Measuring Activation Forces of Button Switches to Support Clinical Practice

Measuring Activation Forces of Button Switches to Support Clinical Practice

Natasha Kay, AAC Consultant and Occupational Therapist at Ace Centre, recently completed a project and presented a poster at the Occupational Therapy Show in 2025, focused on the measured activation forces of a selection of switches. Read more about her project below.

**Resources:** [Access the dataset] | [Open the poster]

Switches are one of many ways people with physical difficulties can access technology. Switches can be used to access everything from toys and computers, to communication aids and environmental controls (Cook & Polgar, 2020). Successful switch use often relies on having the right switch in the right position.

One important factor when exploring switches is the activation force — the amount of effort needed to press the switch. This can vary between different switches as well as across different areas of the same switch.

If the activation force needed is too high, people may get tired or be unable to use the switch consistently. If it’s too low, people with tremors or involuntary movements may press the switch accidentally (Simpson, 2013). For example, someone with Motor Neurone Disease may benefit from a lighter touch switch that reduces effort, while someone with a tremor or Cerebral Palsy may need a heavier touch switch that resists accidental activations.

Why This Matters

Manufacturers often publish activation force figures, but these aren’t always accurate. They may not include the switch casing, and the force can change depending on where the switch is pressed (centre vs edge). Without reliable data we’re often left guessing, and trying various switches until something works.

Through this project I wanted to measure the activation forces of a wide range of commonly used button switches and make the results openly available.

How Activation Force was Measured

For the project, I adapted a method used for testing mechanical keyboards. I connected the switch to a switch tester, placed it on a kitchen scale and reset the scale to zero (so it would only measure the force of pressing, not the weight of the switch itself), pressed lightly until the switch activated, and recorded the weight in grams. Each switch was tested three times at both the centre and the edge, and the average force was calculated. This captured the small differences that can make a big difference for clients.

I set out to test a variety of common button switches, with the aim of creating a dataset that can directly support clinical decision-making. While my measurements of activation force may not be fully accurate, they do allow for comparison between switches and centre/edge forces, as all included switches were all tested in the same manner.

Results and Findings

The measurements showed considerable differences between measured activation forces and manufacturer specifications, as well as clear variation between pressing the centre and edge of the same switch.

Large discrepancies from manufacturer data:

• Petite Pillow switch: ~109 g on average — over three times higher than the stated 30 g. This could be due to the thick layer of foam which needs to be compressed before the switch can be activated.
• Microlight switch: ~20 g — around double the published 10 g. As the force required is so light this is unlikely to be noticeable for clients, but is still a significant finding.
• Mini Cup switch: ~205 g compared with a listed 130 g — about 60% higher. This difference could make it very challenging to use, especially given the small size of this switch.
• Pal Pad: A lot of variability between tests (44–139 g) despite an official figure of 34 g. This inconsistency could be frustrating for a client as the switch may not always respond to the same force and movement.

Differences across a single switch surface:

• Buddy Button: ~110 g at the centre but only ~57 g at the edge — nearly half the force.
• Jelly Bean: ~66 g at the centre vs. ~28 g at the edge — over 50% less force.
• Egg Switch: ~443 g at the centre compared to ~296 g at the edge — a 33% reduction.

• These findings show that edge presses typically require less force. This was consistent with my expectations, but useful to have clearly reflected in the data. It also has clear implications for clinical practice, namely for considering the location and position of a switch. If less force for activation would be beneficial, can the switch be positioned to be activated on the edge rather than the centre.

Switches close to expectations:
Some switches, such as the Piko and Smoothie, closely matched manufacturer specifications.

All results are available in an open dataset, giving everyone access to measured activation force data which could be useful when comparing switches and making decisions about which switches to trial and use.

Real-World Example

Shortly after finishing the project, I was able to use the data in practice. I was working with a client who had a Buddy Button switch (around 111 g force), and he was having trouble consistently activating it. Switching to a Jelly Bean switch (around 66 g) made activation much easier and more reliable. Having the information on the switch activation forces meant I could do a straight swap to a lighter touch switch, and there was no need to try various switches to find an easier option. Changing the switch was a small adjustment that made a big impact, and gave the client a consistent way to access his device.

Impact on Clinical Practice

Through this project, I hope to help clinicians feel more confident when exploring and using switches with their clients. Here are some ways I hope this dataset helps:

• Evidence-based decision-making: Clinicians can use the activation forces data to support their decision-making on which switches to use and try.
• Better outcomes: By having comparable information on the activation force of different switches, therapists are better able to match switches to clients’ physical abilities and reduce fatigue and accidental activations.
• Interdisciplinary collaboration: The dataset can be useful for Occupational Therapists, Physiotherapists, Assistive Technology specialists, Speech and Language Therapists, Educators, and anyone else involved in trialling and using switches.
• Awareness and education: Sharing this project raises awareness of switch access and the range of switches available, and encourages Occupational Therapists and other clinicians to consider switches when completing their access assessments.

Practical Tips for Clinicians

• Start with the client: Look at strength, movement patterns, and consistency of a movement. A switch can be activated with any reliable body movement, such as a hand, finger, head, or knee.
• Test different points: Activation force often varies across the switch surface, and the edge may be easier than the centre. Consider the position of the switch and the movement, and which part of the switch is being activated.
• When testing switches with a client: A simple way to hold a switch in any position is by attaching it to a wooden spatula (or similar) with Velcro. This allows the switch to be moved into any position without fingers getting in the way, and also allows the switch to be moved away slightly to support with learning switch scanning skills.
• Use the data: Check the open dataset to guide switch choice, especially when considering the need for a switch with a lower or higher activation force.
• Record and review: Note which switch and body part are used, and share with the wider team to support consistency and skill development.
• Explore our Switch Assessment and Planning Framework. This is currently being updated, and we are hoping to have a new version available in 2026.
• Explore our work with CENMAC on FUNctional Switching for practical activity ideas to support switch skill development.

Next Steps

I hope to expand the dataset to include other factors, starting with switch travel (the distance the switch must be pressed before it activates). I would also like to continue testing new switches as they become available. I am open to suggestions for any switches which are not part of the dataset, and any other features that would be useful to have included.

Access the Dataset

All activation force measurements are available in an open-access spreadsheet, including raw data, a comparative graph, and a pivot table for easy comparison. Follow the link to explore the data.

Conclusion

By measuring the activation force of a range of switches and making the results openly available, my goal was to support clinicians with their switch selections. I also hope this project highlights the versatility of switches as an access method, and their benefits for increasing people’s independence and communication.

References

• Cook, A. M., & Polgar, J. M. (2020). Assistive technologies: Principles and practice (5th ed.). Elsevier.
• Simpson, R. C. (2013). Computer access for people with disabilities: A human factors approach. Taylor & Francis Group.

Written by Natasha Kay, Occupational Therapist and AAC Consultant at Ace Centre