Category Archives: probeware

Cheap sensor help students answer real questions

I gave a presentation a couple months ago at the Spring meeting of the Michigan section of the American Association of Physics Teachers highlighting a project a pair of my electronics students did last school year. My students used an Arduino to read a 250g accelerometer to investigate the force a brain might feel in a violent football tackle.

From an Arduino point of view it was a trivial program. However, it was still a cool project for a variety of reasons. There were many opportunities for problem solving. They had to figure out how to embed the sensor in a meangingfull way, mount the helmet, and simulate a rough tackle. First task was determining how to mount the sensor. They asked if they could 3D print a head. This seemed reasonable to me, but I wasn’t sure if they’d have to design it or if we could find one. The head of Stephen Colbert was readily available and made us laugh, so that’s the one we printed after modifying it to accommodate the sensor. In retrospect this was not the best head to print as Colbert’s hair when 3D printed doesn’t squish the way real hair would. For this project it worked out fine, but for a side impact would not be ideal.

3D Printed Stephen Colbert in Helmet
I really like this project because it gave students a chance to investigate something of interest to them that is also very topical. As football players, this was of direct interest to them and something with wider potential impact as well. When they finished it I immediately wanted to share this project with other physics teachers. It would be cool to see other teachers working with their own students to do similar projects. However, whenever I try to show teachers how to use Arduinos to collect data, their eyes start glaze over as soon as the code hits the screen.

I decided to attempt to meet my physics colleagues where they are rather than where I am. Most of the physics teachers I know have access to either Vernier or Pasco interfaces and sensors. At our school we have Vernier, so that’s what I used. I assume you could do something very similar with Pasco equipment.  Vernier sells a cable you can use to make your own analog probeware. It turns out this was very easy to attach to our $30 accelerometer.


The Black Wire goes to GND, the Orange Wire is +5V so goes to the VCC, and the Red Wire attaches to OUT. The other wires were not used. All you need to do is solder these three wires to the sensor and plug it into a LabQuest or LabPro. This is something pretty much anybody can do. However, if you’ve never soldered before I recommend this tutorial from SparkFun Electronics.

The 250g Accelerometer we used is an analog sensor. This makes it easy to interface with Vernier hardware. Nerd Alert: If you need to know, basically we are using it as a voltage comparator. On the LabQuest (or LabPro) we set up our sensor to read Raw Voltage (0 – 5V). For our sensor, zero volts corresponds to -250g’s, five volts with 250g’s, and at 2.5 V we have zero g’s. In reality the 5 V wire gave me 5.2 V (the USB standard is 5 V but can be up to 5.25 V or as low as 4.4 V), so zero g’s was at 2.6 V and 250 g’s would be 5.2 V. Since the output from this sensor is linear, I used the LoggerPro program to convert the voltage readings to g’s by creating a “New Calculated Column”. I ended up with a slope of (500 g’s)/(5.2 V) and a y-intercept of -250 g’s.

Screen Shot 2016-07-28 at 8.36.54 PM

The graph of my calculated column resulted in a graph of force vs. time. In the example graph below, the hit lasted for about 0.003 s and reached a peak of just over 63 g’s. Based on readings from the literature, a hit of this magnitude and duration would be unlikely to cause a concussion.

Football graph

With the growth of the Maker Movement there are now a lot of cheap sensors out there that can be interfaced in exactly the same way. Adafruit makes a 200g 3-axis accelerometer that looks promising, but you’d need 3 Vernier cables to read all thee axises simultaneously (also true with Vernier’s 3-Axis Accelerometer).  I’ve also been thinking about using some flexiforce pressure sensors to measure the force/area actually applied to the head in a collision. This would be a simple modification of this lesson on the Vernier site.

My Stuff from the NECC

Well, as of this morning my handouts still haven’t appeared on the ISTE-NECC site for my session, so I’ve converted my pdf files to jpg and uploaded them to Picasa Web Albums (owned by Google).

Here are all the handouts I had posted to the backboard behind my table. I created them using Comic Life on my MacBook.

I also have them as pdf files. If you’d like a copy of the pdfs just shoot me an email and I’ll send them along (

You may also want to see my step by step instructions over on

Me at the NECC

I’ve been hurriedly getting my stuff together for the upcoming NECC. I’d be doing great as far as time goes if it weren’t for the fact that I’m also working with a team of students who are trying to finish their invention project. They won a Lemelson-MIT InvenTeams grant and will be presenting their project in Boston from June 19th thru the 23rd. I’ll be going with them, which will be cool, but I’m running out of time!!!

Any way, on with my stuff. I’ve been uploading directions to This site is pretty cool and they have a competition running right now where the best project wins a laser cutter. While I don’t think I’ll win the laser maybe they will send me a free T-Shirt. Although if I do somehow with the laser cutter the science club next year will have the best fund raisers ever.

Below you will find links to the projects I’ve submitted so far. I will have at least one or two more to put up yet before I’m ready for Atlanta.

I’ve been contemplating ways I can use Instructables in class. I’ve used some of the projects either for demos or student projects, but I haven’t had students upload their own yet. Their had been a problem with the Instructables web site and our network firewall, but this seems to have been resolved. Next year I’ll have to use this. I just have to figure out a good way that won’t swamp the site with 90 projects for the same thing.


I’ve been enjoying many of the projects on Instructables from some time. Today I contributed my first project.

Instructables is a site for people to “share what they do and how they do it.” It is an incredible site. There are projects on nearly any subject you can think of including: cooking, electronics, robotics, catapult making, programming, paper airplane making… the list goes on and on. Anyone can see them, but if you create a login ID you can comment on the projects or ask questions of the project creators. A login is also required to submit your own projects.

The project submission process is no more complicated than writing a blog entry and there is the possibility to collaborate on projects through the site, although I haven’t tried this yet. Even if you don’t use the collaboration tools on the projects, the ability to leave and receive comments can lead to an informal collaboration. Within a few hours of posting my project it had already been commented on and I was able to elaborate a bit to make everything more clear.

My project deals with the creation of the solar cell probeware I’ve outlined previously. In the future I’ll be adding more instructables detailing how to use the probe and software (Audacity and Visual Analyser) for a variety of lab activities or teacher demonstrations.

I’m considering incorporating this site in future student building projects. I’ve already referenced it for my electronics students and some students searching for good science fair projects.

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Way Cool Probeware

I just managed to acquire more HOBO data loggers. Now I need to play with them so I can demo them at the meetings I’ll be presenting at in October (DMAPT Oct. 3, MDSTA Oct. 21, and hopefully MiAAPT Oct. 14). I’ve played with some of their other products before and have been impressed with their ease of use, portability, and affordability. Now I’m even more impressed.

About a year ago Onset Computers and the HOBO Depot released their first pendant logger, which measures light and temperature. The pendant loggers are fully sealed and waterproof. They communicate with the computer through an optical coupler plugged into a USB port. There is a magnetic switch inside the pendant to tell it when it is in the coupler. The switch can be used, with a magnet, to trigger the logger to begin taking data.

The basic HOBO interface is easy to use and quick to master. You plug the HOBO into the computer and then use the HOBO software to configure the logger. You “launch” the logger and put it somewhere you want to record data. The logger will collect and store data until its memory is full or you connect it to the computer again. The data are stored and plotted. The data can also be exported into Excel or another spreadsheet to be analyzed.

Until recently the main focus of the HOBO loggers has been environmental (light, temp, humidity). The newest logger is aimed squarely at physics. The new pendant measures acceleration/gravity. It contains a three axis accelerometer and is capable of collecting data much more quickly than the older loggers. The g-pendant can take up to 100 samples per second. The older loggers won’t log data faster than once a second.

G-Pendant Stats:

  • Max 3 g in any one direction (very easy to max out)
  • Should survive a drop from 3.5 m
  • Accuracy: 0.753 m/s^2
  • Operating range -20 Deg. C to 50 Deg. C
  • Submersible up to 30 m
  • Weight 18 g
  • Cost – Complete Kit: $99 (until January), Individual Pendant: $69 (volume discount available)

I put the G-Pendant in the hands of a couple students I had in physics last year to see what they could do with it. After extensive training (about 2 minutes worth) they were off and running and having lots of fun. Below you can see the results of one of their experiments.

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Cheap Probeware

iScience Project is clearing out their stock of Serial Hobos for really low prices, but you have to act before August 25th, 2006.

Officially it’s an Auction with a minumum bid of $18 for a kit or $35 for buy it now (normally $139/kit).

That buys you a small device (half the size of a deck of cards) that will record temperature, light, and humidity. It also comes with an external temperature probe on a 6′ lead (so you can take two temps at the same time).

Hobo’s are pretty cool. You plug them into the computer and use their software to set them up (what type of data to record and how often a reading is taken). Then you unplug it and leave it where you’re collecting data. Once done you plug it back in and download the data to the computer.

These are cheap enough you could send them home with your kids for at home experimentation. There are hundreds of activities on the iScience Project page to use with Hobos if you can’t think of any yourself.

They also have a loaner program so you can borrow Hobo’s before you buy and there is usually some sort of contest you can enter to win a Hobo as well.

I’ve played with some Hobo’s and will be more than happy to share my thoughts with you. AFAIK the serial ones are Windows only. They do sell USB ones that will work with Mac OS 10.2 or later (but they’er not super cheap right now)

Here’s the info for the auction:

The Auction will begin now and end at 12 noon EST on Friday August 25, 2006. You will be notified by email within 24 hours 1) when you are the high bidder and 2) when you have been outbid. On Friday August 25 from 8AM until Noon (EST) you will be notified instantly. There will be a minimum bid of $18 per kit and $10 per individual HOBO to cover the cost of a new battery, shipping and the full 1 year warranty that will come with your HOBO. You can also use the “Buy it Now” option to own it immediately. All transactions must be on a Visa, Mastercard, AMEX or a school PO.

FAQ – What is demo stock at The HOBO Depot and Onset Computer Corporation? Any product that ever has been returned used or unused and any product that ever had a blemish or misprint on the casing. All of our demo stock has fully functioning components that we warrant for a full year. If any product is not working we guarantee we will replace it ASAP. All of these products come with a PC serial port connection and serial port cable (9 pin trapezoid). You would either need an available serial port (older computers have them) or a new serial to USB Keyspan adapter ($39 at any store that sells computers). All of these kits come with free PC Boxcar 4.3 software which is compatible with Win98 to WinXP and one free serial (9 pin) cable and one new battery.

So here you go – just put in your bid (minimum $18 for kits & $10 for the individual HOBO units).

#1) “Brand New” boxed serial HOBO Henry Kits – Minimum Bid =$18, My Bid =_$, or Buy it Now = $35 Each (Sells for $139) Includes (1) H08-004-02 HOBO data logger (Temp/RH/Light/Ext), (1) 6 Ft External Temp Cable, (1) PC Serial Cable, (1) HOBO Henry & Activity Book, 300 Labs on CD, (1) BoxCar PC Software

#2) Demo Serial Intro Kits – Minimum Bid =$18, My Bid =_$, or Buy it Now = $30 Each (Sells for $139) Includes (1) H08-004-02 HOBO data logger (Temp/RH/Light/Ext), (1) 6 Ft External Temp Cable, (1) PC Serial Cable, (1) BoxCar PC Software

#3) Demo HOBOs only – Minimum Bid =$10, My Bid =_$, or Buy it Now = $18 Each (Sells for $95) Includes (1) H08-004-02 HOBO data logger (Temp/RH/Light/Ext) or any HOBO on this web page and that is all. We assume you want the H08-004-02 unless you indicate differently. Great place to stock up on class sets.

#4) Demo External 6 Foot Temperature sensor TMC6- HA (same specs as TMC6-HD that replaced the HA) – Minimum Bid =$10, My Bid =_$, or Buy it Now = $18 Each (Sells for $30) Includes (1) TMC6-HA Sensor and that is all.

#5) Demo HOBO H9 Shuttle Data Transporters H09- 003-08 – Minimum Bid =$18, My Bid =_$, or Buy it Now = $30 Each (Sells for $159) Includes (1) H09- 003-08 HOBO H9 Shuttle Data Transporter – Perfect for collecting the data out in the field for up to 50 of your Demo HOBOs on one Shuttle (Palm like HOBO data storage).

Auction Contact Information
phone: 877-564-4377

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Do solar cells react fast enough?

A friend asked me this question when I shared my idea of using one as a light probe. I replied by asking are they fast enough for what?

Here is my VCR remote control. The first track is channel up and the second is channel down. If you look close you can see differences in the patterns. The IR from the remote is easily picked up by the solar cell.

The second picture shows the fluorescent light in my basement and my computer monitor respectively. The monitor is set to 85 Hz, I was able to determine this in Audacity. Actually I got a value of 84.8 Hz, but I figure that’s close enough.

On to light – More sneaky uses for free software

We started light this week in my physics class. I do a set of labs using CBLs (from TI) with the TI83/84 graphing calculators. We look at bulb wattage vs. brightness and distance vs. intensity (finding an inverse square relationship). I also have students see the fluctuations in a regular light bulb just caused by alternating current.

For those peope out there who don’t have CBL’s, LabPro’s, or PASCO probeware all you need to do these labs is a cheap solar cell and a computer running Audacity and/or Visual Analyzer. You’ll also need a 3.5 mm headphone jack. You can pick this up at Radioshack or you can go to the dollar store and pick up a cheap set of headphones.

Headphones will typically be stereo so there will be two leads, one for each ear. You only need one ear’s worth of wire. When you strip the lead you will find two wires, solder one wire to each of the leads on the solar cell. Then simply plug it into the microphone jack on your computer and load up Visual Analyzer. Point the cell at a light and see the 60 Hz alternating current (shows up as the light turns on and off 120 times a second).

You can use this to determine relative intensity, but to get exact lumens or lux you’ll have to find a way to calibrate your probe. You’ll need a volt meter for this. You can find them for under $10 if you look around a bit (assuming you don’t have any already).

The solar cell will also pick up infrared light. Just point a remote control at the cell and record in Audacity, zoom in to see how the pattern is different for different buttons and different remotes.

For under $5 you can have a very versitle light probe suitable for a number of great labs or demos.

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Teaching Sound

I’m finally up to teaching sound in my physics classes. This week we did a number of sound related labs/activities. One was determining the speed of sound using a long tube and a flat surface.

The tube (1.5 – 2 m) is stood up on a hard surface (tile floor). Using Audacity you can record a snap at the top of the tube and the echo of the snap off the floor. It’s really quite cool. Once you zoom in quite a bit it looks something like this. I’ve written up fairly comprehensive instructions. If you have any questions or need further clarifications feel free to respond to this post.

Audacity Echo.pdf (Sorry, my link is broken. I’ll fix the link to the document soon. Just drop me an email and I’ll send you the directions)

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New Version of Visual Analyzer

I’ve talked about Visual Analyzer in the past as being a great free oscilloscope/function generator program. The author has recently released another new version. He has also created an English language website. The previous site was in Italian and used frames. Someone told me the Italian site doesn’t work if you use Safari (Macintosh web browser). The English site is a very simple site with no frames.

Visual Analyzer can be downloaded from:

New Stuff in the new version and/or new stuff I’ve discovered that may have been in the previous version:

  • “Peak Hold” in the spectrum window. There is a check box in the spectrum window that will capture the peak frequencies. This is really helpful for sounds that are of very shot durations.
  • X-Y Graph: You can do an X-Y graph of the right and left channels. It’s been too long since I’ve used an actual oscilloscope to remember why you might want to do this.
  • My desktop computer had problems with VA 7.0. I have an Intel motherboard with an integrated sound card. VA 7.0 did no like this and I was only able to use the microphone as my input device. VA 8 has resolved this problem.

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