Pitch base help.

[AuntEggma]

I've read through a lot of descriptions of how to set up a pot for pitch control, but I'm having trouble understanding what the "pitch base" is.  Is it the node that drops pitch in response to touching it with a screwdriver or finger?

I'm attempting to circuitbend a Speak and Math and tried soldering one of the touch-sensitive nodes onto the center lug of the potentiometer.  Then I attached the left and right to positive and negative, as per this picture:  

http://casperelectronics.com/finished-pieces/circuit-bending-tutorial/pitch-adjustment/

(I used the taper pots as the picture instructs.)


That just dropped the pitch and gave me no control over it, except by touching the metal to drop the pitch lower.

What should I be looking for with this "pitch base?"
If I've already got it, what do I need to fix about my wiring or whatever it is?
Thanks for any help.

[Circuitbenders]

I think the more important question might be, what are you using as the positive and negative?

The 'pitch base' can be one of the resistors at the bottom of the board where touching the solder point lowers the pitch.

[AuntEggma]

Oops...  Sorry for breaking the page boundaries.

Ok, that's what I thought.  I've got the pitch base right, then.
Well, I'm using the positive and negative battery terminals for positive and negative.  Is that a no-no?
What should I be using?



On a side note, and I don't know if you can help me with this or not, I've got one specific solder point that reacts VERY well with multiple other points on the board.  The problem is that I can't figure out how to wire switches in such a way that only allows one connection to be made at a time.

If I want to connect point A to point B, C, and D, but only allow one connection to function at a time, what do I need to do?

Also, thanks for actually responding and keeping up with your forum.
Nothing is nicer than asking a question online and seeing it answered.

[Circuitbenders]

You can probably follow this diagram, assuming your machine looks anything like that one. Using the battery terminals probably mean you end up with very variable results as the batteries run down.
http://casperelectronics.com/images/finishedpieces/speak-n-spell/Speak-n-Xbending/ASSEMBLYdiagram.jpg
I think i usually use pins 2 and 4 in from the left of the second row down of solder points for the big chip in the middle, but its probably much the same thing as that diagram.

You could use a rotary switch if you wanted to connect one point to various different points with only one connection at a time, but you'll probably find that the various points interact with each other quite well, so it might be more useful to just connect normal switches across them.

[AuntEggma]

Thanks a lot for the help.
I followed that diagram and the two points for + and - work well.
I don't have the largest assortment of resistors at the moment, so I'm having trouble getting the pot to make it to the far left and right without crashing.  Is it just a matter of finding some sort of a "sweet spot" in terms of the amount of resistance?  I find that I get really close sometimes without it crashing, but I can't quite get it just right, even when I combine resistors.

I tried using trimmer pots, but they're a bit more confusing to utilize than the resistors, so I had little luck in that department.

[Bogus Noise]

Trimmers are definitely worth using for the pitch control. Two 100k trims - one on each outer lug of the pot - will do it, though I usually use a 100k and a 50k, not sure offhand which way round. The trick is to solder them into place and set them to the highest resistance possible - check with the multimeter to make sure. Then you should have a pitch pot that sweeps from low to high without crashing. Now you turn the pitch pot right down, reduce the low trim resistance until it crashes, then turn the low trim up again slightly. Turn the pitch pot right up and repeat the same process with the top trim. Now you should have a full range pitch pot without any crashes!

[AuntEggma]

I had two 10k trim pots which probably had something to do with my lack of success.  I'll make sure to get trim pots with a wider range next time.

With my speak and math, I wound up just messing around with a whole bunch of resistors until I finally got a wide range without a crash.

[Bogus Noise]

Ah, yeah that'd do it! A good way to find trim values is to use a couple of regular size pots as they're easier to turn to get it into the right ballpark. I usually start with 100k but it depends on the bend, if it still crashes with the pot at the maximum resistance use a higher one. Then you can just switch pots in and out until you're about at the right point, and then disconnect the clips/desolder the wires to test it with a multimeter to find the resistance. Then choose a trim pot higher than but as close to the resistance value as possible.