THE
TOMTECH
HC160
HORTICULTURAL COMPUTER
THE HC160 ENVIRONMENTAL CONTROL COMPUTER
CONNECTION TO A PERSONAL COMPUTER
| HEATING | VENTILATION | THERMAL SCREEN | HEATING PUMP | BOILERS |
| TRANSPORT MAIN | LIGHTING | MISTING/WATERING | NUTRIENT FEED | CO2 |
THE HC160 ENVIRONMENTAL CONTROL COMPUTER
The HC160 is an environmental control computer designed for controlling the climate within one or more glasshouses. The
HC160 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 HC160 is designed to control 16 systems within the glasshouse or glasshouses, these could be vents, boilers, etc. and to
measure 16 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 HC160 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 HC160 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
HC160 system.
PROGRAMMING THE HC160
The HC160 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 HC160 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 HC160 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 HC160 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 HC160 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 HC160 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 HC160 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 HC160
The HC160's control capability can be easily extended by adding an expansion board which may be plugged into the HC160
giving an additional eight control channels.
Where a single HC160 does not have adequate control capability for the whole nursery, the HC160 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 HC160. 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 HC160 has 16 control channels, fourteen of these channels (channels 1 to 14) may be used to provide proportional
control or simple on/off control while the remaining two channels (channels 15 and 16) 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 HC160
to add 8 control channels giving a total of 24 an extra 6 proportional and 2 on/off channels.
The HC160 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 HC160.
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 HC160 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 HC160 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.
HC160 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: 16 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: 16 inputs, one associated with each of the control channels. Digital inputs are low voltage through
opto-isolators.
Control Channel Outputs: 16 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.