Duty Cycle & Uptime: Simple Timing Tricks for Low-Power IoT

There is no question that the Internet of Things (IoT) has profoundly reshaped how devices communicate. This technology has assumed central importance across today’s leading smart home sensors, industrial monitoring systems, and all manner of other products and solutions.

If, however, you are a developer or engineer involved in designing IoT solutions, one challenge you will often face will be the task of optimising power consumption to extend battery life.

In this article, then, we will explore certain practical timing techniques you might pursue when you are seeking to craft low-power IoT systems, placing an emphasis on duty cycles and uptime management.

Understanding Duty Cycle and Uptime in IoT

Before we go further, it is worth us setting out exactly what we mean by these terms:

• In IoT design, “duty cycle” refers to the proportion of time a device is active (transmitting, sensing, or processing), as opposed to idle (in a low-power or sleep state). For example, if a sensor is described as having a 10% duty cycle, this means it spends 10% of its time being active, and the other 90% in an idle state.
• “Uptime” is the duration of a device’s operation, prior to it entering a sleep state or requiring maintenance.

Bearing in mind that most IoT devices spend the majority of their time in low-power modes for energy conservation purposes, if you can minimise the duty cycle of your IoT designs, this can enable you to drive down power consumption.

Through the skilful management of duty cycles and uptime, engineers can create IoT devices that strike the optimal balance between performance and energy efficiency.

3 Timing Tricks for Your Low-power IoT Projects

So, let’s put the magnifying glass on some of the practical strategies to which you might turn to finetune your low-power IoT systems’ duty cycles and uptime:

• Leveraging Sleep Modes Aggressively

Most microcontrollers (MCUs) that see use in IoT devices offer multiple low-power modes, such as “deep sleep”, “idle”, and “standby”.

In accordance with this, it can be a good idea to configure your device so that it spends as much time as possible in the lowest-power mode compatible with its functionality.

If, for example, your project involves the use of a temperature sensor for a smart greenhouse, you might configure it to wake up every 10 minutes, taking and transmitting a reading each time, before it resumes deep sleep.

• Optimising Duty Cycles with Precise Timing

Power usage in your IoT system can be significantly reduced when you exercise precise control over when the device is active.

One way in which this can be done, is by shortening the device’s active periods. If, for example, a sensor only takes 100 milliseconds to read and transmit data, leaving it active for a full second doesn’t make much sense from a power consumption point of view. You might therefore tweak the timing to minimise the system’s active window.

In addition, certain IoT systems are designed to operate in dynamic environments, which can present opportunities to adjust the duty cycle in accordance with the conditions. For instance, if you are developing a smart air quality monitor for use in a busy urban setting, this could be configured to sample more frequently during rush hour and less often at night.

• Using External Timing Circuits for Ultra-low Power

If you are putting together simple IoT devices, external timing circuits – such as the classic 555 timer IC (integrated circuit) – can offload timing tasks from the MCU. This can free up the device to spend longer periods in deep sleep.

The 555 timer is a chip that is renowned for its low cost and versatility. With its ability to generate precise pulses or oscillations, this circuit can be invaluable for controlling duty cycles or triggering wake-ups.

When you are looking to get the best out of 555 timer ICs across your IoT projects, it is well worth having to hand a 555 astable/monostable calculator, as can be easily found online.

The output of a 555 timer, after all, depends on the values of resistors (R1, R2) and a capacitor (C) in its circuit. It can be a complex process to determine the correct component values for a desired frequency (in astable mode) or pulse duration (in monostable mode); fortunately, the right 555 timer calculator can greatly simplify this task.

Don’t Overlook the Many Ways You Can Optimise Duty Cycles and Uptime

In your position as a developer of IoT solutions, you will be able to much more easily create energy-efficient and long-lasting devices if you can master uptime and duty cycles.

Timing tricks like those we have explained above may seem almost disarmingly simple. However, such methods can be easily overlooked by many engineers, despite the profound impact they can have on bolstering a given IoT system’s battery life.