External accelerometer and gyro sensor

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seba76
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External accelerometer and gyro sensor

Post by seba76 » Fri Jun 01, 2018 8:59 pm

Hi,

I wonder if is possible to connect any external accelerometer and gyro sensor via bluetooth to iphone which will work with Laptimer ?

It is just because build in (iphone) accelerometer is extremly slow (I'm using laptimer on the bike).

Does any one of you know any supported sensor like this ?

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Sebastian
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Harry
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Re: External accelerometer and gyro sensor

Post by Harry » Fri Jun 01, 2018 9:22 pm

I have not yet added support for an external accelerometer. There are some solutions, but I do not see it is worth the effort.
The reason you see a slow rate for the internal accelerometer is that data is fused to GPS fixes for LapTimer up to v21. This means independent from the acceleration rate measured, only one value is stored per second when using the internal GPS.

But there is good news: a) you can increase the rate up to 100 Hz - which is easily enough for anything.
LapTimer v22 will come with adjustable storage rates. As an example, you can set a 20 Hz storage rate and LapTimer will fuse the 1 Hz GPS and e.g. 30 Hz acceleration to the database. You just need to wait for some more days / weeks and get it for free.

- Harry
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seba76
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Re: External accelerometer and gyro sensor

Post by seba76 » Sat Jun 02, 2018 6:46 pm

Harry,

About second part of your answer - it is a good news.

About first part of your answer:
Do I understand correctly ?: If I will use external GPS with Ex. 10Hz rate then acceleration will be also 10Hz from internal (iphone) sensor ?

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Sebastian
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Harry
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Re: External accelerometer and gyro sensor

Post by Harry » Sun Jun 03, 2018 7:58 am

Yes. Acceleration is sampled at 30 Hz by default, smoothed to approximately 10 Hz and stored by fusing it to GPS fixes for v21 and before. So if you add a 10 Hz GOS, you get 10 times the amount of acceleration data. NB: due to a problem with v21.2 on Android, this works for iOS only currently.

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Re: External accelerometer and gyro sensor

Post by teo_parvu » Sun Jun 03, 2018 1:27 pm

Hi,
Did I understand correctly? This feature is already working on HLT 21.2 IOS? Should I set anything after i choose a 20HZ VBOX Sport as the default GPS sensor? I need more accurate g force data on corners.
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Harry
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Re: External accelerometer and gyro sensor

Post by Harry » Sun Jun 03, 2018 3:45 pm

teo_parvu wrote:Hi,
Did I understand correctly? This feature is already working on HLT 21.2 IOS? Should I set anything after i choose a 20HZ VBOX Sport as the default GPS sensor? I need more accurate g force data on corners.
Thank you.
Yes. You may try an accelerometer update rate of 20 * 3 = 60 Hz instead of the default rate (30 Hz) optimized for 10 Hz GPSes and below.

- Harry
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Re: External accelerometer and gyro sensor

Post by M0DRN71 » Wed Sep 11, 2019 5:24 pm

Harry wrote:
Sun Jun 03, 2018 3:45 pm
teo_parvu wrote:Hi,
Did I understand correctly? This feature is already working on HLT 21.2 IOS? Should I set anything after i choose a 20HZ VBOX Sport as the default GPS sensor? I need more accurate g force data on corners.
Thank you.
Yes. You may try an accelerometer update rate of 20 * 3 = 60 Hz instead of the default rate (30 Hz) optimized for 10 Hz GPSes and below.

- Harry
So if I am using a Dual 160 External GPS with my iPhone 8+, I can set my Accelerator Tweaks to 20, and leave my GPS Storage Rate setting to GPS Rate, or should I also change that to 20Hz?
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Re: External accelerometer and gyro sensor

Post by Harry » Wed Sep 11, 2019 5:36 pm

For the XGPS I recommend to use GPS Storage Rate and an acceleration rate of 30.

- Harry
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M0DRN71
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Re: External accelerometer and gyro sensor

Post by M0DRN71 » Wed Sep 11, 2019 5:39 pm

Thank you!
terrylb
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Re: External accelerometer and gyro sensor

Post by terrylb » Wed Oct 09, 2019 5:51 am

Hi Harry,

What about using the accelerometer of the Kiwi4? Wouldn't this reduce the problem of phone mounting location and vibration? I've had no luck trying to find a sturdy mount that's not a windshield suction cup (not allowed at our track events). Using HLT as a data recorder with a Kiwi4, external GPS and GoPro seems like it would be a good solution. Any thoughts on this?
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