The Pulsinator Info Request

[Henry89789]

I was doing some searches looking for projects I would like to build. One pedal I want to build is a tremolo pedal and I came across Jdansti's Pulsinator. I saw his pics and the youtube video. I loved the sound! There were some links to posts for the schematic, BOM and layout but those links are now dead. This is basically an open appeal to Jdansti asking if he could provide the schematic, etc. he had originally posted in November 2012, I think. I searched the site and found only two responses to "pulsinator."  Neither had any info.  I also looked through the schematics link above. I found that a lot of the links I clicked were no longer any good. Thanks.

[Jdansti]

Sorry-I just ran across this!  Thanks for the compliments on the Pulsinator.  Sorry about the missing links for build docs, but I think I accidentally screwed up my Dropbox file structure.

I'll repost them here this evening or tomorrow.

[Henry89789]

JDansti:
  Thanks for the reply. No hurry. Whenever you can get around to reposting them. I appreciate it.

[Jdansti]

I've pulled the Pulsinator docs together as shown below. There are a few things you need to know.

I was in a big rush when I did this project, trying to meet the deadline on Thanksgiving day while doing family stuff. As such, I had to make some last minute changes. When I looked at my files last night, I couldn't find the very last change, so I took the last version I had, compared it to the actual build, and revised the PCB and layout art as shown below.

Here are some tips:

1) I replaced D4 with a jumper. I don't recall exactly why, but I think that it helped keep the effect really choppy in rotary switch position #1.

2) To keep the 555 timer from ticking, you need a big cap connected very close to Pin 8. I learned this from Jon Patton (Midwayfair) very near the deadline, so I modified the PCB after it was etched to accommodate the cap. The problem is that there's not much room next to the 555 for a gigantic cap, so I had to mount it off-board. The problem with that is now I had long wires connecting the cap to the board!  I might have been able to get by with a 1000μF cap mounted directly next to the chip, but since I didn't have room and had to mount it off board, I had to increase the value to 4700μF.

I've moved C10 to a location on the PCB that should give you more room. See the last two images below.  I haven't physically tried the version with the new cap location, so you should probably print out the layout and test your fit on paper before etching.

3) Re the LED/LDR combo, I just butt the LED and LDR together inside a piece of heat shrink tubing. Make sure you don't allow stray light to hit the LDR during testing or after it's boxed up.

4) You can use a CMOS version of the 555, but I tried both versions and found no difference.

5) You might want to breadboard this puppy before commiting to a PCB.

6) If you decide that you like just one of the smoothing filter settings, you could hard-wire it and skip the rotary switch.

7) You could replace the VR2 trimmer with a fixed resistor as all it does is determine the brightness if the rate indicator LED.

Let me know how it turns out, and definitely let me know if you have any questions.

[Jdansti]

I almost forgot, see the schematic for the functions of the pots.

[Henry89789]

Jdansti:

Thanks for putting the Percolator info and documents up.   I don't have any questions yet but I am sure I will, eg., about the LED/LDR combo.  I haven't gotten into etching PCBs yet so I am going to put it on a perfboard. Will this go on a A-O/1-25 perfboard or should I go with a A-Y/1-30 perfboard? First the breadboard and then drawing up a perfboard diagram ....

[Jdansti]

I'm not sure about the perfboard. Just guessing by looking at the PCB, it looks about 25x25, which would be closer to the A-Y/1-30 size (but I could be wrong ).  There's a lot of wasted space on the PCB. You should have a pretty good idea once you get something on paper. I generally build on a lager perfboard than I think I need and then use wire cutters to snip off the excess around the edges.

[Henry89789]

Jdansti:

Well, I have been working on a perf board diagram to work from as I put this all together. After studying this I think I understand most of it. There's a copy of the diagram below. But I do have a few questions.

1. Does the input jack tip connect to 3pdt lug 3?

2. Does the output jack tip connect to 3pdt lug 9?

3. For purpose of the 3pdt bypass switch; where is the "board in" that the 3pdt  lug 2 connects to ?   
and where is the "board out" that the 3pdt lug 9 connects to?

4. In regard to connecting the SP4T switch:  do I need a switch with 5 connections so that the LFO out tip connects to  one terminal and SW1a-SW1d goes to the other 4 terminals? Am I understanding this part right ?

Thanks for your help on this.

[Jdansti]

Your layout looks great overall. There were a couple of mistakes on the board, which I've fixed and noted on the drawing below. The jacks and 3PDT switch weren't wired correctly, so I've modified them on the drawing also.



Let me know if you need anything else.

[Henry89789]

Jdansti:  Thanks for your reply with the details drawn  into my diagram.  I see I had the 3pdt all wrong; I think I understand it now but I have been studying the schematic to try to figure it out and came up with another question.  What is the LFO out jack in the schematic for and what  gets plugged into that?   
Also are your pics and you tube video of the Pulsinator still up? A search of the word "pulsinator" does not turn them up. I want to build this and am tempted to skip the breadboard step and get right to it. But it might be time well spent to breadboard it.  Thanks again I appreciate your help.

[Jdansti]

The LFO jack is optional. It allows the Pulsinator to act as a controller for another effect that requires an LFO. For example, you could build an auto wah and send the LFO signal from the Pulsinator to the wah and control the timing of the wah by changing the controls on the Pulsinator. 

Here's the post that has the photos and video you requested: http://www.diystompboxes.com/smfforum/index.php?topic=99142.msg879572#msg879572

Doing a breadboard prototype is always a good idea, but perf is pretty forgiving. If you want to change something, you don't have to worry about screwing up traces and pads like you do on a PCB.

[Jdansti]

BTW, I just noticed that I gave you the pinout for the MPF-102, but it's the same as the J201.

[Henry89789]

Jdansti:
I'm working on it.  Here's a pic of all the components I have on the perf board. Everything can be spaced nicely so that the components aren't cramped. But to have a big 4700 uf cap close to the chip on the board means it's not going to fit in a standard box. I guess one has to weigh the benefits of having the cap close to the chip with the convenience of wiring it off board so you can lay it down in the box. You obviously opted for the latter. I suppose I will also. Yours sounds damn good with the cap off board; can it really sound noticeably better with it close to the chip?  Also. I see your el caps are pretty big, I suppose yours are at least 50v, mine are 16v; Is 16v good enough?  I am studying your pic to see how you did the optocoupler.  you said to butt the LDR with the bright white LED insidce shrink wrap so that no light escapes. The only thing that could be that in your pic is the black component attached  to the board by two white wires. What is that red thing at the end of that component that you can see wrapped in black? The other end of the "abutment" seems to be missing there. I also see you used all carbon film resistors except for the 51k. How does the difference between the two affect the sound ?

Well, I am at a standstill until I receive the parts I need.  Thanks for all the feedback.

[Jdansti]

Your board looks nice!

> But to have a big 4700 uf cap close to the chip on the board means it's not going to fit in a standard box. I guess one has to weigh the benefits of having the cap close to the chip with the convenience of wiring it off board so you can lay it down in the box. You obviously opted for the latter. I suppose I will also. Yours sounds damn good with the cap off board; can it really sound noticeably better with it close to the chip?

I couldn't even get a 1000 μF cap close to the chip on my PCB because it was an after thought. I recommend that you try a 1000 μF first and see how it sounds and work up from there. You might be able to test caps without soldering them. Solder temporary 1/2" leads on the solder side of the board (pointing straight out like a component inserted from the other side of the board) to pins 1 and 8, and then place a cap on the board, but just twist the cap's leads with the temporary leads instead of soldering them for testing. Once you figure out which cap you want, clip or unsolder the temporary leads and permanently install the cap.

Also. I see your el caps are pretty big, I suppose yours are at least 50v, mine are 16v; Is 16v good enough?

16v is fine. I just used what I had available.

I am studying your pic to see how you did the optocoupler.  you said to butt the LDR with the bright white LED insidce shrink wrap so that no light escapes. The only thing that could be that in your pic is the black component attached  to the board by two white wires. What is that red thing at the end of that component that you can see wrapped in black? The other end of the "abutment" seems to be missing there.

That's the rate LED. I used a tiny LED that has a square housing. I picked it up at the local electronics surplus shop. Any LED will work.

The LDR/LED from the LFO is shown on the photo below. Just place the LDR into one end of a piece of shrink tubing and the LED into the other so that the tip of the LED is touching the face of the LDR, then shrink the tubing.



I also see you used all carbon film resistors except for the 51k. How does the difference between the two affect the sound ?

Here again, I just used what I had. I wouldn't expect any perceivable difference in sound between resistor types.

You might want to consider making VR 3 an external control (off-board pot) so you can easily change the brightness of your LFO LED. This is just an option, and might not be possible if you use a smaller enclosure than I did.

[Jdansti]

Another thought for saving space is that you might want to make the volume pot a trimmer and adjust it to unity or just a slight boost. The preamp section will give you some boost that some pedals might not like, so you wouldn't want to eliminate it all together.

[Henry89789]

Jdansti:
Thanks for the explanations. I should have been more observant and noticed the optocoupler there on your board. I think I pretty much understand what's going on now. One more minor thing, Re: the sp4t switch; Small Bear (the only place I could find with the 51k and 3.0M resistors) has rotary switches  that look just like the one in your pedal (black on top & cream color on the bottom) but I could only find a 1P2-12T; Is that the one you used?  (it doesn't look like it because yours doesn't have all the terminals). Thanks again.   

[artifus]

most rotary switches have a removable collar with a little tab that can be positioned into one of 12 slots to limit the number of turns available. you could then use your meter to find which terminals to use with a continuity test.

[Jdansti]

I got that rotary switch at my local electronics surplus store, but it's definitely a SP4T. You could use a SP(4+n)T, or a DP(4+n)T switch and adjust it as Art described.

[Henry89789]

Okay, thanks. I'm set. The next post here will have a pic of a completed, working, luscious sounding pedal.   

[Jdansti]

Cool!