Building a flaglight for my recumbent bike

A few months ago I had a test drive on a recumbent bicycle and was instantly hooked. Suffice it to say that a few months later I am the proud owner of one myself. Being the cautious cyclist I am, my top priority especially on a recumbent is visibility. The bike is quite low, my head is around 1m of height, for me coming from an upright that’s low. Therefore visibility means adding a bikeflag. The one I went for is quite big and reflective. Nevertheless I’d still prefer some active visibility. The shop I ordered the flag from also has flaglights but basically it’s three LEDs for 70€. Knowing the material cost must be in the one-digit euros I found it hard to go for it. Especially since it is designed for bike dynamo operation requiring extra weight and extra money to be put into the bike as well. I planned on using battery operated lights already in my possesion so I don’t need dynamo equipement or cabling.

Long story short: I over-engineered the whole thing and now I want to show it off. My choice of LEDs are 4cm long chip on board bar-shaped LEDs. I got one white and one red so I would be visible both from front and back. Both are 300mA versions so I can connect them in series. Because the voltage regulator promised PWM brightness regulation so I added a controls to the handlebar to remote control brightness and allow for blinking. The LEDs are glued to a hand-milled aluminum carrier and covered by transparent heat-shrink tubing against the weather. The control electronics are also covered by heat-shrink tubing. The switch should be weatherproof given that it’s one meant for motorcycle use. Power is supplied by a weatherproof box with four 18650 lithium batteries. Remember that the pictures below are taken in daylight — When it is dark the light is pretty bright and the movement of the flags makes it even more visible.

Nevertheless I tend to drive way more defensive on the recumbent than on the upright. I wonder whether it’s more safe than the upright due to my defensive driving or still more dangerous because it’s so low.

Arduino and battery pack attached to the bike rack
Arduino and battery pack attached to the bike rack
Battery pack and arduino on bike rack
Battery pack and arduino on bike rack
Flag with light from the back
Flag with light from the back

Flag with light from the front
Flag with light from the front



Control on handlebar
Control on handlebar

COB LEDs
COB LEDs

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