Humidity sensor and PICAXE

G

gamesguru

Member
Hello,
Can anyone reccomend a relatively cheap humidity sensor that is readily calibrated to for use with a PICAXE to display relative humidity on a LCD display?
If its easy to wire that would be great too.

Thanks
 
G

gamesguru

Member
Relative humidity should be fine, I live in the UK so I need local suppliers. So when you say I2C connection does that mean that I need a PICAXE X2 series? Also if someone can give me a easy guide/ circuit diagram that would work that would be great, I'm not the best at deciphering such datasheets. Also at hand I have a HCZ-J3 humidity sensor but I cannot not work out how to use it, if someone can that would be great. However if it is too difficult to implement with picaxe, feel free to reccomend a easy solution to the problem.

Thanks

EDIT: Links dead? : http://www.hoperf.com/pro/hh10d.html
 
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W

westaust55

Moderator
The HopeRf HH10D humidity sensor which electic has in his second link is extremely easy to use.

The link he gave is working - just checked it.

You only need i2c comms once to read some calibration values from the onboard EEPROM which are specific to each module.

Thereafter a single wire as an input to a PICAXE (even an 08M) and use the count command.
The required maths are in the same thread: http://www.picaxeforum.co.uk/showthread.php?t=11749


The module operates from 3.0V or 3.3V and NOT 5V. But then, so can the PICAXE 08M and others (such as 18X).

As a joint article with manuka, we wrote an article for SIlicon CHip magazine using this humidity module. See: http://www.siliconchip.com.au/cms/A_111451/article.html

See also manuka's (Stan's) website here: http://picaxe.orconhosting.net.nz/hopehum.htm
 
G

gamesguru

Member
I can't find UK suppliers for this humidity sensor,I can only find the Honeywell HIH4000-001 as listed by eclectic. Do you know how to get that working on a PICAXE?

Thanks
 
G

gamesguru

Member
OK, forgive me for my ignorance. So if I ahve understood this correctly, one leg goes to the positive rail, one to the negative and one to the adc on a PICAXE. I then have to make some linear equation for the value to go through to display relative humidity? Thanks

EDIT: No I haven't, I currently have a HCZ-J3: www.rapidonline.com/netalogue/specs/61-0984.pdf, but I can't figure out how to get it working, at first glance it looks something like the humidity sensor you have suggested. If you can help me figure how how to get it working that would be great.

Thanks
 
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R

Ruzzz

Member
If you think of that sensor as a thermistor with a resistance that varies with RH as opposed to temperature then it should work.

You will need to work out how to calibrate it.
 
G

gamesguru

Member
Thats what I thought, I don't want to purchase the AXE board and looking at the sheet it seems its possible to do it on a PICAXE 08M or something similar. Is my analysis correct?
 
E

eclectic

Moderator
The program

Code: 
main:
readadc 1,b1 ‘ read humidity value
let b1 = b1 - 41 * 100 / 157 ‘ change to %RH
debug b1 ‘ display on computer screen
pause 500 ‘ wait 0.5 second
goto main ‘ loop
takes ~20 bytes.

On an 08M, it leaves plenty of room to do other things.

It's now your choice and your money.

Can I suggest that you now read the relevant data-sheets, thoroughly,
and write out a plan of your project.

e
 
E

eclectic

Moderator
Sorry, but I've never "done" pressure.
Lots of others on the Forum have.
I'm sure that they'll help.

Just one major thing though:
That Sparkfun sensor is "SPI".
Lots of other sensors are "I2C"
Not available on an 08M.

You'll need one of the bigger, more capable Picaxes.
( X1/X2)
e
 
W

westaust55

Moderator
gamesguru said:
now . . . . can you help me figure out now to measure barometric pressure with a PICAXE.
Click to expand...

Have you actually arleady purchased the VTI sensor?

Again HopeRF has the HP03 series of barometric pressure sensors (available thru Futurlec). They also require an i2c comms interface and work at 3.3V.


The 18X is quite capable of handling i2c comms and will operate at 3 or 3.3V (including capable of being programmed at that voltage).
 
G

gamesguru

Member
No, I haven't but I want to know that I can actually use these sensors vefore taking the plunge. Recession :D.

Can you give a more specific link and do they have a UK local branch?

THanks
 
W

westaust55

Moderator
I have the HopeRF humidity and barometric sensors working with an PICAXE 18X.

The Sparkfun module is SPI comms. Which can be bit-bashed (have a look at the end of the section for the SHIFTOUT / SPIOUT commands inthe PICAXE manual 2)

http://www.sparkfun.com/commerce/product_info.php?products_id=8161

Not it also requires around 2.6 to 3.3V for operation so voltage level shifting for the signals will be needed unless you run the PICAXE at 3.3V also.
 
G

gamesguru

Member
I can't find any suppliers of Hoperf components in the UK can anyone help out?

If you can reccomend local alternatives that would be great too!

Thanks

EDIT: Just another thought, would it be possible to buy an absolute pressure sensor and convert that to barometric pressure. It seems that there are more absolute pressure sensors avaiable.
 
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W

westaust55

Moderator
Do you have a limitation on buying from overseas?

While Futurlec have pseudo "shop fronts" in Sydney and somewhere in the US their single warehouse is in Thailand from which they dispatch all parts.
I have made a number of orders from them and all parts have arrived. About a week by normal mail.

These days, distance is nothing.
Sydney is around 4000 km away from my home.
Singapore is around 4000 km from my home
Thailand is not much further from me.

In the UK, no guarantee, but:
Presto advertise they stock HopeRF modules (look under products/modules.
http://www.presto.co.uk/
http://www.presto.co.uk/pdf/data-0458.pdf

Circatek also sell the HopeRF radio modules and maybe more. http://www.circatek.co.uk/

try a Google search for yourself.
 
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G

gamesguru

Member
Well, I suppose that would not be a problem if you put it like that, however is the HP03 easy to use? Like the humidity sensor?
 
W

westaust55

Moderator
gamesguru said:
Well, I suppose that would not be a problem if you put it like that, however is the HP03 easy to use? Like the humidity sensor?
Click to expand...
For the HP03 sereis of barometric Pressure sensors, the datasheet gives the formula requred. About 7 in total to complete the calculation

I have it working in an 18X. HP03 maths required 925 bytes out of 2048 bytes of memory and uses some SFR/GPR ram memory locations as well. I also store the calibration constants in around 30 bytes of the 18X data EEPROM area.

I submitted an article to Silicon Chip magazine on the HopeRf HP03 sensor complete with the PICAXE maths about a month ago. My guess is the earliest it might appear is Nov and maybe later depending on what other projects they already have in the pipeline.

Have a read at the datasheet and see what you can make sense of for yourself first.
Then ask your specific questions
 
W

westaust55

Moderator
Lets see,
- you started with asking about a humidity sensor
- you have then asked about a pressure sensor

so what does you complete schematic include?

But to get you started attached are:
- A HH10D humidity sensor conencted to a PICAXE 08M (courtesey of manuka) for our recent Si Chip mag article files
- A HP03 barometric pressure sensor connected to a PICAXE 18X

Recommend that for now stay with a 3V supply for the entire circuit
From these two schematics , try to draw your own schematic along with whatever other components you intend and we can review it for you.
 

Attachments

tommo_NZ

tommo_NZ

New Member
Cheap Humidity Sensors

Ruzzz said:
Have you seen this ?

http://www.mutr.co.uk/product_info.php?products_id=267

I've used MUTR in the past and found them very helpfull.
Click to expand...
Hi All, I have checked out this sensor on MUTR, cheap ($0.75NZ ea), looks simple to use, resistance easily read by picaxe ADC. Only problem, MUTR quote incredible price to ship to New Zealand, like 30 pounds mininum.
Does anyone know where this can be purchased locally or even what make/model it is?
Regards, Kevin T
 
W

westaust55

Moderator
tommo_NZ said:
Hi All, I have checked out this sensor on MUTR, cheap ($0.75NZ ea), looks simple to use, resistance easily read by picaxe ADC. Only problem, MUTR quote incredible price to ship to New Zealand, like 30 pounds mininum.
Does anyone know where this can be purchased locally or even what make/model it is?
Regards, Kevin T
Click to expand...
Cannot help with you specific query.

It is great to find such cheap items but freight can often bee exceedingly high. I have found this applies for purchasing items out of the US for example.

Have you done a Google search?
"Humidity Sensor" and within that do a sub search for "Capacitive"

This is the same sort of thing if you can find a seller local to yourself.
http://www.humirel.com/product/fichier/HS1100LF&HS1101LF-HPC052C.pdf

While it costs a lot more, the HH10D is available form MicroZed
http://www.microzed.com.au/sensors.htm

or

from Futurelec at www.futurlec.com.au

The Item costs more AUD$13-50 but maybe only AUD$5 for postage and you are still in front relative to something like NZ$60 or $70 with postage included for the MUTR item.
 
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tommo_NZ

tommo_NZ

New Member
Cheap Humidity Sensors

westaust55 said:
Cannot help with you specific queri.
It is great to find such cheap items but freight can often be exceedingly high. I have found this applies for purchasing items out of the US for example. -END QUOTE]

Thanks for the quick reply, and the links.
I have searched, but never seen anything as cheap as the ones at MUTR, nor as easily interfaced. I will keep looking.
May I take this oportunity to say I have never seen a forum as well run as this, nor one so well used. The quality of members and postings is a credit to you all.
Thank you,
tommo
Click to expand...
 
M

MartinM57

Moderator
...which looks sufficiently physically similar and electrically pretty similar to the MUTR one that you might believe they are pretty much the same device...

...so maybe the MUTR also requires an AC voltage. In th absence of a MUTR spec sheet, hard to say.

I don't know squat about RH sensors but these simple ones presumably need AC to drive them or they turn into electrolysis devices if powered by DC?

The MUTR site inspires me in places since some of their products are remarkable; in other places it makes me despair (specs, P&P prices and delivery dates etc) - almost like it's an academic institution that hasn't quite got a grip on the real world :D
 
Technical

Technical

Technical Support
Staff member
We've also tried the MUTR ones and they do work at DC e.g. as an LDR would, ie stick them in a simple potential divider with 10k at bottom and you will get quite a large change over changes in humidity. But calibrating it is probably a different matter! They are designed for AC so how long they will continue to work for when used like this is a different matter, the datasheet does say it will damage them....

They are unmarked and if you open them up just have two zig-zag tracks over a substrate. The tracks don't touch, so must be printed on some kind of sensitive material. In fact they look just like this inside:

http://www.rhopointcomponents.com/products.asp?recnumber=311


So we guess they are these:

http://www.rhopointcomponents.com/images/SYH-2R.pdf
 
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