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Power Transmitter controlled by ProMicro

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ibwev

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MikeMl

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That connection will not work. The base of the PNP transistor switches from 9.0V to 8.3V to turn on the transistor (and transmitter). The port pin on the micro switches between 0V and 5V; see the problem?

You need a "high side switch". Google it.
 

MikeMl

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Here is the basic idea:

D19.png
 

ibwev

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Thank you for the help. I have so many questions. I am going to do some more googling. Is there an "electronic bible" that all electronic hobbyist should read? I would love to have a better understanding of what is going on in the above circuit but I don't know where to start. I understand the role of the resistors and transistors but I don't understand how the above circuit all works together.
 

MikeMl

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Basically: when V(portpin) is oV (logic low), the voltage across the "TX" load is 0V. When V(portpin)=5V (logic high), the voltage across the "TX" load is ~9V. As configured, I am assuming that the TX requires ~100mA when keyed. If it is more, then we need to change some resistor values...

Q2 acts as a level-shifter to get from the 5V at the port to the base of Q1.

The Art of Electronics
 
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MikeMl

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Unless you put proper antennas on both the TX and RX, your next question is going to be "why am only getting a range of a few feet"?
 
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