Expedient solutions for a custom electronic bike bell?

Thread Starter

Just Another Sparky

Joined Dec 8, 2019
244
I'm looking for solutions to piece together a custom electronic bicycle bell using components that are as plug-and-play as possible.

Problem: Pedestrians on local bike trails wear ear buds, talk on cell phones and are distracted by pets. In many cases traditional voice call-outs such as "On your left!" are wholly inadequate to get their attention until I am right behind them. This is problematic on an E-bike with thumb throttle wherein speeds near 20 MPH (legal) are typical. I also operate in territory with lots of tunnels whose portals open up directly into sharp, blind curves.

Existing solutions all produce sounds at very high frequencies which modern earbuds are remarkably efficient at attenuating.

Solution: Assemble a very loud, forward-facing speaker unit capable of projecting reasonably crisp locomotive bell sounds. The idea being it will serve as a gentler, "less-lethal" tool that I can employ before escalating up to a car horn. It will also serve to provide a steady, continuous warning when approaching tunnel portals and blind curves.

Example:

What are my most efficient options for realizing this project? Electronic locomotive bells are already a reality, but the genuine article is prohibitively costly and bulky - neccesarily having been ruggedized for railroad service. The application is a 52V E-bike with 1kWh battery, so power is not a limiting factor. Would it be possible to modify an existing bicycle bell by reprogramming it's audio bank and upgrading the speaker & amplifier? Or would it be easier to start fresh with something like an Arduino and build from the ground up?
 
Last edited:

xox

Joined Sep 8, 2017
838
I'm looking for solutions to piece together a custom electronic bicycle bell using components that are as plug-and-play as possible.

Problem: Pedestrians on local bike trails wear ear buds, talk on cell phones and are distracted by pets. In many cases traditional voice call-outs such as "On your left!" are wholly inadequate to get their attention until I am right behind them. This is problematic on an E-bike with thumb throttle wherein speeds near 20 MPH (legal) are typical. I also operate in territory with lots of tunnels whose portals open up directly into sharp, blind curves.

Existing solutions all produce sounds at very high frequencies which modern earbuds are remarkably efficient at attenuating.

Solution: Assemble a very loud, forward-facing speaker unit capable of projecting reasonably crisp locomotive bell sounds. The idea being it will serve as a gentler, "less-lethal" tool that I can employ before escalating up to a car horn. It will also serve to provide a steady, continuous warning when approaching tunnel portals and blind curves.

Example:

What are my most efficient options for realizing this project? Electronic locomotive bells are already a reality, but the genuine article is prohibitively costly and bulky - neccesarily having been ruggedized for railroad service. The application is a 52V E-bike with 1kWh battery, so power is not a limiting factor. Would it be possible to modify an existing bicycle bell by reprogramming it's audio bank and upgrading the speaker & amplifier? Or would it be easier to start fresh with something like an Arduino and build from the ground up?
You don't really need electronics to accomplish that. For years I have simply used two DIFFERENT bells, one on each handle-bar, and both being of the loud and sturdy type. Works just fine for (most?) e-bikes.

Ringing them in alternation is a very effective way to alert approaching pedestrians. You should however be mindful to slow down if necessary and of course be sure to start ringing them early enough, otherwise accidents will be inevitable.
 

Ya’akov

Joined Jan 27, 2019
9,079
Thanks for the detailed problem specification, it's always nice to have enough information to work with.

The expedient aspect is a bit ambiguous, but here's my first pass take on it.

You need three things:

a sound source,
an amplifier,
and a transducer.

For the source, there is a MP3 player module I favor—quite capable with a nice feature set, and quite cheap.
1682498948853.png
The board is designed to compose sounds from stored samples which you put on it via an ordinary USB connection (it appears to the host computer as a mass storage device)—this feature alone is enough to make it my favorite. You can play back samples via switch closures and/or serial commands.

The multi-switch input to select sounds is done via a resistor matrix connected to the AD_KEY pin of the chip. It has a small on-board amplifier as well, but I suspect it will not be sufficient for your application. In any case, this is my first choice for your source.
For the amplifier, I have to be a bit speculative. Fortunately you have a lot of power available, unfortunately the transducer (see below) is a bit ambiguous until you do some testing so the actual choice of amp is a bit in the air until then. However, this board of one like it is a potentially very good option.

1682499516796.png
It claims 60W, though I don't trust that. I still think it has a very good chance at being the right choice. The price is stunningly low (I would buy more than one as insurance against magic smoke loss or manufacturer defect). It operates in a good voltage range, and it has nice mute feature.

The transducer is a bit more of a project. You might be able to find something that doesn't require modification but a quick look failed for me. And it was a very quick look so do investigate further. That being said, my first pass on this is to buy a small, cheap alarm siren of the horn type and excise its alarm circuitry to use the horn speaker.

1682500380800.png

This one looks extremely promising based on size and likely frequency response. It also has two visible screw on the back making disassembly apparently straightforward.

One more thing is the switch, and there is an embarrassment of options. Most are designed for motorcycle handlebars to you may need a spacer. If you are anything like me, you have more than one from something you've already installed that will do the trick but even if you don't it's a trivial problem to solve.

1682500838899.png

This one is presented as an example (and because it is kind of cool looking) rather than a suggestion. You'll have to look around (search: "momentary handlebar switch) but at least you will certainly find something to consider a good option.

I hope this was helpful. Please don't hesitate to ask about any part.
 

MrChips

Joined Oct 2, 2009
30,720
I am an avid cyclist too, riding both regular and power assisted bikes. In my jurisdiction a bell or horn is required by law.

The safe and courteous thing to do when approaching pedestrians and blind corners is to slow down to a safe speed.
 

Audioguru again

Joined Oct 21, 2019
6,674
The safe and courteous thing to do when approaching pedestrians and blind corners is to slow down to a safe speed.
Of course. Old people without hearing aids and all the people with blasting ear buds might not hear the train noise from the horn speaker but everybody else do not want to hear it. There is enough noise from modified car, truck and motorcycle exhaust systems.
 

crutschow

Joined Mar 14, 2008
34,285
I'm sure pedestrians on the trail, who are out for a quite walk, don't appreciate someone on an E-bike blasting a loud horn behind them and racing by at 20MPH.
Much more considerate to use a standard volume bell and slow down to a safe speed when passing.
 

MrSoftware

Joined Oct 29, 2013
2,188
I'm sure pedestrians on the trail, who are out for a quite walk, don't appreciate someone on an E-bike blasting a loud horn behind them and racing by at 20MPH.
Much more considerate to use a standard volume bell and slow down to a safe speed when passing.
It sounds like a bike trail where pedestrians are allowed (bikes have right of way), as opposed to 50/50 mixed use. We have similar mountain bike trails here where walkers are allowed but must walk against the flow of bike traffic and yield to bikes. Walkers are notorious for not following the rules. We've had several close calls while bombing down a hill and some walker doesn't follow the rules to step out of the way.

That said; maybe an analog mechanical solution would be more effective. Such as a small megaphone around a regular bell facing forward. Perhaps that would give the desired amplification without the complexities and challenges that come with an electronic solution?
 

Ya’akov

Joined Jan 27, 2019
9,079
On multiuse trails in my jurisdiction, pedestrians have right of way over cyclists.
As a matter of law, a vehicle—which a bicycle is one of—must always yield the right of way to a pedestrian. This is true even if the pedestrian is on a limited access roadway. That they should not be there is a separate issue.

On the other hand, in places were there are segregated foot/cycle paths it is downright rude and even foolish to walk on them. People don't seem to pay any attention to the clear signage demarcating bicycles only paths.

In mixed use cases, the cyclists need to accommodate the pedestrians but in my experience pedestrians don't bother to do what they could do to accommodate the cyclists. For example, keeping to the right; not letting dogs on telescopic leads cross the path creating an impassable barrier, etc. It is shared use and awareness should go both ways.
 

MrChips

Joined Oct 2, 2009
30,720
As a matter of law, a vehicle—which a bicycle is one of—must always yield the right of way to a pedestrian. This is true even if the pedestrian is on a limited access roadway. That they should not be there is a separate issue.

On the other hand, in places were there are segregated foot/cycle paths it is downright rude and even foolish to walk on them. People don't seem to pay any attention to the clear signage demarcating bicycles only paths.

In mixed use cases, the cyclists need to accommodate the pedestrians but in my experience pedestrians don't bother to do what they could do to accommodate the cyclists. For example, keeping to the right; not letting dogs on telescopic leads cross the path creating an impassable barrier, etc. It is shared use and awareness should go both ways.
True. But some people don't use common sense, rational and courteous behavior.
 

Thread Starter

Just Another Sparky

Joined Dec 8, 2019
244
Not here to get political.

At the end of the day this is simply going to be another tool at my disposal with which I can provide an effective, clearly audible warning far enough in advance of my arrival for pedestrians who are not staying on right side of the path (as they are required to) to clear the way. In this jurisdiction, slower traffic keeps to the right.

It will also provide an early warning to oncoming traffic approaching blind tunnel entrances that something is about to emerge from said portal. Some of these in particular are notorious for collisions because of the fact that they open up directly into blind 'T' intersections where the intersecting trails descend towards the portal parallel to it's face at a steep grade. A steady, continuous warning signal is absolutely warranted in these hazard areas, especially when children are apt to bolt out into the path of travel from a place of concealment due to their sheer and utter ignorance of the danger. Some of these corners and intersections are so sharp that even at low speeds a collision can be difficult to avoid if someone suddenly rounds the bend on the wrong side of the trail.

Myself? I generally slow down to pass people unless they are clearly aware of my presence as indicated by a sustained shift to the extreme right or left of the trail.

The trouble with passing arises:
- On busy days when people are out with their friends and walking side by side across the full width of the path.
- When people are talking on the phone while they walk their dog(s).
- Are jogging in the center of the path while wearing ear buds.
- When there are simply so many people bunched up together heading in the same direction (often field trips or extracurricular/group exercise excursions) that a vocal warning is not sufficient to get the group's attention.
- When people are in the middle of the path and distracted with snapchatting, taking selfies, on video calls, etc.

Bottom line, the use case here is when there is a clear, potential (or present) danger or when people have put themselves into positions where their situational awareness is impaired; Thus shifting the onus onto me to resort to progressively louder measures to get their attention without having to slow down to a walk myself.

If you still think I'm just a conceited asshole on a bicycle, watch this and then tell me with a straight face that a locomotive E-bell would not be a gentler, more effective and all-around ideal solution:
 
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Ya’akov

Joined Jan 27, 2019
9,079
They call it a "bell" but then a "horn", and further on in the copy it says "this is not a bell".

It seems it makes a horn sound, which is not what the TS wants. Also, in some places (like where I live) it would be prohibited on a bicycle because if would be similar to a "siren".

I also question the output ratings and they are a bit too pricey to try it and find out.
 

Audioguru again

Joined Oct 21, 2019
6,674
The horn sounds like a small car horn.
The bell might not be heard by old people like me (77) without hearing aids. I took off my hearing aids and barely heard the bell.
But everybody heard the guy shouting.
 
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