Kickr Teardown

[tuna-f1sh]

I finally got around to taking the flywheel off my Kick 2017 (V3?). Until this point, I'd been going off the FCC teardown and some photos found online of the original until this point. Some signals appear to have been value engineered out:

• EMF voltage sense: there is still a TP6 but no resistor divider; it's connected just to uC.
• Current sense: still not fitted but also no sense resistor on EMF path, only a 0R that could be replaced with a sense resistor on the VIN supply to digital electronics.
• VIN sense: no resistor divider on VIN any more.

Current sense had some integrated electronics so I get that but seems heavy handed to remove four resistors for the other two! Cleans up the power path and if they're not used in the firmware then makes sense I guess...

I've left these analogue readings (via ADC circular DMA buffer) in the firmware for support on custom boards or other trainers however.

See photos of my tear down below.

The electro-magnetics that keep me in the hamster wheel! Note the flywheel key that these Kickrs had issue with being too loose, causing a rattle.

My first surprise after single light trigger per revolution (white patch) - old models had a full circumference encoder pattern. This considerably reduces the resolution of the speed sensor. I know they had issues with light ingress and moved the sensor to the edge here. I guess creating and placing a full sticker on a narrow surface like this was too challenging and deemed unnecessary.

It's a very simple board - quick sketch of signal paths.

Debug harness added

And board put back. I can now use the Kickr, whilst taking samples and testing the firmware. Note I replaced the cheese head screws with T8.