Black Box Creation Help

Projects General Guidance
1

Hi all,

First post on the forum and was looking for some pointers. So we are tasked with a project to basically create a black box similar to one on a car. Basically we have to create a small box that will monitor temperature and humidity (and take a reading every 5 minutes), measure and record 6-DOF when a certain parameter is exceeded, measure and record up to 3 external accelerometers (MMA8451), and measure and record up to 3 external strain gauges (have not chosen part yet).

The only sensors that are going to be hooked up within the box are the 6-DOF sensor in which we are going to use the BNO055 sensor, and the temperature / humidity sensor is going to hang outside of the box (we are going to use the AM2315 sensor). The additional accelerometer and strain gauges are basically going to be external connections, so they want it so that they can just hook up a strain gauge or accelerometer and take readings. It could be one accelerometer or all 3, same with the strain gauges.

The temperature and humidity has to constantly be monitored and recorded every five minutes, while the other gauges only have to record when a certain parameter is exceeded and then they will record every quarter second until they fall below the parameter.

This whole system has to run off of a battery, and last at least a week on the battery and obviously the data will be stored and recorded onto an SD card so it can be reviewed.

Now onto the help part, we were thinking of using two Arduino Pro Micro's, and the sensors that were previously mentioned. We are going to first try and make it work using dev boards that are already out there. We were going to use a RTC (DS3231), an SD breakout board (MicroSD card breakout board for Arduino) and a I2C level shifter (BSS138). The only sensor that is analog would be the strain gauges in which we could probably use an HX711 for load cell amplification.

We want to eventually just use the Arduino's and create a PCB that houses the RTC, SD module, I2C Level shifter and any other components needed to make this project work.

Basically I am asking you guys if I am on the right track, or if there is anything I am missing or should look into. We have to start designing the project extremely soon and I would rather go with one Pro Micro if possible, but was not sure because of the possibility of all the sensor information.

Would these parts all work together to get done what I need done? Thank you so much for any and all help.

2

At first thought, sounds like you are on track.

Who is this we you keep referring to?

What battery?

What’s is the experience here?

Start with some basic block diagram and check things off your list.

3

Also posted at:
https://arduino.stackexchange.com/questions/56218
If you're going to do that then please be considerate enough to add links to the other places you cross posted. This will let us avoid wasting time due to duplicate effort and also help others who have the same questions and find your post to discover all the relevant information. When you post links please always use the chain links icon on the toolbar to make them clickable.

4

Sorry, my apologies in regards to the different links. I had no idea that would be a problem so I am sorry about that. The "we" is the team that I am working with for a school project. As for the battery, we are unsure what size battery we would be using. We were going to wire everything up and see what the average current output was to try and get a feel for the size of the battery that was required.

As for experience, I am a junior in college studying Electrical Engineering, and the only other ECE person is a senior who is studying Computer Engineering. I am currently taking an Arduino programming course as part of my curriculum and have taken the average circuits courses offered for normal ECE students.

We have already created a decent block diagram and just wanted to see if we were in the right direction. I was looking at whether we would be needing an I2C Multiplexer, and if we would need an HX711 for the analog strain gauges if we were to use them.

Would a Pro Micro be sufficient enough to hold all of these sensors or should we go with two separate ones? Is there anything else we should add to the order list?

So far my order list consists of:
Arduino Pro Micro
AM2315 Temperature / Humidity Sensor
BNO055 Orientation Sensor
RTC
SD breakout board

5

You can start with a Micro, UNO or ProMini, if you find you need more memory or IO, you can get a Mega or Bobuino, the code is easily transferred.

There is a chance you may need a SMPS but you will need information on the battery.
Maybe some switches, LEDs, or display, you know how things keep expanding. :wink:

Oh, you need a back box to put everything in.

6

Larryd,

Thanks! I have not heard of an SMPS but am going to do some research on it now. We will definitely be including some switches and possibly creating an LCD display, but that is not necessarily a must for the project. Our Mechanical guys have the box design under control. I was trying to convince the team to use a Mega 2560 but they are against it for now.

7

SMPS, Switch Mode Power Supply (high efficiency).

Such as

8

I would strongly urge you to get a 4 line LCD going FIRST. You can use it to debug the rest of your programming. There will be times you need to see more than 1 variable and watching them on a laptop screen is pretty boring.

Paul

9

PowerPro25:
I was trying to convince the team to use a Mega 2560 but they are against it for now.

Have you or 'the rest of the team' actually tried to see if the software libraries you will need for the hardware you want to attach will fit into the relativly limited memory of a Pro Micro ?

If not on what basis are 'the rest of the team' against the use of the Mega 2560 ?

How can you 'have the box design under control' if you are not sure which Arduino will actually do the job ?

Also if you use a Pro Micro you seem to be converting all the stuff you want to attach, 3.3V based, into the 5V that the 5V Pro Micro requires.

Might it be an idea to use a 3.3V device ?

10

Srnet,

We have not checked to see if the libraries will fit into the limited memory of the micro. That is one of the things I was against when using the micro though because we do not really have a limited amount of space, and a mega 2560 seemed like it would hold more sensor information.

In regards to the box design under control, I mean we are not really worried about that part right yet, we have the entire year to figure that out. Plus, the mechanical guys are pretty knowledgeable and can get that done relatively quickly.

The AM2315 temp/humidity sensor runs off of 5V and the BNo055 can also use either 3.3 or 5. We decided to go with 5V because of those major factors alone. Those are the only sensors that HAVE to be in the project, the others are just wants.

11

PowerPro25:
We have not checked to see if the libraries will fit into the limited memory of the micro.

Then that is what you need to check first.