We have 40 Watt solar panel which gives upto 18 voltage during good days,We have 12v dc pump which draws 1.86 A..can we use that L7812CV ic to regulate voltage?But max output current from that ic is 1.5A...If we can use that ic,what happens when voltage coming from panel is 11v or less than 12 V?

 

Hello,

Keep in mind that the L7812 regulator needs 2 to 2.5 Volts to regulate.
So with an input voltage of lower than 14 Volts, the output voltage will drop.

Bertus

 

Hello,

Keep in mind that the L7812 regulator needs 2 to 2.5 Volts to regulate.
So with an input voltage of lower than 14 Volts, the output voltage will drop.

Bertus

you mean if output from panel is 11V then only 9v will be available for pump of 12v?...if pump draws more than 1.5 amps then won't that ic be damaged?

 

Hello,

The IC will shut down if there is to much power drawn.
In the datasheet there is a schematic how to boost the current using a power PNP transistor.

Bertus

 

You need a 12V, 2A, low dropout regulator such as this.
It has a dropout voltage of only 0.5V
If the solar panel voltage drops below 12.5V then the output voltage will follow the panel voltage with a voltage drop as shown in this graph;


Note that it will need to be mounted on a good heatsink.

 

When high currents are needed (above 1 amp) it's better to use dc-dc converters.Buck-boost ones keep the desired voltage(12volts) even if the input is above or under the desired output(within limits of course).
For example I have a lipo battery that gives a voltage between 2-5 volts and I need 3.3 volts.A small buck-boost converter will do the job efficiently(above 75%).
Liniar voltage regulator are indeed simple to use and provide unmatchable noise rejection but are highly ineficient.
A liniar regulator's efficiency is calculates as follows:
n=Vout/Vin
Where n is your randament(multiplu by 100 to get percents)

Vin voltage regulator input(higher than Vout with at least Vdropout)
Vout- output voltage
For example if you want to regulate from 15 Volts to 12volt you will have a efficiency of 80%.
And for 1A a power dissipation of (Vin-Vout)*I wich is equal to 3W(watts ).
Even 1 W is a lot of power that is dissipated as heat.
I suggest trying a prebuilt PCB dc-dc converter.Try sites like Polou.
As a side note ...a dc-dc converters efficiency is maximum at the max load curent...look for the graphs to see if it fits your needs.

 

I don't think efficiency is a big factor here since the TS is apparently is only running a motor from the solar panel.
As long as the panel generates adequate voltage and current the only advantage to higher efficiency is to reduce or eliminate the need for a heatsink (which may be a sufficient reason).

 

I wouldnt worry to supply directly to the pump.

These motors usually can take overvoltage and anyway, when loaded, the voltage will break down somehow.

Guess youd need full sunshine to see the pump working at all.

 

hello guys,the maximum current output of L7812 IC is 1.5 amps,our load draws about 2 amps,can we use two L7812 IC and get 2 amps output from it,connecting in parallel ?
or we have to make current booster circuit?
What type of capacitors are used here?
Here 15watt resistor is kept here,is there any alternate for this?

 

hello guys,the maximum current output of L7812 IC is 1.5 amps,our load draws about 2 amps,can we use two L7812 IC and get 2 amps output from it,connecting in parallel ?
or we have to make current booster circuit?
What type of capacitors are used here?
Here 15watt resistor is kept here,is there any alternate for this?

take a look at the example schematics on this data sheet

 

Paralleling those IC is highly problematic and unrecommended...better use the external transistor method

 

You have a 22.3 watt motor. Your panel provides 18 volts at 40 watts. That's 2.2 amps. Just guessing here, but if you run the motor directly from the PVP (Photo Voltaic Panel) the loading of the motor will likely drop the voltage down quite a bit. Likely you won't hurt the motor.

Your panel (at peak daylight) produces 2.2 amps and your motor only drains off 1.8 amps. I see this as working directly without the need of a regulator. Besides, the regulator will waste some amperage as heat. That's why people are saying regulators are not efficient. They convert excess power into heat. You can't ignore the loss.

When the sun goes down the motor will slow because the energy produced by the panel will diminish. The motor will eventually stall when the sun has gone down far enough, but the next day when the sun's energy is sufficient it will start up again.