Log-a-Long Timer Kit

$7.00 to $24.00

Price includes US shipping.

How many?


With some careful soldering, this kit will make a little timer circuit which can control an Arduino-based data logger. At the desired logging interval, the timer supplies power to the logger. When the logging event is complete (e.g., data is written to an SD card) the sketch on the Arduino signals the timer to cut power. Until the next logging event, the Arduino logger is turned off and uses no power. The timer itself consumes very little power (30µA) and the Arduino logger uses power for only a few seconds during each event. So small batteries can last many months powering the whole system.

The kit includes two key components: a TPL5110 low power timer chip, and a P-channel mosfet. These are surface mount components and require some care to solder onto a PCB. The PCB included is a generic SOIC8 to DIP8 adapter which is intended for other types of use but works perfectly for this circuit. 

A Log-a-Long Timer Kit can be included as an option with the Mini Pearl and Mini Pearl Pro logger kits.

Eight surface mount resistors are also included. One of them must be soldered on to determine the timer interval. The included resistors offer a choice among intervals of about 2, 5, 7.5, 15, 19, 29, 55, and 105 minutes. Other resistors can be substituted for different logging intervals (see table below). 

A 1MΩ through-hole resistor is also included for cleaning up the Done line. This is optional but can be added between the Done pin and ground to ensure that the signal sent from the Arduino to the timer to cut power is read clearly.

Some male header pins are also included if you want to make temporary connections to the timer with DuPont wires. Alternatively, wires from the battery and Arduino can be soldered directly to the PCB. Wires are not included in the kit.

The TPL5110 IC component is designed for low power applications and cannot tolerate more than 5.5 volts. So do not connect batteries that supply more than that. This timer can control 3.3 volt Arduinos, but not 5 volt Arduinos.

Step-by-step instructions for assembling the timer are included and can be downloaded at the Guides page. Sketches which work with this timer and a Mini Pearl Logger are available for download at the Guides page with the documentation for the Mini Pearl Snap and Mini Pearl Pro logger kits. Notes about assembling and using the timer are here: https://publiclab.org/tag/log-a-long-timer.

Soldering can be done with any good soldering iron, but this is not a good project for your first soldering experience.

Options for multiple purchases are in the drop down menu above.


Table of intervals.  A resistor of the listed resistance will produce the indicated logging interval. The eight resistors included in the kit are in the third column with the approximate interval (min.) and the designation on the resistor (e.g., "3002"). Find a more complete list of resistor values here (page 13).

1 Second

5.2 KΩ

2 Seconds

6.79 kΩ

3 Seconds

7.64 kΩ

4 Seconds

8.3 kΩ

5 Seconds

8.85 kΩ

6 Seconds

9.26 kΩ

7 Seconds

9.71 kΩ

8 Seconds

10.18 kΩ

9 Seconds

10.68 kΩ

10 Seconds

11.2 kΩ

20 Seconds

14.41 kΩ

30 Seconds

16.78 kΩ

40 Seconds

18.75 kΩ

50 Seconds

20.047 kΩ

1 Minute

22.02 kΩ

2 Minutes

29.35 kΩ

2 min. "3002"

3 Minutes

34.73 kΩ

4 Minutes

39.11 kΩ

5 Minutes

42.90 kΩ

5 min. "4302"

6 Minutes

46.29 kΩ

7 Minutes

49.38 kΩ

7.5 min. "5102"

8 Minutes

52.24 kΩ

9 Minutes

54.92 kΩ

10 Minutes

57.44 kΩ

12 min. "6202"

20 Minutes

77.57 kΩ

19 min. "7502"

30 Minutes

92.43 kΩ

29 min. "9102"

40 Minutes

104.67 kΩ

50 Minutes

115.33 kΩ

1 Hour

124.91 kΩ

 55 min. "1203"

1 Hour 30 Minutes

149.39 kΩ

2 Hours

170 kΩ

105 min. "1603"