How to add a 12 V power to Arduino?

Using Arduino Motors, Mechanics, Power and CNC
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I know this is a old topic. But I found it is am still full of questions/

So my project contains a 315MHZ transmitter and a 315MHZ receiver. The receiver connects to 5V which provides by the board through USB.

Now I want to feed 12V to the transmitter. Since the uno doesn't have a 12V pin, I use a separate power adpater to provide 12 to the transmitter. So the GND and VCC of the transmitter connects to the 12V, and the third data pin to connect to UNO. It works but it affects the receiver, which doesn't work.

I think for both the receiver and transmitter to work, they should use the same GND, but when I measure the GND of the 12V and the GND on the uno board, I see a 0.8V difference.

The uno can have a external power, but I wonder if I connect to it, how will it work with the power from the USB?

Any idea? Thanks

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The Arduino Uno has a raw power input (the barrel jack) that accepts 12V. The same power supply can also be used for the transmitter.

All grounds must be connected together for your circuit to work.

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jremington:
The Arduino Uno has a raw power input (the barrel jack) that accepts 12V. The same power supply can also be used for the transmitter.

All grounds must be connected together for your circuit to work.

Two questions:

1, There is no 12V pin on uno, where to connect even I plug a external power to uno?

2, How uno decide which power to use? the external or the USB's? is that true once external power connected the USB's will be disconnected?

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The barrel jack is the "12 V pin". You need a barrel plug to make the connection.

Why not read the Arduino introductory tutorials?

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jremington:
The barrel jack is the "12 V pin". You need a barrel plug to make the connection.

Why not read the Arduino introductory tutorials?

I ask here because I could not find the answer.

I know the barrel jack is 12V, but I cannot connect my component to the barrel jack directly, right? I don't see any pin there marked 12V. I only see 5V

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You connect a 7-12V power supply to the Arduino, using a barrel jack.

Barrel jack:

600×600 66 KB

Using wire, you can connect the SAME power supply to other things in parallel.

Use your imagination.

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315Mhz transmitters work between ~3-12volt.
Did you try if you have enought range if you power it from 5volt?
Leo..

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Wawa:
315Mhz transmitters work between ~3-12volt.
Did you try if you have enought range if you power it from 5volt?
Leo..

I am using 5V, doesn't have enough range, and connected to 12V, worked fine, but made the receiver on the same uno failed to work. So I am looking for using 12V on transmitter and 5V on receiver on same uno

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jremington:
You connect a 7-12V power supply to the Arduino, using a barrel jack.

Barrel jack:

600×600 66 KB

Using wire, you can connect the SAME power supply to other things in parallel.

Use your imagination.

Ah, finally understand, it is the VIN that connects to the external directly. Thank you very much

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You need antennas on both the transmitter and receiver for good range.

23 cm of straight wire works for 315 MHz.

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jremington:
You need antennas on both the transmitter and receiver for good range.

23 cm of straight wire works for 315 MHz.

I used a TV coax cable, cut to about 50 cm, and stripe one side out of shield and plastic for 23 cm. I build one for receiver and one for transmitter.

My garage is 35 meters away, seems the transmitter works fine with the antenna under 12V power. But the receiver cannot receive in that distance. Now I have no clue how to make the receiver better.

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Did you fold back the shield of the coax, so you have a ~46cm 'sleeve aerial'.
And is the oriention of the transmitter aerial the same as the receiver.

Thin 50ohm coax with braided shield is easy to use.
Leo..

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If you power up a transmitter next to a receiver for the same frequency, you are most likely to deafen
the receiver.

Which modules are you talking about - the OOK ones?

Normally if you want to transmit and receive a transceiver is used, with transmit normally disabled
completely. Thus the receive side can be listening most of the time. This is half-duplex communication.

Note the need to completely disable transmit - just having the transmit oscillator idling can deafen
a receiver, as the ratio between transmit power and receive power can be around 10 to 20 orders of
magnitude - imagine listening for mosquitos while operating a power-tool and you'll get some idea of
the difficulty!

Being able to switch the 12V to the transmit module off in-between transmissions may help.

Using more advanced modules like RFM12 transceivers or similar will have many benefits.

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