24V to 5V conversion with high efficiency?

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5V/ 1.5A Switchmode Regulator with input up to 36V

datasheet

(buy as many as you need and use the 24V as the input for all of them and put them wherever you want)

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This is their 3.3V version.

distributors

Similar efficiency, but more suitable max current for your "at least 1.5A": http://de.aliexpress.com/item/5PCS-Ultra-small-power-supply-module-DC-DC-BUCK-3A-adjustable-buck-module-regulator-ultra-LM2596S/32559848206.html

Annoyingly, these are not 2.54mm pitch, but can be connected to a prototyping board with slightly bend pin headers.

Similar efficiency alternative , but more suitable max current for your "at least 1.5A"