Skandia Freki Connection Possible ?

[hardy12344]

Hello, I own a Skandia Freki magnetic rowing machine. I'd like to use my VR headset for rowing, but I can't connect it to my computer's Bluetooth. Kinomap works. According to Holofit, the Concept 2 should work. I have the following signal cables connected to the speedometer. My question is, would connecting a Raspberry Pi work? What exactly would I need to do? I've attached a picture. Perhaps someone can help me.

[JaapvanEkris]

Hi,

I looked at the exploded view of this rower, and it is a bit unclear where these end. It seems to be two reed switches. Easies it to follow the wire and see where it ends.

OpenRowingMonitor can be made to work on almost any machine. Only the amount of work to be done differs. Sometimes these sensors don't measure on the flywheel but on the pulley, so you have to glue on your own magnets to the flywheel and add a new sensor. Doable, but requires some work. Technically it could work with a pulley, but metrics will not be reliable at all.

Please note that this repository is as dead as a Dodo. An active branch is maintained here: https://github.com/JaapvanEkris/openrowingmonitor

It can install on more recent Raspberry Pi OS versions, and is much more robust in its approach.

[hardy12344]

I've now opened it up. So, yellow and green are reed contacts 1, and red and blue are reed contacts (blue, for some reason). There's a magnet on the shaft. White and black go to a circuit board for adjusting the selector lever's steps. See pictures.

[hardy12344]

So, will I need a reed switch and a magnet, or magnets on the flywheel? How are the magnets attached? And can I also use the shear rate from the lever? The technical implementation and calibration aren't entirely clear to me yet.

[Abasz]

You need a reed/hall sensor that measures the magnet passing which are attached to the flywheel.

Your current setup measures the handle pull and uses fixed constants to calculate random metrics. The circuit board on the leaver is 90% a variable resistor that indicates theoretical resistance so the machine can be slightly more accurate.

The point is ORM will only work after some hardware changes (fitting magnet(s) on the flywheel as well as adding a hall/reed sensor)

You can look at Jaap's repo as that is maintained. You should use the documentation their, it is very through you will find answers to 90% of your questions. For instance here is a discussion on the reed/hall retrofit (though its an air rower but the principal is the same):
JaapvanEkris#140

[hardy12344]

Thank you very much, I'll take a look at it. Using a magnet and reed switch wouldn't be a problem; I'm technically skilled.

[Abasz]

The recommendation is to use hall sensor if you can :) and more than one magnet produces more accurate data (though you will need to place the magnets as accurate as possible in terms of relative distance, people tend to use 3d printed brackets ) :)

sorry I was keeping to the minimal as people with various skillsets are implementing :) With hall the only thing that is important is that rpi can only take 3.3v on its gpio's but most halls need more than 3.3v to operate properly so selection is crutial.

Reed is as easy as it gets but it does not create as clean signal as hall (no hysteresis, potential bounce etc.). Here is a video on the reed: https://www.youtube.com/watch?v=7LimjYS04FQ&t=278s

[hardy12344]

Yes, there's a magnet size that works particularly well; I have a 3D printer. It reminds me a bit of a filament runout sensor (speed-dependent) that I once designed. I'll attach the circuit diagram for the tachometer signal. But for Gear

[Abasz]

For this tachometer probably your proposed circuit is a bit of an overkill (though if you have one already lying around it might work). But you need to bear in mind that the rotation frequency will be massively higher than for the run-out sensor (keep this in mind when selecting appropriate hall). I would simply go for a digital hall sensor (omni or unipolar) though its not easy to find one with as low as 3.3v so it can be supplied with voltage directly from the rpi without extra circuit.

Also recommendation is not to go above 6 magnets as the higher you go the more computational expensive (its exponential). 6 works fine and provides sufficient resolution. Any way starting with 3 first is probably a safe bet.

Please note that Rpi uses internal pull-up resistors on the pin set in the software. I think its ~50k (so you avoid a voltage divider since you are pulling on the drawing the output to low).

The default signal detection setting in ORM is rising edge. However, with halls using an open-drain output with a pull-up gives a slow rising edge (since rpi internal pull-up is rather week). A slow edge makes for more margin of error, because some noise may cause the IO to detect a '1' slightly earlier or slower. The steeper the edge, the less margin of error. So I suggest to have a falling edge detection by changing this in the cofing.js: gpioTriggeredFlank: 'Up', to this gpioTriggeredFlank: 'Down'.

[JaapvanEkris]

Also recommendation is not to go above 6 magnets as the higher you go the more computational expensive (its exponential). 6 works fine and provides sufficient resolution. Any way starting with 3 first is probably a safe bet.

Given the flywheel construction with three "spokes", I guess three would be the easiest to start with. Perhaps @Abasz has a better informed opinion, but I'd keep the sensor as far away as possible from the huge magnet array, as this might interfere with detection.

Please be sure to use OpenRowingMonitor version 0.9.5 or higher (current version is 0.9.6) as we improved the spontanuous stop/pause detection quite a bit for magnetic rowers. Magnetic rowers tend to have quite a short spin-down time (often less than our usual 6 seconds) where air based rowers spin down for minutes. As a full flywheel stop kills the datastream, older versions of OpenRowingMonitor simply didn't detect a full stop/pause.

[hardy12344]

I currently have no idea how to attach the magnets to the flywheel. How big should they be? And can you recommend a link to a Hall sensor? According to the instructions, the flywheel weighs 8 kg.

[Gordon-Shumway2]

The flywheel should be magnetic, that's why the magentic brake works. So you just need to position the magnets on the flywheel - they should cling to the wheel by themselves.
The magnets I used on my Tunturi magnetic rower were 5mm x 5mm if I remember correctly.

Cheers,
Michael

[Abasz]

DRV5023 this is a low power (min v is 2.5v!!!!!) hall that was confirmed to work in ESP Rowing Monitor

It is sold on Digi-key and Mouser

[beavis69]

take a look at my setup on magnetic rower : #121

[hardy12344]

Hey thanks
Aother Mindstorm

Could you also use an IR sensor? Then you'd only need a piece of aluminum foil. I found something about a treadmill here

https://github.com/benb0jangles/Smart-Treadmill-Adapter-FTMS-Bluetooth

[Abasz]

Could you also use an IR sensor? Then you'd only need a piece of aluminum foil. I found something about a treadmill here

Yes that can work too of course. I never tried though its accuracy.

https://github.com/benb0jangles/Smart-Treadmill-Adapter-FTMS-Bluetooth

Thanks for this link! I was literally thinking about this because at our boat house we have an old treadmill. Actually yesterday I already ordered IR sensors, but I was looking for whether there is any existing project for ideas :D:D:D:

[hardy12344]

Hello, I'm pursuing a new strategy. I recently acquired a Concept2 Model C rowing machine at a good price. However, the PM2 monitor is defective. I'm now considering buying a PM5. My question is, how good is the PM5? I'd like to row using apps/VR. Is your solution better than the PM5, or are there features I'm missing? Can I run both systems simultaneously—a Raspberry Pi and the PM5—or is it one or the other? How much effort would this require? Abasz ***@***.***> schrieb am Di., 6. Jan. 2026, 21:07:

…

The recommendation is to use hall sensor if you can :) and more than one magnet produces more accurate data (though you will need to place the magnets as accurate as possible in terms of relative distance, people tend to use 3d printed brackets ) :) sorry I was keeping to the minimal as people with various skillsets are implementing :) With hall the only thing that is important is that rpi can only take 3.3v on its gpio's but most halls need more than 3.3v to operate properly so selection is crutial. Reed is as easy as it gets but it does not create as clean signal as hall (no hysteresis, potential bounce etc.). Here is a video on the reed: https://www.youtube.com/watch?v=7LimjYS04FQ&t=278s — Reply to this email directly, view it on GitHub <#186 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ASDKSWDTCIYWMKZ43GN7IM34FQIXJAVCNFSM6AAAAACQ2VLXOCVHI2DSMVQWIX3LMV43URDJONRXK43TNFXW4Q3PNVWWK3TUHMYTKNBSG44DKOA> . You are receiving this because you authored the thread.Message ID: ***@***.*** .com>

[Abasz]

Here are some resources:

#38

Also I am working on a FAQ: https://github.com/JaapvanEkris/openrowingmonitor/blob/create-faq-from-discussions/docs/faq.md#17-older-concept2-rowers-model-c-and-earlier--sensor-compatibility

its not perfect yet but it could help as it tries to aggregate community wisdom. It has references to discussions that relate to the topic you are seeking (there are typos where Model B is shown as C it will be fixed nonetheless contentwise its fine)

[JaapvanEkris]

Hello, I'm pursuing a new strategy. I recently acquired a Concept2 Model C rowing machine at a good price. However, the PM2 monitor is defective. I'm now considering buying a PM5. My question is, how good is the PM5? I'd like to row using apps/VR. Is your solution better than the PM5, or are there features I'm missing? Can I run both systems simultaneously—a Raspberry Pi and the PM5—or is it one or the other? How much effort would this require?

I use them side by side on almost a daily basis, for over three years now. I've come to the point where my PM5 is actually tilted down, and ORM is my main monitor. ORM has always fed EXR (and the PM5/ErgData as backup). I typically program both via ErgZone, giving them an identical training plan.

We are accurate to the point where it is unclear who is better: the PM5 or ORM. I'm currently testing version 0.9.7, and our deviation is within 0.5 seconds, even on half marathons. Some results of the PM5 are puzzeling, so it actually might be we are already surpassed the PM5 in terms of accuracy. When I look at our force curves versus the PM5 on EXR, we are already way better. C2's force curve is a mess in EXR somehow, while ours looks good.

In terms of connection reliability, we clearly win by a mile. The EXR-PM5 interface (and the PM5-ErgData interface) has been plagued with disconnection issues. Last year I had periods where at least once per week ErgData and the PM5 would disconnect mid-session, often permanently. In the meantime, our PM5 emulator has logged hunderds of hours without any of these issues.

Same goes for the ANT+ HR data: I link my Garmin HRM Dual to both the PM5 and ORM. The PM5 drops out at least twice a month, ORM sometimes misses a message, but always re-acquires.

Our GUI is ugly, but much more flexible than the PM5's. We can't program a workout via the GUI yet, but any C2 compatible program can via bluetooth (I use ErgZone).

Looking at data recording, we are lightyears ahead of C2, especially as PainSled has ceased supporting their app. We record all data of every stroke and produce a csv for it (including force curves), which can be used by RowsAndAll. We actually directly upload to intervals.icu, Strava and RowsAndAll, without the need for an app. So as soon as ORM completes the session, it is directly uploaded. The most elaborate data functionality is migrated from RowsAndAll to intervals.icu in 2026, making this a really rich analysis experience for all your activities. C2's ErgData just records strokerates, pace and heartrate. PainSled used to fix that, but they are getting out. And as you only have one BLE connection, when you use EXR or any similar app, no additional data can be retrieved from a PM5.