Responsive all purpose bike light

by mwilford   November 4, 2013  

Hi, I'm a third year student at University currently carrying out a project designing a responsive bicycle light, mainly aimed at mountain biking, but that is also versatile for use on the road.

The concept is to have a mode that uses a light dependent resistor to alter the headlight intensity depending on the light conditions. The original idea was generated from mountain biking in the day, to illuminate dark patches on the trail caused by tree shadows. However the other intention is from cycling on roads with street lights, to turning onto an unlit path or trail, without the need to toggle between modes.

Any feedback would be greatly appreciated, and is vital to ensure I design something useful!


5 user comments

Oldest firstNewest firstBest rated

Can't comment on LDR's, but I do like the way that the less powerful Lezyne lights attach to my handlebars with the rubber toggle thing.

Sir Velo

Raleigh's picture

posted by Raleigh [1734 posts]
4th November 2013 - 22:09


Question: how will you ensure that the light doesn't turn itself off when passing under street lights or past well-lit shop fronts?

Kickstarter is already littered with nice-sounding ideas that have limited appeal or real world use. I wish you well, but speaking as someone who designs stuff for a living, the devil of your use case will be in the detail.

Boardman CX Team '14 | Cannondale CAAD8 '12 (written off, SMIDSY) | Scott Sportster '08

Gizmo_'s picture

posted by Gizmo_ [1140 posts]
5th November 2013 - 19:07


you wouldn't want it switching off when someone is coming towards you with their headlights on full-beam in the dark ... I guess the placement of your LDR will be quite important.

posted by Jez Ash [213 posts]
6th November 2013 - 14:20


My first thought was this will be a challenging control theory design, for example you enter a dark area and the light turns up, which immediately causes the light to turn down Thinking

However a much more serious, and dangerous, risk then becomes obvious - a car approaches with full beam headlights, your light responds by turning off. As a minimum this could cause you to break the law (no front light in hours of darkness).

Potentially this can be resolved with a slower response time before turning down, but equally you will need it to power on quickly if, for example, approaching a tunnel.

Some cars are being fitted with this technology, they are easy to spot as the lights turn on *just after* passing under a motorway bridge on my morning commute Applause

posted by kegere [5 posts]
6th November 2013 - 14:23


Thank you for all your comments.

The problem of oncoming cars potentially turning the lights off would be solved by programming the circuit to have upper and lower limited voltage, this would prevent the light dropping below a certain voltage even if there is a lot of light emitted; so on this mode, once the light is on, it stays on, even if there is a lot of light it would maintain at 50 lumens for example, but if the ambient light reduced, the intensity could increase to 400 lumens.

posted by mwilford [16 posts]
7th November 2013 - 11:23