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Unread 02-21-2018, 11:00 AM
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mrnoble mrnoble is offline
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LIDAR and Bluetooth Assistance Requested!

Hello, post-build season CD. Congrats on making it through!

I have a non-robot project that a group of girls are working on for their senior thesis in my engineering class. They are designing a system for skiers that detects dangerous motion approaching from the rear; in other words, if another skier or snowboarder is approaching you at high speed and may collide with you, you would get a notification (through a buzz on either your left or right arm, depending on where the threat is approaching from) and you can turn to avoid the collision. They are planning to use the Scance Sweep LIDAR unit, mounted on a ski helmet, and connected via Bluetooth to two armband-mounted buzzers. They have requested that I ask you for assistance with the following items.

1. Integrating hardware with software. They are learning to code in Python and have set up a computer with Ubuntu. The hardware includes the Scance LIDAR, as well as:

*WRL-12577 ROHS SparkFun Bluetooth Modem- BlueSMiRF Silver
*WRL-12574 ROHS Bluetooth SMD Module- Rn-42 (v.6.15)
*ROB-08449 ROHS Vibration Motor

They can purchase additional materials if these aren't the correct items, or if they need to add more parts. Their remaining budget is $100.

2. Creating a compact circuit that activates the vibration motor via bluetooth.

Anyone have any expertise? They are looking for advice, consultants that they could work with via email or Skype, and sources for supplies. Thank you all in advance for your help. I'm more of a mechanical person, so this project is challenging for me too.

Remember why you're doing this.
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Unread 02-21-2018, 03:37 PM
scjosh scjosh is offline
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Re: LIDAR and Bluetooth Assistance Requested!

I'm not speaking from experience here w.r.t. LIDAR, just throwing out another option. I'm sure someone else will have the knowledge of an algorithm for LIDAR.

You might have an easier time with a stereo vision camera system rather than using the LIDAR. Of course, if the LIDAR is a requirement than this point is moot. Combining the two images through OpenCV will let you calculate a depth map. Your range might be limited here, though. You could also do some other filtering as well.

I have little experience with LIDAR (more with CV), but the one thing that concerns me is how to analyze the distance data while the skiers head can pivot. This is my main reason for suggesting the computer vision based method (as well as CV being the more used option in FRC). I'm sure someone has come across this issue before.

(As I type this, I realized you had already purchased another solution for BT; the following might not be applicable). Finally, there are some pretty cheap bluetooth breakout boards on eBay you can begin testing with. Search terms such as "HC-05 Bluetooth" and "HC-06 Bluetooth" will get you started. There's a ton of tutorials available on how to interface these with popular micro controllers, such as an Arduino. (They're essentially wireless serial/UART) Finally, searching for the model number (HC-05/06) and "standalone" on Google will get you started with only relying on the IC, rather than the large breakout board.

Good luck!
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Unread 02-21-2018, 06:13 PM
Techhexium Techhexium is offline
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Re: LIDAR and Bluetooth Assistance Requested!

Hi there, I think I can provide some advice or (free) consulting to help your students. For my senior design project a couple years ago I worked with a team on a Bluetooth Low Energy based embedded system, and I knew a couple other teams that also used BLE. In my current position I worked on a Raspberry Pi based BLE application, so I done some with BlueZ in Linux. Here I'll share a few thoughts from my experience:
  • It looks like the Bluetooth modules you listed here are for Bluetooth Classic instead of Bluetooth Low Energy. I suggest BLE instead, because it consumes less energy which allows a smaller battery or a longer run time, it is likely simpler to program with (also if they choose iOS as a platform then BLE is required), and if high bandwidth is a requirement then they can choose a module which supports Bluetooth 4.2 or 5.0 for 1 Mbps or 2 Mbps bandwidth.
  • I noticed that most of the BLE modules you can find in Amazon, Sparkfun, or Adafruit don't allow you to reflash the firmware, so instead of acting like a microcontroller they only provide serial interfaces so you would need another microcontroller to work with. Personally I don't like this because in my SDP my group used a TI MSP430 and a Adafruit Bluefruit LE Friend module and spent a lot of time working on integrating the two together, basically the module served as a pipe to our mobile application. If you choose a microcontroller that allows you to write your own firmware you can control whatever electronics you want directly without needing a microcontroller for that purpose, thus less things that can go wrong. I would suggest using a development kit from TI or Nordic Semiconductor. I use the nRF52832 development kit, but you could go for the TI CC2640 kit. Both support BLE 4.2 and 5.
  • For whatever module they choose, if they plan on creating a PCB version, they need to keep in mind that Bluetooth modules are surface mounted and come in different shape and sizes. In our case a member in my team had to learn how to create a PCB design, then we would get it fabricated and shipped to us in order to solder on the module.
So yes, there's a lot of pitfalls to avoid at choosing the right parts, but it's all part of careful engineering! I hope that's helpful, PM me if you or your students need more advice, I'm happy to spread my knowledge in my free time.

Last edited by Techhexium : 02-21-2018 at 06:20 PM. Reason: Hit the submit button too early :)
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Unread 02-23-2018, 01:20 AM
BrianK BrianK is offline
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Re: LIDAR and Bluetooth Assistance Requested!

It sounds like a really great project. One thing that I would ask though is whether any research has been done into how the lidar will perform in bright daylight with bright snow as a background? I know cameras tend to have a difficult time in such a situation. A quick look at a manual for a Garmin lidar product stated that it works best with diffuse reflective surfaces and poorly against highly specular surfaces (e.g., mirrors and glass at an angle). My guess is that bright snow would challenge the lidar.
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