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Topic: Appliance Status Detection (Read 2769 times) previous topic - next topic

Nate1206

So there are a lot of home appliances that I would like to detect status of.  Examples would be is the coffee make brewing, what cycle is the washing machine on, things like that.  All of these statuses are usually indicated by an LED light on the appliance.   I's it out of the realm of possibilities to plug into these LED lights to see if they are on or off?  Not by light sensing but through splitting the wire to the led and detecting the voltage?

Thanks for the input!

Paul_KD7HB

So there are a lot of home appliances that I would like to detect status of.  Examples would be is the coffee make brewing, what cycle is the washing machine on, things like that.  All of these statuses are usually indicated by an LED light on the appliance.   I's it out of the realm of possibilities to plug into these LED lights to see if they are on or off?  Not by light sensing but through splitting the wire to the led and detecting the voltage?

Thanks for the input!
I have no idea what you mean by "splitting the wires". Do you mean cut the legs on the LED if they have legs or unsoldering them from the circuit board if they are SMD LEDs?

There is nothing stopping you from trying your plan and seeing if it works. Probably nice to have a DVM to check what you are working with.

Paul

chopsuwe

You can measure the voltage across the LED but it's not very safe. Some LEDs will be connected directly to the mains. I highly recommend using a light sensor, or an optocoupler across the LED if you really must make a connection.

steve_mcdonald

ChopSuwe is right but to clarify, in many appliances, the low voltages to drive logic and LEDs is derived directly from the mains supply and may be at or nearly at live mains voltage.  What that means is the circuits themselves may operate on low voltage but those low volts are not isolated and contact with a live, low voltage circuit can expose you to mains voltage to earth. 

With the right knowledge and expertise, optical couplers can safely be used to connect to such a circuit, but there are usually other ways to read the status of the appliance.  There's not necessarily one way as appliances vary so much in their design and implementation.  Many "intelligent" appliances (as in "having a microcontroller") will have some sort of bus available for control and status.  Such buses are usually one of a small number of common bus types. 

Simply put, you need to get to know the appliance itself if you intend to hack it.  That's always the case.  A hacker needs to learn a lot about the target system.

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