PCB Step 3: Make Some Noise
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GoalFinish the timer circuit, add the amp circuit, and test the speaker.
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Components- Timer circuit
- 100k resistor * 1
- 100 resistor * 1
- 10k resistor * 1
- .1uF ceramic capacitor * 1
- 4.7uF electrolytic capacitor * 1
- 10nF ceramic capacitor * 1
- 1k trimmer potentiometer * 1
- IC socket * 1
- 555 timer chip * 1
- Amp circuit
- .1uF ceramic capacitor * 1
- 47nF ceramic capacitor * 1
- 10 resistor * 1
- IC socket * 1
- 220uF electrolytic capacitor * 1
- 1k trimmer potentiometer * 1
- 100 resistor * 1
- speaker * 1
- 386 amp chip * 1
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Steps- Finish that first timer circuit
- Solder the 100k resistor to R2.
- Solder a 100 resistor to R3.
- Solder the 10k resistor to R4.
- Solder a .1uF ceramic capacitor to C1.
- Solder the 4.7uF electrolytic capacitor to C2.
- Solder the 10nF ceramic capacitor to C3.
- Solder a 1k trimmer potentiometer into RV1.
- Solder an IC socket into U1.
- The legs of the socket may be bent from shipping. Make sure they're all straight and intact when inserting into PCB and before soldering. De-soldering a damaged socket is no fun! Do this for all the IC sockets for the rest of the assembly process.
- Solder the amp circuit
- Solder a .1uF ceramic capacitor to C62.
- Solder the 47nF ceramic capacitor to C63.
- Solder 10 resistor to R83.
- Solder an IC socket into U22.
- Solder the 220uF electrolytic capacitor to C64
- Solder a 1k trimmer potentiometer into RV21.
- Solder a 100 resistor to R82.
- Solder the speaker.
- Strip about 1/8" of the insulation off wire's ends.
- Solder wires to speaker, if necessary.
- Just like you did for the battery snap, feed wires through the relief hole above SPK, then solder them into place: red for + and black for -.
- Insert IC chips
- Insert the 555 timer chip into its socket at U1.
- Insert the 386 amp chip into its socket at U22.
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It should look something like this when doneremember
The components' brands and PCB/LED colors may look different from yours, and that's okay! What's important is that the part types and values are in the right spots.
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Test it- With the battery attached, turn the power switch on. You should hear a little "boomp" noise from the speaker as it's powered by the amp.
- Press S1 again. In addition to the LED being lit, you should now hear an audible tone out of the speaker!
- Try adjusting the pot at RV1. Turning it clockwise should make the frequency go up, and vice-versa.
- Try the same on the volume pot at RV21. Clockwise should make the sound quieter, and counter-clockwise will be louder.
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Troubleshooting- Do all the usual debugging steps like checking solder joints, etc.
- Check to see that the volume potentiometer at RV21 isn't turned all the way down.