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Tips

Here are some tidbits I picked up in the time I've been working with the EV3. 

What's that weird angle in the angled beams?

You may have assumed that the 'bent' Lego Technic beams are bent to an angle of 45° but that is usually not the case. It IS the case for the white beams that have two 45° bends (as shown in black at the left side of the above image from here). The other angled beams have an angle of 36.87° or 53.13° - why such weird numbers? By studying the other black beam in the above image you can get the answer: these are the angles in a 3:4:5 triangle, the simplest right triangle with sides that have integer ratios. This makes such triangles more useful in making Lego models than 45° triangles would be since the ratio of sides in a 45° right triangle is 1:1:1.414 and there's not much you can do with that hypotenuse since it's not an integer.



Motor speeds
Did you know that if you set a large motor and a medium motor to the same power value the medium motor will turn much faster than the large motor?
  • For the large motor, the rotational speed of the motor in degrees per second should be 10 times the power setting. For example, if you set the power to 10 then the rotational speed should be 100 degrees per second.
  • For the medium motor, the rotational speed of the motor should be 16 times the power setting, so for example if you set the power to 10 the rotational speed should be 160 degrees per second.
These ratios are only valid up to power values of about +-80, beyond which the motors 'saturate' and are no longer capable of rotating as fast as they should. You may well find that a motor set to power=100 rotates no faster than a motor set to power=90! So if you want to be able to make use of the ratio numbers I just gave you, you should avoid using power values beyond +-80.



How to change language in the EV3 Education software
Did you notice that in the EV3 software (education version) there is an item 'Change Language' in the Modify menu that does not seems to work? Being able to change language could be useful in the context of an international school like mine so I tried to sort this out by trial and error and found this solution: If you install the software in one language and then install the software in another language using the default locations then both software configurations will exist within the computer and you will now be able to use that menu item to switch between them (you have to restart the software after requesting a language change).



Type conversion
You may have assumed that, when using data wires, the output of one block must be fed into an input on another block that has the same type. Recall that there are five different kinds of data wire: numeric, type, logic, numeric array and logic array (but not type array). While it is generally true that the output and input must be of the same type, it turns out that there are some exceptions. Here are the exceptions, i.e. connections in which the Lego software is able to convert one type to another. You can connect:
  • a numeric output to a text input (the number will be converted to a string)
  • a logic output to a text input (the value true will be converted to '1' and the value false will be converted to '0')
  • a logic output to a numeric input (the value true will be converted to 1 and the value false will be converted to 0)
  • a numeric output to a numeric array input (the number will be placed in the first element of the array and this will be the only element)
  • a logic output to a logic array input (the logical value will be placed in the first element of the logic array and this will be the only element)
The shapes of the inputs and outputs in the Lego software cleverly give clues about what data types are compatible. for example, a semicircle will fit in a square, indicating that a numeric value can be fed into a text input.



Connecting data wires into a switch block from outside
You CAN connect data wires to the interior of a switch block from outside but only if the Switch block is in 'tabbed' mode.



How to reset a frozen brick
In my classes the Lego brick has frozen a half dozen times in hundreds of hours of use. To unfreeze a frozen brick:
  • Hold down the Back, Center, and Left buttons on the EV3 Brick.
  • When the screen goes blank, release the Back button.
  • When the screen says “Starting,” release the Center and Left buttons.
  • Resetting the EV3 Brick does not delete existing files and projects from previous sessions in the EV3 Brick memory. Files and projects from the existing session will be lost. If resetting doesn't work then you can always unplug the battery.
  • Although I have read that you must hold down the Back, Centre and Left buttons it seems to me that holding down the Back button and then just the Centre button (for several seconds) is sufficient. Do you agree?


'Frozen keyboard' bug
In my experience of working with the EV3 for hundreds of student-hours it is not uncommon for the computer keyboard to become unresponsive while the EV3 software is running. It's happened to my students at least a dozen times, and once the mouse froze rather than the keyboard. I haven't seen this bug reported anywhere else, but I'm convinced it exists. If your keyboard freezes you will have to try to save your work and then restart the software, but it's hard to save your work once your keyboard has stopped working so take my advice and SAVE OFTEN in case the keyboard bug strikes you, too.



Warning: your Lego hardware could destroy your home!
I'm not joking. I came home one day to find a strong smell of burning in my house. I traced the smell to the charging base of my Philips wireless phone. Like many people reading this page, I have on my desk not only a phone-charging base but also my Lego EV3 with its rechargeable battery and my Lego battery charger. Unfortunately the electronics industry has not had the bright idea of inventing different plugs for chargers that deliver very different voltages. My phone charging base and my Lego EV3 rechargeable battery both use the same plug but my phone charging base is designed to work at 6V and the Lego charger delivers 12V. You've guessed it - one day I plugged the Lego charger into the phone charging base by mistake, before leaving the house. This is the result:


The phone was very hot when I found it like this, and the plastic was molten, so it's clear the phone wasn't far from catching fire. My desk is covered with papers and surrounded by bookshelves, so I leave the rest to your imagination...
As I said earlier, this situation could easily be avoided if the electronics industry had invented different plugs for chargers that deliver very different voltages, but they haven't, so it's up to us to take great care. I hear you say that I could also have paid attention not to plug the Lego charger into the phone base, but since the two plugs are identical it is a mistake anyone could make.

My advice then: be aware of the risk, stick some tape to the Lego charging cable to clearly mark it as a Lego charger, and TRY NOT TO SET YOUR HOME ON FIRE!
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