[sdiy] Expo question and unrelated dumb matrix idea

[David Moylan]

Inverse of expo is log.

Dave

Tom Arnold wrote:

>First, the expo question.
>
>Is there such a beast as an inverse expo converter, or is there a different
>name for this that I'm not thinking of at 2:30am?  I'm doing a pot to
>current->voltage converter and the responce I'm getting acts very Expo (
>lots of movement for not much voltage change and them whammo ).  The pot
>*is* linear.
>Unfortunatly I'm trying not to modify the control the pot is in, so
>connecting it across the supply rails and taking a voltage from the wiper
>isnt an option.  I dont need to be exact, just need to compensate in a rough
>way for the crappy curve I'm seeing.
>
>Next, the dumb matrix idea.
>
>Since I obviously have too much spare time and too few projects, I played
>with something else tonight too.  I want to build a small pin matrix with
>small being the operative word ( I'd like 15x15 in about 2" square ).  The
>idea I tried that actually seems to work is taking strips of machinepin
>sockets for SIP IC's, trimming the pins off then grinding the bottom lightly
>with a dremel until I hit the cavity.  I was afraid the contacts might pop
>out the bottom once it was open but in this case ( Augat sockets ) they did
>not.  Now an actual sewing pin goes right through the top socket and can be
>lined up on a second set of SIP sockets which are unmodifed to provide the
>second contact.  Its less work then it sounds although I only made a 5x5 as
>my test matrix.  May be cool for matrix patching a noise box or something.
>
>Next run to the surplus places I'm going to try and find some older
>microprocessor sockets that are solid pins across the bottom unstead of
>having an empty area around the die as this would give me a solid top and
>bottom structure to play with.
>
>I did mention it was a dumb matrix idea... but it may be a fun toy for
>someone.
>
>  
>