The current [ISET] for the LEDs, vis-a-vis the MAX7219, is established by RSET. There is a value below which that should not go (too much current). I don't know what the range of a flexsensor is, but I think that you may not want to substitute it directly for RSET.<speculation> Maybe the better way would be to use the flexsensor with analogRead and result a variable RSET that way. </speculation>As this is for a "task light" then perhaps the "7219" may not be necessary. Do you require just an arrangement of LEDs to vary (dim as a whole) or is the arrangement required to do patterns and so on? If you need just to vary the lot, it'd be easy to read the flexsensor (analogRead) and result a PWM result (analogWrite) for the LEDs based on that.
What colour/s ?> > > Avoid at this time arranging the LEDs in an electrical matrix, that may make things more complicated than necessary. There's a physical bunch of LEDs, but how to connect them [i.e. what to do] depends on some other factors.What's the power source (a 12V battery pack)?> > > http://arduinobasics.blogspot.com/2011/05/arduino-uno-flex-sensor-and-leds.htmlhttp://garagelab.com/profiles/blogs/tutorial-flex-sensor-with-arduino
You don't have to run a wire from each pair back to the MOSFET.The pairs and resistors would be assembled in the "head" with two wires running out of it back to the "control box" (one for +12 and the other to the MOSFET's Drain.)
Yes, that will be easy to do.Obtain a 0.1uF and a 1uF cap also for the MAX7219.Wire up the matrix and the display per the MAX7219 datasheet to start.http://datasheets.maximintegrated.com/en/ds/MAX7219-MAX7221.pdfSeg0-7 go to the Anode pins, and Dig0-7 go to the Common Cathode pins.