Hall-effect sensing with Gateron

Hi Intech team/community!
Quick note: I’m not 100% sure this is the right place for these questions — apologies if not; happy to move the post wherever’s best.

First, huge thanks for open-sourcing Grid — it’s super inspiring.

I’m a hobbyist building a DIY synthesizer and I’d love to experiment with your velocity-sensitive approach using Gateron Hall-effect switches. I have a few technical questions:

Hall sensor choice: You use OH49E-S. What drove that choice versus other options (e.g., sensitivity/hysteresis, linearity, noise, temperature stability, cost/availability)?
Magnets & interference: With N52 magnets above PCB-mounted Hall sensors, did you encounter issues like excessive field strength, crosstalk between keys, or long-term drift/stability concerns?
Top-side vs bottom-side mounting: You seem to use custom Gateron switches to place the OH49E-S on the top side of the PCB, whereas Gateron’s Hall-effect datasheet suggests bottom-side mounting. Why this choice? (Mechanical stack-up, signal quality, calibration range, EMI/ESD, manufacturability, serviceability?)

Any pointers to docs, schematics, or relevant code sections/threads would be amazing.
Thanks again for sharing your work — it’s been incredibly educational!

Replies (4)

sukuwc · September 24, 2025

Hi, thanks for reaching out

We chose the OH49-S because we already use it on the interface boards for detecting the magnetic field of the neighboring module.
We are also evaluating the Hallwee HAL403SO because it is much lower current consumption and seems to have better sensitivity
We mounted the the hall sensor on the top of the board because this way the sensor produces bigger voltage swing on the output
I have seen that in the gateron reference design it is mounted on the bottom side but I do not see a good reason why they did that (especially since there is a perfectly sized cutout on the bottom of the switch to fit the actual sensor)
The measurement range is effected by external magnetic fields and the magnet strength variation from switch to switch. We implemented an automatic calibration in the firmware that monitors the min-max range of the ADC input and scales values accordingly

Jeandupont · November 24, 2025

Hi everyone,

Hope you are all doing well. It has been a while since my previous message, sorry for the long delay, but I’ve kept experimenting with Hall-effect switches for my DIY synth project, which has been strongly inspired by your work. Thanks again for the answers you shared earlier, they were really helpful.

While working on a prototype PCB, I ran into something I still can’t quite figure out. On the Gateron Hall-effect switches I have, there is no space that would allow placing the OH49E-S sensor on the top side of the PCB, whereas your design seems to use that kind of layout.

This makes me wonder whether you are using a modified Gateron switch, or if there is an off-the-shelf model that I have not been able to identify. I went through Gateron’s documentation but couldn’t find any switch that matches your mechanical configuration.

If this is not sensitive information, could you clarify:

whether your switches are custom versions
or, if they are not custom, what exact model you are using

This would really help me adjust my PCB design correctly and better understand the mechanical constraints in your implementation.

Thanks again for everything you share about the project — it has been a huge source of inspiration.

kkerti · November 24, 2025

Found a PI for gateron low profile jade swithes, KS-33CF10B030NW-D272. Should be available in retail packaging via gateron webshop.

SzelleyGabor · November 27, 2025

Hi OP,
Maybe to understand better our design I can share some photos of it. The sensor is top side but we use bare pcb-s (2pcs spacer layers and 1pcs plate where the switch clicks in) so the switch sitting above and touching the sensor.
We use basic gateron low profile jade and jade pro switches. nothing custom as @user mentioned.
Btw if you want to try out other KS33 low.prof. mechanical switches you can solder them in (even possible with the hall sensor on the board already).

Good luck on your projects!