Brake cutoff switches in the cold

[ccihon]

I am using magnetic lever-attached brake sensors on my mid-drive trike, and normally they work great. They have allowed me to use some short-pull flat bar style levers that do not have any built in switching. I have noticed that on cold-weather rides, the sensors often stay "on" even after releasing the levers and allowing the magnet to re-contact the end of the switch. I am guessing maybe these are not a solid state design switch, or if they are, that they are adversely effected by cold?

I can usually get them to return to normal by squeezing and dropping the levers. Any one share similar experience, or am I crazy? I think these are a three-pin design that is sold directly from Bafang.

Options might be to use the "hidden-wire" style that have the brake cable passing through them, or even looking for some other switched levers etc. I know another suggestion might be to dispense with cutoffs altogether, but I have gotten used to riding with them.

 

[amberwolf]

At least two possible problems; the switch might be affected by temperature directly, or things might be changing relative position in the cold.


Things generally shrink in the cold, depending on the material. If the magnet that operates the switch is right on the edge of not untriggering the switch when in the lever-released position, then depending on the specific materials and the design, a sufficient extreme of temperature could put it into the range it doesn't untrigger the switch. (a switch like these has hysteresis, which means there is a point at which it turns on, and a different point at which it turns off).

"snapping" the lever shut may momentarily push the magnet just close enough to the switch to disengage it, for one of a few possible reasons.

Moving the magnet just a tiny bit closer to the switch would correct this type of problem.



If they are reed switches, they might be internally sticking in the cold. Not usually a problem, but have seen this with all sorts of mechanical switches when it gets cold enough, though this usually has to be *very* cold, below freezing at least.

If they are hall switches, those usually have a temperature range they are guaranteed to work thru, and at the extremes of that range it might be less reliable.

Does the switch require 5v to work? If so, it's usually a hall sensor (like those in a motor). If not, it's usually a reed switch.


The HWBS works using a magnet and a sensor as well--it just has the magnet slide along with the cable, and a small spring to push it back in place, just outside the tube the cable passes thru. If it's cold enough to affect your other switch, it may well affect these, too.