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I have a very simple project where I have a ttp233 touch sensor which I'm using to control my relay module which in turn switches my fans on and off. The problem here is whenever there is a power loss the relay defaults to a low state and I have to touch the sensor again to turn on my fan (My house has an inverter so power outage is not the main issue but when there is a power loss my inverter takes about 2-3 sec to kick in and in this gap the relay returns to default of off state).

So I thought of using a battery to compensate ,so I want help regarding this. I want to have it in such a way that when the power is there the relay and sensor should run on wall power and the battery also should be charged but when there is a power loss the battery should kick in and power the circuit with no delay so that my appliances stay on during power loss and when the power comes back on again the circuit should again go back to using wall power or any other way that my relay state remains where it is after a power cycle(The state of the relay is determined by the state of touch sensor so if there is a way to power my touch sensor during this brief power cycle please tell me.). Is there any way I can achieve this?

This is the touch sensor im using and this the relay module im using the power consumption of touch sensor is 1.5 U to 13 uA and the relay is about 100-120 mA.

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The most straightforward way to solve this problem is to use a latching relay, and configuring your TTP233 to give a momentary, rather than a latched output.

A latching relay works on a mechanical latching principle, and will remember it's state even through a power outage. To change the state of a latching relay, one applies a momentary current, which can be provided via the TTP233.

An electronic replacement for a latching relay is possible, but seems unnecessarily complex for what you are trying to achieve.

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  • \$\begingroup\$ Ya I know I can use a latching relay but the problem is that, where I live there are none avilable online and offline. \$\endgroup\$ May 23 at 15:32
  • \$\begingroup\$ And do you think a capacitor will do the job of just keeping the touch sensor(about 0.000013 A of current usage) on during the 2-3 sec period like a 1000microfarad one? \$\endgroup\$ May 23 at 15:57

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