Looping Foot Pedal

This guitar pedal can record, playback, and modify samples. [Colin Merkel], also know for his work on electronic door locks, built this to replicate some guitar effects he heard in recordings. By tapping the button at the bottom with your foot the device begins recording. Another tap stops the recording and starts the loop. That’s where the rest of the controls take over, with settings to adjust the speed of playback, volume, and the type of playback looping. The video after the break gives a great demonstration of these features.

[Colin] built this around a PIC 18F877A with a 256k RAM chip to store the sample. There’s a bunch of other components that go into this and we’re dumbfounded that he built it on protoboard. This would be a multi-breadboard prototype for us and we wouldn’t think twice about laying out and etching our own PCB. He admits that the point-to-point soldering stretched his skills to the limit but he doesn’t say how many hours it took to get the circuit up and running. This is a great addition to the cool guitar pedals we’ve seen here.


23 thoughts on “Looping Foot Pedal

  1. @Murdo:

    On my pedal it is possible to play along with yourself by switching “Byp/Kill” to “Byp” (although I didn’t demo that) I don’t know if that is what you mean by overdubbing.

    It would be possible to continually add sound to the loop with software modifications only, but I fear that the sample rate would be reduced by a lot. I guess I’ll have to try that.

  2. @Roon, I read H.A.D. and don’t play the guitar, yet I’m working on a guitar project using a Propeller micro(overkill). Admittedly I will be learning the instrument soon though.

  3. The Chicago area musician Andrew Bird has been doing this for a while. I don’t know what kind of setup (self built or otherwise) he’s got, but he uses several switches/loops in any given song and toggles them on and off with his feet as he plays violin or guitar standing up. I’ve witnessed him nearly fall on his ass while trying to hit two switches, one with each foot, at the same time. He does some pretty incredible stuff.

  4. For the technical aspect of the project I give it a 9 or 10 out of 10. Excellent work, and I too was surprised that you could do all of that with a PIC. However, from the guitar player’s perspective, it’s really just an “oh cool” pedal that doesn’t have much use at all in performance. A looping pedal without Overdub is useless in live situations for getting any kind of a rhythm section going. It’s really only useful for the pitch effects, as demoed in the video. I see no reason why any guitar player would ever use the burst mode, because you can’t get any kind of feedback as to when the pedal stops recording. You may want to play around with some of the low-end looping pedals out there, like the Boss RC-2 or digitech JamMan, and observe how overdubbing works. I personally wouldn’t look at a looping pedal twice if it couldn’t overdub, but I understand that this was more of a proof of concept and a fun project, and in that sense you succeeded. So again, good work, I’m not trying to discourage, just providing feedback.

  5. This is a GREAT project :o)
    This idea reminds me of the oldschool
    tape looping machines from the 1960/70
    By the way yes it would not be of much use
    without overdubb , but it can easy be added :o)
    The old tapemachines work with an endless tape
    in the machine and it perform an endless loop
    with overdubbing but those machine could be
    extremely noisy eg with all those tapehead and
    noise on the tape but if you masterede the use
    you could bennefit from the analogue sound it has.
    This project is wery interesting because on the
    page where is is posted some people thought it to
    be 16 bit but is is only 8 bit and this is why the
    old 8 bit sounds has the right good warm/fat sound. OK this project is a good start for him :o)
    He started with the right sound and now (if he want to ) he can add features as endless running overdubbing feature :o)
    Normally it is hard to get a good sound with digitally equipment for guitars because of the
    instruments naturally analogue nature :o)
    Good project and started with the most importent
    GOD SOUND :o) Better sound than this will be more
    Thanks to Hack a Day for posting this :o)

  6. Very well done, especially for a young guy. It’s sad to see all the lame and ‘unimpressed’ comments on here, this is no easy pedal. while it may not ‘overdub’ onto the same loop you can still play over the top of your loop, witch is the basic necessity in one of these pedals, and that fact that pitch shifting and the interesting ‘burst’ option was included certainly makes this A+ work.
    Very well done Colin, I’d buy this myself!

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