Cable mounted brake light switch anyone?
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You might try checking with a motorcycle shop.– Daniel R HicksMar 11, 2017 at 0:42
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1Consider expanding your question - what's the purpose? Do you want to have additional rear lights that illuminate when you brake? Or is it for something else? Consider taking the site's tour to learn how SE works.– Criggie ♦Mar 11, 2017 at 5:15
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I've got a "nano" brake light that mounts on v-brake cables (probably caliper as well). It might be somewhere to start looking for something to modify.– Chris HMar 11, 2017 at 7:41
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if your trying to make a brake light you may check out this one, Sigma already makes an inline brake accuated light. heres their site: sigmasportstore.com/Sigma-Sport-Brake-Light-p/brakelight.htm– Nate WMar 13, 2017 at 23:32
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2 Answers
Cable mounted switches exist, both in the motorbike world and the electric bike world.
Two main sorts are available - switching via mechanical means, and switching via a magnet. Your application may require one or the other.
Switching mechanically is nothing more than having a toggle switch fastened to your bowden cable inner, and mounted rigidly so that pulling the inner cable switches the switch. Poor picture but imagine this with the bowden cable inner clamped to the slider. Downside is the switch will limit the travel of the inner.
Electronic/magnetic switching straps a permanent magnet to your bowden cable inner, and then runs that magnet past a reed switch. They relay will be either a Normally Open or a Normally Closed, and will close or open as the magnet moves. Downside is that these cannot take much current, so are often used to drive a relay capable of higher currents.
You haven't explained your need, but there are brake levers that incorporate a switch. These are found on electric bikes, and are normally wired to cut power to the motor if the rider brakes. Some electric bikes will take that signal and cut in electric braking.
If you had hydraulics then there are all manner of pressure switches, used in automotive brake systems. However they would affect the speed at which your hydraulic brakes activate and would void any warranty.
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Not being an expert in hydraulic brake systems, I wonder how easy it would be to integrate a pressure switch (bike stuff doesn't appear to be compatible with much else). The effects on the braking wouldn't be too bad fitted to the back brake, at least from the point of view of someone used to rim brakes. I'm sure good e-bike brake levers exist, but the ones I've seen haven't been great. (+1btw, this comment might sound more negative than it should)– Chris HMar 13, 2017 at 16:27
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@ChrisH Fiddling with the pressures of hydraulic brakes is asking for a bike that doesn't stop like it should. I'd be very leery of doing anything. Even automotive systems have a whole lot more fluid in them than a bike hydraulic. Some systems have as little as 15 mL of brake fluid in them, so adding any pressure switch means a significant change in system volume. We still don't know what OP is trying to do.– Criggie ♦Mar 14, 2017 at 0:29
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1System volume is an issue, you're right. The one time I've used a pressure switch (for air) the change in volume was miniscule but I've no way of knowing whether that could be achieved here. So it sounds like it would be a bad idea. Hopefully the OP is using "cable" literally rather than to mean "hose" in that case.– Chris HMar 14, 2017 at 6:47
This is the brake light I've got. It's not really in the right place for visibility on my bike, or bright enough to be worth much in traffic, so I've been considering how I might use it as a switch. One way would be to replace the battery with a piece of metal of the same size and bring wires out the LED hole. Another would be to attach a phototransistor and use that to switch a bigger light. Because it uses a piece of spring steel to actuate the switch, it doesn't restrict the brake cable travel. It must incrase the force required to use the brake, but only marginally -- I certainly can't feel it.
