and humidity which give rise to condensation in the interior of the building.
A device for controlling electrical equipment associated with a building in response to selected pairs of exterior temperature and interior relative humidity signals derived from temperature and humidity sensors, the pairs of signals being preselected such that the electrical equipment is activated only for those combinations of temperature and humidity which give rise to condensation in the interior of the building.
Description
115~743 ~1--This invention relates to the sensing of exterior temperature and interior relative humidity and to providing an output control signal which is zero for selected combinations of the temperature and relative humidity and which is finite for other selected combinations. The invention has particular but not exclusive, application in the control of an extraction fan which is activated in response to the control signal when it becomes necessary to remove moist air from the interior of a building.
The principle behind this controller is that in order to eliminate water damage to house interiors due to condensation, the moisture laden air has to be exhausted when the relative humidity (R.H.) reaches certain critical levels. Since condensation inside will occur at different levels of relative humidity depending on the outside temperatures, the controller has inputs from an interior R.H. sensor and an exterior temperature sensor.
The invention to be described, provides a controller which compares an output signal from a temperature sensor and the output from a relative humidity sensor and decides whether to turn the exhaust fan on to remove moist air there-fore reducing relative humidity or leave the fan off since for the given outside temperature the inside relative humidity is acceptable. By controlling the fan to the condition of a Selection Table the device will allow the relative humidity to be higher at warmer temperatures. The control unit is a self contained unit, with sensors being remotely connected, and consisting of prescaling resistor input networks, analog comparators, digital comparator fan relay actuating circuit and power supply.
It is a feature of one object of the invention to provide a controller having an output signal which is finite for selected pairs of values for temperature and relative humidity and which is zero for other selected pairs of values for temperature and relative humidity.
1 15~7~3 It is a feature of another object of the invention to utilize the controller described in the previous paragraph to selectively activate atmospheric extraction apparatus.
In accordance with the foregoing features, there is provided, a temperature/humidity responsive device for controlling auxiliary equipment as a function of combinations of selected pairs of discrete values of temperature and relative humidity, said device comprising a temperature sensor having an electrical output signal which varies with temperature, a relative humidity sensor having an electrical output signal which varies with relative humidity, a first analogue comparator connected to receive said output signal from said temperature sensor and producing a selected number of digital output signals corresponding to an equal number of discrete selected values of said output signal from said temperature sensor, a second analogue comparator connected to receive said output signal from said relative humidity sensor and producing a selected number of digital output signals corresponding to an equal number of discrete selected values of said output signal from said relative humidity sensor, and a digital comparator connected to receive the digital output signals from said first and second analogue comparators, said comparator producing an output signal in response to said combinations of said selected pairs of discrete values of temperature and relative humidity.
A preferred embodiment of the invention will be described with reference to the accompanying drawings, in which:
Fig. 1 is a circuit diagram of a fan controller.
Fig. 2 is a graph of the electrical output signal derived from a typical temperature sensor versus temperature and the digitized equivalents of the output signal for four selected temperatures.
Fig. 3 is a graph and digitized equivalents similar to Fig. l, but for a typical relative humidity sensor.
115~743 Referring to Fig. 1, the output A from a temperature sensor Sl is applied to pins 4, 6, 8 and 10 to an analogue comparator IC1. A suitable temperature sensor is an AD590 manufactured by ANALOGUE DEVICES, INC. and a suitahle analogue comparator is the LM339 manufactured by NATIONAL SEMICONDUCTOR
CORPORATION. The temperature sensor Sl is such that the electrical output therefrom changes 1 microamp/ K and the value of Rll is found to be 10K ohms to vary the voltage of output signal A with a slope of 10 millivolts/ C. This characteristic is shown in Fig. 2. A pre-scaler, shown at 102, may be incorporated to modify the signal A before application of the signal to the analogue comparator ICl.
As indicated in Fig. 1, four selected threshold levels of signal A are utilized and these levels are set by a potential divider comprising Rl, R2, R3, R~ and R5. The analogue comparator has four switched digitized outputs from pins 1, 2, 14 and 13 corresponding to the respective ones of the four threshold levels of the input signal A.
The output B from a relative humidity sensor S2 is applied to pins 4, 6, 8 and 10 of an analogue comparator TC2 which may be similar to TCl. A suitable relative humidity (R.H.) sensor is a BR-lOlB manufactured by THUNDER SCIENTIFIC
CORP. The R.H. sensor is such that the electrical output therefrom changes approximately 1.0 volts over the range of 10% to 90% R.H. This characteristic is shown in Fig. 3.
A prescaler, shown at 104, may be incorporated to modify the signal B before application of the signal to the analogue comparator TC2. As indicated in Fig. 1, four selected threshold levels of signal B are utilized and these levels are set out by a potential divider comprising R6, R7, R8, R9 and R10.
The four selected values of R.H. are so made so that the outputs from the digital comparator TC2 change at critical levels of humidity (HCl, HC2, HC3 and HC4) as indicated in Fig. 3.
I l SB74 3 The analogue comparator TC2 has four switch digitized outputs from pins 1, 2, 13 and 14 corresponding to respective ones of the four threshold levels of the input signal B.
The four outputs from pins 1, 2, 13 and 14 of the analogue comparators ICl and IC2 are connected to input pins 2, 7, 10 and 15; and 1, 9, 11 and 14, respectively, of a digital comparator IC3. The digital comparator may be an MC 14585 manufactured by MOTOROLA, INC. The A~ B output from pin 13 of the digital comparator IC3 drives a transistor stage Ql which activates a relay to control a fan or other device, via relay coil Kl and contacts SWl.
A mains transformer Tl and rectifiers CRl and CR2 provide a B+ supply which may be regulated by a voltage regulator VRl which may be a 7812 manufactured by MOTOROLA, INC.
The circuit will respond according to the truth table below:
20 TE~PERATURE TEMP. R.H. R.H. A<B FAN
F ANALOG ANALOG DIGITAL STAT
COMP. COMP. COMP. US
OVTPUT OUTPUT OUTPUT _ -20 or below 0000 15% or less 0000 0 OFF
25 -20 or belo 0000 15% to 25~ 0001 1 ON
-20 to 0 0001 15~ to 25~ 0001 0 OFF
-20 to 0 0001 25% to 35% 0011 1 ON
0 to +20 0011 25~ to 35% 0011 0 OFE
0 to +20 0011 , 35% to 45% 0111 1 ON
30 +20 to +40 0111 35% to 45~ 0111 0 OFF
+20 to +40 0111 45% or above 1111 1 ON
+40 or above 1111 45~ or above 1111 0 OFF
1 i5~743 s Since the fan is controlled by the A~B output of the digital comparator IC3 as long as the output from the temperature analog comparator ICl is a greater digital word than the digital output from the R.H. analog comparator 5 TC2 the fan can remain off. As soon as the humidity rises above an unacceptable level with respect to present outside temperature the fan turns on.
By controlling to more than one set point of humidity it is possible for the fan to be off for longer 10 periods if control were to only one set point which would have to be quite low (i.e. 15-20%). The fact the fan is off means no warm air is being exhausted to the outside and interior heating is more efficient.
NOTES:
(i) Some or all of Rl through R18 may be ajustable for calibration.
(ii) The bank of comparators is an economical method to establish activation breakpoints for non-linear sensors.
(iii) As the temperature and humidity change, they are constantly being compared and a decision is made to turn the fan on or off.
(iv) As many analog comparators as necessary may be used to linearize, to a given accuracy, any of the sensors.
(v) It may be possible to be able to eliminate the prescalers.
(vi) Any temperature or humidity transducer may be used providing it presents the comparator inputs with a varying electrical voltage or current.
By choosing the breakpoint for the analog comparator as shown on the graphs of sensor outputs digital value can be assigned to that value of temperature or relative humidity.
Using digital comparison techniques the circuit is con-figured so that if the digital representation of temperature 35 is larger in value than the digital representation of R.H.
the fan is to remain off. In other words the outside tem-perature is high enough that condensation will not occur at ~ ~5~743 the present inside R.H. When the digital representation of temperature is equal toor less than the digital representation of humidity the fan is turned on to prevent condensation.
Other embodiments falling within the terms of the appended claims will occur to those skilled in the art.
The principle behind this controller is that in order to eliminate water damage to house interiors due to condensation, the moisture laden air has to be exhausted when the relative humidity (R.H.) reaches certain critical levels. Since condensation inside will occur at different levels of relative humidity depending on the outside temperatures, the controller has inputs from an interior R.H. sensor and an exterior temperature sensor.
The invention to be described, provides a controller which compares an output signal from a temperature sensor and the output from a relative humidity sensor and decides whether to turn the exhaust fan on to remove moist air there-fore reducing relative humidity or leave the fan off since for the given outside temperature the inside relative humidity is acceptable. By controlling the fan to the condition of a Selection Table the device will allow the relative humidity to be higher at warmer temperatures. The control unit is a self contained unit, with sensors being remotely connected, and consisting of prescaling resistor input networks, analog comparators, digital comparator fan relay actuating circuit and power supply.
It is a feature of one object of the invention to provide a controller having an output signal which is finite for selected pairs of values for temperature and relative humidity and which is zero for other selected pairs of values for temperature and relative humidity.
1 15~7~3 It is a feature of another object of the invention to utilize the controller described in the previous paragraph to selectively activate atmospheric extraction apparatus.
In accordance with the foregoing features, there is provided, a temperature/humidity responsive device for controlling auxiliary equipment as a function of combinations of selected pairs of discrete values of temperature and relative humidity, said device comprising a temperature sensor having an electrical output signal which varies with temperature, a relative humidity sensor having an electrical output signal which varies with relative humidity, a first analogue comparator connected to receive said output signal from said temperature sensor and producing a selected number of digital output signals corresponding to an equal number of discrete selected values of said output signal from said temperature sensor, a second analogue comparator connected to receive said output signal from said relative humidity sensor and producing a selected number of digital output signals corresponding to an equal number of discrete selected values of said output signal from said relative humidity sensor, and a digital comparator connected to receive the digital output signals from said first and second analogue comparators, said comparator producing an output signal in response to said combinations of said selected pairs of discrete values of temperature and relative humidity.
A preferred embodiment of the invention will be described with reference to the accompanying drawings, in which:
Fig. 1 is a circuit diagram of a fan controller.
Fig. 2 is a graph of the electrical output signal derived from a typical temperature sensor versus temperature and the digitized equivalents of the output signal for four selected temperatures.
Fig. 3 is a graph and digitized equivalents similar to Fig. l, but for a typical relative humidity sensor.
115~743 Referring to Fig. 1, the output A from a temperature sensor Sl is applied to pins 4, 6, 8 and 10 to an analogue comparator IC1. A suitable temperature sensor is an AD590 manufactured by ANALOGUE DEVICES, INC. and a suitahle analogue comparator is the LM339 manufactured by NATIONAL SEMICONDUCTOR
CORPORATION. The temperature sensor Sl is such that the electrical output therefrom changes 1 microamp/ K and the value of Rll is found to be 10K ohms to vary the voltage of output signal A with a slope of 10 millivolts/ C. This characteristic is shown in Fig. 2. A pre-scaler, shown at 102, may be incorporated to modify the signal A before application of the signal to the analogue comparator ICl.
As indicated in Fig. 1, four selected threshold levels of signal A are utilized and these levels are set by a potential divider comprising Rl, R2, R3, R~ and R5. The analogue comparator has four switched digitized outputs from pins 1, 2, 14 and 13 corresponding to the respective ones of the four threshold levels of the input signal A.
The output B from a relative humidity sensor S2 is applied to pins 4, 6, 8 and 10 of an analogue comparator TC2 which may be similar to TCl. A suitable relative humidity (R.H.) sensor is a BR-lOlB manufactured by THUNDER SCIENTIFIC
CORP. The R.H. sensor is such that the electrical output therefrom changes approximately 1.0 volts over the range of 10% to 90% R.H. This characteristic is shown in Fig. 3.
A prescaler, shown at 104, may be incorporated to modify the signal B before application of the signal to the analogue comparator TC2. As indicated in Fig. 1, four selected threshold levels of signal B are utilized and these levels are set out by a potential divider comprising R6, R7, R8, R9 and R10.
The four selected values of R.H. are so made so that the outputs from the digital comparator TC2 change at critical levels of humidity (HCl, HC2, HC3 and HC4) as indicated in Fig. 3.
I l SB74 3 The analogue comparator TC2 has four switch digitized outputs from pins 1, 2, 13 and 14 corresponding to respective ones of the four threshold levels of the input signal B.
The four outputs from pins 1, 2, 13 and 14 of the analogue comparators ICl and IC2 are connected to input pins 2, 7, 10 and 15; and 1, 9, 11 and 14, respectively, of a digital comparator IC3. The digital comparator may be an MC 14585 manufactured by MOTOROLA, INC. The A~ B output from pin 13 of the digital comparator IC3 drives a transistor stage Ql which activates a relay to control a fan or other device, via relay coil Kl and contacts SWl.
A mains transformer Tl and rectifiers CRl and CR2 provide a B+ supply which may be regulated by a voltage regulator VRl which may be a 7812 manufactured by MOTOROLA, INC.
The circuit will respond according to the truth table below:
20 TE~PERATURE TEMP. R.H. R.H. A<B FAN
F ANALOG ANALOG DIGITAL STAT
COMP. COMP. COMP. US
OVTPUT OUTPUT OUTPUT _ -20 or below 0000 15% or less 0000 0 OFF
25 -20 or belo 0000 15% to 25~ 0001 1 ON
-20 to 0 0001 15~ to 25~ 0001 0 OFF
-20 to 0 0001 25% to 35% 0011 1 ON
0 to +20 0011 25~ to 35% 0011 0 OFE
0 to +20 0011 , 35% to 45% 0111 1 ON
30 +20 to +40 0111 35% to 45~ 0111 0 OFF
+20 to +40 0111 45% or above 1111 1 ON
+40 or above 1111 45~ or above 1111 0 OFF
1 i5~743 s Since the fan is controlled by the A~B output of the digital comparator IC3 as long as the output from the temperature analog comparator ICl is a greater digital word than the digital output from the R.H. analog comparator 5 TC2 the fan can remain off. As soon as the humidity rises above an unacceptable level with respect to present outside temperature the fan turns on.
By controlling to more than one set point of humidity it is possible for the fan to be off for longer 10 periods if control were to only one set point which would have to be quite low (i.e. 15-20%). The fact the fan is off means no warm air is being exhausted to the outside and interior heating is more efficient.
NOTES:
(i) Some or all of Rl through R18 may be ajustable for calibration.
(ii) The bank of comparators is an economical method to establish activation breakpoints for non-linear sensors.
(iii) As the temperature and humidity change, they are constantly being compared and a decision is made to turn the fan on or off.
(iv) As many analog comparators as necessary may be used to linearize, to a given accuracy, any of the sensors.
(v) It may be possible to be able to eliminate the prescalers.
(vi) Any temperature or humidity transducer may be used providing it presents the comparator inputs with a varying electrical voltage or current.
By choosing the breakpoint for the analog comparator as shown on the graphs of sensor outputs digital value can be assigned to that value of temperature or relative humidity.
Using digital comparison techniques the circuit is con-figured so that if the digital representation of temperature 35 is larger in value than the digital representation of R.H.
the fan is to remain off. In other words the outside tem-perature is high enough that condensation will not occur at ~ ~5~743 the present inside R.H. When the digital representation of temperature is equal toor less than the digital representation of humidity the fan is turned on to prevent condensation.
Other embodiments falling within the terms of the appended claims will occur to those skilled in the art.
Claims (9)
1. A temperature/humidity responsive device for controlling auxiliary equipment as a function of combinations of selected pairs of discrete values of temperature and relative humidity, said device comprising:
a) a temperature sensor having an electrical output signal which varies with temperatures, b) a relative humidity sensor having an electrical output signal which varies with relative humidity, c) a first analogue comparator connected to receive said output signal from said temperature sensor and producing a selected number of digital output signals corresponding to an equal number of discrete selected values of said output signal from said temperature sensor, d) a second analogue comparator connected to receive said output signal from said relative humidity sensor and producing a selected number of digital output signals corresponding to an equal number of discrete selected values of said output signal from said relative humidity sensor, and, e) a digital comparator connected to receive the digital output signals from said first and second analogue comparators, said comparator producing an output signal in response to said combinations of said selected pairs of discrete values of temperature and relative humidity.
a) a temperature sensor having an electrical output signal which varies with temperatures, b) a relative humidity sensor having an electrical output signal which varies with relative humidity, c) a first analogue comparator connected to receive said output signal from said temperature sensor and producing a selected number of digital output signals corresponding to an equal number of discrete selected values of said output signal from said temperature sensor, d) a second analogue comparator connected to receive said output signal from said relative humidity sensor and producing a selected number of digital output signals corresponding to an equal number of discrete selected values of said output signal from said relative humidity sensor, and, e) a digital comparator connected to receive the digital output signals from said first and second analogue comparators, said comparator producing an output signal in response to said combinations of said selected pairs of discrete values of temperature and relative humidity.
2. A device as defined in Claim 1 wherein said analogue comparators are each provided with a plurality of threshold input terminals, each of said threshold terminals having a selected threshold voltage applied thereto, said selected threshold voltages being derived from voltage dividing means.
3. A device as defined in Claim 1 wherein the output of said digital comparator is applied to a switching device for control thereof.
4. A device as defined in Claim 3 wherein said switching device is connected to and actuates a switch.
5. A device as defined in Claim 3 wherein said switching device is a transistor .
6. A device as claimed in Claim 1 wherein each of said temperature sensor, relative humidity sensor, analogue comparators and said digital comparator are provided with a B+ supply, said B+ supply being derived from a voltage source.
7. A device as defined in Claim 6 wherein said source is a mains transformer and rectifying means.
8. A device as defined in Claim 7 further including a parallel connected smoothing capacitance.
9. A device as defined in Claim 6 wherein at least said sensors and said analogue comparators are provided with a voltage regulated B+ supply.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000359475A CA1156743A (en) | 1980-09-03 | 1980-09-03 | Relative humidity/temperature sensing control |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000359475A CA1156743A (en) | 1980-09-03 | 1980-09-03 | Relative humidity/temperature sensing control |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1156743A true CA1156743A (en) | 1983-11-08 |
Family
ID=4117796
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000359475A Expired CA1156743A (en) | 1980-09-03 | 1980-09-03 | Relative humidity/temperature sensing control |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1156743A (en) |
-
1980
- 1980-09-03 CA CA000359475A patent/CA1156743A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |