Project 7 and Parts Question

I finished all of the projects in the book but there were a couple parts I never used. I used the large blue capacitor, the one pictured in the center on page 6. But I never used the other two next to it.

On page 9, I used the transistor on the right, with the big metal plate, but I never used the other one in any projects.

So I have no idea what the point of those are, or why I have them.

Also, on project 7, I wanted to try modifying it, so that there was also an LED associated with each button, instead of just a sound. I tried using what I learned in the first project to add an LED to the breadboard, but I got some strange effects. The LEDs started working when I pressed the buttons, but the sounds stopped playing.

I took it apart because I don't really know what I'm doing yet, and I don't want to break something. Can anyone tell me how I can modify project 7 to assign an LED to each button? I thought it would be cool to have an LED light up every time a different button/sound was played. But I don't know enough to do it correctly myself yet.


Hi CSGuy,

Like you I've just finished the Starter Kit , so I hope I've learnt enough to make a worthwhile contribution :grin:

The extra parts are presumably for expanding any projects & of course if you blow a part

With project 7, it may make a difference where you place the Leds. I'd try

  • connecting the gnd from the LHS of the board to the RHS gnd.
  • add the Leds to the RHS side of the board with the anode connecting to RHS output pin of ea switch & the cathode the the RHS gnd
  • At least, for the first switch put a 220 ohm resitor between the rhs switch output & the Led anode pin.

I'm not sure if you need a resistor for all the leds as there is a resitor on the other side, to be safe, do so anyway. If they don't work or are too dime try removing it & see if that helps. The bottom 3 should be protected by the resistor on the input to the swith. So an extra one may be unnessessary or make them too dim.

Maybe try, test one switch & resitor/led at a time.

Hope this helps


hi csguy!

i dont know if it is still necessary, but i think i have the answer to your led-question on project 7:

just simply add 4 leds with resitors as you can see in project 3 (there are but only 3 leds!).

put the code for the leds within the if-else-code: just add a digtialWrite command to the tone command.

and then it should work!

good luck!

I've since torn that project apart to move on to something else. But that sounds like it might work. I was trying to control everything with switches. I forget sometimes that I can do it via code, and just use signal wires. I'm sure that would have worked.

Even though it's too late for that project (I was just playing around anyway), it still helps because now I already have new ideas on how to solve a similar problem in the future.

And for those of us without a starter kit and projects book, what are you talking about?

CrossRoads: And for those of us without a starter kit and projects book, what are you talking about?

Project 7 shows how to built a piano keyboard. You have a line of buttons that play all the notes, so you can play music. I thought it would be neat to add an LED to each note as well, instead of just sound.

Is it polyphonic? I did a polyphonic one using a '1284P over the summer:

Extreme blink without delay, you might say ...

I'm not sure what you mean by, that. But here is the one I built this after noon. I just made up some random stuff.

Polyphonic, meaning more than 1 note at once. My demo: You only demo'd one note at a time - monophonic.

"extreme blink without delay" - my code is based on blink without delay style coding, checking 13 inputs and if a note is playing, checking 13 different time intervals to see if its time to make a high/low or low/high transition. I only play 8 notes in the demo because that was all the buttons I had that day. My code is at reply #4 in topic I posted above.

hi again csguy!

well done! i am just wondering if you did the programming, as i gave you the tip?!?

jn-wp: hi again csguy!

well done! i am just wondering if you did the programming, as i gave you the tip?!?

Yes, I used the idea you gave me.