This is a very rough feedback-gathering question. I have a project in mind, and it would require a fair bit of technical testing. If I may I’ll put down a written sketch - do please suggest ideas or steering that comes to mind. 🏆
I am a keen cyclist, and I ride on streets in a fairly bike-hostile city in the UK. I can easily have a serious near-miss every fortnight; it’s worse in the winter months. I’ve been clean knocked off by car drivers twice (one stopped to help, one fled the scene). So I have started riding with a helmet cam. I tried a cheap one, and it broke after a few months. I am then started using a GoPro hand-me-down. I melted this with a battery cable (don’t ask 🙈) so I bought another.
In my view, the broad design of standard-fare helmet cams is in need of improvement. Camera units are too expensive, and they are too easily grabbed and stolen by a road-rage driver or mugger. With rare exceptions, cameras only point one way (usually forward) even though cyclists can easily be impacted or attacked from behind. Nearly all cameras use an on-board battery, which provides around an hour of shooting time (this can be improved to around 1.5 hours by reducing resolution and frame-rate).
I carry several batteries, but in the wet and the cold, it is no fun fumbling around with a battery replacement operation, especially late at night. So while it is sensible to carry spares, continuity of power is a problem.
I’d like to build a helmet cam that can do this:
- 2/3/4 cameras pointing around the cyclist
- Clips into a standard GoPro mount
- On-board battery for short-term power
- USB power lead going to a meaty powerbank in a jacket pocket
- Tough and shake-proof (admittedly challenging with hobby electronics)
- Eye-line or handlebar indicator for low battery/storage warnings
I’d also like to move the expensive bits off the helmet section, so that if the camera is grabbed by an assailant, only a small part of the system needs replacing. Moreover, I’d like to move storage to a separate box in a backpack, and maybe also into the cloud - so if everything is stolen, footage can still be accessed.
To this end, one of these designs might be appropriate:
- The helmet enclosure is just 2+ cameras with HMDI/power leads going to a storage unit, which goes in a pocket, backpack, or chest-strap enclosure
- The helmet enclosure is 2+ cameras with a USB power lead, local card storage, and data is streamed continuously to a backpack box via WiFi
- As per (2), but the data is streamed to the cloud via a 4G/5G dongle (may be problematic in poor signal areas)
- A mix of (2) and (3) - data is streamed from the helmet to a local box via WiFi, and from there to the cloud via the mobile network. But that may be over-complicating it.
The issue with introducing WiFi is whether data can be streamed off the helmet unit at least as fast as it is written, with some headroom for noisy radio environments. My ancient GoPro produces around 200MB for a minute of 1920x1080x60fps footage (though that res is almost certainly overkill). This would require a sustained transmission of around 35 Mbit/s (comfortably within the ability of a 802.11n personal-area network).
With more than one camera of course this gets trickier - one would reduce the res/framerate of course, but now each camera needs its own WiFi transmitter (probably a Pi Zero W). On the receiver end (something like a M5Stack Core2 or M5Stack Tough) the write rate would be reduced due to the increased contention from several sender devices.
Most WiFi devices can be put in a hotspot mode, but one would have to check that was actually possible for the product being selected.
The night footage performance needs to be reasonably good. Most night cycling is going to feature some light, if only the light from cars and the bike lights. In a city environment there are more street lights, but a moving camera being subject to patches of light and dark can produce over- and under-exposed footage (reducing its usefulness). Some RPi cameras have IR lighting, but I am not sure the current draw for those devices would make them practical for this project.
Finally, home-made stuff tends to be fragile, but this system would need to be built like a marble toilet. It may be that reliability is only available with custom manufacturing parts (particularly for soldering and electrical connections).