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Prafull
01-03-2010, 01:02 AM
Hii eveybody..
Please help me...

I need to make a solar boat for a project. the problem is this that i have two options of buying the solar panel which suits my max. dimension of solar panel. one is 6V 300mA and other one is 4V 400mA.(both come under the given dimensions)

Now i am a bit confused about which one to buy.as i need both the speed and torque in the motor to run the race,,
In the event(Solar splash IIT b techfest) i just need to run my boat in a straight track of 1.4 m with 3 halogen bulbs and a dark zone near the end of the track....Please check the length of the track and suggest me to choose either of the panel which one will be better if i use them to power a single motor to run my boat..


Thanks in advance !!!!

vikas
01-03-2010, 01:10 AM
Please give a link of the problem statement.

Prafull
01-03-2010, 01:15 AM
http://www.techfest.org/competitions/torque/solarsplash/
Here's the link....
also...the 6 V 300 mA is giving 1.8 mwatt while the 4 V 400 mA is giving 1.6 mwatt but the latter is giving more current(hence more torque.....since i need my propellor's to run inside the water)...so i am confused what to use...which should i prefer....more current or more voltage or more power....

vikas
01-03-2010, 01:45 AM
More power :) .

Prafull
01-03-2010, 01:55 AM
@ vikas
sir,
someone told me that since the track is just 1.4 m it would be completed in seconds .....and so if I give more torque in the starting it would be beneficial for me as the starting torque and hence the thrust would help me because the race would be only of seconds,so more current would be beneficial.........but then some other told me, like u, that more power would be better .....so what should be explanation for these.....or am i right or wrong for the more torque reason... and would the difference of 0.2 mwatt matter anything????

vikas
01-03-2010, 01:57 AM
which motors are you planning to use ?

Prafull
01-03-2010, 02:05 AM
i am using some dc motors , giving the links
http://robosoftsystems.co.in/roboshop/index.php/solar-robotics/components/mini-dc-motor.html
http://robosoftsystems.co.in/roboshop/index.php/solar-robotics/components/coreless-motor.html
and some more motors from the junk...of voltage rating 3V,6V and don't know about current.....I'll just experiment them in the boat

allbits
01-03-2010, 09:21 PM
> Connect the motor, drive it with your load and see how much current it takes. You are gearing it, right??
>The voltage WILL drop when load is connected. You need good CAPS.
>As vikas said, Power !!!!
>WHat material are yu making the boat?? and the weight?

Prafull
01-03-2010, 09:34 PM
I am not gearing it.....i am using biofoam for my boat....and actually i am using a solar engine(most probably that wud be miller's engine),which stores energy and then gives it to the motor in bursts....and i wud try to make the boat as light as possible

vikas
01-04-2010, 01:59 AM
Why not go for soemthing which will last the entire stretch, than going for bursts ?

Prafull
01-04-2010, 02:20 AM
actually the solar engine(and hence the bursts) are needed because the solar panel will alone not be able to give that much power to that motor to atleast start and run so solar engine is required to collect an optimum energy and then provide to the motor when a particular level is reached as specified by the engine....so now the problem comes that what should I give the engine....more power or more current.....????

vikas
01-04-2010, 02:53 AM
Here is a video ...


http://www.youtube.com/watch?v=YrtygB2tSDc <- traditional boat design is the fastest .

BTW i think a simple cap would do for this race , i think the momentum would anyway carry the boat through the dark part.

docel
01-04-2010, 05:44 PM
The technique in the Video is different: it is just a Solar panel driving a motor.

The TECHFEST solarSplash restricts the Solar cell to 150sqcms. This cannot drive motors continuously and push the boat due to small current output from the cell.

The idea is to use BEAM principles of charge -discharge cycles of a 1F- 4.7F capacitor. This is done by using a Solar Engine, which intermittently charges- discharges a capacitor through the solar cell and active electronics.

The video shows an array of cells. It means that the motor is constantly driven by a number of Solar cells in series-parallel.

@Prafull:

I'm not too sure that the Solar cell will output 400ma/600ma. these are the maximum ratings @ maximum incident sunlight at no load conditions. You will only get a fraction of that current under load andf under a Halogen lamp with varying angle of incidence.

There are 2 ways to to this:

1. Use a SE
This you have thought about and have probably been testing.

2. Use a charge trigger:
This is by charging the Cap fully and discharging it into the motor.
The problem here will be the Time for the Cap to charge. A simple calc of the RC time constant will give you an idea. This is similar to charging a battery to full and then connecting it to the Motor.

Stick with the SE but make sure you have good motors.

vikas
01-04-2010, 06:06 PM
In the video i had pointed hull design , to me simple boat design looked fastest.

Experiments would have to be done to find the best circuit , Also a good efficient motor will help you a lot.


Its also unclear weather that the boat is allowed to charge at the start line, It makes a big difference - you better mail them and ask them this.

docel
01-04-2010, 10:46 PM
That wont be allowed Vikas. It will be equivalent to a Battery if they do.

Prafull
01-05-2010, 12:47 AM
so it means that now I have to think of that, which panel to use so that my SOLAR ENGINE works more efficiently .....so any of u hav that idea of solar engines which can help me in choosing the solar panel....actually i am in grave need of this answer b'coz these panels are costly and i need to buy them online so once I hav decided i cannot step back...so i want my decision to be a good one...

vikas
01-05-2010, 07:27 AM
Here are some cheap ones http://robotz.in/catalog/index.php?cPath=3 , others are selling them at double the cost.

Prafull
01-05-2010, 08:18 PM
These panels are of very low current rating....sorry but I dont think so that these are worth my project.......and also can anyone tell me that where can i find the IC 1381 online at a low cost...I found one in the robosoftsystems.co.in...but its rate is too high including the shipping cost...around 300/- Rs....I have one 1381 but its trip voltage is more than 4 volts and i needed a 1381 with trip voltage less than 4 or 3.5 volts....so is there any way to convert my 1381 into what I need using some resistors or anything....

vikas
01-06-2010, 12:20 AM
I just pointed you to some cheap ones which when made into a panel will give more than the current 6V at 400 mA . There are much more better and efficient ones but they will get expensive .

No you cannot modify 1381 to trip at different voltage , use the correct series of 1381 and you should do fine. Maybe try a zener based one if Rs 300 is too much.