Spectacular Butter

Hi, this is supposed to be my final year group project. A solar toy car that can be controlled from a PC.

--About the project---

The solar panel can give around 8-10V output. Then the output goes through a boost converter to charge up the battery (planning to use a battery from the motor bike). The output from the battery will be used to power up the motor for the solar car.

We intend to develop a program using Visual Basic as interface to control the car which communicates with the user using an RF link. The user should be able to control the movements of the car and the car should feedback the status of the car for monitoring.

-----

The planning seems good but the problem is that it seems mighty hard to implement because it involves electronics, programming, communications and mechanical.

We are still in the planning stage but having problems with the car controlling part using RF transmission due to lack of knowledge. Anyone have any experience on this kind of thing? welcome all the helpful advice that i can get.

Attached Images

solarcar.gif (6.1 KB, 587 views)

Nigel Goodwin

Use a pair of licence free radio modules, you can either use the basic modules and encode yourself using PIC's (or similar), or you can buy more expensive ones with coding built-in, these simply accept RS232 style serial data. From your point of view I suspect the more expensive serial data versions would be better, as it's one less thing for you to do.

Have you evaluated the performance of your solar panels yet?, I suspect you are going to require pretty large ones!.

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Russlk

You can get 433 mhz transmitter and receiver from Qkits (http://store.qkits.com/), the price is under $10 each. Small and efficient antenna is available from Mouser (www.mouser.com), part number 240-4311-121-20043.

Mouser also has RS232 modules.

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Electric Rain

I like these guys myself: http://www.rentron.com/PicBasic/RemoteControl.htm They walk you through every step. :wink: Their prices aren't bad either.

Rain

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williB

You dont need the DC to DC Converter..
here's why..
the solar panel output is more like 12-15 V ( mine was 18V no load)
and will adjust itself to the battery that you are charging..
what is the voltage of the battery in question 6V ? 12V?

Russlk

Even if the battery is 48 volts, you are better off to increase the solar collector voltage than use a DC to DC converter which will waste power.

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Spectacular Butter

Thanks for the advices.

The cheapest solar panel that we can find only provides around 8-10V. The battery would be around 12V. Therefore was planning to use a DC/DC converter to boost the voltage. Is there another workaround to this problem?

Oh i am also very new to the remote control concept (that's why i am an electronics newbie ops: ). So am i supposed to get a transmitter that can connect directly to my pc using serial or parallel port? There is such a thing right?

How do i control the movement of the wheels? Where to turn etc... I heard that i should use a servo motor instead. Does it turn according to the servo motor or the servo motor turns to activate some circuitry that allows it to turn in a certain direction?

Sigh... so much to read and learn.

Nigel Goodwin

I asked above if you've evaluated the performance of the solar panel yet?, I'm presuming you haven't done so? - I suggest you do that before you do anything else, you may well be VERY disappointed how many panels you're going to require!.

Not usually directly, an RS232 port uses +/-12V, the serial connection to a transmitter is more likely to be 0/5V - you use a MAX232 (or similar) to connect the two. But you need to ensure you get radio modules with processors on board that allow you to use simple serial connections.

If it's got conventional car steering, you normally use a servo, for tank type steering you use differential steering with a drive motor each side. I would suggest you try looking at 'proper' radio control cars (not the cheap toy ones), such as those by Tamiya - probably one of those would make a good host chassis for you!. Servos are easy to use, they just require a variable width pulse every 20mS, the width of the pulse tells the servo where to turn to.

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williB

speaking of cheap toy ones .. i got the chassie for my robot car from K-Mart.
$10.00 american and it came with a simple radio control to boot.!!

Spectacular Butter

Yikes. I am only getting the solar panel in a day or two because it costs $$$ and we have limited budget. Besides testing the output voltage, what else do i have to test on?? Current? How do i know how much current i need to run the whole thing?

Thanks again for all the helpful advice.

Nigel Goodwin

Yes, you need to know the voltage and current (the power) it will provide under the lighting conditions you plan using it under - the specifications are usually highly optimistic, based on the absolute maximum amount of light falling on the panel - my usual comment is 'think sahara desert at midday!'.

What are the provided specifications for the panel?.

As for the current required, it depends on a great many different things, and also what you require from the finished device. As it's going to contain a rechargeable battery you could let it charge all day, then have ten minutes running time - but if you require the panel to provide power for the unit continually, it will need to provide more than the complete power requirements of the unit.

For a start I would do two things:

1) Find out how much power the panel can supply.

2) Measure how much power the rolling chassis is going to require, bearing in mind increased load will increase motor consumption drastically. Measure with different weights on the chassis, and climbing up slopes. The rechargeable battery will provide the extra power for high loads, but the solar panel needs to provide enough to drive the unit normally, and have enough over capacity to recharge the battery.

This should give you some indication of how much power you may have left (if any) for the electronics involved!.

For an educational project it gives lots of scope for interesting design possibilities, marks will probably be improved by including the design challanges you meet, and how you overcome them!.

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Spectacular Butter

Newbie questions on RF.

1) How do i know how much frequency do i need for my design? Do i really need to go up to MHz if my transmission range is around 7-10m?

2) Will any antenna suffice for a 10m transmission?

3) Which do you think is better? AM or FM?

thanks