adding led delay time indicator to rebote 2.5

[deadastronaut]

hi guys,as a sucker for an led or 2... i want to add a delay time led indicator to the rebote 2.5 tonepad...

anyone done this?...can it be done?....thanks...

http://www.tonepad.com/getFile.asp?id=98

[nexekho]

Is the amount of clocks per full memory cycle power of two?  Might be as simple as a frequency divider IC attached to pin 5 (looks like it's a clock output?)  It says 44k though so probably not...

The digital logic to count up to that value wouldn't be hugely complex though a low-end microcontroller interrupting on the clock pin would probably be simpler.

[Seljer]

Is the amount of clocks per full memory cycle power of two?  Might be as simple as a frequency divider IC attached to pin 5 (looks like it's a clock output?)  It says 44k though so probably not...

The digital logic to count up to that value wouldn't be hugely complex though a low-end microcontroller interrupting on the clock pin would probably be simpler.

The datasheet shows the clock going from 22MHz to about 1Mhz for the range of delay times from 30ms to 500ms. That works out to the formula for the relationship between them being being delay time = 6.84*10^8/oscillator frequency. Not the prettiest ratio but its something to start with.

[slacker]

Someone did this using some cmos dividers like suggested above. There's a schemo and layout for it on here somewhere. A search will probably find it, if not it's in the big Echo Base thread somewhere.

[deadastronaut]

cheers guys...found it.  wow a lot of diodes eh!...

http://www.diystompboxes.com/smfforum/index.php?topic=60662.msg604091#msg604091

[nexekho]

That's a lot simpler than I was expecting. 

[deadastronaut]

yeah not too bad really....not sure if its verified though!!!....

[merlinb]

That seems overcomplicated to me, since the brightness of a light has no meaningful relationship to delay time...

The VERY simplest method would be to put a cheap red LED directly in series with the delay pot, and reduce the 1k end-stop resistor to about 330 ohms...
This is quite crude of course, and the LED will probably appear off once you get ebove about 150ms, but you get what you pays for.

Slightly more sophisticated would be to take the voltage across the delay pot, buffer it, and use that to drive the LED in your preferred fashion. This could be arranged to get a smoother brightness-versus-delay taper, if you're willing to put in the time.

[deadastronaut]

very simplest sounds good to me!...great i'll gve that a go when i populate the pcb.(etching now)..cheers merlin.

so its... pin6 > 330r > +led- to pot 3/2..

[nexekho]

Perhaps I misunderstand (don't know much about the specific functions of the PT2399 pins) but wouldn't that just result in a LED that pulses on every tick of the VCO (which I believe is kHz/mHz - you're not gonna see it flash, it'll look half bright if the duty is 50/50) with the delay pot changing the brightness by limiting the current?  By dividing the clock output down you should get a LED which turns on and off once per full delay cycle meaning you can see how often you'll hear an echo which seems more useful.  That is if I understand properly.

[deadastronaut]

LED which turns on and off once per full delay cycle meaning you can see how often you'll hear an echo which seems more useful.  That is if I understand properly.

yep thats what i'm after...the speed of the delay indicator..

[slacker]

cheers guys...found it.  wow a lot of diodes eh!...

http://www.diystompboxes.com/smfforum/index.php?topic=60662.msg604091#msg604091

Yep that's the guy, supposedly flashes the LED in time with the delay.

[merlinb]

By dividing the clock output down you should get a LED which turns on and off once per full delay cycle meaning you can see how often you'll hear an echo which seems more useful. 

Ah, yes, that is more complicated than what I was thinking of.