Humidity Sensor Options?

[rossw]

DS2438 is a Smart Battery Monitor.  How does that help with a Temp Humidity sensor?
 

 
It's a temperature sensor and analog input. So using one of the other humidity sensors and the DS2438, you make another analog input connected to another humidity sensor. (Doesn't seem to be any real benefit to me. At least the current humidity input has a curve matched to the honeywell sensor, which is itself a more precision device)

 

[CallRET]

Ya, i eventually caught up with what all they cool kids are talking about. 
 
It seems some of the cool kids are actually using the H4000 (or h5000) behind the DS2438 in some cases,  Ya you lose curve fitting, but still.  And one can use more accurate sensors if one wanted, or cheaper sensors.
 
It seems this adds flexibility and, potentially, accuracy.  Also, perhaps the DS2438 might be able to do a little curve fitting on its own, as it can be calibrated.  But I have only browsed the datasheet.

 

[az1324]

The benefit is locating remotely and multiple units. 
 
Vendors include:
 
hobbyboards.com
midondesign.com
opnode.com
ibuttonlink.com
sheepwalkelectronics.co.uk

 

[CAI_Support]

Does DS2438 being sold as a chip or it must go on a board mentioned in the az1324's post?  Since DS2438 has built-in temp sensor, each ID can be used for both temp and voltage input.  It will cause a lot data structure change. We will look into that....

 

[az1324]

You don't have to read the temperature.  Most of those boards include a separate DS18B20 for better accuracy anyway.

 

[CallRET]

Does DS2438 being sold as a chip or it must go on a board mentioned in the az1324's post?  Since DS2438 has built-in temp sensor, each ID can be used for both temp and voltage input.  It will cause a lot data structure change. We will look into that....

This might explain better?
http://owfs.org/uploads/File/humsensor.pdf
 
As az1234 points out, you can just add the DS2438 and the Voltage.  Perhaps that will fit your data structure?  Perhaps convert the voltage to Relative Humidity or just the raw Voltage, like the C or F reporting option for temp? 
 
Then we could have up to 8 temp OR up to 8 RH/Voltage's or a combination.  You dont even have to add H1...8 as I/O identifiers, as we could just use (overload) T1 to 8, and the user would manage if the IO is a temp or RH/Voltage.
 
Of course if you WANT to add more...
 
Sorry did lots of edits.
 
Adding the DS2438 could also allow people to use WC to charge battery packs.

 

[CAI_Support]

In our firmware, any storage will require allocation of RAM, that is being accessed by all other functions.  Since the CPU only has 3008 bytes RAM, we must carefully dice it.  When a new sensor added in, we must re-arrange many things to make it fit, including removing something to free up memory.  That is the details end user does not need to know.  However, we have to explain that to let everyone know we did not do certain things not because we are not willing, but the chip resources is limited.

 

[CAI_Support]

Our engineers looked the DHT11 and DHT22 sensors, we found those sensor will require one IO pin per sensor.  So if you have 8 sensors, it will require 8 dedicated pins for those sensors.  Since Dallas patented the 1-wire protocol, it does not allow anyone implement a device address scheme like DS18B20 or any other 1-wire device.  They only allow 1-wire bus controllers, like WebControl, to talk to their devices on the 1-wire bus.

 

[CallRET]

any update on adding the DS2438

 

[CAI_Support]

DS2438 is an interesting sensor.  It has temp sensor, voltage A/D and current accumulator all in one chip.  Its current accumulator can store how much in current and how much out current.   However, to use all three features, we will need to allocate 6 bytes memory for each chip.  How many of this chip do you think we should support? 
 
We need to balance between memory usage and features.  If we make a firmware without DS2450 support, we could allow up to four temp sensor to be replaced with DS2438, so that user can have four battery banks to be monitored.  Also, the current accumulator will need to be cleared and calibrated, that is additional logic user must handle in PLC code.
 
We will order some chips to experiment, while we discuss this at the same time.  It is likely once we added initial support, it will need to be updated based on real use feedback.