With some development boards, low power usage is an afterthought. Especially when price and usability is the main selling point. So what should you do when it's time to turn around and make that project of yours run on a battery or solar? Sure you could try to hot-air that regulator off, or you could jerry-rig a relay. Or, use a 555? Ugh, the options aren't that great.

The Adafruit TPL5110 Power Timer is a stand-alone breakout that will turn any electronics into low-power electronics! It will take care of turning your project on/off using a built in timer that can vary from once-every 100ms up to once every two hours. Basically, the TPL will turn on periodically, adjustable by potentiometer or resistor, and turn on your project's power. It will then wait until a signal is received from the project to tell the TPL that it can safely turn off the power. If the TPL does not receive a signal by the set time-out, it will reset the device like a watchdog timer.

Usage is easy. First, disconnect from power and set your desired delay by adjusting the on-board trim pot: all the way to the left is once-per-100ms an all the way to the right is once-every-2-hours. Then, connect VDD up to your 3-5V power supply and then your project's power-in to the Drive pin. Finally, select a signal pin from your project to the Done pin. In your project's code or design, just make sure that it sets the Done pin high once it is completed with its task. That's it!

While the TPL5110 is running (but the remainder of the project is de-powered) the current draw is about 20uA (according to our Monsoon Power Meter)

If you want to turn the device on by hand, you can also activate the TPL by pressing the onboard tactile switch (or wire your own switch to the Delay pin) See? Your power problems just got solved!

Comes as a fully assembled breakout board with a TPL5110 chip, all components on-board, and some header. A little light soldering is required to put it together for breadboard use.

There's a lot going on with this compact breakout, and many ways to do one thing so reviewing the pinouts is a really good idea!

Power Pins

  • VDD - this is the power input pin for both the TPL5110 chip and the device you want to control. Make sure this is always connected and powered. This has to be 3-5VDC so don't give it 12VDC power.
  • GND - this is shared ground for power and signal.

Control Pins

  • Delay - this is the delay control pin. By adjusting the resistance (not voltage!) connected to this pin through to ground, you can change the delay between powerings. By default this is connected to the onboard trim potentiometer. However, you can cut the trace on the back and then connect your own resistor between Delay and GND. Also, if this pin is connected directly to VDD (say through a switch) it will activate the output instantly.
    Note this pin is not continuously sampled. You need to remove and re-apply power once you change the resistance!
  • DRV - this is the Drive output pin, the TPL5110 will power this pin with the same voltage as from VDD when the timer activates
  • Done - This is the signal pin from the driven electronics back to the TPL5110 to let it know that it is 'done' with whatever it had to do, and the TPL5110 can turn it off

There is also an 'active' LED in the top right. This will let you know when the DRV pin is powered. It does draw some current so if you need ultra-low current draw, cut the trace behind the PCB!

This page shows the TPL5110 but the TPL5111 procedure is identical!

Prepare the header strip:

Cut the strip to length if necessary. It will be easier to solder if you insert it into a breadboard - long pins down

Add the breakout board and Solder!

Place the breakout board over the pins so that the short pins poke through the breakout pads


Be sure to solder all 5 pins for reliable electrical contact.

(For tips on soldering, be sure to check out our Guide to Excellent Soldering).

You're done! Check your solder joints visually and continue onto the next steps

Using the TPL5110 isn't too hard but there's a few things to watch out for. First up, do not give it 9V power, use 3-5V only!

Make sure to provide the power to the VDD and GND pins. Then connect your project to the DRV and GND pin. Use a DONE pin from your microcontroller to signal when the TPL can disable power: when the DONE pin goes from low to high, that will turn off the TPL's power transistor.

In this project I'm using A3 as the DONE signal pin. You can use any pin you like as long as the wiring matches your sketch. The pin is lightly pulled down so just set to an Output and High when you're done!

If the TPL doesn't get a DONE signal, it will reset the board with a short ENABLE toggle when the timeout is reached (e.g. before the next cycle)

Notes on the Delay Pin

The delay pin is a little more complicated than you may first think!

  • First, do not connect a voltage here, instead it uses a resistor to determine the delay timing.
  • Second, it does not continuously sample the resistor, it only does it once when power is applied. So set the delay you want, then power up the breakout.
  • Third, you can instantly turn on the project by connecting Delay to VDD. By default we have a pushbutton on board, you can connect your own button if you like
  • Fourth, the resistance is not linear with the time delay, rather there is a complex algorithm to set the time based on resistance. You can check the datasheet for the precise calculation, or use this rough table:

1 Seconds

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

3 Minutes

34.73 kΩ

4 Minutes

39.11 kΩ

5 Minutes

42.90 kΩ

6 Minutes

46.29 kΩ

7 Minutes

49.38 kΩ

8 Minutes

52.24 kΩ

9 Minutes

54.92 kΩ

10 Minutes

57.44 kΩ

20 Minutes

77.57 kΩ

30 Minutes

92.43 kΩ

40 Minutes

104.67 kΩ

50 Minutes

115.33 kΩ

1 Hour

124.91 kΩ

1 Hour 30 Minutes

149.39 kΩ

2 Hours

170 kΩ

Given that we put a 200 kΩ trimpot on the board, you may find it difficult to get precise timing if you need short delays. In that case, you can use any resistor you want. First, cut the trace on the back of the PCB

Then install your desired resistor:

Don't forget to hard-reset the full setup!

ESP8266 Feather Example

ESP8266's are a little finicky and may need some tweaks to get working. Note that some pins have special purpose so are not suitable for a DONE pin. Here's a demo of an ESP8266 Feather with a NeoPixel ring. We power from a microUSB cable through a breakout adapter. The USB power goes through the TPL5110 to the power rail. We added a 47uF capacitor to stabilize the power rail.

For the code, we toggle the DONE pin high and low forever to make sure it gets 'caught' by the TPL (it may not be necessary but it doesn't hurt!)

While we've used this breakout with Huzzah ESP8266 Feather successfully - other people have said it doesn't work for them. So use with ESP8266 is not guaranteed.
// SPDX-FileCopyrightText: 2017 Limor Fried for Adafruit Industries
// SPDX-License-Identifier: MIT

#include <Adafruit_NeoPixel.h>

#if defined(ESP8266)
  #define NEOPIX   4
  #define DONEPIN  5
  #include <Adafruit_SleepyDog.h>
  #define NEOPIX   13
  #define DONEPIN  12

Adafruit_NeoPixel strip = Adafruit_NeoPixel(12, NEOPIX, NEO_GRB + NEO_KHZ800);

void setup() {
  digitalWrite(DONEPIN, LOW);
  Serial.println("Light up NeoPixels!");

  strip.show(); // Initialize all pixels to 'off'

void loop() {

  Serial.println("NeoPixels done, sleeping");

  // toggle DONE so TPL knows to cut power!
  while (1) {
    digitalWrite(DONEPIN, HIGH);
    digitalWrite(DONEPIN, LOW);

// Slightly different, this makes the rainbow equally distributed throughout
void rainbowCycle(uint8_t wait) {
  uint16_t i, j;

  for(j=0; j<256*1; j++) { // 5 cycles of all colors on wheel
    for(i=0; i< strip.numPixels(); i++) {
      strip.setPixelColor(i, Wheel(((i * 256 / strip.numPixels()) + j) & 255));

// Input a value 0 to 255 to get a color value.
// The colours are a transition r - g - b - back to r.
uint32_t Wheel(byte WheelPos) {
  WheelPos = 255 - WheelPos;
  if(WheelPos < 85) {
    return strip.Color(255 - WheelPos * 3, 0, WheelPos * 3);
  if(WheelPos < 170) {
    WheelPos -= 85;
    return strip.Color(0, WheelPos * 3, 255 - WheelPos * 3);
  WheelPos -= 170;
  return strip.Color(WheelPos * 3, 255 - WheelPos * 3, 0);

Video Example

You can also watch me put together a project using a prototype of this board (the shipping version has a pulldown resistor on DONE which i had to manually install in the video)

Handy Accessories

Here's some items you may find useful!

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Breadboard-friendly 2.1mm DC barrel jack
This power jack is designed to fit 2.1mm power plugs snugly and securely. Perfect for adding a power connector to your project. We went for the more expensive "thin pin" type...
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This guide was first published on Mar 08, 2017. It was last updated on Apr 22, 2024.