Is anyone familiar with this new product for temperature and humidity sensors? This was posted on the Charmed Quark web site. I was wondering if this item could be integrated with the ELK M1. It would be an alternative to the 1-wire integration many of us have been waiting for. Plus I really like the unobtrusive tempurature probes. High WAF. Spanky, any thoughts about this?
"DataMod Series I/O Modules and Temperature Sensors. These Modules can also be used for Contact Closures, Humidity, CO2, Pressure, Flow, Voltage, Current... The first module to be supported by the driver is the MD01 which has 32 Analog Inputs. Other modules include the MD02 providing 8 Analog Inputs and 8 Analog Outputs rated 0 to 10 volts and the MD03 providing 8 Analog High Speed Pulse Inputs and 13 Relay 1Amp @ 24VAC Outputs.
These products will hopefully provide users with an economical way of monitoring and or controlling of Temperature, Humidity, CO2, Pressure, Flow, Voltage, Current, Dry Contacts, Dampers, Valves VFDs, Pumps and the list goes on.
More information on the Modules and Temperature Sensors can be found at:
www.kanak.com/datamod.asp and www.kanak.com/tempsensors.asp"
The breadth of the services offered by Kanak through the INTERSCIENCE INTERNATIONAL web site reminds me of Dr Bonner's original soap label (Wars quelled, Revolutions started ... ;-)
I also have several more serious observations:
1) Perhaps the most important step forward would be if Dean/CQC did indeed support a Modbus-over-RSxxx interface. To the best of my knowledge, this would be the first readily available HA application of that venerable and highly appropriate industry standard. Visit www.modbus.org/
2) The modules, sensors and acccessories themselves all appear to be rebranded/debranded items from other sources of the sort that have been around for decades. I see nothing "new". The sensors themselves are generic and not specific to the input modules. In the realm of scientific/industrial sensors, $15 for a thermistor assembly may indeed be a good price . But what is offered apears to be a $1-$2 thermistor attached to a $2 stainless steel plate.
3) The 10-bit analog input resolution of the analog-to digital converters cited is a modest step up from the 8-bit resolution of existing HA devices such as Elk, Ocelot &etc. but is no better than that built into a $1.50 AVR microcontroller. This is not a Modbus limitation, but of the particular modules offered. For many/most purposes 10-bit resolution and accuracy is sufficent, but folks wanting to make full simultaneous use of the accuracy, range, and resolution available from (eg) the thermistors they tout will/may be disappointed. As may folks wanting to (eg) make light measurements that begins to approach the actual range of environmentally significant illumination levels (eg 0.1 to 10,000 lux).
4) The modest ADC resolution helps explain the relatively low price. IC's with sixteen analog inputs with 24-bit analog resolution and eight DIO wholesale for $8.00
http://focus.ti.com/docs/prod/folders/print/ads1258.html
5) Assuming for the moment that Elk did offer a way to communicate with Modbus over RS-xxx, the M1G might be challenged with respect to providing calibration and conversion from a voltage to engineering units. Unlinearized themistors, for example, are typically converted to temperature using equations that may be outside ithe panels' capabilites ( eg Steinhart-Hart uses natural logs).
6) There are reasons why HA "panels" historically have not provided analog inputs and some of the reasons revolve around the facts that 1) "panels" typically have no/negligible data storage capabilites so most anything other than a real-time reaction to the data is not practical/posssible) and 2) it greatly simplifies the manufacturers task if the analog world is converter to an 'Event" with binary outcome (ON/OFF; TooHot/NotTooHot; etc) before the data arrives at the panel.
7) It follows (at least in my mind) that making full use of analog inputs requires addressing points 1) and 2) in the paragraph above. That would be the most time-consuming part of building a Modbus 'interface' for CQC, not downloading the measured voltages from the devices.
8) Compared to other 'dumb' devices that have been available for DIY HA, these are relatively expensive ( but not when compared to scientific/industrial devices). For example, the LCD+ from Netmedia has been around for 7-8 years, provides eight 10-bit analog inputs, eight DIO with built-in relay driver IC, a small multi-line ASCII LCD display, and a 16-input keypad interface -- all for $60. And a USB data acquisition module with eight *12-bit* analog inputs, 16 digital I/O lines, two programmable
pulse-width output channels, and one 16-bit counter channel cost costs ~$100 shipped (Seach eBay for " iUSBDAQ")
Reading what I just wrote, the remarks seem to be more negative than intended ...
Having a Modbus interface, sensor calibration and conversion front-end, and historical data storage and display would be a dynamite addition to CQC !
... Marc
Marc_F_Hult
www.ECOntrol.org
