Object was to make, a simple circuit, with digital control of a 12Volt DC motor.

Resistor R2R ladder and switching DC circuit, for adjustable motor control.
R_2R_Switcher.jpeg

SIOP_switching_DC_control.jpeg
 My own trash being my treasure.


Speed Control Menu.


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Click on links to view images.
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Making homemade photo-switch.


LM2575 "PCB Art".
  

LM317_circuit.jpeg Videos showing both running with latest setup, to compare performance.


Click chart to see full size.
317compare2575icon.jpeg
LM317.jpeg

R 2R = Resistors 1 to 3, value is times two for resistors 4 to 8.

R-2R_Ladder.gif Resistor Total "RT" value was measured.

  This is showing output of ohm meter, as 2R resistors are switched in and out, from ground reference to RT point with the circle.
  Doing a standard binary count from 0000 to 1111 we get a variable resistor measured from 124.8k ohms to 24.9k ohms. Calculations of:
0000 R4+R3+R2+R1 = 124.6k
1111 1/(1/(1/(1/(1/R4+1/R5)+R3)+1/R6+R2+(1/R7)+R1)+1/R8) = 24.9k

Link to spreadsheet r2r_calculator.ods which you can plug in your own values.
Has been updated for 32 bit.