SmplRsrchr

Hi,
I am new to this topic, and if anybody could help me, I would be grateful.
We are trying to do academic research by utilizing power meters. Right now, we are in possession of the “QUARQ DZERO DUB POWER METER”.
The problem is the frequency, and at least for normal commercial applications, we can’t get anything better than 1 Hz, which is nowhere near enough.
Has anyone had any experience with a better frequency while using power meters?
Thanks.

unterhausen

The problem with power meters is they are meant to measure power of a cyclic power application which is then sent to a display/storage device. A 60hz upper limit seems a bit weird, it's not uncommon for people to pedal at twice that. Otoh, if it gives you data for the entire time, but only at 60 hz rate, that makes sense because the data doesn't need to be updated to the rider any faster than that.

You may possibly be the first engineers in history that looked at power meters and didn't immediately think they could make one, no problem. I commend you for that. But you might have to make one.
I don't know how the bottom bracket power meters for ebikes work. It's possible one of them would be more useful though, if it's just raw strain data.

adamrice 

SRM is the grandaddy of the power-meter market, and even makes (or made) special power meters for researchers with additional sensors. They also make this thing, specifically for labs.

There are a number of power meters that will show your power continuously through the pedal stroke, and I am surprised to learn that the Quarq doesn't do that. DC Rainmaker is the go-to guy for cycling gadget reviews, and he has a bunch of power-meter reviews. It looks like the industry jargon for high-frequency power monitoring is "cycling dynamics."

SmplRsrchr

You are 100% right. Building one is the best possible option.
Thank you

SmplRsrchr

Thank you, Adam!

Buzzkill53120

I've done some poking around in the past and found this link: https://sensitivus.com/products/diy-bike-power-meter/
They sell modules that interface with a load cell and send data to an app (not sure sure if it's ANT+ or BT). There some talk of an Android/IOS app called TeamZWATT.

I found another link that may help building your own: https://www.instructables.com/Homema...ng-Powermeter/
Datasheet for load cell: https://www.creatroninc.com/download...-Datasheet.pdf

Possible concept: LOAD_CELL ----> LOAD_CELL_AMP (HX711) ----> ESP32 ----> WiFi and/or ----> SD card
SparkFun makes a HX711 board that looks easy to use and inexpensive. ESP32 is an microcontroller with WiFi. You can also interface an SD card to it for data collection.

SmplRsrchr

Dear Buzzkill53120

Thank you for your help!

Barry2 

Garmin introduced a standard (now open) that follow the entire pedal stroke and adds many parameters to that of a "normal" power meter.
Give "Garmin Cycling Dynamics" a look.
Even the Garmin spec for pedal battery life change with the Cycling Dynamics (Ant+ high speed data) enabled.

If you'd like to get a look at a Fit file using Garmin Rally Pedals as captured using a Garmin Edge 830 contact me via PM.
EDIT: You're going to need 10 posts before you have access to the PM menus.


Barry

chaadster

Wahoo just offered an update to their smart power meter trainer, the Kicker v.6, called Race Mode, which samples at 10hz when ethernet-cable-connected to a router via their Direct Connect box.

unterhausen

We used that SparkFun HX711 board to read strain gauges in a project hooked up to an arduino tiny. Probably work with a blue pill, but that's not quite as tiny.
I have always thought that it would be best to have a bridge of 4 strain gauges at 45 degrees to the long axis of the crank, but I never actually tried it. IIRC, the chip data sheet shows how to hook it up to a full bridge

He can always leave a visitors message on your profile without getting to 10 posts.

I suggest searching for "PAS electric bike torque sensor for bottom bracket"

There are a lot of people that have posted online about DIY power meters. At least they aren't all starting companies like they used to do.

GhostRider62

Nyquist is a *****.

I think the overall (more sensors) sampling rate is better on the old SRM (not SRAM....SRM) crank power meters. Apologies if my memory is incorrect.

JohnJ80

By frequency, do you mean sampling rate? 1 sec is pretty standard across the industry. I doubt you would find anything appreciably faster in the cycling industry.

RChung

Sampling rate is different than reporting rate. Sampling rates are hardware dependent, and typically range from around 64 Hz or so up to 200 Hz or so. ANT+ protocol is for the power meter to send packets to ANT+ compliant head units at a max of 4 Hz, though most head unit manufacturers opt to throw away 3 of 4 packets and just keep one, for 1 Hz. There are a handful of power meters that have a higher reporting frequency: the SRM Scientific used to have a reporting rate of 10 Hz, but most of the packets were identical replicates. Some manufacturers have a special transmission channel that typically uses BT rather than ANT+; Stages, for example, has a "high frequency" mode that sends time-stamped torque values at a nominal 64 Hz. I've only seen the high freq data stream from one side of a Stages so I don't know what it would look like from both right and left.