Have you tried to measure the soil resistance using a multimeter? Just to see if the specimen or the system using resistance works.

Btw, has anyone here tried to make closed loop speed controller from a normal DC motor and self made parts? Meaning that we can run the DC motor at specific speeds even with variable load (within tolerable limit). I've always been fascinated by the Micromouse. But I've always stuct at that part. Never had enough motivation to go around doing that these days....

This post has been edited by elm383: Mar 5 2009, 03:33 PM

That part I know.. whats the motor for?

this is the idea of the project... this is how it basically work's

Basically there will be a grounding electrode between the measuring rods.. My objective is to lower the soil resistivity in order to maintain the resistance between the grounding electrode to soil.. This is important in order to maintain grounding electrodes resistance at an acceptable range.
So the measuring rods gives me an indication of the soil resistance (this is not a valid measurement since its not the 4 pole testing arrangement) but it gives me an indication.. Meaning that at this point the grounding resistance is at an acceptable value. So when ever the resistance between the rods goes above this value.. my valve need to be open and sprinkle the solution on the test area.. And it should close when the resistance between the rods decreases to the earlier acceptable value. So my control circuit only powers the valve to open and close.. Meaning the water pump is powered by a separate power supply.

oo..interesting stuff. hav u got it patented? =p
sounds something useful for d agriculture stuff

dello,

what is the U1 opamp doing?

i think it is better to separate the motor control circuit and the resistivity sensing circuit.

make ur U2 opamp into an upper bounded comparator that output on or off signal into the motor control circuit.

as u asked why the voltmeter didn't work, i couldn't see a problem with the voltmeter part of the schematic. try to make a measurement to make sure the voltmeter is fine, and proceed to verify ur component one by one.

if you're building the prototype using breadboard, make sure all components is inserted properly that they are completely a closed circuit.

I have a better version of the circuit... wat do u guys think about this..are the components easy to obtain? where should i put the voltmeter in between the probes would be fine right?

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Added on March 6, 2009, 5:00 pm

I tried making this circuit on multisim... can someone verify that its similar to the original circuit above...

http://www.fairchildsemi.com/ds/LM%2FLM311.pdf here is the data sheet for the comparator.. are they way i connected the pins right? im unsure coz im still a newbie in electronics

This post has been edited by dello: Mar 6 2009, 05:03 PM

Yeah.... It is the same.

Why do you draw it out on Multisim? I assume that you can't test the circuit using software since you cannot input the soil into Multisim.

Why don't you just build the circuit and test it?

i tested it in multisim..it works.. the soil can be assumed as just a resistance.. so can realize this using a resistor.. thats how i tested it

Then start building it. Tell me if it is working.

If you can't get LM311(which i don't know if it is hard to get), you can always use other voltage comparator like LM339 or LM393 (which is easier to get)

i hv done it already.. it works... the output are also working..

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Added on March 8, 2009, 11:47 pmnow need to build the circuit in real... and need to do some measuring for the soil.. how long will it take me to interface the reading to a pc? is it complicated? any comments

This post has been edited by dello: Mar 8 2009, 11:47 PM

Hi all....please let me know if i am in the wrong forum....hope you guys can help me out

I am building a space craft and wanted to add a couple of led lights to it. Its a simple circuit connecting the led lights to 2 AA batteries. I need help on how to make the led blink with an interval like those on commercial airline...

Thanks in advance

You can build a spacecraft but dont know how to build a blinking circuit? jk

Try google for "RC circuit LED", or "555 Timer LED".

engineer and electrician different mah....
hey bro thanks ...hope this things can get at jalan pudu

Or you can rip the RM3 to RM5 led torch lights... some which have intermitent functions

hey guys, just to ask some questions....i'm trying to make a SMS controlled application which i'll b able to turn on/off home appliances by SMS, if i wan to write it in assembly language (.asm) which software is recommended and have any source of downloading it? thx, FYI i'm doing it with PIC16F873A, GSM modem, controlled by RS232 interface. If u guys happen to have the source code of it, mind to share?Thanks

This is a typical final year project. I know there are people who are willing to get paid to do this project for you.

PIC16F873A is a microchip product, try download MPLAB from microchip website. It’s a free assembly software and compiler.

You should be doing your research, and generate your own source code…. No offense, but this is as much as I can help (unless I get paid if you want free info )

Haha,thx for the info bro,yup it's a final year project, and i guess i'll be taking ppl's source code to do editing, due to the fact dat engineering students (not all, but most) suck at programming ....anyway, MPLAB huh?ok will try 2 dl it, how about MikroC does it supports ASM?if yes...can teach me?thx

mikroC is a C compiler, using C language, not assembly. I am not familiar with mikroC codes, but generally it should be identical as other C compiler. I am using PIC C Compiler.

C is easier than assembly, why not use C?

I assume that your uni use mikroC product and programmer?

Hi guys,

I'm in need of a Gogo Board in my project.

I get to know tis board thru my friends and online : http://www.gogoboard.org

But I can't find it in electronic stores.

Does anyone know where I can buy the board in kl or selangor?

Plz guide me...thx a lot ^^

OOh... a live-size... 1:1.. robot-girl... walks like a zombie though... cost USD 200, 000 (like an expensively taxed euro car) by Honda...