You don't need the diodes in the feedback path, but you may need a ~1k resistor between the non-inverting input of each amp and its respective 470k feedback resistor (otherwise the smoothing caps will slow the feedback action).I've added positive feedback
Should be fine.I've dropped in the 1μF capacitor around R7 but I don't have a clue whether that's appropriate?
Inter-component wiring acts as an antenna and can pick up all sorts of radio-frequency garbage, e.g. from fluorescent lights nearby, or from fridges etc switching on and off. There may also be residual ripple on the power supply.Would you mind clarifying for me what the interference is that I'm trying to smooth out here and where it comes from?
R14 is not needed (it will reduce the sensitivity of the circuit to temperature change). I assumed it was just part of your simulation (as, presumably, are the 470Ω resistors near the Peltier).I'm also wondering if I'll need to do the same around R14?
They'll likely do. Depends on their output swing capability and the pull-in/drop-out currents of the relays.unless these chips are likely to give me problems?