The_Official_Raspberry_Pi_-_Beginner’s_Book_Vol1,_2018 (1)

190 THE OFFICIAL RASPBERRY PI BEGINNER'S GUIDE

5 Figure 7-29: Lighting the pixels in random colours

The sparkler isn’t very interactive, though. To change that, start by dragging a wait 1 secs

block so it’s under the set pixel block but within the forever block. Drag a ● / ● Operators

block over the 1, then type 10 in its second space. Finally, drag a temperature block over the

first space in the divide Operator block.

when clicked

setallpixelstooff

forever

setpixel pickrandom^0 to^7 ,pickrandom^0 to^7 toRpickrandom^0 to^255 Gpickrandom^0 to^255 B pickrandom^0 to^255

wait temperature / 10 secs

Click the green flag and you’ll notice – unless you live somewhere very cold – that the

sparkler is considerably slower than before. That’s because you’ve created a temperature-

dependent delay: the program now waits the current temperature divided by 10 number of

seconds before each loop. If the temperature in your room is 20°C, the program will wait 2

seconds before looping; if the temperature is 10°C, it’ll wait 1 second; if it’s under 10°C, it’ll

wait less than a second.

If your Sense HAT is reading a negative temperature – below 0°C, the freezing point of water

• it’ll try to wait less than 0 seconds; because that’s impossible – without inventing time travel,
  anyway – you’ll see the same effect as though it was waiting 0 seconds. Congratulations: you
  can now look at integrating the Sense HAT’s various features into programs of your own!
  For more Sense HAT projects, follow the links in Appendix D, Further reading.