Intelligent bi-colour backlit LCD display’s thermometer ICL7106 PIC16F84A LM324 74HC148


Fig.1 - The thermometer with the green backlight

Fig.1 – The thermometer with the green backlight

What I’m getting ready to explain below, is an original solution I adopted to backlight the thermometer’s project SP0003. Thanks to this, I solved quite easily the main difficulty that consists in generating an even illuminated background to the LCD display using some common LEDs.

At that time, I was also learning how to use the microcontrollers and I wished to make my first real project (and not only on a breadboard) with the PIC16F84A. I programmed the µC for changing the backlight’s brightness according to the room’s light intensity because it could be annoying in the dark, or insufficient in the opposite condition. I also thought that it could be nice switching the LCD backlight colour by pressing a push button.

To complete the project, I inserted a power supply to the thermometer capable of accepting a wide range of DC or AC voltage.

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Basic JDM PIC Programmer


Fig.1 - The basic JDM programmer

Fig.1 – The basic JDM programmer

Some years ago, in order to make some experiment at home with the PIC16F84A microcontroller, I needed to build a programmer. Surfing on internet I found lots of solutions and I decided to realize one of the easiest ones: a JDM programmer.

The cost of the project is probably a couple of Euros. In the PCB in figure 1, I used only components I had available at home and for that reason the DIP socket is 20 pin instead of 18.

I remember leaving the schematic as it was and drew it directly on Eagle, as shown in figure 2. Today I tried to find on the web the original project with no success. A similar one is published on the PICPgm‘s website (figure 3) but others are available on various websites as well. So, I don’t know exactly who to thank for this :-)

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Three-ways Automatic Watering System PIC16F84A

If you are interested in buffering for a short time frame (ex. a holiday) this is the right solution for you, otherwise go to the project BP005 for a self-controlled watering system that operates 365 days per year.


Fig.1 – The three-ways automatic watering system's central unit

Fig.1 – The watering system’s central unit

Some years ago I had the opportunity to spend a whole month holiday in Portugal. I didn’t want to ask my friends, or neighbours, to water my plants everyday for me. I thought therefore to build a system for that purpose using the most common microcontroller PIC16F84A.

I thought and tested lots of different solutions in order to find the best one. Reliability was the most important aspect to ensure: a fault could have killed my plants or, worse, flooded my neighbour’s house. Once the system was built, only a few days remained before my departure. So, I set the irrigation timing as best as I could, I asked a friend of mine to go and check once if everything was fine and I left the house crossing my fingers.

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