ELECTRONICS

TTP223 Touch Switch for AC Appliance

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UPDATED 2026-08-13
EXAMPLETTP223 Touch Switch for AC Appliance
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CASE ANALYSIS

Scenario

A TTP223 capacitive touch sensor needs to switch a mains-powered AC appliance safely through a relay, with transistor drive and flyback protection.

Key decisions

  • Use an NPN transistor to sink relay coil current from the TTP223 output
  • Keep AC and DC grounds isolated by using a separate neutral net
  • Include flyback diode across relay coil and fuse on live

When to reuse this

Reuse for any low-voltage touch or control signal switching an AC load via relay.

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