Bike Light Testing with TinkerKit

Posted by Christian on May 10, 2013

Today I picked up a couple of bike lights from our offering. I was off to go home and test fit them on my bikes at lunch, but upon looking out the window, we're currently experiencing monsoon-type weather. So instead we'll be spending our lunch testing these things out, namely the brightness on always-on mode. I was about to go bug the Tools and Test product manager for a Tenma Compact Light meter, but remembered I've got a light meter at my desk already in the form of an Arduino Tinkerkit. We'll use the light sensor mated to the sensor shield to take some measurements of both lights.

The Lights

While these aren't the uber high quality lights you'll find at your local bike shop, they appear to be fit to serve at least as a safety light (which is how they're touted, to be fair). And for the price (roughly $4 at the time of this writing), they are worth a shot. The 29-5795 has only one LED, but shines through a magnified lens and requires only three AAAs. The 29-5540 has five LEDs and requires four AAAs. So between the two styles, which is better?

The Setup

I attached the light sensor to the back of a folded paper plate to stand it up at the end of my desk. With the overhead lights out, each light will be pointed directly at the light sensor. The light sensor will measure the brightness every second. We'll pick the highest value from each light and compare to determine our winner. Upload the code below to your Ardunio and click the Serial Monitor button at the top right Arduino Serial Monitor Button to view the data as it comes in.

#include <TinkerKit.h>

// create the object
TKLightSensor ldr(I0);

// value read from the light sensor
int brightnessValue = 0;

void setup() {
// initialize serial communications at 9600 bps

void loop() {
// get the brightness value:
brightnessValue = ldr.get();

// print the results to the serial monitor:
Serial.print("brightness = " );

// we don't want a ton of readings, so delay


Both lights were fair. As you can see below, the five LED light was brighter when comparing the lights on always-on mode, maxing out at 914 (out of a max possible value of 1023) from the sensor while the single LED light maxed out at 910 for a second. I did notice that the single LED light looked brighter on flashing mode. Running it in flashing mode put it on par with the five LED unit in terms of max brightness.

(click to enlarge)

This turned out to be a fun lunchtime project with the TinkerKit and my new toys!

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