Nearmiss-o-meter, Bill of Materials

Bill of Materials (BoM)

Apologies for the delay since the last nearmiss-o-meter post. Sometimes life throws you higher priorities than the side project you happen to be working on...

These are the items I have used to build a near-miss-o-meter (version 04). Prices are approximate and primarily from UK suppliers. You may be able to buy cheaper directly from China/US.

I have not provided direct links for some suppliers (e.g. eBay) because the items seem to change so rapidly. If you search for the title or quoted description it should return the correct items. Where I've used 'standard' components, I've linked to the the appropriate manufacturer or supplier.

I've tried to brush up on my old photographic knowledge, so a click on the images should provide a higher resolution version.

Adafruit Feather M0

Adafruit Feather M0 Adalogger

This Arduino has an on-board Micro SD card plus Lipo battery charging. See Adafruit website for details. Make sure you are buying the M0, not the 32u4.

The Micro SD card is only used to store the configuration file and the near miss log files. The logs are in CSV format, generating less than 1kB of data per hour, so any standard capacity/speed card you happen to have lying around will likely be enough.

Cost: ~£21.00

uBlox Neo 6M Module

GPS Module uBlox Neo M6

The uBlox Neo 6M GPS module seems to give the right compromise of price, accuracy and reliability. Often listed as an 'Aircraft Flight Controller' for Arduino, there are a couple of different form factors - both work, but only the one with the loose antenna will fit the case properly.

Cost: ~£12.00

The Neo 7M has slightly better 'accuracy' (uses GLONASS) but is more expensive and will need a modified case because the antennae is thicker.

US-100 Serial Sonar

US-100 Ultrasonic Sonar

The US-100 does all the range timing 'on-board' and has temperature compensation too. More reliable, consistent & robust than the ultra-cheap (HC-SR04) sensors.

Cost: ~£7.00

An alternative is the MaxSonar (I have tested the MB1010 EZ1 at ~£20.00, but using outdoors voids the warranty. Weatherproof versions are ~£100). The PCB is designed (but not yet tested) to use either US-100 or MaxSonar via solder jumpers.

Round Pin PCB Headers

Low Profile Round Pin PCB Headers

These are fairly unusual (I could only find them in small quantities from Hong Kong), but allow the Feather board to be mounted 'upside down', making it a similar height to the GPS+antennae.

Usually described as 'Male Female Black 40 PCB Single Row Round Pin 2.54mm Pitch Spacing Header'...

You need both male and female.

Cost: ~£1.00.

Molex Connector

Molex Connectors and Terminals

This is a 4 way/pin right angled socket attached to the PCB and a plug attached to the ribbon cable.

Socket: 70553-0003

Plug: 50-57-9204

Crimp Terminals: 16-02-0086 

I chose these because they are the smallest form factor that still has a 2.54mm pin spacing. The specified plug is a friction type which will help protect the unit if the cable is snagged, but the socket will also take a latching type for extra security if desired.

These are sort of optional as you could solder the ribbon cable directly to the PCB.

Cost: ~£2.00 per set, but may need to order multiples.

Toggle Switch

PCB Toggle Switch SPDT

Used to disable the Adafruit Feather by grounding the ENable pin. This does not isolate the battery (so it can be charged).

This is from RS Components: 734-7220

Manufacturers Part Number: 2MS1T2B4M6QNS

If using the PCB, the pin arrangement needs to match (2.54mm spacing).

Cost: £1.00.

Momentary Switch

PCB Momentary Switch

Used to start/stop recording and for tagging. This is a cheap and dirty switch but we do some 'debouncing' in software to overcome its limitations.

If using the switch case, this will need to be the 1.5mm button version (the lowest available).

Cost: ~20p, but may need to order multiples.

Red, Green and Blue LEDs

3mm LEDs

Three 3mm LEDs are used: Red for GPS status, green for record status and (optionally) blue for near miss indication and sanity check.

I have used cheap 3.3 volt versions from eBay but the light output is not consistent across the colours. The PCB design includes provision for resistors, so a lower forward voltage can be used with the appropriate resistor in place.

If you're using 3.3v LEDs, then you'll need some short lengths of insulated wire to use as jumpers in place of the resistors.

The LEDs for the switch PCB need to have 2.54mm spacing on the legs, and if using the switch case sit no higher than 5.5mm when mounted on a PCB.

If using the blue LED, you'll also need a short piece of insulation (shrink wrap or pulled from a piece of wire) as the legs are quite close to metal parts of the sonar.

Cost: ~20p each, but may need to order multiples.

Light Dependent Resistor

LDR [optional]

An optional Light Dependent Resistor is used to dim the GPS and record LEDs according to ambient light level. You'll also need a resistor.

I implemented this because 'superbright' LEDs are needed for daylight but at night (or when testing) you'll end up with spots before your eyes...

I'm using a 100KΩ (Ohm) resistor with a 70-200KΩ LDR from Maplin.

Cost: ~£1.00

Resistors

You will need three resistors (or jumper wires) to match the red, green and blue LEDs and one for the LDR.

There are several online resources to calculate the resistors required for the LEDs. eg: LED Center or LED Calculator.


Evil Mad Scientist has a bit more in-depth information.

Cost: ~£1.00

Ribbon Cable

This is used to connect the remote switch. I have used ribbon cable but any four core cable will do. If you're planning to use the near-miss-o-meter case with the optional cover, then you'll need to use thin flat cable.

Cost: Free if stripped out of an old PC...

Oshpark PCBs (front and back)

PCBs (or Pegboard and Patience)

All of the components have been chosen for 2.54mm (0.10") spacing on the pins. This is, first and foremost, to allow easier soldering, but it also allows the same circuit to be implemented on both a PCB and a pegboard.

I really cannot recommend a pegboard. It's perfectly doable, but tedious and time consuming if your soldering skills are not ninja level.

Cost: The two PCBs (main board and switch board) are approximately £4.00 per pair (ordered in sets of 3 from Oshpark).

The Eagle .brd files are here on GitHub - just upload them to Oshpark or your favourite PCB manufacturer.

500mAh LiPo Battery

LiPo Battery 500mAh

If using the near-miss-o-meter case, this needs to be a 500 mAh measuring approximately 44mm x 25mm x 9mm.

Cost: ~£3.00 each (ordered as a set of 5 with a charging fly lead)

The Adafruit Feather M0 can also be powered from the USB port, but it would be a shame to not use the onboard charging...

Walkerman and JST Fly Leads

Battery Fly Lead

The battery connector on the Adafruit Feather is a 'standard' JST. Most easily available LiPo batteries have a different (Walkerman) connector. You have a number of options:

1. Use a male Walkerman fly lead (on left in picture above). There are various vendors who sell 5 LiPo batteries with a charging fly lead... This is the route I took.
2. Swap the female Walkerman connector for a JST connector and connect directly to the Faeather board. This was the first route I took, but BE WARNED! There is no standard for the positive and negative terminals. The leads I obtained (on the right) were opposite the the implementation by Adafruit (centre in photo), so I managed to fry my charging circuit. I notice Adafruit now have a warning notice on their site...
3. Solder the battery leads directly to the PCB. Not my favourite option as I like the idea of being able to quickly isolate the battery should the need arise.

Case

I've created a case suitable for 3D printing. The parts are on github here. If you don't have a 3D printer (why not?), they can be printed via 3DHubs - just upload the files choose 'PLA' material and search for a suitable printer (often quite local).

You'll also need two 40mm M3 screws and nuts to hold the base and lid together.

The 'case04-cover.stl' is optional - intended to keep the SD card and USB slots clean and a little dryer if it rains (Although I have used this case in the rain, it is not waterproof in any way shape or form. Use at your own risk!)

Cost: ~£12.00

Handlebar Mount

The case has a GoPro mount on the top, so any mount should fit. Search for 'Camera Handlebar Seatpost Clamp Roll Bar Mount for GoPro Hero' and you should find one like this. Be warned: They are useless for cameras (too much wobble).

If you don't already own a GoPro, you'll also have to buy a 'GoPro long thumbscrew' separately to attach it to the mount.

Cost: ~£4.00

Next up: The Build

I have photographed the build and am currently writing it up...