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How to switch on a 9-33v DC LED light using 3.3v as the 'trigger'? Answered

I have a difficult entrance into garage and want to use an orange 9-33v DC LED as a marker light when the garage door is opened. I would like to be able to connect the marker LED to the 3.3v LED that comes on when the garage door is opened. This is on a timer, so I envisage both the garage door LED and the marker LED switching on/off when the remote is activated.

Tags:DCVLED

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steveastrouk
steveastrouk

4 years ago

What current does the marker light need ? Where are you getting the power for the marker ?

I'd probably use a transistor, but if the current was high, maybe a little relay.

The relay option means you could keep the marker LED power separate from the opener power.

Steve

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-max-
-max-

4 years ago

Comparators are devices that have 2 inputs and normally one output. The output depends on the voltage at the 2 inputs. If the noninverting input voltage is higher than the inverting input, then the output goes high. Likewise, if the inverse is true the output will go low or off.

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What's cool is that comparators are really nothing more than very fast very high gain differential amplifiers optimized for comparing 2 voltages and giving a binary (digital) signal. Operational Amplifiers (op amps) are almost the same thing but they are indeed designed to amplify signals instead. You can use op amps as comparitors but they don't work as well.

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Because the output of common comparators is "open collector" they can only sink current and not source current. A pullup resistor is normally required. (1k----10k is fine.)

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So you need to set up a voltage threshold on one input, and your signal can go into the other signal. Then you need a way to amplify the signal output from the comparator using transistor(s). If you are powering the comparator with a regulated voltage, like a 5V rail, using a resistor divider is fine.

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Downunder35m
Downunder35m

4 years ago

Either get a 5V relais and hope 3.3V is enough for it (3.3V relias are hard to come by), or use a transistor.