A really simple Pt2399 delay

[Ginsengbob]

Please help !

I've been trying to make a real simple, easy and small pt2399 delay board to add to some small toys.
I would just buy a couple of the get lofi kits but they are sold out and the new version hasn't
come out yet.
Does anyone have a schematic for the old get lofi delay or one small like that.


thanks

[Gordonjcp]

The datasheet does.  Hit google for "pt2399 datasheet" and it's on pretty much every link on the first page ;-)

[Ginsengbob]

the GetLofi Delay uses only 10 or 12 other parts.
Here is a link to the assembly instructions.

http://www.getlofi.com/wp-content/uploads/2008/12/pt2399-lofi-delay-11.pdf

I was looking for something quick and easy to add to a bent toy.
The lofi delay looks perfect with a small parts count but I can't see all the connections in the pdf.

I've never tried a schematic as complicated as the pt2399 datasheet and I plan to give it a try but
right now it sure would be great to be able to make a really simple version like the lofi one.
Can you look at it and see if you can come up with a simple schematic?
I wish he would hurry up and make a batch of the new boards, I think a lot of people would buy them.

Looking at the datsheet...........
What are     AGND  and DGND?

Thanks, I know I'm being a pain in the ass.

[Ginsengbob]

Sorry
Now I see AGND and DGND on the pin configuration.

[Circuitbenders]

Looks like its time to buy a breadboard and learn how to put together simple circuits. Thers plenty of freeware software out there that will allow you to draw out the schematic from the PT2399 datasheet and automatically position the components on stripboard / veroboard for you.

In fact you could probably work the schematic out just using the photos on the getlofi site and the build pdf. You know what the components are and its a one sided board, it can't be that hard, just trace the connections out by hand. You can see everything on the photo from the top on page 3 of the pdf and elsewhere.

[Ginsengbob]

Ok Ok
I get ya
Teach a man to fish and all that.
At least can you tell me your recommendation of the software that will translate to a breadboard?

The thing on the lofi instructions that was messing me up was the 1m at the top of the socket under the
audio jacks.
I didn't see 1m resistor in the parts list and the 1m pot is at the bottom.


Thanks

[Circuitbenders]

http://www.marlwifi.org.nz/other/stripboard-magic is a simple but effective schematic to veroboard layout program, i'm not so sure about breadboard. Theres some more software at http://www.printedcircuitsboards.com/software/88/veroboard-stripboard-software.html

I'd say that the 500k replaces that 1M on the board, as i can't see where the 500k is meant to go in otherwise. On the pdf for the thru hole version of the board theres 2 1M resistors in that position and it says 'The two 1 M Resistors are wired in parallel to produce roughly 500K, this appears to help to keep the noise levels low.'

Keep in mind that there are at least 2 or 3 connections to the chip that go in under the socket, although you can pretty much see where they go from the pictures.

[Ginsengbob]

Thanks  


Just to show that I've been trying..............






No sound yet
Am I correct in thinking that I could bypass the 78L05 by using the 3 double a batteries?

[Gordonjcp]

Yes, your 3 AA Duracells (I remember when they were called HP7s, and all this was fields...) will put out a little more than 4.5V - probably pretty close to 5V, if the batteries are good and fresh.  Alkalines have a cell voltage of about 1.7V, slightly more than zinc-carbon which give out 1.5V.  If you use that with the 5V regulator, it won't work because the regulator won't have a high enough input voltage to even turn on properly, and may be putting out as little as 3V.

[goat destroyer]

in the Datasheet what are the two ground symbols referring to? Is one ground only for the output and a separate ground for the - battery ground?

[Gordonjcp]

Wire both grounds together, it'll be fine.

[Z3R0]

Yes, your 3 AA Duracells (I remember when they were called HP7s, and all this was fields...) will put out a little more than 4.5V - probably pretty close to 5V, if the batteries are good and fresh.  Alkalines have a cell voltage of about 1.7V, slightly more than zinc-carbon which give out 1.5V.  If you use that with the 5V regulator, it won't work because the regulator won't have a high enough input voltage to even turn on properly, and may be putting out as little as 3V.

Yes, 3AA's will do the job fine for quite a while if they're good quality. Some cheap batteries can't even power the thing properly from the word go so it does pay to use good quality. As the batteries deteriorate the delay will start to squeal and break up. I modded a few ELC keyboards with them in and they last for ages on a set of duracell. I also didn't use voltage regulators since the chances of overloading the 2399 with three batteries seemed pretty slim and with such a fine line between adequate power and fade out it seemed to make sense to make as little work as possible for the power supply.