Dual channel linear power supply
Try adding input and output caps to the "precision" regulator because if you don't it may bounce current back and forth with the current drawn by lm317. if you're not familiar with pcb traces and decoupling it's recomended to add one regulator for the digital 5v line and one another for the opamp. or powerup the opamo directly from the arduino? depending the power cycles consumed. that may add complexity to the design but provide a perceptual of higher quality design isolation from 15v.