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I'm building an IR blaster with an LED that will be wired 50 feet away from the circuit. I'm going to use this 18 gauge wire to extend the LED connection.

I'm using a GPIO pin connected to a BC547b transistor. The Pi and circuit will be kept together. The LED will be 50' away from the transistor and other components.

The LED works fine when it's powered by the Pi but I'm assuming 50' of wire will have significant losses and the Pi's power won't be enough. I'm OK with an external power supply but it'll need to be close to the Pi and the rest of the circuit. So, the power will be sent over the 50' of wire.

Would a 5v 0.5amp power supply be enough? How would that supply be added to the circuit?

EDIT: My schematic is wrong (transistor is NPN) but the physical circuit is correct and working.

Thanks!

Schematic

Michael Khalili
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    The Pi itself seems to be irrelevant to the question. – joan Jan 03 '20 at 18:32
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    BC547b transistor is PNP transistor ? I don't think. You 'draw PNP transistor' here your base is connected to the Ground. – Ephemeral Jan 03 '20 at 19:12
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    @Ephemeral - The transistor is NPN. I'm just learning about circuits and drew it wrong. – Michael Khalili Jan 03 '20 at 20:04
  • @joan - I'm new to electronics and figured the Pi would be important. Maybe the power would be enough? Maybe the GPIO signal can't handle this design? Who knows? I sure don't. The Pi is driving this circuit, so I'm asking here. – Michael Khalili Jan 03 '20 at 20:07
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    @MichaelKhalili, no problem I learn also – Ephemeral Jan 03 '20 at 20:38
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    @MichaelKhalili, you can check my question and the answers on electronics stackexchange about GPIO and LED driver, calculate your wire resistance and the include it into power consumption of your circuit. (I calculate ~0.3 Ohms for 50 feet or 15.24 meters of 18 AWG). You can post your question on electronic forum it is more appropriate. Also specify what is your LED specs ? – Ephemeral Jan 03 '20 at 20:54
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    Hio @Michael Khalili, Welcome and nice to meet you. Ah, let me see. Using 50ft long AWG18 wire to drive BC547 is a bit amateurish. I am afraid the Anono guys watch our discussion would LOL again. Some brain storming suggestions: (1) Use low speed (96008N1) 5V/12V UART to do long distance (up to 200 ft) serial communication. (2) Instead of single transistor, use cheapy UART IR transciever modules for prototyping, (3) Do not use newbie scary LIRC, which is for hackers only. You might like to read the following discussions: / to continue, ... – tlfong01 Jan 04 '20 at 03:20
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    (1) https://raspberrypi.stackexchange.com/questions/103452/rpi3-lirc-library-and-uart-ir-transceiver-setup-problem (also read the chat record) (2) https://raspberrypi.stackexchange.com/questions/104201/rpi3b-buster-usb-to-serial-dev-ttyusb0-communication-problem

    (3) https://raspberrypi.stackexchange.com/questions/104554/lirc-tutorial-for-rpi2b-buster-too-old-problem

     – tlfong01 Jan 04 '20 at 03:21
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    I forgot to mention that it is not practical to use plain wiring for 250kHz transistor communication, because you would pickup too much noise along the wires. UART serial is designed for long distance, and at 5V or 12V, and low speed 9600baud, there won't be too much noise problems. One more thing, you don't need to use any commercial (NEC etc) IR protocol. You can start playing with sending serial 9600,8N1 High, Low, High, Low IR signals and see if heard a the other side. Then you can use Rpi to DIY building up UART based talking standards. – tlfong01 Jan 04 '20 at 04:02
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    @tlfong01, what is typicallly the noise in wire , the wire act same as an antenna and AC current can be induce ? Who are the Anono guys :) ? – Ephemeral Jan 04 '20 at 06:00
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    @Ephemeral - I created a new question there with more details and a correct schematic https://electronics.stackexchange.com/questions/474553/do-i-need-additional-power-for-an-ir-led-diode-50-feet-away-from-a-raspberry-pi – Michael Khalili Jan 04 '20 at 15:41
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    @Ephemeral, usually line noise (might pass through ground line, not the positive wire) is of the order 50mVpp. But there are surges, spikes etc to consider. If using the cheapy UART interfaceing IR transceiver pair for protyping, I would recommend to use single or double shielded DB9 cable, or twisted cable (CAT5). And noise is not the only problem. Long wires are usually inductive (picking up noisce) but also capacitive. Capacitance varies with frequency, so 9k6bd is OK. I am not sure the OP is passing IR frequency which might make the whole thing a big capacitor. – tlfong01 Jan 05 '20 at 02:23
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    @Ephemeral, My I2C projects using only short wires less than 1m, 100kHz to 400kHz, hits the 400 pF limit, already causing me big trouble. Just a quick, not proof read reply – tlfong01 Jan 05 '20 at 02:23

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