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Sensors on Willem's Blog

Improve your sleep by blocking light

On the benefits of wearing a sleep mask in bed

Jan. 24, 2020
I have been wearing a sleep mask in bed, blocking all light. It has been amazing for my sleep's quality. Read along for my findings!

Over the past few weeks I have been experimenting with wearing a sleep mask in bed, blocking all light. Our bodies produce the sleep hormone, melatonin, in darkness. Living in an environment awash in artificial light, is therefore exactly the sort of thing that disrupts one's circadian rhythm. Can a simple mask help?

Whoop strap review: 24/7 wearable sensor

Beyond fitness tracking and smartwatches

Dec. 31, 2019

The past months I have been wearing the WHOOP Strap 3.0, a wearable sensor that collects health and fitness data. It's different compared to most other fitness bands as it was designed with professional athletes in mind. It is focussed on daily strain, recovery and sleep. Read along to find out how this works.

Realtime human pose recognition through computer vision

Using TensorFlow and PoseNet on a video feed

Dec. 1, 2019
For an exciting new project I have been experimenting with TensorFlow, enabling realtime pose detection using PoseNet.

For an exciting new project I have been experimenting with computer vision using TensorFlow. I wanted to achieve realtime human pose detection to drive interactive video projections and games. Time to dive into the world of machine learning, tensors and computer vision!

Riding with a power meter on your bike

Installing and using the 4iiii Precision Powermeter

Aug. 28, 2019
In this post I describe my experience with installing the 4iiii Precision Powermeter on my road bike.

After I created a minimal road bike, I decided to install a power meter to find out what's it like to measure the power output of my legs. What can you learn from a power meter? Is it difficult to install? Is it worth it? Read along to find out.

Limitations of sleep tracking using a wearable

Comparison with a chest strap HR-monitor

July 16, 2019
Limitations of heart rate analyses during sleep, why you should reconsider tracking your sleep.

Sleep monitoring is a popular feature of many smartwatches and wearables. Devices like Fitbit, Withings, Apple Watch and Biostrap analyse biometrics during your sleep. These wearables are worn on the wrist and use optical sensors to capture your heart rate. I wondered how the optical sensors would compare to a high resolution chest strap HR-monitor.

Optical vs chest strap heart rate monitors

Measuring beats per minute using different sensors

July 15, 2019
Understanding the differences in common HR monitors used in wearables, smartwatches and fitness trackers

With modern wearables, smartwatches and fitness bands, it has become easy and common to measure your heart rate. There are however fundamental differences in sensor types. Some sensors capture the electrical signal from your heart while others use light to analyse the blood flowing through your vessels. If you're interested in measuring heart rate, it's good to understand these differences.

Solo around the Markermeer (211KM)

Tips to prepare, to endure and to enjoy long distance cycling

May 29, 2019
This week I took my bike for a long distance (211)KM ride around the Dutch Markermeer, solo! Read along for practical tips for long distance cycling.

This week I took my bike for a long distance (211KM) ride around the Dutch Markermeer, solo! Unlike participating in an organised event with service, support and company along the way, going solo requires a different preparation, mindset and planning. Read along for some practical tips for long distance cycling.

The best bike computer app: Cyclemeter

Get advanced ride data with a flexible setup

Apr. 30, 2019
Collect advanced bike ride data using your smartphone connected to external Bluetooth sensors and a steer mounted display.

This month I have intensified my training to become fit for this year's Fietselfstedentocht, a 235KM bicycle ride through Friesland. Over the years I have tested different kinds of bike computer setups: from dedicated (and expensive) Garmin Edge bike computers to no data at all. Eventually I came up with a flexible setup to gather advanced ride data using my smartphone, let me explain how this works.

Swimming and cycling with Apple Watch

Different activities in the workout app in watchOS

Sep. 27, 2018
This month I tested the newest watchOS while swimming and cycling.

This month Apple launched a new Apple Watch series and released an update to watchOS. The focus of the smartwatch is more and more gearing towards health and fitness. This made me curious, how well does Apple Watch work for different activities?

Listen to your body

Why I stopped using health and fitness sensors

May 17, 2018
Using health data gathered by sensors and wearables I learned to listen to my body. Now I have stopped using bluetooth sensors all together.

A good customer of mine was once a physiotherapist, he told me about people asking him to "feel their muscles" to tell them how they where doing. "Crazy!" he told me: "I can never feel better than the people themselves, if they only would listen to their body". This caused me to question the health and fitness sensors I use.

Outside the comfort zone: amateur acting

Wearing an heart rate monitor during my debut performance

Apr. 18, 2018
This month I strapped myself with sensors during a little experiment outside my comfort zone: I debuted as amateur actor!

This month I made my debut as amateur actor. I am no Hollywood star, nor do I envy to become one. But I do like crazy experiments and operating outside of my comfort zone often leads to new and refreshing insights. I took part in an amateur drama play and - in the name of science and fun - strapped myself with sensors to measure what happened to my body.

Commuting by bike

One week (240KM) on the VanMoof Electrified S

Dec. 2, 2017
One week on the VanMoof Electrified S E-bike testing it for commuting and comparing it to a normal bike.

For a few years now, I commute to work using a bicycle. I have lost more than 15KG since I stopped using my scooter. This week I tested a VanMoof Electrified S, an electric bike with an industrial, minimal design. Is it any good? How does it compare to a normal bike? Will an electric bike make you lazy? Read along to find out!

Collecting health data with Biostrap

Wearing a clinical-grade photoplethysmography (PPG) sensor for a month

Nov. 15, 2017
Wearing a clinical-grade PPG sensor for a month to collect advanced biometrics from my wrist.

Most wearables (smartwatches, fitness trackers, etc.) use very basic sensors to capture heart rate. Their signal is binary: just counting beats. Biostrap is different, instead of just checking pulses, it captures a high-fidelity PPG waveform. These waveforms are the same kind that doctors use, making me wonder what I could learn from them!

Fietselfstedentocht 2017

Cycling the 235KM bicycle tour through Friesland

June 30, 2017
Cycling the 235KM long Fietselfstedentocht through Friesland

This month I cycled the Fietselfstedentocht, a 235KM tour through Friesland. This tour brings you through various Frisian cities throughout one of the most Northern provinces of the Netherlands. The tour was first organised in 1912 and has grown to become legendary due to its history, challenge and popularity; well worthy of a blog post!

One year of cycling

GPS recording an entire year of bike rides using Garmin and Strava

Dec. 31, 2016
GPS recording an entire year of bike rides using Garmin and Strava.

One year ago I started recording all my bike rides, including commutes, short grocery trips and long Gran Fondos. I equipped my bicycles with Garmin Edge computers that recorded location (GPS), speed, cadence and my heart rate. I covered more than 7683 kilometers during 320 hours of riding. It's time to review all the data and share some photos I took along the ride!

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Resting heart rate no longer has any red spikes - relatively stable since I stopped drinking beer
Resting heart rate no longer has any red spikes - relatively stable since I stopped drinking beer
The box contains three straps, charging cable, charger and two sensors
The box contains three straps, charging cable, charger and two sensors
After some long haul rides I disassembled the bike to get home.
After some long haul rides I disassembled the bike to get home.
Playing drama is a team effort - and the on stage interaction is what makes it fun!
Playing drama is a team effort - and the on stage interaction is what makes it fun!
Chain guard made from flexible plastic is resilient to damage
Chain guard made from flexible plastic is resilient to damage
Using Cyclemeter as my bike computer to collect advanced ride data
Using Cyclemeter as my bike computer to collect advanced ride data
Instead of just counting beats, the Biostrap cloud services analyses the PPG waveform captured by the sensor.
Instead of just counting beats, the Biostrap cloud services analyses the PPG waveform captured by the sensor.
Measuring heart rate at different speeds on both a normal and electric bike
Measuring heart rate at different speeds on both a normal and electric bike
Around the Markermeer, through the former Dutch
Around the Markermeer, through the former Dutch "Zuider Zee"
VanMoof Electrified S
VanMoof Electrified S
Lock chain inside a small luggage compartment
Lock chain inside a small luggage compartment
Quick start guide installing and using the power meter
Quick start guide installing and using the power meter
Wind blowing strongly over the water with Amsterdam on the horizon, as seen from Almere
Wind blowing strongly over the water with Amsterdam on the horizon, as seen from Almere
Seiko 5 mechanical watch with WHOOP strap 3.0 sensor attached
Seiko 5 mechanical watch with WHOOP strap 3.0 sensor attached
Heart rate during my debut - with annotations explaining what happened
Heart rate during my debut - with annotations explaining what happened
Effects of a nap during the day: around 2pm you'll notice a steady decline in heart rate
Effects of a nap during the day: around 2pm you'll notice a steady decline in heart rate
Smile inducing speed advantage over other traffic during rush hour
Smile inducing speed advantage over other traffic during rush hour
In the Netherlands there is no shortage of dykes. Many of them have long straight bike lines on them. This one is near
In the Netherlands there is no shortage of dykes. Many of them have long straight bike lines on them. This one is near "Hoek van Holland", you can see the Rotterdam Maasvlakte industry at the horizon.

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