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Moderators: Ajay, Junied , abbas1707, Arun Kumar V, pdi33, Shailesh NAYAK, ۞ TPS ۞, shyam, sashijoseph

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sashijoseph

Mon Apr 28 2008, 01:37PM

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Hi Amit.
What value base resistors have you used for the relay drivers?

Let there be music........

Amit Radha

Tue Apr 29 2008, 04:01AM

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Joined: Sun Sep 30 2007, 04:52AM

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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?

Chiru

Wed Apr 30 2008, 03:45PM

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Joined: Tue Feb 12 2008, 10:15PM

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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.

Amit Radha

Fri May 02 2008, 12:59AM

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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 :'(

pdi33

Fri May 02 2008, 04:22AM

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Joined: Mon Jun 04 2007, 09:28AM

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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.

* inspired to develop,developing to inspire *

Amit Radha

Fri May 02 2008, 04:40AM

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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

pdi33

Fri May 02 2008, 05:15AM

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Joined: Mon Jun 04 2007, 09:28AM

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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.

* inspired to develop,developing to inspire *

Amit Radha

Sat May 03 2008, 02:25AM

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Joined: Sun Sep 30 2007, 04:52AM

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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...

Chiru

Sun May 04 2008, 03:27PM

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Joined: Tue Feb 12 2008, 10:15PM

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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.

Amit Radha

Tue May 06 2008, 01:19AM

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Joined: Sun Sep 30 2007, 04:52AM

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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