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PIC Training Course
Grow Light Controller

building a grow light and creating software for controller
Second Edition December 2025

This second edition has all the features of the original version but has been fitted with a larger regulator. The regulator is important if your system includes a grow light and a 12 volt battery. The regulator for the first edition is limited to a maximum charging current of 2 amps. The regulator for this second edition is able to run continuously at 5 amps. This can be very important on a bright sunny day in the middle of sommer when a 100 watt solar panel will provide more than enough power for the grow light.

This shows the grow light controller with a P205 programmer attached.

This short course is for hobbyists who have an interest in experimenting with new ideas. As you work through the training manual you will build a grow light which runs with 80% efficiency with any input voltage between 10v and 24v. We start by using the controller as a simple time switch, then add the circuits and update the software to run the grow light from a solar panel and a 12v battery.

I have enjoyed the challenge of writing the code to run my grow light from a 12v power supply, a 100w solar panel and a 12 volt lead acid battery. But if you cannot justify buying this course and a 100w solar panel there is no problem using this system powered only by a 12v power supply. If you do this you may be inspired later to buy a solar panel.

I have been rasing tomato, cucumber, pumpkin and courgette plants using my own design of grow light since 2013. Just over a year ago I bought a 100w solar panel with the intention of using it to power my grow light. The basic system to do this is very straightforward but the problems arise because the solar panel only produces significant energy in sunshine two hours either side of midday. We add a battery to store the excess energy around midday and the simple idea becomes complex.

This short course starts using the PIC circuit as a simple timer and power switch to turn the grow light on each day between 6am and 8pm. To do this we load the real time clock software from the Brunning Software library then add the simple test instructions to monitor the hours counter.

It is good to know the power that goes to the grow light so we load the analogue to digital library routines and add the instructions to write the voltage, current and power to the LCD.

In this way we gradually work through the task of designing the PIC circuit and creating the complex software needed for using any of the three power sources efficiently.

We start in chapter 2 by learning about grow lights and the theory of which colour LEDs are required. Then I give details of how my grow light is put together using araldite, two strips of ply wood and six lengths of heatsink.


The LEDs are glued to the heatsinks using a very thin coat of alraldite and wired in six groups of three LEDs. Two groups of three are wired in parallel to one of three constant current circuits. This system creates a grow light which runs with over 80 percent effeciency with any input voltage between 10v and 24v.

This ensures that the grow light can be run from a 12v battery at its lowest voltage and from a 12v solar panel at its highest voltage.



The GrowCon module can be programmed using a Brunning Software programmer or PICkit3/4. The book assumes a P205, P931, P942 or P955 Brunning Software programmer is being used.

The software is usually supplied on CD. If you require software on a memory stick send an email request
to pic(at)brunningsoftware(dot)com

Price List
If you already have a Brunning Software programmer (P205, P931, P942 or P955) you need option 1.
If you do not have a Brunning Software programmer you need option 1P.

Option 1:

Grow Light Kit and
Fully Populated GrowCon20..... £77.00
including delivery to UK

GrowCon20 supplied built and tested.


Book: Experimenting with Grow Light Controller
        100 pages 210x150mm.
+ GrowCon20 fully populated, built and tested.
+ Constant current & voltage requlator fitted.
+ 2 line 16 character LCD.
+ Lead to connect contoller to grow light.
+ Kit of parts for grow light:
      10 Red LED 3w 660nm
      8 Blue LED 3w 445nm
      6 Heatsink 150x20x6mm
      3 Constant 700mA regulator
      1 DC input socket
      1 Slide switch
      Glue & wood not supplied
+ PIC assembler and assembler text on CD
+ 12v 2a plugtop power supply

Option 1P:

Grow Light Kit and
fully populated GrowCon20..... £97.00
including P205 PIC programmer
including delivery to UK

GrowCon20 supplied built and tested.


Book: Experimenting with Grow Light Controller
        100 pages 210x150mm.
+ GrowCon20 fully populated, built and tested.
+ P205 PIC programmer
+ Constant current & voltage requlator fitted.
+ 2 line 16 character LCD.
+ Lead to connect contoller to grow light.
+ Kit of parts for grow light:
      10 Red LED 3w 660nm
      8 Blue LED 3w 445nm
      6 Heatsink 150x20x6mm
      3 Constant 700mA regulator
      1 DC input socket
      1 Slide switch
      Glue & wood not supplied
+ PIC assembler and assembler text on CD
+ 12v 2a plugtop power supply


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