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Remove voltage monitor logic - no longer relevant

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Rhys Weatherley
2012-06-15 14:42:46 +10:00
parent f5f4282e1a
commit e9a5287b32
8 changed files with 1 additions and 433 deletions
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doc/alarm-clock.dox
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@@ -119,59 +119,3 @@ as follows:
\li BAT, 32K, and RST left unconnected.
*/
/*
NOTE: The following has been commented out for now. More work is needed
on the wind-up power supply.
\section clock_power Power supply
This section describes the power supply for the wind-up alarm clock,
which consists of a hand-cranked dynamo, a 3.6 volt NiMH battery, and a
charge pump DC-to-DC converter to boost the voltage up to 5 volts.
Here is the circuit:
\image html dynamo_power_supply.png
The dynamo must be based on a DC motor rather than AC (bicycle light dynamos
are typically AC). If you are using an AC dynamo, then replace D1 with a
full 4-diode rectifier bridge to convert the AC into DC first.
In Australia, <a href="http://www.jaycar.com.au">Jaycar</a> sells a suitable
<a href="http://www.jaycar.com.au/productView.asp?ID=MD7000">DC dynamo</a>.
Diode D1 stops the voltage in the battery from flowing backwards into
the motor. If you hook things up the wrong way around, then the motor
will spin without being cranked! In this case, reverse the + and - leads
on the dynamo and try again.
After D1, the main energy storage for the circuit is the 3.6 volt NiMH
battery (at least 1000 mAh capacity). These are commonly used in
cordless phones and can be obtained from most consumer electronics stores:
\image html battery.jpg
The main part of the circuit is next, consisting of a MAX619 regulated 5 volt
charge pump DC-to-DC converter chip. This chip boosts an input voltage of
between 2 and 3.6 volts up to 5 volts and regulates it into a nice flat
supply for the rest of the alarm clock.
Note: the MAX619 has a maximum rating of 3.6 volts, but when the dynamo is
being cranked rapidly the voltage at the cathode of D1 can spike to 4 volts
or more. The battery is fine with this for short periods of time,
but the MAX619 won't be happy. Hence the forward voltage drop on D2
is used to drop the supply down by 0.7 volts which will keep it within
the MAX619's input range. If the dynamo is rated higher than 5VDC,
then add extra diodes at D1 to drop the voltage down before it
hits the battery.
For normal uncranked operation the battery will need to be between 2.7 and
3.6 volts. If it falls below 2.7, then the battery is considered "empty".
A diode with a smaller voltage drop can be substituted for D2 for longer
operation times as long as the maximum dynamo output minus the voltage
drop is less than or equal to 3.6 volts. The "Sense Battery Status" output
is hooked up to an analog input pin on the Arduino to let it monitor
the battery voltage and display the current status to the user (after
adding 0.7 to account for the voltage drop on D2).
If you don't have 1N4001 diodes to hand, then 1N4004 will work just as well.
*/