arduino datalogger?

I'm less than novice here and don't even really have time to start from scratch so i'd like to find and pay somebody in Orange County, CA to build a data logger (maybe a using the data logging shield from Adafruit?) to attach and read output from a flexiforce sensor device from Tekscan (www.tekscan.com/store/flexiforce-sensors/a401-25-sensor-4-pack.html). It's going to be a one-off device and I can't afford the cost of the off the shelf devices by the various suppliers. I need a device that can measure/retain data then send the data to a PC. Thanks!

I'm not in CA but I have a datalogger of my own design (based on Arduino) that might work. What sample rate is required, and how many samples will be collected before uploading to the PC?

Thanks for the reply, Jack. I think 10-100Hz for 3-5 seconds would provide me with plenty of data. Primarily, I need peak force measurements from various positions while standing on a balance board to be recorded but if I can get time resolved data that I can chart, that would be better. I can set up the pressure sensor to connect to a multimeter fairly easily but I don't want to have to try to catch the exact peak output in real time; I'd rather record and view all my data after my experiment.

Is that a single sensor? I guess even if it's several, it's still a modest amount of data.

My logger is battery powered, meant to operate standalone and while it's primarily aimed at low rate monitoring for long periods, the firmware could be tweaked to fit your requirements. Its main limitation is fairly modest logging memory, 512kB of EEPROM. So not quite the same as having a 16GB SD card. It has four analog and four digital input pins available.

How much have you worked with those sensors? I see from the link you provided that they show an op-amp sensing circuit. I've worked a little with this force-sensitive resistor but it looks like the Tekscan units are a different technology.

Yes, I'll use a single sensor. I haven't purchased the part yet but I spoke with them and they said as long as I follow the wiring diagram I can connect to anything. They do offer two starter kits; one includes a breadboard, wire kit, etc. that has an op-amp. I just haven't decided which kit is better to start with. As for sampling rate and amount of data you can store; I can use 10Hz for 2-3 sec but I have no idea much of the 512kB that will use.

The Arduino analog-to-digital converter (ADC) has ten bit resolution, which means it outputs numbers between 0 and 1023. These would normally be stored as 16-bit integers (two bytes). So 512kB will hold far more samples than required here.

I have a datalogger of my own design (based on Arduino) that might work.

@Jack, Is this shareable?

LarryD:

I have a datalogger of my own design (based on Arduino) that might work.

@Jack, Is this shareable?

Actually, I hope to be sharing it in Atmel's "Simply AVR" contest soon as I can get a video made.

In the meantime, hardware design is here and firmware is here.

There's a User's Guide in the firmware repo and a photo here.

Thanks Jack. You haven't been discovering any weird problems with data sheets lately ;)

LarryD: Thanks Jack. You haven't been discovering any weird problems with data sheets lately ;)

You're welcome. Yeah I've been slacking a bit, not reading enough of 'em :D Reading tax forms tonight $) :fearful: =(

Jack, sounds like your data logger might work for me. Just a few more questions? 1) How do I get the data to my PC? 2) How do I buy it and get it sent to me? Thanks.

GeorgeChris: Jack, sounds like your data logger might work for me. Just a few more questions? 1) How do I get the data to my PC?

A USB-to-TTL serial converter (e.g. FTDI) along with a terminal program on the PC is required. I've used Adafruit's FTDI Friend and Sparkfun's FTDI Basic and both work well. For a terminal program, I seem to use CoolTerm mostly, but TeraTerm, puTTY, or others will suffice. A "capture to file" function is good to have if there's a lot of data to download but I think most terminal programs support this.

2) How do I buy it and get it sent to me?

I'm not offering them generally ATM. I could work up a price and build you one, but there are a couple things to think about. (1) It's not a real inexpensive solution. I used two or three components that are a bit pricey but there weren't less expensive alternatives that met my requirements. Ballpark only and not an official quote, but I'm guessing $75-$85 to build one.

(2) Coding will still be required. My standard firmware isn't geared for data rates faster than one sample per second.

As I've learned more about your requirements, I'm coming to the conclusion that my logger probably isn't any better fit than just an Arduino with an SD card for logging. My logger is aimed at low-power long-term logging, neither of which are key requirements for your project.

Glad to discuss further if you like, but I don't want to lead you astray either.

Not to demean Jack’s stellar contribution, but have you looked at Spark Fun data loggers? The simplest and cheapest was the uLog but sadly, they’ve retired it. Glad I got mine! The next up is the open source OpenLog: https://www.sparkfun.com/products/9530 which records serial data streams (e.g. from the Arduino that interfaces your sensor).

I also want to build a data logger. What's the advantage of the $25 Sparkfun logger over a generic data logger shield? I'm looking to store data for an accelerometer operating at 200 Hz.

Gerry

Thanks for your help Jack! Between work, wife n kids, I'm feeling pinched for time to get my major project finished. I may have to work on this particular aspect of it later. Pardon my absence if I don't get back on here in a timely fashion. I"ll try to do a little bread-boarding when I can free up some time. I'll certainly be back if I can't figure it out. jrem...thanks for the sparkfun tip.

I'm looking to store data for an accelerometer operating at 200 Hz.

What accelerometer? The OpenLog is claimed to work well at 115200 baud, which means it can store about 800 lines of 15 ascii characters of data/second to an SD card. I haven't personally tried that high of a data rate, though.

I'm using the ADXL345. I don't think the baud rate is that big a deal. The SD card write latency is the weakest link. I'll probably have to store the data in RAM first.

Gerry