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I have one of these transmitter modules attached to an Arduino Mega and currently powered by the Arduino Mega 5v pin. I have locations that cannot receive the radio transmission because of lack of power so I need to boost the power transmitted and wish to transmit using 12v power supply.

It would have been easier to append this question to this post. However I can't do that because I don't have enough points.

Questions;

  • I see that this circuit will work. Can someone recommend a specific component / characteristics for the transistor. T1 NPN seems to me a genetic type.
  • Can someone recommend a specific (240vac to) 12v supply. (I can remember V=IR and the basics of Ohms law but can't remember what determines how much current is drawn by a load).
  • It seems to me that a mains powered 12 volt supply and arduino board ground should not be mixed, so how do I wire this up? Is it a case of simply attaching 12v -ve terminal to GND as shown in the circuit?

ps for switching speed considerations, my Arduino transmission pulse/ pin is typically 275uSecs HIGH then 115uSecs LOW (or in reverse order). Mostly I shoot 25 of these sequences at once. Then I have some slower pulses at 1168uSecs HIGH and 397uSecs LOW.

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    \$\begingroup\$ It might have been easier, but it would have been very wrong to add it \$\endgroup\$ – PlasmaHH Jan 14 '16 at 10:53
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    \$\begingroup\$ @PlasmaHH that sentence to me reads as "I have, in fact, not read the rules before I clicked accept and/or posted and only just said I did". \$\endgroup\$ – Asmyldof Jan 14 '16 at 10:56
  • \$\begingroup\$ Gentlemen/ Ladies, It's there for the caveat which is "answered a million times already". Looks Like I was not able to win that one. Any answers? \$\endgroup\$ – Kes Jan 14 '16 at 11:03
  • \$\begingroup\$ Go for a BC547 and if you can't get them where you live, please make a long list of every NPN transistor you can get. \$\endgroup\$ – Andy aka Jan 14 '16 at 11:03
  • \$\begingroup\$ Thanks Andy. Do I simply attach the 12 volt -ve to GND? Any ideas about a power supply? \$\endgroup\$ – Kes Jan 14 '16 at 11:12
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  1. The supplier of that transmitter/receiver set has let you down. There is no useful documentation that would allow you to figure the power consumption. You will have to guess how much current it will draw.
  2. Specific recommendations for a product aren't allowed here - nobody is going to say "buy model X power supply from supplier Y."
  3. Looks like your highest rate is around 2.5kHz, so you should be fine as far as speed is concerned with the level shifter.

I'd just go with a 12Volt wall wart that provides 1A. It is probably too much, but it won't cost much more than a power supply rated for a lower current. Once you have it running, you can measure the current draw and see how much it really is and maybe switch to a smaller power supply.

Do you have antennas on the transmitter and receiver? It might help to experiment with the length and placement of the wire.

Just connect the negative lead of the power supply to the ground on the transmitter and to the ground on the arduino.

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  • \$\begingroup\$ Thank you :) I am not using the receiver that comes with the transmitter, I'm sending to sealed energenie wall sockets and other sealed 240ac wall switches. I will consider opening these and experimenting with the antennas. Thanks; good thought. The 12v 1amp wall wart and an assortment of transistors including the BC547 is ordered. Thanks everyone :) \$\endgroup\$ – Kes Jan 14 '16 at 12:24
  • \$\begingroup\$ @andy-aka Andy, Hope an assortment of transistors including the BC547 meets your requirements of a list! :) \$\endgroup\$ – Kes Jan 14 '16 at 12:25

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