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I have this 433 MHz transmitter attached to my Arduino 5v Vcc pin.

I asked this question so I could deliver 12v to the transmitter chip, effectively boosting the transmitted power output, allowing me to reach the furthest corners of my house.

To prevent continually powering the transmitter; transmitting 433Mhz low level noise all the time around the house I have added the box outlined in yellow. This yellow box contains a very simple circuit with one transistor that only turns on power to the transmitter when the arduino 5v datapin goes high.

Can anyone suggest what the simple circuit in the yellow box should look like, particularly which transistor.
Circuit

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  • \$\begingroup\$ Is VCC at 12v? Also you have a potential difference of 24v is this correct? \$\endgroup\$ – Dean Jan 21 '16 at 9:33
  • \$\begingroup\$ Thanks @Dean That made me think about it, my diagram is wrong; -12v dc should read 0v dc. \$\endgroup\$ – Kes Jan 21 '16 at 11:20
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The circuit in the yellow box is not as plainly simple as you think because, you want power to be switched to the RF module at the beginning of a data stream and power to stay applied (despite data changing up and down) and then finally, after a short period after the data has finished, you want power to become removed.

This is basically the function of a retriggerable monostable: -

enter image description here

You have to decide how long a gap might exist in your data that you want to to keep power applied for. When you have determined this then you have to ask yourself if, after the data has completed, will this "excess" time at the end of the transmission be a problem. If it is you have to find a different mechanism for controlling power.

If you are OK with this then you might consider using a timer chip like so: -

enter image description here

Taken from here. Clearly you need to then attach the output to a transistor to control power to the radio module. I'd consider an N channel MOSFET that switches power to the negative connection on the RF module. Choose something with quite low on-resistance. If you don't want to go this route and still prefer top-side switching then a P channel mosfet is also good but, you'll need to invert the output of the CD4047 (or use pin 11 instead of pin 10).

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