Temperature Sensors

[nov0798]

Does anyone know why you cannot plug a temp sensor into an input expander on the M1G? Why do they have to be plugged into the main board?

 

[felixrosbergen]

Don't know why not, but from what i know they only work on the main board.

 

[nov0798]

Yea, you would think that an M1XIN would/should accept them. Has anyone tried to hook up a temp sensor to an M1XIN?

 

[Lagerhead]

Does anyone know why you cannot plug a temp sensor into an input expander on the M1G? Why do they have to be plugged into the main board?

This was just discussed, more or less...

See http://www.cocoontech.com/index.php?showtopic=11718, Spanky's post #9

The Elk temperature sensors communicate measurements using a serial protocol and it seems that only the main board zones have the programming (and/or the speed) to handle the protocol. A clever and bizarre use of the zones.

 

[nov0798]

Well that post really doesnt explain why you cant hook up a temp sensor to an input expander. I guess I just dont understand how you can run just about everything else off of the 485 bus, just not the temp sensors. Spanky, can you chime in? Also, how is it that you can monitor the keypad temp sensor over the bus, but you cant monitor a stand alone temp sensor over the bus? It doesnt make sense to me!

 

[dutchyn]

Well that post really doesnt explain why you cant hook up a temp sensor to an input expander. I guess I just dont understand how you can run just about everything else off of the 485 bus, just not the temp sensors. Spanky, can you chime in? Also, how is it that you can monitor the keypad temp sensor over the bus, but you cant monitor a stand alone temp sensor over the bus?

I suspect that the meaning of can't is relative in this context. Instead of meaning, this is logically/electronically impossible and no-one can ever do it, I think it may mean we chose not to support temperature sensors attached directly the bus and the input expanders. A likely reason for this decision could be financially pragmatic: why increase the cost of devices by integrating a temperature encoder on the RS485 buss or a Manchester differential decoder into the M1XIN expanders, when you can attach 16 temperature sensors already.

Chris D.

 

[nov0798]

While I understand that you can already hook 16 into the main board, wouldnt the temperature encoder or a Manchester differential decoder already be on the main board? Do the 16 on board zones sit on the 485 bus, or do they not? The ability to hook up temp sensors via an input expander would be extremly beneficial, rather than having to run a wire all the way back to the main board.

 

[Lagerhead]

Chris nicely summarizes the engineering and financial tradeoff that is fundamental to any product design. One can say that they understand these tradeoffs without necessarily agreeing with them.

Not sure that sheer speculation is warranted, but I will go out on a limb anyway. ...Dave

wouldnt the Manchester differential decoder already be on the main board?

It is most likely implemented in the software.

Do the 16 on board zones sit on the 485 bus, or do they not?

Probably not. Why introduce the complexity of a communications interface when you have the zones already on the board.

The ability to hook up temp sensors via an input expander would be extremly beneficial, rather than having to run a wire all the way back to the main board.

I'm pretty sure that Elk knows this and would make it available if it were straightforward to do so.

 

[nov0798]

How is it then , that you can monitor the temp of the keypad via the bus? Does the keypad itself have this logic built in? If so, then why not build in the logic to the temp sensor itself, and put the data across the bus, the same as a keypad?

 

[Lagerhead]

why not build in the logic to the temp sensor itself, and put the data across the bus, the same as a keypad?

Now there is a product idea for Elk. Spanky did say that it was getting time to address the issue.

 

[nov0798]

I guess well have to wake Spanky for some insight on this.