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What's the transmit power of the IR on the CPX?
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What's the transmit power of the IR on the CPX?

by kevinjwalters on Sun Aug 19, 2018 12:56 pm

What's the type of infrared LED and the transmit power (current) on the Circuit Playground Express board? I was pleasantly surprised by its ability to control a remote controlled light bulb without even having to point it directly.

I found the forum post Help designing infrared remote control which looks useful if I want to add more components to up the power.

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Re: What's the transmit power of the IR on the CPX?

by adafruit2 on Mon Aug 20, 2018 2:08 pm

its an Everlight IR95-21C/TR7 or Everlight IR91-21C/TR7

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Re: What's the transmit power of the IR on the CPX?

by kevinjwalters on Mon Aug 20, 2018 3:46 pm

Thanks, I see the datasheets are the same for these numbers, max continuous forward current is 65mA and "Radiant Intensity" is (typ.) 5.0 mW/sr at 20mA. The schematic shows it (D5) without a current limiting resistor. Does it rely on D11_REMOTEOUT only producing very short pulses to limit current and stop bad-things-from-happening(tm)?

I found an Arduino infrared example which is similar and mentions:

Note that the current passing through the LED will in all likelihood will exceed the maximum continuous current rating. However because the signal is modulated and sending a sequence of pulses that will only last a few milliseconds the circuit will work fine.

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Re: What's the transmit power of the IR on the CPX?

by kevinjwalters on Tue Jun 11, 2019 5:19 pm

The "pulse it and do not turn it on for any length of time" discussion for infrared diode can also be found on Circuit Playground shorting? Gets really hot.

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