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PIC Controlled Experimental Plant Propagator
Spring 2014: Free grow light components - If you buy the PIC Controlled Propagator further training course as detailed below and add the heater option (just £6 more) we will include ten 3 watt LEDs, a 12 volt 2 amp power supply and three 5 watt resistors so you can build the oblong grow light. There are pictures near the bottom of this page. You will need to buy 5 heatsinks from Farnell and make a marine plywood frame to hold the heatsinks. Construction details are in chapter 8 of the updated book supplied with this course.
5th March 2013

PIC Controlled Plant Propagator
with Unique Brunning Software
160 LED Grow Light
(New 25th April 2013)

The use of LED lighting for plant propagation is relatively new. This extension to our PIC training course is an opportunity for you to further your knowledge of PICs while experimenting with this fascinating subject. The book starts with an introduction from first principles of which wavelength of light is best for growing plants and how an adequate brightness can be achieved at reasonable cost.

The P206 grow light control PCB uses a 28 pin PIC with real time clock and temperature measuring routines. An alphanumeric LCD displays the real time and soil and air temperatures, and three high current MOSFETs are used for light control, flowerpot heater control and for automatic watering or to drive a cooling fan. These are low cost circuits so two or more can be used when more controls are needed. There is almost no limit.

The tomato seedlings in the picture took 5 days to germinate at a steady temperature of 25 degrees C and have been growing one week when the picture was taken. Their study and healthy appearance indicates that the wavelength and brightness of the light is a good choice.

The seedlings close their leaves before the light is timed to switch off which suggests that the selected 14/10 ratio of day to night is a little longer than the plants needs.

This picture shows the control circuits for the PIC Controlled Propagator. Just plug the circuits together plug a 12 volt 2 amp power supply into the P206-IO (input/output) module, connect the grow light, heater and water pump to the high current screw terminals, connect the thermistors and moisture probe to the top most socket, and move the 5v out switch on the P206-IO to the ON position.

The circuit in the middle is the P206-28 which has a 28 pin PIC18F2321 fitted. This does all the work. The P206-IO provides a 5v supply, four high current MOSFETs for switching the external circuits, and two push buttons which are used to set the real time clock which runs in the PIC.

The idea of this arrangement is that the P206-28 can be easily disconnected from the wires which go to the grow light, heater, water pump, thermistors and moisture probe so the P206-28 can be updated with new software ideas and tested on its own. Then when ready for live tests it simply plugs back in with no rewiring necessary.


The P206-28 can be programmed using a P206 programmer or any other Brunning Software 16F and 18F programmer. This picture shows the full set of module which make up the P206 PIC training system. The P206 hardware is a modular version of the P931 hardware. Both offer the same training and operate in the same way. So far only the first P931 book has a P206 edition. The other two book will be available as P206 editions in the next month or so.

The circuit at the top right of the picture is the P206-18 which is the test bed for 18 pin PICs.

The P206-28 is shown here plugged into a P942 programmer using a P206 to P928/P931/P942 adaptor. When the P206-28 is plugged into the programmer in this way the P206-28 has access to the LCD, LEDs, two push buttons and keypad which are part of the P942 programmer circuit. When the P206-28 is detached any or all of these items can be connected directly to the P206-28.

Price list:-

If you DO NOT already have a Brunning Software 16F + 18F PIC programmer you need to purchase the following....

Order code PICprop1DN:-
  1. P206 USB powered 16F & 18F programmer module
    + P206-28 module with PIC18F2321
    + P206-IO input/output module
    + 16 char 2 line plug in LCD
    + Book: Experimenting with PIC Controlled Propagator
    + PIC assembler BSPWA v9.82 & library code on CD
    + USB lead........................................................................£89.00
  2. UK postage and insurance...................................................£ 6.00
    (Europe postage and insurance.......£20.00. Rest of world......£30.00)


If you DO already have a Brunning Software 16F + 18F PIC programmer you need to purchase the following....

Order code PICprop2D:-
  1. P206 to P928/P931/P942 adaptor
    + P206-28 module with PIC18F2321
    + P206-IO input/output module
    + 16 char 2 line plug in LCD
    + Book: Experimenting with PIC Controlled Propagator
    + PIC assembler BSPWA v9.82 & library code on CD............£59.00
  2. UK postage and insurance...................................................£ 6.00
    (Europe postage and insurance.......£20.00. Rest of world......£30.00)

Spring 2014 offer: If you buy the PIC Controlled Propagator further training course as detailed above and add the heater option (just £6 more) we will include ten 3 watt LEDs, a 12 volt 2 amp power supply and three 5 watt resistors so you can build the oblong grow light. There are pictures near the bottom of this page. You will need to buy 5 heatsinks from Farnell and make a marine plywood frame to hold the heatsinks. Construction details are in chapter 8 of the updated book supplied with this course.

To create your order click: Go to PIC Controlled Propagator - item selection page


14th March 2013

Just after the first picture was taken the three strongest tomato plants were separated into individual flowerpots. At that point in time all three were at about the same stage of development. One tomato plant was kept under the grow light and the other two were moved onto the kitchen windowsill.

This picture was taken 9 days later. The compact, strong growing tomato plant on the left is the one which has spent all its time under the grow light and never seen normal daylight. The weak rather tall tomato on the right is the one kept on the windowsill in mostly overcast but occasionally sunny natural daylight.

The tomato plant on the left has been kept at a steady 25 degrees C soil temperature, with the air temperature dropping to around 19 degrees C at night and rising to 23/24 during the day.

The tomato plant on the right has had a lower average temperature to help it to have sturdy growth but still it has grown rather tall.

21st March 2013

Another week has passed and the tomato plant under the grow light is looking very strong and healthy as can be seen by this picture. This variety of tomato has been bred for growing in a container. Unlike most tomato varieties with this one the side shoots are not to be removed.
21st March 2013

This picture is of one of the tomato plants which are growing on the windowsill. It is the best of the three but even so it is growing weak and lanky.
29th March 2013

The objective of the this extension to our PIC training course is not to sell you a finished plant propagation system but to introduce you to the process of experimenting with you own ideas. This picture shows our own ongoing experiments to try to establish how different single wavelength lights affect the growth of different plants. Here we have one chamber of pure red light and another of pure blue light. This is a long term project but some initial results are already starting to become apparent. The large tomato plant at the right hand corner of each chamber have both spent two weeks or so in normal day light. Now after a few days in single wavelength light the plant in the red chamber is suffering. Yet the tomato seedlings which have only seen red light are so far growing normally.

7th April 2013

Nine days later on 7th April the tomato plant on the left is being grown under the red light and its yellowing leaves shows it is slowly dying. The tomato plant on the right is being grown under the blue light and it is looking healthy. Notice that the baby leaves are still attached but it does give the impression of surviving rather than thriving.

7th April 2013

The tomoato seedlings on the left of this picture were germinated under the red light. The seedlings on the right were germinated under the blue light. The difference is small but it is apparent that the seedlings on the left have grown taller which does show a lack of suitable light wavelengths.

This tomato variety is Matina which is ideal for growing outdoors in the English climate. This variety has potato style leaves.
7th April 2013

Both of the tomato plants in this picture were germinated under the Brunning Software circular grow light. The plant on the left spent about two week on the windowsill then two weeks under the pure blue light. The tomato plant on the right has spent all its time under the circular grow light.

The tomato plant on the right has one tiny tomato. The plant on the left has a tinge of yellow from one of its flowers. So the difference is small but the plant on the right is more advanced.
7th April 2013

This is a close up of the tomato plant which has been under the Brunning Software circular grow light all the time. Notice the tiny green tomato and how healthy the flowers and stems look.

This has not been a fully controlled test so we must be careful of what we conclude but it is clear that tomato plants do not thrive on single wavelength light and have a particular dislike of single wavelength red light. The Brunning Software experimental grow light does seem to provide an adequate replacement for sun light when growing tomato plants.

About six weeks later in the middle of May the tomato plant which had spent all its time under the circular grow light was replanted into a large self watering plant pot. By then the warmth of the summer was just starting and so it was moved away from the grow light into the front porch which on a sunny day has the sun from miday until late. There it produced a steady crop of very taisty tomatoes right through the summer and into autumn. As the chilly nights of October/November arrived so this tomato curled its leaves and prepared to sleep. Then we had a few weeks which were unusually warm and sunny and the tomato sprung into new life with several strong new shoots. I trimmed off all the old canes which had no fruit and as the nights were turning cold again I moved the tomato plant into the office under our new oblong grow light.

29th January 2014

This grow light uses ten 3 watt LEDs. Four red, five blue and one white. There are five heat sinks mounted across the short side of the oblong. Each heat sink carries two LEDs.

Notice that the tomatoes are on rather long stalks. This is because for the first month or two that the new shoots were growing the old stems were carrying their crop of tomatoes. Later when the tomoatoes had rippened (and been eaten) the old stems were cut off.
29th January 2014

This photograph was taken with a short exposure. This allows the true colours a better chance of being seen but gives the impression that it is rather dark around the plant. In reality the lights are strong enough to replace sun light. The white light appears to be the brightest but the blue and red LEDs actually give off more light.
29th January 2014

This photograph was taken in daylight with the grow light turned off. The tomato plant has been growing since early February 2013 and has now produced its last crop. We will now pick the tomatoes and uproot the plant ready to make space for the new seeds which will be planted in a week or two.

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