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Use a MOSFET to control the radio

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This commit is contained in:
Rhys Weatherley
2012-06-15 15:07:45 +10:00
parent 30ab66e934
commit 08ba3a7d0f
9 changed files with 171 additions and 166 deletions
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29
doc/alarm-clock.dox
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@@ -38,12 +38,13 @@ Field, SoftI2C, DS1307RTC (or DS3232RTC), Melody and
\li Configurable alarm timeout between 2 and 10 seconds.
\li Single button to activate the back light and/or stop the alarm.
\li Up, down, left, and right buttons to change clock settings.
\li Relay that controls the power to a separate radio circuit.
\li MOSFET that controls the power to a separate radio circuit.
\section clock_main_circuit Main circuit
The main clock circuit consists of an Arduino Uno compatible board, a 16x2
LCD module, a realtime clock chip, and a piezo buzzer for the alarm:
LCD module, a realtime clock chip, a piezo buzzer for the alarm, and an
MOSFET for controlling the radio:
\image html alarm_circuit.png
@@ -59,7 +60,7 @@ clock module instead of a DS1307-based module.
The whole circuit is built on a prototyping shield, with ribbon cables
connecting to the LCD. The Stop Alarm button, piezo buzzer, and radio
relay are not shown in this picture and some of the components are
controller are not shown in this picture and some of the components are
soldered to the bottom of the shield:
\image html clock_shield.jpg
@@ -90,17 +91,21 @@ Arduino designs should also work.
\section clock_radio Controlling a radio
The relay connected to D11 can be used to control the power to a separate
radio circuit so that the radio can be used as an alarm. The relay switch
should be inserted between the radio's power supply and the main radio circuit.
When the relay is off, no power is applied to the radio. If the radio is
powered off 5V, then the relay circuit can be altered as follows to power
the radio directly from the Arduino's power supply:
The MOSFET connected to D11 can be used to control the power supply to a
separate radio circuit so that the radio can be used as an alarm. In the
following circuit, RadioV+ is the radio's power supply voltage (which may
be the Arduino's 5V supply if the radio can run off 5V):
\image html relay_control.png
\image html radio_controller.png
Double-tapping the Alarm Stop button will turn the radio on. Single-tapping
the Alarm Stop button will turn the radio off. A settings field can also
The output of the MOSFET can be used to control almost any kind of
circuit; for example an extremely loud mechanical alarm bell. It doesn't
have to be a radio. A 2N7000 or equivalent MOSFET is suitable for light
loads up to 200mA. For larger currents, a higher-rated MOSFET should be
used instead.
Double-tapping the Stop Alarm button will turn the radio on. Single-tapping
the Stop Alarm button will turn the radio off. A settings field can also
be used to turn the radio on and off.
\section clock_ds3232 Using DS3232 instead of DS1307