External Wireless Temperature measurement

This project was required so that I could monitor the temperature inside a temporary lean-to / greenhouse I made to winter some frost hating plants in.

There are basically two modules, the transmitter and the receiver.

Receiver

Transmitter

The transmitter uses a Jeenode from Jeelabs to read the temperature from two DS18B20s, one inside the greenhouse and the other in the form of a probe placed outside the greenhouse to measure the ambient temp.

The receiver uses one of my own PCBs which is essentially a jeenode with an added uSD card slot, the display is from Jeelabs and is designed to sit directly on top of a Jeenode but it's not the cheapest display you can use.  The receiver can also be made using a standard Jeenode instead of my PCB.

I run the transmitter off some old lithium rechargeable 1850 cells taken from an old laptop battery, the receiver also runs on a lithium battery from a mobile phone but you can use any batteries you like from 3 to 5 V.

The battery voltages of both the transmitter and receiver are monitored and displayed on the LCD, the code for the battery monitoring was taken from the Jeelabs blog here and the sleep functions were also from the same post using the Jeelib libraries.

Sketches can be downloaded for transmitter and receiver.

Any questions or comments, feel free.

Chronograph - Part 5

Latest project update for 2026 here

Files
Here are the various files etc. if you want to make your own Chronograph.

Rar file with the files required to make the PCB using Seeedstudio.com are here

A copy of the sketch I'm currently using with my PCB is here, please note it's definitely a work in progress, use at your own risk.

Please note that the connections to the LCD are not the standard ones, I have changed them to suit my PCB requirements.

Items needed
8x2 LCD (16x2 can be used, just modify the code to suit) from here
5V Step-up converter from here
Arduino Mini Pro clone from here (check the pin out is the same prior to buying)
Switches from here

Circuit diagram

PCB

My Alternate Jeenode

The Processor board for my shields arrived this morning and I've finished assembling the parts and tested the GLCD, RFM12B and the SD Card socket.

One of the main reasons behind this PCB is so I can have a driver for the Jeelabs GLCD that is physically smaller than the GLCD PCB and will be easier to mount in an enclosure but now all sorts of ideas are now springing forth!

This is the first time I've used a few SMD components, I'm using the 1206 size because I can just about manage them without too much eye strain.

So far I've tested the GLCD, RFM12B and SD card reader and all seems OK so far.

Eagle Files for PCB are here.

Top view

Bottom View

Screen grab of SD card info sketch.

So far so good, all going to plan.