Elk M1 zone differences

[WayneW]

kind of directed at David, but if anybody knows or I missed it in the docs...

What is different about the first 16 zones? Why are temperature probes required to be on the first 16 zones? Are the zone physically different than the expander modules or is it a software limitation? Are there any other differences between zones 1-16 and all the rest?

How hard is it to build our own temperature probes that are compatible with yours and the software support?

 

[Spanky]

The M1's temperature probes pulse out a manchester encoded temperature value. The first 16 zones of the M1 have the capability to decode the manchester encoded data where the M1 zone expanders do not have that capability (yet).


If you want to make your own temperature or humidity probe for the M1 use the following protocol:

M1 Temperature / Humidity probe

Bitrate: ½ second per bit, 1 second per Manchester encoded bit.

Data Output Protocol:


1. Average temperature for 5 seconds.
2. Send three one bits (Manchester 1,0) for timing synchonization
3. Send Manchester Temperature/Humidity byte normalized to:
0 = -60 degrees Fahrenheit,
60 = 0 degrees Fahrenheit, 0% Humidity
130 = 70 degrees Fahrenheit, 70 % Humidity
160 = 100 degrees Fahrenheit, 100% Humidity
210 = 150 degrees Fahrenheit
4. Odd Parity bit. Add up all the 1 bits (10 Manchester) and this bit ensures the number of 1’s in the packet is an Odd number.
5. Repeat…

Example: temperature = 70 degrees Fahrenheit or 70% Humidity
0 bit value = 01 Manchester code
1 bit value = 10 Manchester code

130 = 70 degrees Fahrenheit or 70% Humidity.
0x82 = 130 decimal = 10000010 binary = 10 01 01 01 01 01 10 01 Manchester

10 10 10-10 01 01 01 01 01 10 01 - 01
start------- temperature byte------------ parity (make total number of 1’s (10) Odd)


The M1 and EZ8 will compare the data that it receives and two data packets in a row must match before the M1 will accept new data.

In reality this data can be sent to the M1 and used to indicate any analog value. The Rules do not care, it is just data.

 

[WayneW]

Thanks, I guess I need to learn about Manchester encoding or just be lazy and buy yours Somehow I got the impression that they were just LM34's or equivalent and sending an analog voltage.

Are there any plans for temp/humidity probes?

 

[electron]

There is no cheap analog temp probe on the market which can be checked by monitoring the voltage values?

 

[Spanky]

The problem with sending analog voltages is the resistance of the wire run. You will get different voltages with a long wire run. ELK chose to pulse the data so the distance of the wire run would not be a factor.

 

[WayneW]

Are there specs for the accuracy or resolution for the temp probes? the pdf mentions the range is -50 to +140.

 

[Spanky]

I recall the accuracy of a calibrated probe is no more than 1/2 degree F at 70 degrees F. You can calibrate the temperature probes also. The sensors are supposed to be linear through out the temperature range, but when it is -50 degrees F. outside, I don't care if it is -48 or -52, it is cold.

 

[BraveSirRobbin]

The problem with sending analog voltages is the resistance of the wire run. You will get different voltages with a long wire run. ELK chose to pulse the data so the distance of the wire run would not be a factor.

There may be probes that use 4-20 milliamps as the output the can run over long lines. You would just have to put a resistor such as a 500 ohm across the terminals (which would yeild 2 to 10 volt output).