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Introduction

The Temperature Multi Controller was developed for my marine reef tank, the main feature of it was, to simply and cheaply, provide accurate temperature control for both heating and cooling in one integrated unit.

Completed temperature multi controller.

Its main functions and specifications are as follows:

• user definable set points for three outputs
• user definable Alarm output for over and under temperature
• a temperature range of 20.0 to 29.9 deg C
• a resolution and accuracy of 0.1deg C
• temperatures and information displayed on a LCD matrix
• a simple two button control for the menu system and data entry

Typical operation would be:

• Heating on at 24.9, off at 25.0
• Cooling Fan on at 25.5, off at 25.2
• Chiller Unit on at 26.0, off at 25.2 (coolers always off together)
• Sound Alarm if temperature goes below 24.0 or above 28.0

The cost of all parts including the case and a small 2 x 16 LCD is GB£31 (source reference – maplin.co.uk).

The unit has been successfully controlling my tank for over two years so I am happy to offer the low voltage dc micro circuit and program to other marine/electronics enthusiasts to use for their own interest and development.

No warranty for its function or reliability is given or implied.

No details of the mains power supply or relay/mains output board will be provided as any constructor should be well able to make up their own - if not then please read the following:

IMPORTANT.

IF YOU CANNOT DESIGN AND BUILD YOUR OWN MAINS BASED CIRCUITS AND IF YOU ARE NOT CONVERSANT WITH YOUR LOCAL ELECTRICAL SAFETY REGULATIONS

THEN PLEASE, STOP READING THIS PROJECT AND GO AND BUY AN APPROVED COMMERCIAL UNIT FROM YOUR LOCAL AQUATIC OUTLET !!

MAINS ELECTRICITY WILL KILL !! - DO NOT RISK YOU OR YOUR FAMILY !!!

The following article provides:

• pictures of the micro LCD messages
• the circuit diagram
• the PCB layout masks - single sided copper board only needed
• PCB board production
• parts list - all readily available parts
• the program hex code – details, downloads and programming
• how to make your own cheap and simple diy programmer
• construction hints and tips
• suppression
• calibrating and operation of the module
• updates, problems & contact address

Updates

Well, I hope your have had an interesting read and that you may decide build this unit and be able to better control your marine tank.

If any degree of interest is shown, then I will be producing updates from time to time.

Current Work:

• Modifying the lcd display routines to show all data on the cheaper 2x16 character units.  It will still run OK with a 2x20 unit – just four unused characters.

Possible plans are for:

• To reinstate the quick calibration routine
• To add in a min/max temperature recorder
• To add in a feeding timer.

Current UK attitude is to feed very little and very often, not just fish foods but tank and coral foods such a Phytoplankton. I have used this method for a year, manually feeding, and feel sure its given me a better tank. I am thinking of three set timers to control the feeding overall period, eg 10 am to 11 pm, the feeding intervals, every mm mins, and the actual feeding time. xx seconds. Two outputs to be used, one coming on say 30secs earlier to activate a food mixer air pump followed by the dosing pump. Any suggestions - ?

A simple temperature controller using 4 status LEDs to run on pre-programmed values, so saving the expense of the lcd, switches, cables etc

Pictures of the LCD Messages

The xxxxx represents on or off for the 6 channel light controller, which worked, but when you take the price of the relay, suppressers, connectors etc. it is simpler and cheaper to use the readily available Plug in mains timers from the diy superstore.

This means there is now 6 channels free allowing for other uses such as feeding timers etc. (See Updates notes.)

LCD image 1.

LCD image 2.

LCD image 3.

LCD image 4.

LCD image 5.

Circuit Diagram

Temperature multi controller circuit diagram.

Printed Circuit Board

The following shows the PCB and the top silk for the components. Unfortunately with the PCB layout program I used, getting a copy of the image to this page has not given the best quality.

Included with the Program file download are the files PCB01.LYT and CIRC01.DSN.

If you download the freeware program Proteus Lite 6 from http://www.lavasoft.co.uk/ you will be able read in both these files and print out first rate copy. In the meantime if I am able to get a better image I will make it available by the Updates page.

PCB top view, looking down at copper tracks through the board.

Silk of PCB with components, top view again.

PCB Production

Thought you might be interested in the following product which makes creating single sided PCB very easy. Press-n-Peel from http://www.bhc-group.demon.co.uk/ and purchased from http://www.maplin.co.uk/ here in the UK – their product code AB15R.

The PCB design is laser printed to the film which is then hand ironed onto the copper board, any slight imperfections touched up with an etch resist pen.

Transfering circuit to PCB.

15 mins later the etched board, after the transfer is cleaned off with acetone.

Final etched PCB.

Parts List

All parts should be readily available or easily substituted . UK suppliers web site given for you to check /compare exact specifications.

Optional* - see notes on Suppression – Hints & tips

Optional** - direct wired on original - pins spaced at .1” X10 if connector preferred.

Website Addresses

• Farnells www.farnellinone.co.uk
• Maplin www.maplin.co.uk
• Microchip www.microchip.com
• RS rswww.com

Microchip

All early work was done on the chip pic16F873, which has now been upgraded to the 16F873A version, although device compatible/upgradable it does mean that two different program versions are required as well a two very different methods of actually burning the code in. For all this project the A version is specified, and should be purchased. Some of the early versions are still around, so check the chip carefully. Should you already have the early chips or cannot get an A version where you are yet, then email me for the early version program. (Not included in the downloads to avoid confusion)

Program Code

The v521873a.hex program file, PCB layout and circuit diagram files pcb01.lyt and circ01.dsn are all available from here: Downloads Temperature Multi Controller .

This code is the standard .HEX code from Microchips MPLAB program suite so should run and any standard programmer able to take their code. The programming of the unit was done with reasonable care, for my own use. It was not done with a view to prevent every possible permutation of erroneous data entry!

Default Temperature Values - deg C

The following shows the currently pre-programmed default values that the micro will revert to when reset for any reason – eg power cut. If you want noticeably different values you can, via most programmers, locate and edit the Hex code with new default values before you program. However, be aware any error can cause all manner of problems – your risk!

VERSIONS 5.21 & 5.21A ONLY

All temperaturess less leading 25.0 and decimal point.

DIY Programmer

If you have your own programmer or access to one by a friend, college or component suppliers etc. all well and good -they should readily program it up without any problems.

If not, the best option is to spend a couple of hours and a couple of pounds/dollars to build the following little programmer, which should work well enough to get you up and running.

There are many web pages devoted to Pic programmers but the one I show is from a standard design which I have slightly improved and built just for this family of 28pin pics, and having used it for a while have some understanding of the minor problems they can occasionally give. NB. A parallel port on a PC is needed to control the programmer.

Rather than add even more pages of notes, another circuit and schematic to this already lengthy document, I would ask anyone who wants details of this DIY programmer to email me and I will send full details and attach the PBC and schematic files in the same format as the main project.

DIY programmer, prototype PCB.

Construction Hints and Tips

The previously shown PC board now populated, in a simple test jig made up of a 9V battery, 22k pot and LED with resistor. (switches and filter not fitted).

Construction should present no problems and use of new DIL sockets is recommended.

The LCD display needs a 10k pot to feed VEE. One is shown fitted on the PCB, but simply omit, if you wish to fit one up on the display itself. If a backlit unit is used you must use a separate power supply for the LEDs (5v reg will blow!) Connection of very short cable lengths runs/testing only is shown with an idc header/cable, but to avoid problems, hard-wiring with a good multicore screened round cable is better.

The original unit was designed around the 2x20 display to accommodate the indicators for the now defunct 6 channel lighting controller. The price of the small 2x16 lcds has fallen to just GB £8 but the 2x20 is still about GB £22. Running the current program will still display on a 2x16 unit, loosing the last four characters, but no crucial information is lost. See LCD images on earlier page. Currently the display routines are being rewritten the show all info on the cheaper 2x16 display. See updates page for details.

The temperature probe is made from the 15K NTC and about 150mm of approx10-16mm diameter, non toxic plastic tube, with the ntc near bottom, and filled with aquarium silicone. Try and ensure the area at the top, where the cable goes into the probe case, is very well sealed and always positioned above the water level. Against perhaps obvious thinking do provide a thickish (2-5mm all round) sealing layer, the NTCs are very quick at reacting to temp changes - a thicker layer means momentary changes, eg adding cooler top up water, are not be sensed as quick and helps improve the overall stability. See operation note on temperature sensing. Again, forgive the obvious, but please make sure you place the probe in an area of good water movement but not in the direct path of a circ pump, the heating or cooling flows.

The 12v input power for this circuit should be from a 12VDC regulated source eg 7812 reg.

Suppression

When the unit was initially set up in 2003 many problems were experience from electrical interference with caused the micro to reset. This did not cause any problem to the tank as default values are programmed in, so it just restarts with those values, but if you have changed any value these will be lost by the reset. There are many ways to overcome this problem by programming, but I preferred to eliminate the cause. A future plan is to upgrade the software to help combat any future problems.

A long exercise followed to cure the problem and, since, for the last 2 years, I have not had any further problems. As each system will be different, ie different pumps, lights etc. I have listed what I did so you can include these and any other items you know will help.

The micro unit and importantly, its three control switches, are now housed in a metal box connected to ground. This was probably the most effective single thing.

All cables serving this box are made with shielded cables and/or if not, fitted with ferrite rings close to the metal box.

The mains power input feeding just the low voltage transformer was fitted with a quality commercial filter unit.

A miniature DC filter was fitted to the micro unit just before the 5 V regulator.

On my power board various efforts were made with suppressers with mixed results.

My power board incorporating a wiring centre,switches and fuses for all tank devices.

Testing of PCB

As shown in the earlier pic its very simple to test the board with just a 9V battery, at 22k pot connected as the temp sensor, and a voltmeter or Led/resistor across the outputs. Without either ICS plugged in, you should measure 2-5 mA current dependant on the exact regulator. If OK , try the chips which should add another 3 mA, and finally the LCD, (no backlights) to give a running load well under 10 mA - typically 7 mA. Adjust RV1 to give best readable display.

Adjust the 22k pot, allowing for the delay, and test the outputs work, inline with the display message. (2.68 V on pin2 gives approx 25deg) Test the three switches for operation.

Calibration of the NTC sensor is best done on an existing tank. Set RV2 to its midway position. Place a good reference thermometer in the tank with the Probe next to it – and leave for 2 mins to stabilise. Please see operation note on temp. sampling. Adjust RV2trimmer to give the correct temp. One full turn clockwise on RV2 should increase the display by 0.2deg C A bit of patience is necessary due to the sampling delay.

Operation

On power up the display will contain invalid characters but the clock colon should blink to show its running – after the first cycle, approx 60-90 sec the display will normalise and the outputs will come on as needed.

Temperature control is done by sampling the NTC probe many times over a cycle of approx 90 secs, an average is produced and the outputs changed if/as necessary. This produces a very even temperature control, eliminating problems like relay chatter etc. A calibration routine to give instant display feedback to any adjustment was in the original design but was disabled as problems were caused when I was having interference problems.

Switches are:

• SW3 - Micro Hard reset.
• SW2 - Menu - and keep pressing to scroll down - until automatic exit,
• SW1 - Data Entry - press to change value–Menu key to exit.

You will see from the menu, reference to the lighting timers – these are currently obsolete and not functioning. Just use the clock, temp and alarm settings.

ADJ TEMP is the temp to keep at – heating comes on at just 0.1degc below that.

The alarm has high and low temp settings and also a separate alarm on/off control.

For cooling, I suggest you allow at least 0.3deg c, above the ADJ TEMP setting, before cooler1 comes on. Both cooler 1 and 2 are switched off by the same value; again allow at least 0.2deg c above the ADJ temp. as once the coolers are switched off a fair bit of temp. reduction can still be given as all the ‘cooling’ is taken out of the unit.

Calibration of the NTC sensor is best done on an existing tank.  Set RV2 to its midway position.  Place a good reference thermometer in the tank with the Probe next to it – and leave for 4 mins to fully stabilise. Please see operation note on temp. sampling.  Adjust RV2trimmer to give the correct temp.  One full turn clockwise on RV2 should increase the display by 0.2deg C.  A bit of patience is necessary due to the sampling delay.

Contact

If you are going to build this unit, in might be worth checking below for any errata before starting.

Also, if you have any ‘clean’ comments, questions or want information on any/all updates, then please email me at:- (sorry no website –only email) .

Comments

DIY Programmer Written by on 2007-03-01 12:00:49 Can you send me the necessary information to build the pic programmer?

Temp controller and Programmer Written by on 2007-04-19 10:24:30 Armand - please contact me direct for full details of the programmer and the much updated temperature controller project -

Written by on 2007-04-19 10:25:16 Could you please send me the info for the programmer. I am interested in trying your multi controller.    Thanks,  Dan

Downloads Written by on 2007-04-24 16:20:43 The downloads don't work. All the files are 0bytes when downloaded??

Temp Controller Files and Information Written by on 2007-05-18 16:24:32 Anyone who wants a valid set of the latest files or wants any info about the Temp Controller - please contact me direct at:-

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