Benjy's Wok-Whoka Bike Horn
What is it? My bike horn
is a prototype that contains a digital sound chip and a
Mallory Sonalert® siren. One tactile switch plays a recorded sound,
while another activates the siren. The ability to record and
playback a sound gives the bike horn a unique sound.
Why I built my own? I
like building unique gadgets. I ride a multi-user trail, and at
times walkers don't hear or respond to "on your left". There
are also a few narrow blind tunnels and hills where it's nice to warn
an oncoming rider of your approach. A friend uses a mechanical
bell that sounds like an ice cream truck. I wanted a unique sound.
What's the prototype like? It
has a commercial sound recorder chip board that will both record and
play sounds. The MX022
is a 3.5" by 2.5" board with a sound chip, 720 mw audio amp, and a
microphone. The recording source can be the onboard microphone or
line input. The MX022 is overkill for this project. I plan
to replace the sound card with a simple playback board that will
contain only the record chip and an audio amp.
I recorded a sample of Fishbelly
Black's "Spontaneous Combustion" from their self-titled CD.
This jazz number includes a Brazilian cuica that, to me,
makes a "wok-WHOK-a" sound. Here's the sample I recorded into
the sound chip: Spontaneous
The other alarm is a Mallory Sonalert MSR516XR.
It has a siren
sound and is rated at 82 to 91 db. I added this alarm before
I knew that the sound chip board would produce adequate volume.
The two sounds are activated using two tactile switches mounted near
the left gear shift leaver.
The remaining parts are a 6 AAA battery holder, an on/off switch, a
speaker, and a quick disconnect connector for the wires going to the
How well does it perform? It
works better than I thought it would in that the sound board/speaker
combination produce an adequate volume level. I can wok-whoka
someone about 30 feet away, and they will typically hear the
distinctive sound. The amp does distort some; however, it's not
too objectionable for a bike alarm.
The Sonalert is loud and too high pitched, perhaps, but the sound has a
noticeable attack delay. So small bursts can be given at close
range. I don't know how dogs will like it.
I definitely need to convert the prototype into a smaller unit.
Because of the bumps on the trail, it's also a good idea to tape the
batteries in the battery holder. A 9-volt battery might work, but
I'm not sure how long it would last.
The components: There is
a 3 1/8" X 5 3/8" board that contains all of the main components and a
with the two tactile switches. The main board contains the
commercial sound card, Sonalert, batteries, speaker, and the on/off
switch. The sound board is mounted over the speaker and batteries
How does it attach to the
mounted the tactile switches
on a small board. The switch board connects to the main board
using a 3-wire cable that can be disconnected at the main board.
Both the switch board and main board are attached to the bike using cable ties.
- Speaker (Elecraft K2
- 2 Tactile switches: Omni 6x6 flat 5mm, Mouser number 653-B3F-1022.
- SPST on/off switch
- Molex pins, housing, and header (Mouser
numbers 538-08-50-0114, 538-22-01-2047, and 538-22-23-2041) for jack
and plug for connecting to the switch board.
- 6xAAA battery holder, Mouser
- Misc. standoffs and hardware.
Contact: hamk2 at