Elk M1 Humidity sensor

[tmbrown97]

On a different project/note... Now if I could just get the specs for talking to the elk via databus.... some of the plans I have in mind would be better off going the databus route. And then there's the software-based AiPhone LEF-5C project.... so many ideas, so little time

And that part won't happen - that's proprietary and Elk doesn't give that to anyone.

 

[Jwbarrett]

You could try adding the network shield to the arduino and talking to the M1 over tcp/ip, Storing the info in a counter. Just a thought

 

[n4hc]

And that part won't happen - that's proprietary and Elk doesn't give that to anyone.

I hear that's encrypted. Makes sense that it's secure for a security system... But it's RS485 if anyone wants to give it a try.

 

[n4hc]

Ah, yes, manchester encoding. That's not proprietary Matter of fact, I think the UART on the arduino can be coaxed into "speaking" manchester by stuffing the right converted values in to it and fudging start/stop/parity etc.

Good info! On the temperature/humidity project, I'll probably continue and roll my own with the SHT21 and arduino, just because I'm more familiar with that than the PIC chips. The arduino seems to have more I/O options built in, so I suspect it would give me more flexibility for future add-ons to the elk.

On a different project/note... Now if I could just get the specs for talking to the elk via databus.... some of the plans I have in mind would be better off going the databus route. And then there's the software-based AiPhone LEF-5C project.... so many ideas, so little time

It's a 1 bit per second datarate. he blinking light on the temperature sensor is the actual data.
Bit-banging is the best and easiest way to go. I'm still looking for the code but I think it's about 480ms per 1/2 bit. And it MUST be connected to the main input zones directly on the Elk panel. No other zone will read this.

So basically it's this:
1. Take reading (temp or humidity)
2. Add offset to it (from the Elk API)
3. Convert into an unsigned 8 bit value.
4. Bang out over a single bit with on pulling down the zone input. Each bit is 1/2 on and 1/2 off or 1/2 off and 1/2 on (Manchester encoding).

Elk input zones are pulled high to +12V via approx 1k resistor.
Connect micro output to a transistor or FET and enable output port to pull zone low.

I'll post code when I find it.

 

[n4hc]

I posted a blog entry with the protocol description and demonstration code for a humidity sensor.

http://cocoontech.com/forums/blog/43/entry-393-elk-m1-zone-temperature-sensor-protocol-decoded/

 

[nlaredo]

Seems to me this would be easier to just control an i2c digipot from a microcontroller to give the elk whatever voltage you want from 0-12v and use the voltage level to represent relative humidity and set the channel to raw value mode... then any input -- even expander (M1XIN) inputs -- would work...

 

[Neurorad]

I don't know why Elk doesn't support humidity sensing.
 
Using the 1-wire system seems like a hack.
 
2 Humidity sensors, 1 in the BA and the other in the BR, and split the difference to adjust for humid summers.

 

[IVB]

Can I assume from this thread that Elk still has nothing to support humidity sensing? I need to install a humidity sensor in my basement, was hoping to find a mechanism to bring it into my HA system and use those rules/controls.
 
I suppose I'll also look to see if there's anything I can suck into CQC...

 

[IVB]

Just got THIS ONE recommended over on the CQC forum.
 
There's an RS232 one, but there's also one with linear analog voltage.  I recall some method of connecting that into the Elk, and using rules to compare voltage and calculating percentage. I'll have to hunt that down.
 
BSR Edit:  Fixed link.

 

[BraveSirRobbin]

A couple of things to consider when measuring analog voltages with the Elk.  First, it's eight bit, so for that sensor you would have 0-5 volts = 0-100% humidity.  So it can only resolve 0.4% humidity steps (not bad for this case as that sensor is only accurate to 2% anyway).
 
Also, there is an internal pull-up resistor that can influence voltage readings for analog measurement situations, especially if the current drive capability of the sensor is low.
 
With that said, you will just have to try it.  You would take the voltage reading in this case and multiply by that value by 20 to get humidity.  As IVB stated, you would most likely have to poll every so often to get a reading updated.  I believe if I'm remembering correctly that expansion boards update differently than inputs on the mainboard.
 
There are a few posts that state all of this (I've done some playing around but it's been a while) on this forum.
 
Here is a guide on analog to digital converters that you may find useful.
 
I use THIS PH Anderson A-D converter to measure my voltage sensors.  I had Dr Anderson custom a ROM so I can get all the values from the RS-232 interface on one line, which made the code (via HomeSeer VB Script) a piece of cake (can provide on request).
 
You could easily write a driver for CQC, but would need an open RS-232 interface (but what home automation enthusiast doesn't have at least eight or ten RS-232 ports on their HA server?).

 

[sbsoftware]

I built a prototype using N4HC's reverse engineering of the protocol. It's been deployed for 2 days now and seems to be working with only one oddity: I keep getting "Zone 14" flashing on my Area 1 keypad. When it flashes it doesn't display any trouble or value, just "Zone 14" (this is my humidity zone).
 
I've placed a write-up with pictures of my prototype at http://www.smbaker.com/a-temperature-and-humidity-probe-for-the-elk-m1-gold

 

[n4hc]

Good job!
I'm not familiar with that micro or language.
 
I know you need some time between transmissions but not too much.  I wait about 10 seconds between sending readings (if I remember correctly).  
That could explain the flashing zone on your keypad.

 

[sbsoftware]

I hit it with ElkRP to disable Chime on the two zones and the blinking "Zone 14" has gone away. So either it had something to do with the chime setting or the panel just needed a reset.
 
It's possible the problem came from a bug I had in my code. I wasn't setting the output line back to zero after outputting the parity and this caused a trailing high state after an even parity and the zone would be ignored until the parity went odd again. So maybe that left it in a confused state.
 
Anyhow, all is working now. 64 degrees and 59% !

 

[crossbar]

So does anyone know of a Humidity sensor that can be used with Elk M1?  Looks like this has been a significant missing feature for many years now.  It would be nice if a Z-wave Temp/Humidity sensor could be used with the ELK but since the Elk does not support Z-Wave sensors that is not an option.  A wired sensor is really a must as well.   I see a few people have made their own.  Are any of these available for sale?   I don't really have the time to make my own at this point.  This seems like a really basic feature to still be missing.

 

[ano]

HAI/Leviton makes a simple temp/humidity sensor. The temp sensor is extended range (digital) so that won't work with the Elk, but I believe the humidity sensor is a simple voltage sensor the an ELK can read like an ELK temp sensor, you will just need to build a conversion chart of read "temperature" to actual humidity.
 
There certainly are Z-wave and Zigbee temp/humidity sensors.  I bought a Zigbee temp/humidity sensor hoping my Omni Pro II would read it, since the Omnistat2 is a Zigbee temp/humidity device which does work with the Omni, but no luck. It pairs, but likely a slightly different protocol.