Smart Helmets

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Milkfloat

An Peanut
Location
Midlands
If it’s Bluetooth you won’t have a range of 900m. Bluetooth has a range of about 10m. So sure if you had 90 or more riders spread out over 900m the person at the back could in theory speak to the one at the front. Though they’d be some latency as the connection would have to go through 90 other helmets. As to the public mode speak to up to 33,000 other users. Sure if you want your brain to explode.
Bluetooth is significantly better than 10m nowadays, not sure about the claimed 900m though. I think they claim up to 6 riders in a mesh, I guess that is to keep the handoff/passthrough manageable.
 

mjr

Comfy armchair to one person & a plank to the next
Bluetooth is significantly better than 10m nowadays,
Bluetooth has always had longer range on devices designed for it. I was using it 15 years ago to browse tutorials on a non-wifi mobile phone from a car park about 50m from home through a couple of walls. Stuff like watches and headsets may be short range but that makes them smaller and is sufficient for their job.
 

Ming the Merciless

There is no mercy
Location
Inside my skull
Bluetooth has always had longer range on devices designed for it. I was using it 15 years ago to browse tutorials on a non-wifi mobile phone from a car park about 50m from home through a couple of walls. Stuff like watches and headsets may be short range but that makes them smaller and is sufficient for their job.

Sure if you have super sensitive antenna , but the Bluetooth specification has limits on max power they can transmit on. So it’ll be limited unless you go against spec. It’s using Bluetooth for something it was never designed to do.
 

markemark

Über Member
If it’s Bluetooth you won’t have a range of 900m. Bluetooth has a range of about 10m. So sure if you had 90 or more riders spread out over 900m the person at the back could in theory speak to the one at the front. Though they’d be some latency as the connection would have to go through 90 other helmets. As to the public mode speak to up to 33,000 other users. Sure if you want your brain to explode.
Bluetooth over certain frequencies can be several hundred meters.
 

mjr

Comfy armchair to one person & a plank to the next
Sure if you have super sensitive antenna , but the Bluetooth specification has limits on max power they can transmit on. So it’ll be limited unless you go against spec. It’s using Bluetooth for something it was never designed to do.
Not really. Class 1 Bluetooth was and still is specified for a typical range of 100m. Class 2 is the 10m-typical stuff, but mine got 50m with nothing special: the phone had a good antenna anyway (many phones did, unless the designer messed up) and the home station was a USB adapter with an antenna sticking up from the USB port, which was not that unusual back then with lots of desktop PCs not having built-in Bluetooth.

Even then, class 2 probably should be thought of as "at least 10m" because if you have a super-sensitive antenna, the class 2 range can be over a mile: https://trifinite.org/trifinite_stuff_lds.html
 

Ming the Merciless

There is no mercy
Location
Inside my skull
Not really. Class 1 Bluetooth was and still is specified for a typical range of 100m. Class 2 is the 10m-typical stuff, but mine got 50m with nothing special: the phone had a good antenna anyway (many phones did, unless the designer messed up) and the home station was a USB adapter with an antenna sticking up from the USB port, which was not that unusual back then with lots of desktop PCs not having built-in Bluetooth.

Even then, class 2 probably should be thought of as "at least 10m" because if you have a super-sensitive antenna, the class 2 range can be over a mile: https://trifinite.org/trifinite_stuff_lds.html

Yeah but who wants to use 30 Hz frequencies, you can’t transmit that fast on that. Shorter wavelength longer range just like SW radio
 

newfhouse

Resolutely on topic
Bluetooth over certain frequencies can be several hundred meters.
Bluetooth is only specified for the 2.4 GHz band. Class 1 (20 dBm Tx power) will link reliably well over 100 metres in line of sight applications with suitable antennas, but helmet mounted or embedded that is unlikely to be achieved, particularly on undulating terrain.

I don’t think the inter-helmet comms are Bluetooth. My guess is WiFi, possibly at 900 MHz, since the Sena blurb talks about 9 channels being available. Bluetooth uses frequency hopping across the entire band while many WiFi implementations are more channelised. Channel bonding is unlikely to be needed for the bandwidths required for low latency voice traffic.

If my guess about the WiFi spectrum is correct the product is unlikely to be legal to use in the UK.

As a non RF nerd point, and as others have said, if you believe that a helmet will protect your head in a crash, why would you insert a lithium battery, PCB and sharp metal connectors in the polystyrene?
 
My sense it will be an initial novelty and helpful if kids are learning to bike. In most instances everyone would have line of sight to the person in front.
 

mjr

Comfy armchair to one person & a plank to the next
if you believe that a helmet will protect your head in a crash, why would you insert a lithium battery, PCB and sharp metal connectors in the polystyrene?

My sense it will be an initial novelty and helpful if kids are learning to bike.
:eek: On the basis that it would be helpful for the kids to be more scared to fall off the bike because a battery, PCB and metalwork might stab them in the head, or what?
 

Cycleops

Legendary Member
Location
Accra, Ghana
Sounds like the sort of thing the Griswold family might buy.
 

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Bollo

Failed Tech Bro
Location
Winch
I do have a use case for this even though I’d be very reluctant to have anything substantial attached or embedded in a helmet, including the straps. My regular ride chum is partially deaf so conversions can sometimes be strained, especially on longer rides where we’re both getting a bit tired. It’s difficult to bellow when you’re already knackered and his hearing does get worse with fatigue. It’s not unknown for me to call a turn and for him to disappear up the road, requiring a pro-style chase-down of his impromptu breakaway.

I’ve looked at some of the walkie talkies out there to rig up some form of race radio but haven't got around to checking whether the sound quality will work for us and the VOX is reliable. Either way, I’d want nothing bigger than an earpiece around my head, helmet or not.
 

mjr

Comfy armchair to one person & a plank to the next
I do have a use case for this even though I’d be very reluctant to have anything substantial attached or embedded in a helmet, including the straps. My regular ride chum is partially deaf so conversions can sometimes be strained, especially on longer rides where we’re both getting a bit tired.[...]
If his hearing is that farked, wouldn't you be better off with some sort of visual cue on his handlebars or glasses? I'm not aware of current ready-made options, but I do remember sat-nav-lite things like the Beeline Velo, but that would only work for preplotted routes, rather than live comms for turns. Maybe someone could interface to it or knock something similar up out of Arduino or Raspberry Pi devices.

Simpler would be for others never to overtake the guide, though some will never stick to that...
 
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