Hey Shashijoseph,
I am using 10K resistors to the base of the transistors. But I sorted out that relay problem today. There was a small communication gap b/w me and my friend who did the worng on the relay and the port pins were wrongly connected. Corrected it and it worked like a charm.

The only problem on my hands now is the HIH4000 which does not seem to be giving correct readings. Can you suggest something in this regard?

Hi Amit, received your mail, sorry for the delay
About your problem, remove the sensor and put a 10K pot and generate the same voltages, as would be by the sensor, at the I/P of the ADC. Check for OK operation by your uC cct. If all OK, check for dry solder, loose GND line, signal & supply etc for the sensor. You may require to decouple the O/P by a 0.1uF capacitor. Avoid long leads, otherwise use screened wires. If the sensor is not spoiled, these should solve your problem. Best wishes.
Take care for static charge buildup while handling IC's specially sensors.

Hi Chiru,
Pls dont apologise!!!
Well my uC ckt n code is fine. All my sensors work fine and for the voltage o/p of the sensor (when checked with multimeter) the reading on the LCD is correct.
I have connected teh sensor to a 3 pin connector which is soldered to the pcb. This I did to avoid damage due to heating while soldering.

I removed the sensor and tried to check it by putting it on another 3pin conector and provide Vcc, Gnd and checked the o/p, the variation in o/p while moving it or bringing my hand close to it or air from a fan! When the sensor was new i had tried it out with the same supply (trainer kit supply)

But now it does not work! Is it broken :'(

try checking one thing,connect ony the supply to the sensor and check the output voltage with a multimeter with the sensor kept hanging in free air.. now check the corresponding humidity value to that output voltage. cross check it with the actual relative humidity of ur atmosphere with another hygrometer(u may be having one in the lab). (do not bring ur hand near the sensor). if they match, then i think the sensor should be o.k. else i think u have a serious problem with the sensor.

Hey pdi,
well i tried checking the sensor by separately connecting it to supply and on different days the o/p voltage was different (and close to the max humidity values specified in the days newspapers) but the sudden variation when air is blown on it or bringing my hand close to it is what is disturbing me because during the demo for my exam those nutty evaluators will love to play around with the stuff!

Dont have a hygrometer in the lab but i think someone i know has a commercial (small time) humidity meter with LCD display so i can try it out with that i think and will post my finding asap.

Else i think i have no choice but to either fight with the dealer for a replacement or worse, buy another one

wel, it may seem odd, but i have seen humidity readings change (very drastically) of a humidity sensor if it is brought in contact with hot air especially if the sensor is fast acting (capacitive humidity sensor in my case). So maybe....just maybe, that the fluctuations u are sensing is actually the true change in humidity of ur sensor as the sensor u are using is fast acting if i am not wrong.

Hmm that is a possibility, but why should the humidity change by just bringing my hand close to the sensor? And i was using an AC cooling fan (.1A) to blow air onto it and the humidity reading jumped by almost over 20%. Now aint that wierd! especially because when it was new, even after blowing on it (that should be quite humid) its o/p dint change!

Well i dunno wat to do now. Il try comparing its reading with another RH meter or something and if it doesnt work out il just buy another one

Should i take any special precautions while using the new one? Any fuses or current limiting resistors etc? I dont have any anti static gloves els i would use them. Btw forgot to mention i was storing the HIH in a plastic airtight bag...

Hi Amit, I went through all the findings you have stated about the humidity sensor, and strongly feel that the sensor is fine .
Mind it, this particular sensor is with amplified output and as such linear humidity sensors are very delicate devices.
You should not handle (mishandle) it for demonstration, need to device some way to show change in humidity .
Being said all these, I can only wish you good luck.

Hey Chiru,
Nice to hear from you after a long time.
But tell me one thing, why do u feel the sensor is fine? I feel it has gone bad because the o/p immdiately jumps to a higher value when u hold it, move it, bolw air on it(from a fan, not self ) or even in a closed container(with silica gel in it also!)

The dealer from whom i bought seems to be a really conked up establishment and am unable to even buy it now, forget asking for a replacement!

Need to do something desperately.

The proj is working fine now except for the HIH4000. Also sometimes the relays turn off when they must not and then turn on again, the base voltage of the transistor is fine there dunno wat exactly is wrong, probably some interference or carbon formation at the relay coil i am assuming!

The rest is fine. Working on the beautification part, il post pics aft its done and even submit the proj here. Working on the report now All this is so boring! 14th is my internal examination for the proj!!! hoping for the best.

Thanks once again guys

well you will get appreciation for your work as you have done everything yourself. You should not worry. Your hard work will show up Best of luck!
Everything will be alright, have faith in you and your project

If interested do share it with us after you finished.

Hey Ajay,
Thanks alot for ur support al this while. I will certainly upload the entire material once am done with the exam. Without this forum i really donot know how I would have completed it!!!
You are doing an amazing job! Thanks once again.
Just a few more hiccups need to smoothen things out and its gonna be perfect i think. Just that humidity sensor is giving me trouble now.

Well this album link has some of the snapshots of the so far completed prject of mine. Pls do have a look when u get the time and post ur comments. Il upload detailed snapshots and other material when the whole thing is completely completed

http://picasaweb.google.ca/amit.radhakrishnan/GreenhouseProject

Pls do have a look, looking forward to ur comments and suggestions.

Awesome Work!!!!!

Must have this on forum so others can comment too

Thanks Ajay

gr8 work ... keep it up!

I am Impressed by your neat and systematic work.

Hey thanks a lot
A lot of credit for it reaching this stage goes to all of u at this forum and my lab foreman, Mr Ramesh

Really well done.....

If I were to do it,the actual hardware would get 'embedded' somewhere beneath a dense foliage of unmanageable wires.

Thanks Sashijoseph,

Tried as much to keep it as neat as possible! After all the evaluators who come are more impressed by looks rather than the work!

Working on the report now and waiting for my new HIH to arrive from the dealer.

Got my internal assesment of the proj on Wednesday that should not be much of a task... hoping for the best

Thanks once again guys

you deserve it

Good job done, Amit, congrats to you and your classmates.
These hard work will payoff in your future. Good luck.

Hey thanks a lot
Had my 1st demo today. ppl liked the idea and we were able to answer al qestions thrown at us, but we were told our "product" is a failure and "ppl wont buy it" because we dont have a facility for the user to enter the threshold levels into the uC and they are pre-set. Thus it is not a flexible system.
It sounds absurd cos, firstly, we are not designing a "product", its just a prototype of a concept! Also, the Embedded system prof who asked this had this concept fixed in his mind that thresholds must be in registers only and not in code ROM.
I tried explaining that if we use the RAM the user wil have to enter the 10 - 12 threshold levels everytime the system is reset or turned off. to which he said, store it in the rom and then put it in registers!!!! how absurd can one get!!!

Tomoro i have my demo and presentation for 70marks. pls tel me if there is an answer to this question! i am perplexed...

Looking for some expert advice on handling this kinda wierd questions!

Also, we were told we have no fault detection system so if any of our sensors go bad the system should have a detection and intimation system in place! that is a valid point... dunno wat to do bout that

o.k. o.k.. well, the inpectors were right to some extent, but what do they expect from u? A full fledged marketable product?. well,they should know that there are some limitations as far as a student knowledge is concerned. So don't worry. The extent of work u have independently acheived is far from ordinary and definetely not substandard and i can assure u only a few students can even think of attempting such a project independently.

As for the threshold levels jus tell them that u can store it in the eeprom if it is connected externally via I2C interface (a 24c02 would be sufficient in ur case to store 10-12 parameters).as far as flexibility si concerned, u can just convince them that adding a few keys to the uC and addition of some code can make the user input the 10-12 parameters . The procedure to write code is lengthy ad may take a lot of time so better try it if u are interested after ur submission. As for the ROM is concerned it is easy to store and fetch data from the ROM (using the movc instruction). but it is very difficult to change that data from program memory( it is possible in a rare few derivatives of 8051 and is called in circuit programming ICP).i hope that is explanation enough for ur queries.

and yes, i forgot to comment that ur project (the image ) is praiseworthy and extremely neat (almost professional) ) I wouldn't be surprised if ur inspectors would give ur team some brownie points on that one . good luck.

welll... u shud not be disheartened...

but what the inspector told u was an important aspect of your project..
projects in BE shud not only be prove of concept like...
u shud accept any suggestions offered with open heart..

but i do beleive he must have been impressed by ur work... though he didnt say it aloud!

aprt from honeywell is there any gud "humidity sensor" available in the market??

m working on greenbee pro.. m nt getting rquired o/p voltag in soil moisture sensor.. cn u pls suggest me ny circuit.. !!!! or is thr ny sensor available whc cn be used directly...??

thanks...

Hi priya
Wow nice to see this thread again after long. But I was hoping that I have asked the silliest of questions here at this thread that any one who reads it will get all the answers!
Regarding the humidity sensor, that is only one i could find in the market (well that is quite difficult to get too). Where are you located? I could give you teh address if ur in bangalore. I think some one had suggested alternate sensors in this thread during the initial days, pls do check if you can find it.

Coming the soil moisture sensor, the o/p voltage need'nt be fixed, you can modify the threshold values depending on the o/ps you are getting.
The o/p depends on a number of factors, like the type/ thickness and length of the probes, distance between them, the type of soil, depth at which they are placed etc. So choose the most optimum combination. Also let me warn you that the soil mositure sensor is the most dicey-est sensor in the entire setup. But it does work and I had got the circuit from a site by a person by the name Rob Faludi. He is using thi scircuit for a commercial product (so he claims)

Good luck hope this helped you and do ping me in case you need any more help.

ps: is the code working?

thanks amit.... i went thru this thread... n it seems u hv really worked hard on this pro yaar...... it reflects in ur marks ..
n if u say ur quests r silly then mine wud be sillier than u..

i live in indore (m.p)... honeywell is nt availble hr.. another sensor is available.. bt its nt tht sesnsitive... right nw m concentrating on the 3 sensors (temp, moisture n light intensity).. regarding soil moisture.. yeh u told me abt the factors on whc the o/p depends.. (guess u remeber it ) ...hv u used the same ckt whc is in ur report??

abt the code... hv nt used it still..

Hey Priya,

Firstly thanks a ton for the appreciation

Now I remember you, you had posted your queries in the project page right? Do try out the circuit. That is the one we have used, (unless I am forgetting, i shall check up with my project batchmates and let you know) also try varying the pot to get a good value of gain. Do one thing, just bring both probes in contact and see what is the o/p voltage, that should tell you if it is working. Try searching Rob Faludi's blog, you'l get the exact circuit.

Also, you could try adding something else to the set up,another sensor perhaps. Which uC are you using? If you have more ports you could really improve upon this. We were planning for making it a multi controller set up and sms based notification! Huge dreams but less time.

Also regarding the HIH4000, you could ask your college "(if they are supportive) to contact the components dealer of your college if he can source it for you. It is very much possible and you can also get free samples.

Good luck.

thanks fr ur suggestions amit.....

m using the same AT89S52 uC... abt HIH4000...i'll ask my H.O.D if they cud provide me any help...... m tyring fr another sensor in the market aswell....

n yes ... i checked rob faludi's soil moisture circuit.... the same ws used by u..i'll be trying it on monday...

i tested the temperature sensor ckt used in GREEN BEE project.. it had lm35 as temp sensor and lm324 to amplify the o/p.. the voltage dint rise if i increased the temp arnd the sensor...

then i used the temp smsr ckt given in mazidi. it .. gt the desired output.. this ckt is given fr adc0848... the adc m using is 0809....can i replace adc0848 with 0809 n use the sensor ckt given in mazidi??
dont knw abt 0848

n one more thing... m nt getting ny gud ADC tutorial... can ny one send me the link fr tht??

Could you tell me what th eissue is that you are facing with the circuit? Well, you can use the LM35 directly with the ADC just like its done in Mazidi, but you will have to deal with some practical issues. The basic reason why we used LM324 was to amplify the o/p of the LM35. Now you can use any op-amp (fir eg. uA741) for this but we had a terri8ble time blowing up circuits to generate + and -5 V and maintain a common ground! LM324 doesnt need a -5V referance. You could use any op amp that gives you this advantage.

You could entirely eliminate the amp, but you will notice that your calculations need to be very precise then cos the variations will become very small. Amplifying the signal does give you some ease and peace of mind.

Coming to th eerror to the circuit, just check if the pins are right with the datasheet. (i.e. th ei/p, o/p, ref. signal, etc.) Some small error may have crept in cos the documentation was done in a hurry and frankly I did not spend much time verifying what went into it and gave it a cursory glance.

You can use the ADC tutorial on thi sforum by Ajay, it is quite good and also try one by "Mahesh Wankhede" www.freewebs.com/maheshwankhede/ a very useful link...

hii amit..
yes... thr is an error in lm324 pin connection.. the vcc and grnd wr swapped...
i connected the ckt correctly... bt initially m getting .28v... (at room temp.. whc is appprox 28 c).. if i increase the temp.. the voltage does nt increase..
thts why i switched over to ckt in mazidi.. this ckt is givin exact outputs.. at every degree rise in temp.. thrs an increase of 10 mv..
at 28degree C- .28 V, at 29degree C- .29 V n so on....the reference voltage i gv ws 5V...

n regarding ADC tutorial... thanks a lot fr suggesting..

u used IC 4083 -a schmitt trigger nand gate for generating clock fr ADC.. nt getting this IC..
i think the IC is nt 4083.. it shud be MC14093BF : Quad 2-Input NAND Schmitt Trigger..thts wat i gt wen i googled fr it..if its nt taking much of ur time.. will u pls confirm this n tell me???
thanks once again!!!!!

Read the mahesh wankhde turorial. I think he has explained why an amp is useful. You will be able to show better variations for starters. Also ease in making a lookup tabl and calculations. A gain of 5 is what I had used. 10 would be too high i think.

The IC is correct. I think it should be 4093 not 4083, could u pls confirm. I had taken it from the National Semiconductors book(mentioned in the bibliography) The IC was available here and the circuit was one of the sample circuits of that IC mentioned in that book. U can check out with that IC u mentioned if it aint too expensive. I remember a friend mentioning that he used the 74HS.. series instead of 74LC.. for the clocking. You can use any clock circuit. Basically u should be able to generate a clk freq in the desired range and it should not be very noisy and as sharp as possible, so go in for a HS (hihg speed) or schmitt trigg gate. We spent many days on getting the exact RC combo for that ckt and had to use DRBs and capacitance bokes and some other kit to give and exact RC combination. Try searching on the net or taking some one more experienced than me here. Ajay, Pdi, sashi or anyone should be able to solve this minor glitch.

Am sorry for the delayed reply and typos. Am a bit busy as I am in the process of applying for my MS. I am online daily but just dont get the time to respond immediately...

Good luck and do tell me how it goes. What happened about the HIH4000 and the moisture sensr?

moisture sensor is working perfectly ...getting the desired results... thanks fr ur valuable suggestions..
abt humidity.. hv dropped it.. nt using the parameter.. cllg is not supportive..:(

by the way all the best fr ur MS.. applying fr this fall??? whc university? no problem at all for delay..

monday will be the last working day fr the project... will continue it in next sem i.e frm feb.. i hv my end sems in nxt month...

Oh thats good and bad news! Are they happy with just 3 parameters then? Well in that case you could try modifying it and trying some more ad-ons to the set up!

Thanks a ton for your best wishes. Yes I am applying this fall for embedded systems and VLSI. Screwed up my GRE Verbal score but got good TOEFL so hoping I get some leeway. Still undecided on all univs am applying to. Everything is in a volatile state and all together its getting in my nerves

Well, I see that you have an entire sem left to complete the project so you have enough time and could most certainly extend the project. I would love to see some improvemnts

Good luck with the exams