IR Development Platform

Thanks. Have gotten the boards and the vishay IR and will try to start soldering stuff together tomorrow. getting the UI up tonight. Will probably try to go the speaker route as we only need beeps.

Thanks again for all the advice.

I would love to see how this pans out. Will you be able to upload pics and stuff?

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Sure! once its done. maybe after the rush

I’ve gotten the receiver to work with the arduboy with a sender on a Uno - but I can’t get the sender working on the arduboys. I am using a 100 ohm resistor inline with the led - don’t remember how to calculate the required resistance - I am using this component (http://www.vishay.com/docs/81931/vslb3940.pdf). This worked fine with the 100 ohm resistor in circuit with the uno but doesn’t work with the arduboy.

Using the calculator here https://www.digikey.com/en/resources/conversion-calculators/conversion-calculator-led-series-resistor - if the input voltage is 4.2v and the forward voltage is 1.35 as per the spec sheet with a 40 ma current (arduino output pin max) then resistor value isa bout 71 ohms? is that right? I fly to bangkok tomorrow and the meetings are day after so I probably have one chance to get this right. The circuit is just an inline resistor with the LED, no amplification.

Thanks!

Your calculations are correct, but you would be better to use the nominal output voltage of the Arduboy battery, which is about 3.6V. And, according to the LED datasheet’s Fig. 3 - Forward Current vs. Forward Voltage, at 40mA forward voltage would typically be about 1.25V, not 1.35V.

So, with a 100 ohm resistor and a 3.6V battery voltage, and a 1.25V LED forward voltage, you would get about 23mA.

However, 23mA is close to the current limit that the pin can provide. (The 40mA you quoted is an absolute maximum. At 3.6V you’re only going to get around 25mA). At such a high current, the pin won’t be able to provide the full battery voltage. It could end up dropping down by a volt or so to around 2.5V or less. With a 100 ohm resistor and 2.5V supply from the pin, the current will likely be around 12mA.

But, even at only 12mA, it should be enough for the receiver to detect it if placed close enough to the LED. Are you sure you’ve wired it to the right pin and with the correct polarity?

As the tutorial mentions, you can see if the LED is lighting by viewing it with a cell phone camera or digital camera.

Thanks. Will check once I’m at the hotel. Will rewire the breadboard so the led is pushing on the receiver - they were only maybe 2-3 pin holes apart anyway.

Thanks again.

I can read the voltage varying wiht a multimeter, but the IR receiver sees nothing. Our coder who is doing this with two leonardo boards wired the LED sans resistor and seem to have it working. I have testing it with the uno and the led is working properly in that case so it doesn’t seem to be an issue with mixed polarities. Someone is bringing me some lower ohm value resistors - will experiment with those shortly.

Closing this off topic post, suggest moving it to a general arduino or open source development forum.

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