Bigfoot has been a long time getting here.  I started developing Bigfoot nearly two years ago.  I initially wanted to make it work without a separate tachometer, but experiments showed that controlling a universal motor at low speed using the back EMF method would be rather chancy.

I suppose I could have gotten done faster, but I backed up and wrote blog posts explaining just why the common sewing machine foot pedals weren't adequate for what I want to do.  I backed that up with some demonstrations, then went on to do some experiments in detecting motor speed with back EMF and PID controllers.  It has been something of a learning experience for me. In the end, I went with a photointerrupter tachometer, and worked out how to attach the controller and the tachometer to the sewing machine all in one piece.

The final product is larger than I originally intended, but it is at least self contained.  It should be possible to make it smaller.  A large as it is, it can still be readily retrofitted to many vintage sewing machines - any machine with an external motor or a boss for a hand crank can use a modern aftermarket sewing machine motor with Bigfoot to control it.

Here's Bigfoot helping my Adler class 8 sewing machine stitch its way through varying thicknesses of Naugahyde (PVC fake leather.)

Where it starts, there's eight layers of fake leather.  It drops down to two layers, then goes back up to four layers.  The speed remains constant through all sections.

The constant speed is needed because if the machine drops below a certain speed, the needle will get stuck in the material.  It isn't as critical with Naugahyde, but in real leather the needle can stick badly enough that it can be difficult to get it moving again even by hand.

The slow speed is needed because I'm not all that good with a sewing machine - I need time to keep things lined up so that the seams are straight and run where they belong.

That's the beginning and the end of the Bigfoot story.  I'll add some logs later to explain what went into getting Bigfoot to do what it does - and just exactly what it is that makes Bigfoot different.