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Arduino Bicycle Approach Warning System

June 15, 2016

I enjoy riding a bicycle in Han-gang(Han river in Seoul Korea).


When passing another bicycle, someone uses a bicycle bell or his own voice(i.e. Excuse me!). But many including me want to pass quietly. Actually it’s dangerous in narrow road.

So, I need a bicycle approach warning system. Garmin did it! but it’s aim seems to be on road.

Arduino supersonic sensor senses objects up to about 4 meters. So, I started to assemble Arduino parts.


When a bicycle approaches behind me(min 50cm ~ max 4m, towards me), Arduino passive buzzer will play some melody.

Arduino pro mini accepts 9V DC through RAW pin. Supersonic sensor’s power consumption is about 0.5A/5V, so I need to check battery capacity.

When connecting Arduino pro mini using USB-to-Serial board, program uploading failed asserting ‘skt500-getsync’ error. After searching Google, I found that when uploading begins pressing reset button on Arduino pro mini board does help.

I bought the case which has a space for 9V battery  and managed to put above things in it.


Tomorrow, I’ll test whether this scenario works or not.

[19 June, 2016]

  • It didn’t work. It can detect only a wall or a fence approaching. 🙂
  • There are several problems.
  • First, 9V battery ran short within two hours. I will change Arduino board which has microUSB port and use 5,000mA rechargeable battery pack.
  • Second, a supersonic sensor covers small horizontal range as you can see in youtube video – Arduino Radar Project( So, I bought servo motor.
  • Third, polling interval should be reduced(one second -> 100ms or else) because another bicycle runs faster than I thought.

[26 June, 2016]

  • I added a servo motor to rotate supersonic sensor(will check another rider left behind me).
  • I changed from Arduino Pro to Arduino Nano, it’s power is from external battery pack(2,200mA, 1A/5V output).
  • But, supersonic sensor reported wrong distance because Nano can’t supply over 500mA. Supersonic sensor requires about 500mA, so power should be supplied directly to supersonic sensor. => 28 June, this is wrong. not 500mA but 15mA.


[06 July, 2016] 

  • Now I connect additional power for Servo motor. GND pin is shared with two power source.
  • It works fine, but some modifications are needed.
  • Based my forward direction, the device monitors between 6 and 8 o’clock direction. But rotational speed is not enough, so can’t detect fast passing rider.
  • Considering power consumption and durability, non-rotational 7 or 7.5 o’clock direction of supersonic sensor will be fine.
  • To avoid useless warning when driving narrow road, it will be helpful to limit left warning distance to maximum supersonic distance * 0.5(0.5 = cosine(60 degree)).


From → DIY, General

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