Bicycle power meter
A power meter for a bicycle includes a body having a torque input section and a torque output section, the body configured to transmit power between the torque input section and the torque output section. The power meter also includes a printed circuit board (“PCB”) having a substrate and at least one strain measurement device attached to the PCB.
1. A power meter for a bicycle, comprising:
a body comprising a torque input section and a torque output section, the body configured to transmit power between the torque input section and the torque output section; and
a printed circuit board (“PCB”) comprising:
a substrate,
at least one strain measurement device attached to the substrate, the at least one strain measurement device configured to provide a signal indicative of strain detected in the body, and
circuitry, attached to the substrate, the circuitry configured for interpreting the signal and determining a corresponding power transmitted between the torque input and the torque output section,
wherein the substrate is of annular construction and disposed in the body around the torque input section.
2. The power meter of claim 1 , wherein the at least one strain measurement device is attached to the substrate such that the at least one strain measurement device is fixed in a plane of the PCB relative to at least one feature of the PCB.
3. The power meter of claim 2 , wherein the feature is formed in the substrate.
4. The power meter of claim 1 , wherein the at least one strain measurement device is a foil or wire type electrical strain gauge.
5. The power meter of claim 1 , wherein the torque output section comprises teeth.
6. The power meter of claim 1 , wherein the torque output section comprises chainring attachment features.
7. The power meter of claim 1 , wherein the at least one strain measurement device comprises planar electrical contact surfaces, and the PCB is configured such that the strain measurement device planar electrical contact surfaces are disposed facing electrical circuitry contacts of the PCB, the electrical circuitry contacts of the PCB communicatively coupled to both the strain measurement device planar electrical contact surfaces and the circuitry of the PCB.
8. The power meter of claim 1 , wherein the at least one strain measurement device is communicatively coupled to the circuitry of the PCB with a volume of an electrically conductive bonding material.
9. The power meter of claim 8 , wherein the electrically conductive bonding material is a fusible metal alloy.
10. The power meter of claim 8 , wherein the volume of electrically conductive bonding material comprises at least one distinct volume of electrically conductive bonding material, and both the PCB and the at least one strain measurement device are in physical contact with the distinct volume of electrically conductive bonding material.
11. The power meter of claim 1 , wherein the at least one strain measurement device is attached to the body with an adhesive.
12. The power meter of claim 1 , wherein the at least one strain measurement device attachment to the PCB comprises a structural support material.
13. The power meter of claim 12 , wherein the structural support material is disposed both on an edge of the substrate and on a surface of the at least one strain measurement device.
14. The power meter of claim 13 , wherein the edge and the surface are oriented substantially orthogonal to each other.
15. The power meter of claim 1 , wherein the circuitry is further configured to wirelessly transmit a second signal indicative of the determined power.
16. The power meter of claim 1 , wherein the at least one strain measurement device comprises a plurality of strain measurement devices disposed about the torque input section.
17. The power meter of claim 16 , wherein the plurality of strain measurement devices are disposed so as to align with strain measurement features of the body.
18. The power meter of claim 1 , wherein the substrate includes at least one strain measurement device attachment feature, and the at least one strain measurement device is disposed on the substrate so as to be aligned with the at least one strain measurement device attachment feature.
19. The power meter of claim 18 , wherein the strain measurement device attachment feature comprises at least one vacancy formed in the substrate.
20. The power meter of claim 19 , wherein the vacancies are configured to provide access to the at least one strain measurement device in an axial direction of the PCB.
21. The power meter of claim 18 , wherein the body further comprises bolt holes in the torque output section configured for attachment to a chainring, and the strain measurement device attachment features are disposed so as to correlate to the bolt holes.
22. The power meter of claim 21 , wherein the power meter comprises a same number of strain measurement features and bolt holes.