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Picoboard and Wedo with Scratch

« Teaching with Scratch
13 replies [Last post]
Ana Santos

Hello everyone!

Have  Picoboards but no Wedo kits.

Is it possible to hook up a Picoboard AND a Wedo kit to the same computer/Scratch program

and get the motor to react to changes detected by the Picoboards light sensor for example?

Would really like to know before ordering.




Lindsay Craig

" I'm also interested in the arduino board and arduino robotics.

From what I've gathered it´s actually much cheaper than the picoboard but the learning curve will be very different because the C type language isn't nearly as "kid friendly" as Scratch. "


Hi guys, I'm new to this forum and all about educational technology.  You guys should check out ModKit if you haven't heard about it already. It's made by these awesome guys who want programming Arduino to be as easy as Scratch. It's going public very soon. Check it out.


Also- I have been developing a scratch project to teach about Arduino. It's definitely not nearly done, but the idea is there. I have been poking around a little and was unable to find anything like this on the site. I would love to share it with people in the hopes that they will take it, make it better, use it for their own classes, whatever. Like I said I haven't posted it yet (got a lot of other stuff going on) but I will shortly. I would also love to hear more about what people are doing with Scratch (and definitely Arduino) and the school systems.

Anders Berggren

Hi Lindsay

Yes it´s interesting with the arduinoboard. If I use a photoresistor with Picoboard it´s easy to get started and understand what is happening (I will soon try the picoboard with kids aged 11-13, a small techproject).


But the Picoboard is too expensive (escpecially if you live in Sweden and order 10 boards, I had to pay somekind of importtax nearly 100 §, puh :(....). So the arduinoboard would be perfect. But it´s not so easy to get going for kids. There is a little bit higher learningcurve before you are up and creating. I would be nice if you share your arduino-experiences with us.

The S4A - scratchclone is interesting


And the ModKit will be really promising...

I stumble upon this nice video about arduino and 8-11 years old girls... even more promising :) Not sooo much Scratch, but the idea is nice...


Hmmm... I couldn´t embed the video...

Lindsay Craig

Hi guys (in particular Anders),

I work for SparkFun Electronics.

I recently posted an Arduino teaching tool I have been working on in my free time here:

It's a little complicated if you don't have experience with Arduino or Scratch or a similar product, but read the project notes for some quick instructions if you are interested.

It is a ruff draft and I posted it in the hopes that other educators would understand the idea and download for further development. Feel free to use it however you like and please post any improvements to the gallery.

Dedicated to educating-


Anders Berggren

Hi Lindsay

I will dig into your arduino teaching tool... I´m a newbie in the arduinoarea, but it´s fun and interesting. I tried the S4A-clone today, and it works well even with one arduino - Uno and a Picoboard connected at the same time. But I´m waiting for the Modkit as well...

And the best part of everything is that I started a Tech/Scratchclub as an afterschool activity (not so common in Sweden...) and have 6-10 interested kids (probably more, when the words are spread). So I will work with Picoboards first... but if they are interested... arduino. And the Kinect hack... for Scratch. So it will be an interesting spring :)

Ana Santos

Replies to Claudia and Anders:

I'm glad to have found this forum. Although Scratch isn't new here I don't know  anyone who has worked with the Picoboard or external Sensors.I love Math and know a bit about programming .

Claudia , thanks for your answer! From below you can see I had already seen your name somewhere!I am very sad to say my laptop was stolen last year but its still all in my head and will be happy, if you're interested and given time to share code examples. Anyway I hope to redo some projects this year as well as try new ones. Wow,the idea you shared has everything to do with my views on the use of Scratch and I actually did that last year except for the humidity sensor! We saved data ( for example pairs of numbers  , time and temperature )in lists , exported as text,  then opened with Excel and did all kinds of graphs.

Found out about Scratch before it was actually introduced in my country, loved it, tried  to learn as much as I could when I could ( time's always scarce...) and am still doing so. Portugal actually has its own Scratch site  only very  recently updated with Scratch 1.4. There is a very comendable organization of teachers here around Scratch.However, although Scratch is great for story telling and getting little kids to learn basic programming skills , here I haven't really seen its use advised for older kids. It has been mostly "promoted" for use in Math with 5th and 6th graders and before I prove them wrong some of my pupils say its " kiddy stuff",which is a pity when you can also create  interesting programs using more advanced concepts  with grades 7 all the  way up to 12 ( get kids to create "missing operators" with exponential and logarithmic functions...)

Hope to hear from you Claudia!

Here are  some ideas I used :

Turned a bycycle upside down, taped a magnetic sensor to one part of the bike and  a little magnet to the wheel.The idea was to get the wheel to spin for a bit and calculate things  like:distance "travelled", speed and rotations per minute. Got the idea from the gadget on my husband's mountain bike.

With the Temperature sensor got it close to really hot  or cold things and with pre-recorded kids' voices you could hear " It's soooo hot" or "It's sooo cold."

I had thought of a " talking" plant who would complain if its soil was too dry but didn't find a humidity sensor in Portugal ( resistive humidity sensor) . I'm going to order from Rhopoint but it's going to really cost me because of shipping. Do you know if can use this sensor to measure soil humidity as well as  air humidity? Another hare brained idea I didn't get to try was a doll with a humidity sensor on an adapted diaper. She would cry out "Change me" when water you put in her mouth trickled down to the diaper...

With four mercury switches taped to a plate which was then covered with transparent hard case with holes as a precaution and we simulated a steering wheel which controlled a car on the screen. We were very, very careful but the Wedo tilt sensor is of course the way to go.

We also filled the screen with flowers of various colours and with the light sensor placed on the screen there was this little bumble bee which flew to where the sensor was.There was only one flower of each colour and at any given time the Scratch program knew exactly what flower the light sensor was on.

Anders, thanks for the info. I haven't tried Mesh but it seems to be the only way to control more than one Wedo kit. Of course you'd need more than one computer but with shared variables and broadcasts there are a lot of possibilities...Regarding  resistance, for example I used Temperature Sensor 10 K OHM, Light Sensor 5K to 20 H OHM. Electronics isn't my specialty but after finding the following info I ordered a Picoboard and later on managed to get the external sensors in Portugal except the humidity sensor.

Hope  the following info answers some of your questions.

Sorry for enormous post.Please excuse any errors!

Very best regards,

Ana Santos

From Sensor Types and Sources: I knew your name was familiar Claudia!

The following list shows different types of sensors that have been used in Scratch Sensor Board projects. (They are typically attached to alligator clip-heads plugged into sensor board jacks A, B, C or D.) Visit the vendor site for pricing and ordering information.

 Name; Description ; Vendor  Part Number

Switch;  Switch lever spdt 3A PCB; SW773-ND.
Temperature; Thermisor NTC 10K OHM 5%; 317-1258-ND.
Light; Photocell 5K-20K OHM 4.20 MM; PDV-P9203-ND.
Magnetic switch - 1; Switch Reed 10-15AT SPST .5A; 420-1047-ND.
Magnetic switch - 2; Switch Reed SPST .5A 12-23 A/T; HE502-ND.
Humidity; Consists of a metal electrode on a humidity sensitive membrane mounted on a ceramic substrate;  SYH-1NC.
Thanks to Claudia Urrea for the initial list.
Note: When using resistive sensors with the XO microphone port, it appears that the interesting resistance range goes from around 2k to 5k. (Experimentally determined; your mileage may vary.)
17. How do the sensors convert their input to values between 0-100?
From the Technical Info document:
"Scratch maps the 10-bit sensor data onto a 0 – 100 scale using a mapping that is different for each sensor type. Users can access the “raw  10-bit values by shift-clicking on the Scratch Board Watcher and selecting “report raw data . Doing so will show sensor values in the range 0 - 1023. Most of the sensors use a generic linear conversion to report scaled values between 0 - 100. Light and sound sensors use piecewise linear functions that take into account the idiosyncrasies of those sensors. (Note that readings for light are reversed so that more light gives larger values.)
Code for scaling functions [are]:


   return round ((100 * n) / 1023)
 if n < 25 return 100 - n
 else return round((1023 - n) * (75 / 998))
 //empirically tested noise sensor floor
 n = max(0, n - 18)
 if (n < 50) return n / 2
//noise ceiling
 return 25 + min(75, round((n - 50) * (75 / 580)) )
//noise floor and ceiling values might vary

18. Um. OK. But in reality, how do the resistance values relate to the sensor value? Is it linear?

Nope. It's not linear. It's logarithmic. From experiments on our board, the resistance sensor value (0-100) that the PicoBoard produces is related to the actual resistance, R, (in KOhms) across the alligator clips by the something like the following equation:

sensor value = a*ln(b*R+1) where, approximately:


BUT, if you are only interested in low resistance values between 0-10 KOhm, the following simple relation works real well (and yep, it's linear):

sensor value = a*x, where a is approximately 5.57






Anders Berggren

Hi Ana

Thanks for your reply. I have orded 10 picoboards recently (waiting for delivery), so I will definitly try some of your ideas. Probably next year (if I can get a teacher interested ;)... or try with some AfterSchool activity)


....and I want to experiment with an arduinoboard as well... So many wishes and time is spread around all over the place, and I don´t know how to catch it...

Ana Santos

Hi Anders!

How I know what you mean!

I'm also interested inthe  arduino board and arduino robotics.

From what I've gathered it´s actually much cheaper than the picoboard but the learning curve will be very different because the C type language isn't nearly as "kid friendly" as Scratch.  I suppose kids would have to be 12 at the very least...

By the way, it snowed in Portugal on November 30. Haven´t seen any because I live in the center near the coast.


Ana Santos

Hi again!

By the way, is anyone out there using external sensores in Scratch? I've used thermisters, mercury tilt sensores ( was very careful), and magnetic sensores. Hoping to trade experiences and ideas...



IrisSophia aka Ana Santos

Claudia Urrea

Ana, I just shared couple of resources:

1) resistive sensors I have used with Scratch board, (

2) example of a lesson you may do with students using the Scratch board  (

Can you share the information on other sensors you are using?




Anders Berggren

Hi IrisSophia/Ana Santos

Interesting with your sensor ideas. I haven´t tried yet. I have seen a list of possible sensors, somewhere... don´t know where. Is the full resistence 100 kOhm (Picoboard input A-D)? Or, what´s the truth? By the way mercury... not a primary/secondary school...? ;)

And I am willing to trade our 10-15 cm snow - 5 C Swedish weather with a 15+ C Portugese weather... :)

And today I tried to connect two WeDo-usbhubs to Scratch. I didn´t work, Scratch found only the first connected hub.


Ana Santos

Thanks Anders and Karen, that´s really good to know. All computers in schools all over the country have W. Vista.LOL Lots of chuckles from  that salesman :)))

Since the Picoboard works on them and on my Win 7 laptop, I'll cross my fingers.  I was even considering  Mesh which allows computers on a local network to view each other's variables and see broadcasts.Theoretically, if you place sensor inputs in variables all computers could see them and one "Master" computer could control motors on other computers based on inputs from a Picoboard or whatever.

I'm green with envy Anders, lived in Canada for many years and I miss the snow. But I do love beautiful sunny Portugal, so there :).




Karen Brennan

Same. Like Anders, I just tested it out and was able to use the sensor board and WeDo simultaneously.

Anders Berggren



Yes. I tried it now. And it works, but you could only use two of the inputs/output from the WeDo. It´s not possible to get all three working (tilt-, distance-sensors and motor).

I haven´t tried to plug in two WeDo usb-units though. But you could use the picoboard lightsensor to control the WeDo-motor. My board is an older USB-Serial Scratchboard, but it should work with the USB Picoboard. Win XP... haven´t tried with Mac or Win 7. (Win Vista is a total disaster so I don´t even get near a Vista computer... ;))



The first snowy day today....