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According to Pete - January Edition

Check out this month's edition of According to Pete!

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In this month's edition of "According to Pete," Pete revisits his basement workspace audio project. It's a thrill-a-minute as Pete delves into wiring up his project, amplifiers, switches, and much more. Check it out:

Yeah, this month's edition is a long one! We hope you found it enjoyable and interesting. As always, feel free to leave any suggestions or questions in the comment section below. Cheers!

Comments 25 comments

  • Why two transistors and four resistors when you could use 1 74LS00?

  • Do you have an instructions pdf on how to do this??? Noobs like me need help

  • How caome NEWS isn’t linked from the Sparkfun banner page anymore. You have to follow link to “sparkfun IRC channel” and then click “News” at the top to find it ??

    I miss the BLOG or NEWS heading….

  • Pete,

    At one extreme of the motorized pots the resistance is zero. Nice short on the 3.3 when the program drive the slider to the limit!


  • Are you going to address the audio taper for the feedback in the code or are you going to set up an op amp circuit to make it linear?

    • I would guess code, it’d be pretty simple to calibrate up a multi-point interpolation. But of course the analog way would provide more educational opportunities…

      • Yeah, prolly code. I generally respect analog solutions more, but I’m no glutton for punishment.

  • Pete, consider using the voxel shield for controlling the display. You guys did a post about it a few weeks ago. I finished designing the commercial version and would be happy to let you have the files to test it and use it on your project.

  • Since D3 and D4 are going to be asymmetric because you are getting a true 5VDC on 3A (D4) through the pullup, and the 2A (D3)line is simply the output of the Mega (3.3VDC). Will the speeds be asymmetric as well?

    • No, the inputs on the driver chip are logic level. They’re either on or off. There shouldn’t be any asymmetry in the outputs.

  • I’d be interesting to know what it does.

  • I imagine that both pots are audio taper so that a single fader can handle a stereo input. Unless it specifically says one of them is supposed to be used for positioning…

  • can you do a video on the placement of different kinds of capacitors? LIke explain coupling and decoupling why put a ceramic vs a tantalum/electrolytic in a certain place? will it make a difference? and for instance if i have a electrolytic rated for 20 volts and give it 5 volts will that charge to 20 volts? I dont think so but im still no too sure.

    • Capacitors act differently depending on the circuit you put them in. If you really want to know the difference between the types of capacitors out there, it would be best to look for college level textbooks on the subject (most Circuits 101 course textbooks will have this).

      I know someone can simplify the differences here, but I feel that pointing you in the direction of where the knowledge is will be a lot better for you in the long run (it will allow you to have a key point to reference to). As for if the type of cap will make a difference in a circuit, it all depends on the signals the cap comes in contact with.

      For your example, you’ll need to consult the capacitor charging equations from AC/DC Discrete circuits.

      Sorry if my reply seems pretty bad (I’m at work and I really only have like 10 minutes to write this before going to a meeting).

    • This might help you:


      and don’t forget part 2:


    • That’s a great idea for a video! In the meantime, a coupling capacitor is a capacitor that’s used to allow the AC component of a signal to pass while blocking DC voltage. A decoupling capacitor is a capacitor that’s used to reduce localized power supply noise, thus “decoupling” the noise from another section of the circuit. The placement of a capacitor can be a critical factor; it depends on the application. Different capacitor types are often interchangeable, but using the appropriate type is sometimes important because different types have different operating characteristics such as the ESR. Most important is to connect polarized capacitors correctly; when connected backwards a polarized capacitor can “pop” or even explode, sometimes violently enough to make you glad that you wore your safety glasses.

      • Didn’t I do a cap video a few months back? I’m not being a snot, my memory’s just that bad. I’m pretty sure I covered at least some of that, but I can’t remember the full scope. Or maybe I’m just making it all up in my head.

    • The capacitor voltage rating is the “maximum” voltage you can put across the terminals before the capacitor breaks down and is effectively broken. Capacitors will charge to the voltage that you apply across the terminals. It’s recommended to only go to 80% of this rating.

  • waiting from a week… Atlast…

    • I was starting to get withdrawal symptoms… An Atlast must be related to an alot.