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I am designing an embedded system where I need to minimize power consumption in standby mode (ideally no additional consumption from the IR receiver circuit when in standby) This system will be running off of coin cell batteries, so its very important to minimize consumption.

Functionality - some microcontroller is connected to an IR receiver circuit. The microcontroller is in sleep mode normally, when the IR receiver is sent a signal (from an IR remote control) it will wake the microcontroller, decode the message, perform some task, and then return to sleep.

how should I configure the receiver circuit to eliminate power consumption when not receiving data?

Can I simply use a large resistor to limit the current to something like 1mA when receiving data? (this is to minimize power consumption both when in standby and when receiving data)

5v---10kResistor---/DataInPinOnMCU/---IRReceiverDiode---GND

or

5v---IRReceiverDiode---/DataInPinOnMCU/---10kResistor---GND

Will ambient light cause the IR receiver to complete the circuit and affect the power consumption?

when waking on interrupt, how can I ensure the microcontroller does not miss the beginning of the message?

Thanks in advance

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1 Answer 1

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Assuming an IR remote receiver as used in TV/PVR appliances...

An IR receiver should be continuously-powered if asynchronously-received light pulses are expected...a receiver hobbled by reduced-power cannot detect signals reliably. Choose one that has been designed for low DC-current from its supply.

When no IR light pulses are detected, these devices pull least current from DC supply. Most have a digital output pin that pulls-to-ground when an IR light pulse is detected. An internal large-value pullup resistor idles at logic high.

IR receivers employ internal circuitry that rejects daylight and ambient light. Automatic internal gain-control adapts to IR light pulses of widely-varying amplitude. These AGC circuits might change current draw by a very small amount, not specified in a data sheet.

Serial protocols often employ a pulse preamble. The leading negative-going edge of the very first IR pulse of this preamble should trigger the microcontroller's wake-on-interrupt.
The length of this preamble is perhaps long enough that the microcontroller will be fully awake some time after the preamble starts. Wake-up latency varies from microcontroller to microcontroller and is carefully specified in data sheets. Some microcontrollers allow a choice of wake-up methods whose timing varies from short to long, often depending on microcontroller clock start-up times.

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