FV-24. FV-1 based pedal.

[deadastronaut]

well i finally got my fv-1 based pedal finished and off the annoying breadboard....thanks to the guys on here for their help, much appreciated guys.

uses the internal fv-1 sounds and 2 extra eeproms, for 24 sounds...

now i can play around with patches/banks without removing eeproms etc just plug in my pickit and voila'....programme on the fly. yay.....

i made the pcb so i could either install an fv-1 smd, or use a pre-soldered fv-1 breakout board.

https://www.youtube.com/watch?v=EiJzAPnQYzA&t=325s

https://deadastronaut.wixsite.com/effects

[Mark Hammer]

Outstanding!

[deadastronaut]

thanks mark.... a big thanks to the guys on here who know what they are doing ,

im just a noob with this digital lark, but it sure is fun...

[Marcvv]

well done! wow

[ElectricDruid]

Very nice! I especially like the "programming slot"! 

How do you know which EEPROM you're programming? Is it whichever one is selected on the front panel somehow?

[deadastronaut]

hi tom, cheers, yeah left toggle is bank A....right bank B.  same as on pcb.

and centre is internal..

[DrAlx]

Pin 14 on the FV1 (SCK) is a serial clock output from the FV1 (presumably used by the FV1 after a power up or reset).
Does your PickIt connect directly to that pin and drive it with its own clock signal, and if so, does the FV1 mind having that pin treated as if it is an input ?

[Digital Larry]

I connect the PICKit 2 directly to SCK & SDA on my FV-1 board without incident.  I guess the FV-1 tri states that pin unless it is doing a read (which it only does at power up or when you change the patch selector lines).

[DrAlx]

I see IC3 is running off 9V supply.  I don't see any measures in place to stop the inputs (pin1 and 2) of the FV1 being limited to the range specified in the Absolute Maximum Ratings on the FV1 datasheet.
Datasheet says voltage to pins 1,2 should be limited to between -0.5 and 3.8V (assuming you are on 3.3V supply).
I am guessing pins1 and 2 are normally sitting there biased at around the halfway level (say 1.65V).
So if a large input signal to the circuit causes the IC3A input buffer to go close to its rails, you'll have a pk-pk signal voltage close to 8V coming out of IC3A. Won't that cause the input voltage limit to pins 1 and 2 to be exceeded?
If so, it might be an idea to add back-to-back protection diodes in there somewhere.  I don't know if exceeding the max input voltage at those pins just leads to clipping in the A/D section of the FV1 or to actual damage of the chip.

The alternative to protection diodes is to just have all the analogue chips running off 3.3V too (which is a redesign as I don't think TL072 works well on such low supply).

EDIT:  One way to do it can be seen on Engineer's Thumb schematic. At circuit input there are back-to-back red LEDs.  You can do similar.  Use Green LEDs as they'll have a larger voltage drop.  You can put that sort of protection off board at the circuit input.
But that won't give protection at startup if IC3A output goes high for some reason.  Best place to put the protection diodes is somewhere after C19 in your schematic.  One 1N4148 going to 0V and another going to 3.3V.

[ElectricDruid]

DrAlx raises a good point. What exactly happens depends on the chip in question of course, and I don't know the answer for the Fv-1 specifically, but it's unlikely to be a fantastic outcome.

I had this same problem with the Druid DigiDelay pedal. On the dsPIC, if the input goes outside the uP's power rails, it crashes the chip. This isn't fatal, but it reboots almost instantly and forgets the tempo it was running at before. Quite annoying. The solution was (as suggested here) to stick some diodes on the input to limit the signal.

[akc1973]

Sensational!!

[bluebunny]

Looks like I picked the wrong week to give up building Rob's projects...

[bluebunny]

Hmmm...  Seems I have an FV-1 going spare...                                  

[deadastronaut]

after C19 in your schematic.  One 1N4148 going to 0V and another going to 3.3V.

cheers alex, interesting, i think i get what your saying. but likely not ha ha..

so a 1n4148 anode points to 3.3v and the other 1n4148 cathode points to ground?  and they join between at the junction between the C19, and R6. ? is that correct?.

[Fancy Lime]

Nice one! Really nice!

[Fancy Lime]

Looks like I picked the wrong week to give up building Rob's projects...



Shirley you can't be serious!

[bluebunny]

Shirley you can't be serious!

You feed me lines like that and expect nothing to happen??

Well, I am serious.  And don't call me Shirley.

[Fancy Lime]

Looks like the foot is on the other hand now, Mr. Kramer!

Anyway, you started it!

[bluebunny]

Rob - have you considered offering some pre-programmed eeproms on your site?

[DrAlx]

after C19 in your schematic.  One 1N4148 going to 0V and another going to 3.3V.

cheers alex, interesting, i think i get what your saying. but likely not ha ha..

so a 1n4148 anode points to 3.3v and the other 1n4148 cathode points to ground?  and they join between at the junction between the C19, and R6. ? is that correct?.

Diode clamps like in the link below. My mistake Rob saying 1N4148 diodes would do it.  Those will not give enough protection as they have forward voltage drop that is too large. You need Schottky diodes like in the link below as they have forward voltage drop under 0.5V.

https://i.stack.imgur.com/Rx33R.png

EDIT: Those clamps should work on either side of R6.  I would put them on the FV1 side right at the ADC input (pins 1 and 2).