THE
TOMTECH
HC80
HORTICULTURAL COMPUTER
THE HC80 ENVIRONMENTAL CONTROL COMPUTER
CONNECTION TO A PERSONAL COMPUTER
| HEATING | VENTILATION | THERMAL SCREEN | HEATING PUMP | BOILERS |
| TRANSPORT MAIN | LIGHTING | MISTING/WATERING | NUTRIENT FEED | CO2 |
THE HC80 ENVIRONMENTAL CONTROL COMPUTER
The HC80 is an environmental control computer designed for controlling the climate within one or
more glasshouses. The HC80 is easily programmed in plain English using the built in screen and
keypad. The screen also provides a means of monitoring conditions inside and outside the houses by
continuously updating the display of all relevant conditions. keeping you fully informed at all times.
The HC80 is designed to control 8 systems within the glasshouse or glasshouses, these could be vents,
boilers, etc. and to measure 8 conditions within the glasshouse. These conditions could be
temperature, humidity, light, CO2, etc. The computer also looks at conditions outside the glasshouse
using a weather station. This measures wind speed and direction, light levels, rain and temperature.
The HC80 is supplied with a complete suite of sophisticated and flexible programmes for controlling all
systems within the glasshouse. In addition Tomtech will provide FREE software updates as new
techniques are developed ensuring that your system remains fully up to date.
Fully programmable alarms alert you to any potentially damaging condition before it becomes a
problem. Performance statistics for all measured conditions and controlled systems allow easy
checking that the best performance is being achieved with the greatest efficiency minimising fuel costs.
A printer and P.C. (Personal Computer) may be connected. The printer will print monitor information
and statistics. The P.C. connection allows full remote programming, system monitoring, data analysis,
and glasshouse costings by using the Tomtech Environment Manager software on the P.C.
For maximum reliability and to minimise the installation costs the HC80 is enclosed in a waterproof and
dustproof cabinet with a toughened glass door meeting the IP55 specification. It may therefore be
installed directly into the glasshouse minimising cabling costs.
Tomtech manufacture a full range of sensors for measuring temperature, humidity, light etc. that are
compatible with the HC80 system.
PROGRAMMING THE HC80
The HC80 is programmed by using the built in display screen and keypad. Options are displayed in
plain English and may be selected using four cursor keys. The HC80 will prompt you for all the
information needed when changing settings. If you are not sure how to answer any of the questions
asked by the HC80 then a 'Help' key can be pressed to explain in more detail what is required. This
effectively means that the instruction manual is built into the computer.
Once programmed the system can be locked against unauthorised programme changes by means of a
key.
ALARMS
The HC80 has programmable alarms with independent high and low thresholds for each of the
sensors. Any alarm condition will be shown on the screen, sound the internal bleeper, and operate an
external alarm or auto-dialler if fitted. Alarm messages may be automatically printed.
In an expanded system where a P.C. is attached alarm messages will also be displayed by this
computer.
STATISTICS
Once the control channels have been programmed then a method of checking that the programmed
environment is being maintained is required. This is accomplished by the HC80 monitoring its own
performance. The system can display this performance record as statistics for each of the sensors and
control channels.
For each of the sensors the MAXIMUM, MINIMUM 6 hour and 24 hour MEAN levels may be
displayed or printed. Graphs and tables of sensor data for the last 24 hours may also be printed at any
time.
For each of the control channels the percentage of time that the channel has been 'ON' for is shown as
an average over the last 24 hours. Where channels are controlling proportional systems such as heating
valves or ridge vents then the percentage use of that system will be calculated.
If the HC80 is connected to a central computer then more detailed information about sensors and
control channels may be stored, displayed as graphs and archived.
CONTINUOUS MONITORING
The screen of the HC80 has a continuous monitoring mode that displays the time, current readings for
all the sensors including the weather station, and the position of the vents, heating valves and screens if
appropriate, in a continuous cycle. This enables the user to check, at a glance, that the system is
working correctly.
This cycle may be stopped at any point to display an updating display of a single parameter, if
required.
EXPANDING THE HC80
The HC80's control capability can be easily extended by adding an expansion board which may be
plugged into the HC80 giving an additional eight control channels.
Where a single HC80 does not have adequate control capability for the whole nursery, the HC80 can
be linked to other Tomtech computers to build up a network of computers that operate together.
Information is shared between the individual computers allowing them to function as a single system.
This has advantages over a single central computer since each computer is checking the others in the
network providing the most reliable system possible. Resources such as the printer and weather station
can also be shared between the computers. The individual computers may be located where needed
around the nursery minimising the amount and cost of cabling required. Adding additional houses at a
later date may be easily achieved by adding to the network without costly alterations to the existing
system.
CONNECTION TO A PRINTER
A printer may also be connected to the HC80. Where a number of computers are interconnected a
single printer will serve the complete system. The printer may be used to print a monitor record of
current glasshouse conditions at regular intervals which may be selected between 15 minutes and 2
hours. Graphs and tables of statistical information may be printed covering a 24 hour period and
setpoints may be printed.
CONNECTION TO A PERSONAL COMPUTER
An I.B.M. P.C. (Personal Computer) or compatible computer can also be connected to the system to
allow central control, remote programming, system monitoring, graphical and statistical analysis and
crop costings to be performed.
Environment Manager Software
CONTROL PROGRAMMES
The HC80 has 8 control channels, 6 of these channels (channels 1 to 6) may be used to provide
proportional control or simple on/off control while the remaining two channels (channels 7 and 8) may
be used individually to provide on/off control or as a pair to give an extra proportional channel. In
addition, an expansion board may be fitted to any HC80 to add 8 control channels giving a total of 16,
an extra 6 proportional and 2 on/off channels.
The HC80 is not restricted to controlling a fixed number of zones. Each channel may be individually
defined as a vent channel or a heating channel etc. The number of zones controlled by each computer
will therefore depend on how many systems are to be controlled in each zone.
The following summary lists some of the control programmes supplied with the HC80.
HEATING CONTROL PROGRAMMES
Four heating programmes provide 'Constant', 'Day/Night', 'Four Period' and 'Light Related' control
regimes. The first three of these allow individual temperature, humidity and if appropriate maximum,
minimum and humidity pipe temperatures to be defined for each time period. The start of each time
period may be independently set and can be set to adjust itself with sunrise or sunset automatically.
The set temperatures will automatically ramp between one time period and the next providing a smooth
temperature profile. The setpoints can be automatically adjusted for solar influence.
The 'Light related' programme controls the heating according to light alone. This programme may be
used to provide higher or lower night temperatures as required.
All these programmes may be used to provide Humidity control. The standard software includes
versions of these programmes suitable for use with hot air, hot water on/off, hot water mixing valve and
steam heating systems.
VENTILATION CONTROL PROGRAMMES
There are three groups of ventilation programmes. These provide on/off or variable speed control of
ventilation fans, proportional control of ridge vents and proportional control of windward/leeward vent
pairs. For each of these types of ventilation there are three venting programmes providing 'Constant',
Day/Night' and 'Four period' control of both temperature and humidity.
For each time period target temperature, humidity, and minimum temperatures may be defined. The
minimum temperature is used to qualify humidity control so that it does not occur if the temperature
drops too far. The temperature targets may also be influenced by light intensity allowing higher
temperatures to be maintained on brighter days.
For proportional vent systems additional minimum and humidity vent percentages can be programmed.
Limits may be defined for maximum and minimum venting under different wind and rain conditions.
THERMAL SCREEN PROGRAMMES
Gapped Timed Screen:
This is the ideal programme for blackout screens. It opens and closes the screen at fixed times at dawn
and dusk. This screen may also be used to provide shading and to help with humidity control by
gapping the closed screen under high humidity conditions.
Gapped Light Screen:
This programme opens and closes the screen as the ambient light level rises and falls at dawn and
dusk. The screen may also be used to provide shading and may be used to help with humidity control
by gapping the closed screen.
Both of these programmes open the screen in two stages, the first stage provides a 'gap' to allow the
air above and below the screen to mix at a controlled rate eliminating the temperature shock which can
occur if the screen is drawn completely in one step.
HEATING PUMP PROGRAMME
Hot water heating systems use a circulating pump to move the water around the house. This pump can
be controlled so that it is switched off when there is no demand for heating. In addition once this pump
has switched off it may be cycled to ensure that the pipe temperature remains even.
BOILER CONTROL
The HC80 has two boiler control programmes. The 'Temperature Control' programme will adjust the
boilers temperature according to the heat demand. This programme is not recommended for all boiler
types while the On/Off Boiler programme can safely be used with any type of boiler to switch the
boiler off when there is no imminent need for heat. This programme will then anticipate the need for
heat and switch the boilers on in advance so that there is heat immediately available when it is needed
in the houses being controlled.
Both of these control programmes can also control the boilers to provide CO2 if required.
TRANSPORT CONTROL
The heating transport valve and pump can both be controlled with this programme to use the heating
transport in the most economical way.
LIGHTING CONTROL PROGRAMMES
Extend Day Lighting:
Provides the most efficient control of supplementary lighting by allowing the minimum natural light
conditions to be defined. When the ambient light level falls below these pre-defined conditions the
supplementary lights will be switched on. Lighting will be used during the natural day.
Retrospective Lighting:
This supplementary lighting programme will provide the artificial lighting at night using cheap electricity.
The length of lighting period each night will be calculated from the natural light received by the plants
during the previous day.
Night Break Lighting:
This programme may be used to change the day length/night length ratio by shortening the night period.
The start and end times for the night break period are set by the user. Between these times the lighting
may be ON continuously or cycled through a repetitive ON/OFF cycle. The start and stop times may
be set to self adjust with natural day length.
MISTING, FOGGING and WATERING CONTROL PROGRAMMES
Maintain Humidity Mist:
Allows day and night humidity thresholds to be defined. When the humidity falls below these thresholds
then the misting system will be cycled to apply moisture while avoiding an overshoot.
Light Sum Mist:
The rate at which plants transpire is largely related to the ambient light level. The brighter it is the more
water a plant will lose. This programme keeps a very accurate record of the light energy received by
the plants. When the defined threshold of light intensity by time, or light integral, is reached then the
misting or watering system will be activated. The light integral will be reset and the process will be
repeated.
Mist By Time:
This is the simplest misting programme. Time intervals between misting or watering cycles may be
defined for day/night periods within each day together with the duration of the cycle. At the end of
each time interval the misting system will be activated for the defined duration allowing different
day/night rates of water application to be defined.
CO2 CONTROL PROGRAMMES
Light Related CO2:
This programme uses measured CO2 levels from an infra red analyser or the CM80 multiplexer and
controls the supplementary CO2 system to maintain a target CO2 level calculated for the light intensity,
time and also vent position.
Best Guess CO2:
The high cost of a CO2 analyser is often difficult to justify. This programme does not use a sensor, but
allows the supplementary CO2 system to be controlled based on estimating the CO2 consumption of
the crop according to light intensity and vent position. This technique, while not as accurate as actually
measuring the CO2 concentration can come very close to providing the performance of a CO2 sensor
at no extra cost.
FEED DOSING CONTROL PROGRAMMES
Where an N.F.T. system is used the HC80 can control the addition of both acid and nutrients for plant
feeding by using two dosing control programmes.
The pH control programme will use measured pH information to control the addition of acid.
The feed control programme will use measured conductivity information to control the addition of
nutrients. The nutrient concentration may be adjusted with light intensity if required.
HC80 SPECIFICATION
Computer Housing: Steel enclosure finished in epoxy-powder paint with a 6mm. thick safety glass
door.
Mains power: 120 or 240 volt AC 50 or 60 Hz. +/-10%
Analogue Inputs: 8 analogue inputs each configurable for measuring temperature, humidity, light,
CO2, pH or conductivity.
Weather Station Inputs: Special purpose inputs for wind speed, wind direction, light, rain, outside
temperature and humidity.
CO2 Input: Special purpose input for use with the CM80 CO2 multiplexer to measure CO2
concentration in up to 8 zones or with a single CO2 infra red analyser.
Digital Inputs: 8 inputs, one associated with each of the control channels. Digital inputs are low
voltage through opto-isolators.
Control Channel Outputs: 8 control channels, 14 of which may be used for proportional control. An
additional 8 channels may be fitted by plugging in an expansion board. Control channel outputs are all
relay isolated. Relays have changeover contacts rated 240v AC 8 amps.
Alarm output: Relay isolated, with changeover contacts rated 240 v AC 8 amps.
Display: 4 lines of 40 characters LCD supertwist reflective display.
Printer: Serial printer output for an Epson compatible printer.
Communications: RS422 communication port for connection to other Tomtech computers and to a
P.C.