RENEWABLE ENERGY EVENT
Make a boat powered completely by solar energy and
no other source.
To design an efficient model so that it works in regions
with less light or even regions with no light for
To design a model that will transverse the longest
distance in the shortest possible time.
Circuit diagram of a typical solar engine
About IC 1381
is a CMOS voltage detector IC used to monitor power supply voltage
supplied to microcomputers and is normally used to reset CPUs when
the power supply drops too low for reliable operation or for preventing
runaway operation when the supply voltage fluctuates
, it detects and switches when the monitored voltage crosses the
rated upper and lower threshold voltages. Say for example the output
(VOUT) remains in the logic HIGH state as long as monitored voltage VIN
is greater than the specified threshold voltage Vth. When VIN falls
below Vth, the output is driven to a logic LOW. VOUT remains LOW, until
VIN rises above Vth
The voltage across the capacitor rises slowly as it is charging from the output of a solar
This voltage also appears at the input pin (no.2) of 1381
E. The output (no.1) of 1381
stays low until the capacitor voltage does not reach
So the base of NPN transistor is at
0V, which keeps the motor in off
Now, the capacitor voltage reaches the Vtrip & the output of 1381 switches to 0.8 Vdd
(the solar supply voltage). This turns on the NPN and it starts to draw current from the
capacitor which flows through the motor and causes it to rotate. The capacitor voltage
starts to drop as the motor is running
When NPN turns on, Vce starts to drop and reach a potential of approx 0V at saturation.
This makes the base of PNP
0V via Resistor and PNP turns on.
Ideally, as the capacitor voltage begins to drop and it reaches the Vth of
1381, its output would be 0v to stop NPN from conducting and thus stop the
But since when NPN turned on it also turned on the PNP which started
giving the required base current to keep the NPN on and motor running . So,
at this point the 1381 is out of the circuit. Now PNP gives the required base
current to keep NPN on. This results in even more NPN current due to
amplification by both transistors, but it also starts to drop the voltage on the
capacitor since it has to now supply most of the current flowing through the
The motor draws current until the voltage in the circuit is able to provide
minimum Vbe to keep the transistors on or able to overcome the motor
Now, the voltage in the capacitor again rises until it reaches the trigger
voltage of the trigger element and the above cycle repeats
MODIFIED SOLAR ENGINE
This is an
effective voltage trigger solar engine with configurable turn
voltage and discharge time. The turn
on voltage is determined by the type of
1381 selected & discharge time is determined by the timer capacitor C2.
While the solar cell charges the storage capacitor C1, the 1381 monitors
the capacitor C2 which is also being charged through diode D1.
At this point, the output (pin no.1) of 1381 stays low until the capacitor
voltage does not reach Vtrip
Now, the capacitor voltage reaches the Vtrip & the output of 1381
switches to high state thus turning on the NPN device. The current then
flows out of the storage capacitor, through the motor, through the transistor,
and back to the other side of the capacitor.
The 1381 output stays in high state as long as its voltage is above Vth. Once
the storage capacitor voltage goes below Vth, the circuit goes in off condition.
Suppose there was no C2 & diode in circuit then 1381 would have been
watching the storage capacitor C1, it would reset as soon as the power dipped
But, here 1381 watches the timer capacitor C2 which is blocked from the
power part of the circuit by the diode.
So, it discharges out through 1381 to transistor. The discharging current is at
operating current of 1381 which is of micro amperes, thus giving longer
runtime of motor.
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HOPE TO SEE YOU IN THE EVENT
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