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please correct me if im wrong. but these small relay boards usulay have a flyback diode on the board right next to the small transistor used to switch the relay, and i think i can spot the coner of it just behind the dupont connector in the picture at step 9, it is probably a very small glass tube that is orange in one end. but it you are in doubt then it can't hurt to add an extra, if you just want to be safe
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