avrdude:stk500 recv):programmer is not responding

Please help, when I tried to download the sketch, I got , avrdude:STK500 recv):programmer is not responding, on project 3 and 4.

on project 3 and 4.

Are any of the other projects loading?

No are they working now?
Yes you might have blown the chip, you have to test to see if you have. You might just have wiped the boot loader. If you have another arduino you could try reflashing it.

Help!! after replacing the UNO at chip, am still having programmer trouble for project 4 colour mixing lamp:
It reads: avrdude:stk500-recv ( ):programmer is not responding.
Much appreciated. thanks.

It sounds like it is broken then if you have selected the correct port in the tools menu.

I just had this very same error on Project 5. However, it seems that the error can occur if the serial port is not selected properly. Somehow in my Tools/Serial Port menu "Blutooth incoming port" was selected. It should have been the tty usbmodem selection. After correcting the serial port selection, all went well. I hope that is your problem and not a bad chip.

Good luck.