How to use a smartwatch as a heart rate monitor sensor for a cycling controller

Posted at: Jul. 21, 2021

This is a summary of how to use a smartwatch as a heart rate sensor for a cyclocomputer. If you meet the conditions on the cyclocomputer side and the conditions on the smartwatch side, you can display the heart rate data on the cyclocomputer with the smartwatch alone, without having to buy an additional heart rate sensor.

Table of contents

How to use a smartwatch with a cycling heart rate monitor sensor

There are two conditions to use a smartwatch with a cyclocomputer.

both the smartwatch and the cyclocomputer are compatible with Bluetooth LE and ANT+.
the cyclocomputer supports the profile used for heart rate data.

In the case of a Bluetooth smartwatch, Bluetooth LE includes a heart rate monitor in the standard profile, so if both of them support Bluetooth LE, the heart rate data of the smartwatch can be acquired in terms of specifications. However, whether the heart rate source is enabled on the cyclocomputer side or the smartwatch side is a case-by-case basis depending on the product.

On the other hand, as for ANT+, as long as both the cyclocomputer and the smartwatch have the ANT+ heart rate profile “HRM” enabled, they can basically transmit and receive heart rate data by pairing.

Therefore, the most reliable way is to use a smartwatch that is listed on the “compatibility list” announced by the manufacturer of the cyclocomputer.

Points to note when using a smartwatch as a heart rate sensor for a cycling controller

There is a possibility of losing the pair with your phone.

Whether it’s Bluetooth or ANT+, most of the time, except for a few products, the only thing that can be paired at all times is a single 1:1 pair.

For example, if you have an Apple Watch or other smartwatch paired to your phone via Bluetooth, you cannot pair it to your cyclocomputer via Bluetooth (there is a way to bridge your iPhone).

Also, while you have a Bluetooth pair connection with your cyclocomputer, it will not be paired with your phone, so you will not be able to receive notifications from your phone.

This point can be avoided with a smartwatch that uses both Bleutooth and ANT+. It allows you to do the following

connect to your phone via Bluetooth
connect to the cycling controller via ANT+.

For example, Garmin’s Instinct Dual Power Tactical supports both Bluetooth and ANT+, but also offers a heart rate transfer mode with ANT+, so you can pair it with your smartphone via Bluetooth to receive notifications on your phone while sending your heart rate via ANT+ to your cycling system.

A connection pair that is not recommended by the manufacturer may cause connection failure or instability.

Since cyclocomputer manufacturers do not check the operation of their products with all smartwatches, most of the products that officially declare that they can use smartwatches as heart rate sensors are from the same manufacturer.

If the manufacturers are the same, even if there is a problem, they may be able to deal with it by updating the cyclocomputer or smartwatch, but if the pair is not recommended by the manufacturer, it is more likely that they will not be able to deal with it.

Also note that a pair that is not recommended by the manufacturer may not be able to be connected in the first place, or the connection may become unstable.

How to find a smartwatch that can be used with a cyclocomputer

When looking for a smartwatch that can be used with a cyclocomputer, look for a smartwatch that meets two key criteria.

Support for Bluetooth LE & ANT+.

As I explained earlier, if you want to use your smartwatch with your smartphone and your cycling controller at the same time, it is best to pair it with your smartphone via Bluetooth and connect it with your cycling controller via ANT+.

In other words, if both your cycling and smartwatches support Bluetooth LE and ANT+, you can separate the communication paths.

bleutooth: phone <–> smartwatch ANT+: Cycling controller <–> Smartwatch

This way, you can get the most out of your smartphone, smartwatch and cyclocomputer.

Most modern cyclocomputers support both Bluetooth LE and ANT+ if they are higher-end models, but there are not many smartwatches that support ANT+.

Heart rate transfer mode” is mentioned in the specifications.

This is a requirement for the smartwatch side.

No matter how many heart rate monitors your smartwatch supports, if it does not have ANT+ data transfer mode, the data cannot be received by the cyclocomputer.

Therefore, be sure to check if the smartwatch’s specification page states that it supports “heart rate transfer by ANT+”.

If you really need both, use a band-type heart rate sensor!

Smartwatches can measure your heart rate, so it would be best if you could use it with a cycling controller as well, but heart rate is useless as a training indicator unless you can get stable and reliable data.

In this sense, using a band-type heart rate sensor that is compatible with Bluetooth and ANT+ is still the best way to go.

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