What are we gonna’ do with all this data? Let’s make it something fun! That’s the point of the just-launched Data Loggin’ contest. Do something clever to automatically log a data set and display it in an interesting way. Three winners will each receive a $100 Tindie gift certificate for showing off an awesome project.
Data logging is often an afterthought when working on a project, but the way you collect and store data can have a big effect on the end project. Just ask Tesla who are looking at a multi-thousand-dollar repair process for failing eMMC from too much logging. Oops. Should you log to an SD card? Internet? Stone tablets? (Yes please, we actually really want to see that for this contest.) Make sure to share those details so your project can be a template for others to learn from in the future.
You probably already have something harvesting data. Here’s the excuse you need to do something silly (or serious) with that data. Tells us about it by publishing a project page on Hackaday.io and don’t forget to use that “Submit Project To” menu to add it to the Data Loggin’ contest.
Logging data with an Arduino is old-hat for most Hackaday readers. However, [Patricia Beddows] and [Edward Mallon] had some pretty daunting requirements. Their sensors were going underground and underwater as part of an effort to study conditions underwater and in caves. They needed to be accessible, yet rugged. They didn’t want to use batteries that would be difficult to take on airplanes, but also wanted more than a year of run time. You can buy all that, of course, if you are willing to pay the price.
Instead, they used off-the-shelf Arduino boards connected together inside PVC housings. Three alkaline AA batteries are compact and give them more than a year of run time. They wrote a journal paper to help other scientists use the same techniques for the Sensors journal published by the Multidisciplinary Digital Publishing Institute.
Hacking and tinkering are always fun and games, but one just has to appreciate when all efforts are additionally aimed towards doing something good. [Nikos] sets an example by combining his interest in technology with his passion for wildlife conservation by creating a low cost and ultra-low power temperature logger — and he is using a coin cell for it.
As the founder of a sea turtle conservation project in Greece, [Nikos] enjoys building scientific instruments that help him and his team on their mission. With a goal to log the temperature every 10 minutes over a period of at least 180 days, he designed a PCB just big enough to hold a CR2032 coin cell. Fifty of them will eventually be sealed in waterproof enclosures, and buried in the sand for the whole research duration.
Limiting the design to its bare necessities, the rest of the PCB is housing a digital temperature sensor, an SPI EEPROM to hold all the recorded sensor values over those 180 days, and an ATmega328PB clocked by a 32.768kHz crystal. Wondering what to do with all the extra, unused pins of the ATmega, [Nikos] simply routed them to be accessible through pin headers, thus turning the data logger alternatively into a coin cell powered development board.
Assuming your logging interval requirements are significantly lower, you might be thrilled to hear that [Nikos] estimates a theoretical 7+ years an average coin cell could power the data logger in sleep mode, which makes him confident to reach the 180 days goal.
Coin Cell Challenge
Build something cool powered by a coin cell, win prizes!
One only has to ship one or two things via a container, receiving them strangely damaged on the other end, before you start to wonder about your shipper. Did they open this box and sort of stomp around a bit? Did I perhaps accidentally contract a submarine instead of a boat? Did they take a detour past the sun? How could this possibly have melted?
[Jesus Echavarria]‘s friend had similar fears and suspicions about a box he is going to have shipped from Spain to China. So [Jesus] got to work and built this nice datalogger to discover the truth. Since the logger might have to go for a couple of months, it’s an exercise in low power design.
The core of the build is a humble PIC18. Its job is to take the information from an ambient light, temperature, and humidity sensor suite and dump it all to an SD card. Aside from the RTC, this is all powered from a generic LiPo power cell. The first iteration can run for 10 days on one charge, and that’s without any of the low power features of the microcontroller enabled. It should be able to go for much longer once it can put itself to sleep for a period.
It’s all housed in a 3D printed case with some magnets to stick it to shell of the shipping container. Considering the surprisingly astronomical price of commercial dataloggers, it’s a nice build!
[Jed Hodson] put together a nice little data logger with a Linkit One board at its heart. It’s capable of logging two analog channels and one digital channel which also has PWM capabilities. A GPS is used to get the correct time and a Freetronics OLED display coupled with a shield lets the user view the data in real time.
The data is logged on the Linkit One’s internal storage as a .CSV file, allowing for easy access via a spread sheet program. A LiPo rechargeable battery keeps the electrons flowing and the system will give a warning once the power drops below 20%. Speaking of system – the Linkit One board features an ARM-7 processor and has headers to fit Arduino shields. It’s targeted for wearable and IoT type devices.
Be sure to check out this project if you’re in need of a nice data logger. All code and details of the build are available on [Jed’s] Blog.
You probably know that to transfer the most energy between a source and a load their impedance needs to match. That’s why a ham radio transmitter needs a 50 ohm antenna (at least, usually). The transmitter is 50 ohms and you want a match. Some test equipment matches impedance, but for multimeters, oscilloscopes and a lot of other gear, the instrument just presents a very large impedance. As long as it is much larger than the measured circuit’s impedance, the effect will be small.
With today’s MOSFET instrumentation amplifiers, it isn’t uncommon to see very high input impedances. However, you sometimes run into something that has a low input Z and that can cause issues if you don’t account for them. On the other hand, where some people see issues, others see opportunities.
A couple of years ago he worked on a standalone chemical sensor and had a few extra boards sitting around after the project was done. As any resourceful hacker will do, he reached for them as the closest and easiest solution when needing to log data as a quick test. It wasn’t for quite some time that he went back to try out commercially available loggers and found a problem in doing so.
The performance of off-the-shelf data loggers wasn’t doing it for [Paul’s] team. They kept having issues with the noise level found in the samples. Since he had been patching into the chemical sensor PCBs and getting better results, the impetus for a new product appeared.
The flagship 24-bit 8-channel Sigzig samples 0-5v with less than 1uV of noise. A less expensive 4-channel differential unit offers 18-bit with 10-12 uV of noise. They are targeting $199 and $399 price points for the two units. We asked about the sample rate in the video below. The smaller version shown here captures up to 240 samples per second. The big guy has the hardware potential to sample 30,000 times per second but since the data is continuously streaming over USB that rate is currently limited to much less.
Update: It has been pointed out in the comments that USB may not be the choke point for sample rate.