My first go at PCB Express...

[SolderBoy]

Well I downloaded PCB Express and Schematic Express the other day.
This is the first time I've used any PCB design software.  Seems pretty easy to get the hang of.  Actually kinda fun in a strange way!
What do you guys think?  Do these look OK?

(This is actually a project I made last year on proto-board, but I wanted to alter it slightly and get it into a smaller box, plus I've had a few people ask me about it, so I thought it would make a good first project).

[no one ever]

what is it? 

[LyleCaldwell]

Are you going to have them make it or just use it for a print transfer?  Because if you're going to have them make it, you can replace those jumpers with a top layer trace and maybe move some other traces to the top for a tighter layout.

[RaceDriver205]

Yeah, what does it do!

[SolderBoy]

Its a mod for my Roland RC-20 Loop Station.  It turns the tempo LED into a click track for live use.

I designed it to etch myself on one-sided board.  That's why I used custom (wider) pads for all the parts.  I guess the standard ones in the programme are so small because they use those plate-through type holes.  I made the earth and 9V rails fatter than the other ones.  Is there a definitive list of PCB guidlines about trace thickness and current etc etc...?  I really struggled to get all of the circuit on a 55 x 72 mm board to fit in a "b" sized box.  Spent a lot of time nudging parts here and there...  I guess there's no reason you couldn't make your own double sided board and squeeze even more in there... 

Hmmm there's always surface mount too...

Actually If I knew how to programme Micro controllers, I'd have it creating a midi tap tempo message as well!

[NoFi]

   

Now i guess i can find out how to add tap tempo to my Vanishing point from that blinking led !!!!!!!!!!!!!!!!!
THANKS for the idea ! That's just great !

[no one ever]

 

Now i guess i can find out how to add tap tempo to my Vanishing point from that blinking led !!!!!!!!!!!!!!!!!
THANKS for the idea ! That's just great !

me too



yeeeep, we want pictures/explanations when this project is finished 

[SolderBoy]

Actually I did this last year and built it on proto board.  I've used it at a few gigs too - works great - as long as your drummer is hip to playing with a click track...   

Try a search on "listening to an led" for the original topic.

The RC-20 is a pretty cool pedal, with 5 mins(!) of sample time, and an internal tap tempo click track plus many more features - it even quantizes the loop to the click on the 2nd pass - very cool.  But I guess the click is only designed to be used at home, when you are recording and storing loops before the gig, because the click only comes out the main output along with the grooves! - what you need on a gig is a separate click to send to the drummer or to your own cans for solo gigs.  I pulled the pedal apart and mucked about for ages, coming to the conclusion that the click is coming off the same chip as the digital sound. (Could be wrong here, but it seemed that way to me.)  Anyway I realized that I could just use the pulse that triggered the two-colour tempo led to trigger an oscillator or something, and listen to that.

The first thing I did was to try the audio probe on the led.  Sounded like a synth playing a low E with a clarinet sound - and when I recorded the pulse into protools and had a closer look at the wave, of course it turns out that this particular pedal uses 100ms square wave pulses at about 160Hz to drive the led.  In other words, in a tenth of a second the led is actually being turned on and off 16 times.  One of the guys on this forum gave me a couple of twin T type oscillators from a drum machine.  The real trick was to turn that pulse into a single logic pulse, so I used a 555 in much the same way as you'd use for debouncing a switch, but with C and R set for about 150ms (from memory) - that way it would trigger on the front edge of the pulse, but not reset til the after the pulse was finished, but always before the next pulse started - even at the fastest tempo I could set the pedal to.  As you can see, the ouput of the 555 triggers the "woodblock" oscillator and it feeds simple line driver and headphone amp opamps. 

If you are using this idea in another application, I guess the trick is to know exactly what is driving the led in your pedal.  You may even be able to simply attach a cap to the led and listen to a click on the other lead!

Originally I had red and green sides of the led feeding separate 555's and oscillators, to give me a "clave" sound on 1, then the wood block sound on 2,3, and 4, but in practice this is not really neccessary on a gig, so in this version I simply combined the red and green outputs into a one-tone click.  The original also had no headphone amp - just an output buffer, and a stomp switch set up as an output mute, which I never used.  I've also added the 5 volt reg because, the place I've taken the power from in the RC-20 is well smoothed, but not actually regulated and even though the 555 has a wide operating range, the sound of the oscillator will change with different voltages if I use a different wall-wart or whatever.

I etched the board last night, and I'm just about to solder the new circuit.  As I mentioned, I'd really love to know how to programme micro controllers because it would be great to have this send midi messages too, so you could control the tempo of drum machines and computers and stuff.  With a micro controller you could also do away with the 555's and the oscillators too.  I guess you could probably find one that can store a couple of 8bit samples for the drum machine sounds...

SB

[no one ever]

Actually I did this last year and built it on proto board.  I've used it at a few gigs too - works great - as long as your drummer is hip to playing with a click track...   

Try a search on "listening to an led" for the original topic.

The RC-20 is a pretty cool pedal, with 5 mins(!) of sample time, and an internal tap tempo click track plus many more features - it even quantizes the loop to the click on the 2nd pass - very cool.  But I guess the click is only designed to be used at home, when you are recording and storing loops before the gig, because the click only comes out the main output along with the grooves! - what you need on a gig is a separate click to send to the drummer or to your own cans for solo gigs.  I pulled the pedal apart and mucked about for ages, coming to the conclusion that the click is coming off the same chip as the digital sound. (Could be wrong here, but it seemed that way to me.)  Anyway I realized that I could just use the pulse that triggered the two-colour tempo led to trigger an oscillator or something, and listen to that.

The first thing I did was to try the audio probe on the led.  Sounded like a synth playing a low E with a clarinet sound - and when I recorded the pulse into protools and had a closer look at the wave, of course it turns out that this particular pedal uses 100ms square wave pulses at about 160Hz to drive the led.  In other words, in a tenth of a second the led is actually being turned on and off 16 times.  One of the guys on this forum gave me a couple of twin T type oscillators from a drum machine.  The real trick was to turn that pulse into a single logic pulse, so I used a 555 in much the same way as you'd use for debouncing a switch, but with C and R set for about 150ms (from memory) - that way it would trigger on the front edge of the pulse, but not reset til the after the pulse was finished, but always before the next pulse started - even at the fastest tempo I could set the pedal to.  As you can see, the ouput of the 555 triggers the "woodblock" oscillator and it feeds simple line driver and headphone amp opamps. 

If you are using this idea in another application, I guess the trick is to know exactly what is driving the led in your pedal.  You may even be able to simply attach a cap to the led and listen to a click on the other lead!

Originally I had red and green sides of the led feeding separate 555's and oscillators, to give me a "clave" sound on 1, then the wood block sound on 2,3, and 4, but in practice this is not really neccessary on a gig, so in this version I simply combined the red and green outputs into a one-tone click.  The original also had no headphone amp - just an output buffer, and a stomp switch set up as an output mute, which I never used.  I've also added the 5 volt reg because, the place I've taken the power from in the RC-20 is well smoothed, but not actually regulated and even though the 555 has a wide operating range, the sound of the oscillator will change with different voltages if I use a different wall-wart or whatever.

I etched the board last night, and I'm just about to solder the new circuit.  As I mentioned, I'd really love to know how to programme micro controllers because it would be great to have this send midi messages too, so you could control the tempo of drum machines and computers and stuff.  With a micro controller you could also do away with the 555's and the oscillators too.  I guess you could probably find one that can store a couple of 8bit samples for the drum machine sounds...

SB

Thank you for taking the time to explain...