Measure external voltage possible (M1)

[znelbok]

Is there a way to get the M1 to measure external voltages (it will only read resistances at the moment)?

It would appear that the M1 supplies the 12V to the circuit and then measures the return voltage. Is there any way that the 12V that is supplied can be removed from the zone (by pulling a resistor or other component on an input board). Doing so should allow an external voltage to be measured.

A copy of the circuit diagram would help immensely, but I doubt that ELK/Ness would want to give out such details.

Mick

 

[BraveSirRobbin]

There is a ton of information on the pros and cons of using an Elk zone as an 'analog input' type on this forum.

Quick summary:

Yes, as an analog type zone.

It is only 8-bit

You can't display the value, but have to do comparison rules to "act" on a value

There is an internal pull-up resistor (surface mounted) that will influence your readings.

There are a lot of other considerations as well.

Do a search for a lot of other details.

 

[Spanky]

For Analog Zone Values, reference the M1 RS-232 Data Protocol which is available on the ELKProducts.com website.

Here is a command that will return the analog value of a zone input:

4.27 Zone Analog Voltage
This command allows automation equipment to request a zone analog voltage level. M1 Version 4.2.8 and after.
Request Zone Voltage (zv)
09 – Length as hex
zv – Get command for zone analog voltage data
ZZZ – Zone number 001 to 208 as 3 ASCII characters decimal
00 – future use
CC – Checksum
Example: 09zv12300B1 Zone 123 analog voltage request data
Reply Zone Analog Voltage Data (ZV)
0C – Length as hex
ZV – Reply with zone definition data
ZZZ – Zone number 001 to 208 as 3 ASCII characters decimal
DDD – Zone voltage data as 3 decimal ASCII characters. Divide data value by 10. Right character is the tenths decimal place.
00 – future use
CC – Checksum
Example: 0CZV123072004E Zone 123 , voltage is 7.2 volts





There is a 2200 ohm resistor on the zone input that pulls to +13.8V. Your voltage drive will have to overcome that resistor to not affect the reading.


Also you can see the the zone voltage with user menu 8,6,3 on the keypad.

 

[znelbok]

Thanks Guys

I have no problems with a standard analog input - All the M1 will do really is measure resistance and not voltage. It does this by applying a voltage across the zone and measures this voltage. (hope this makes sense).

If I remove the pull up resistor, will that remove the 13.8V from the zone?

If so then I can apply my own voltage to measure

Mick

 

[BraveSirRobbin]

Did you do a search for topic items on Elk Analog Inputs?

 

[znelbok]

Yes and nothing comes up that is relevant

If you know of anything specific then please point me to it.

As an example, take the ultimate garage door monitor - it uses a pot to measure the door position and then then elk measures the voltage.

A LDR is a resistor that varies resistance with light input - the elk measure the voltage across the resistor.

Here is an example (not real but hopefully gets the point across)

I have a temperature sensor that outputs a voltage (0-12V) over the 0-100C temp range. Therefor 0C = 0V and 100C = 12V and it is linear. THis usint has an external 12V power supply.

The elk cant read this voltage as it has its own 12V on the zone and this is the voltage that I want to turn off

Mick

 

[rocco]

The elk cant read this voltage as it has its own 12V on the zone and this is the voltage that I want to turn off.

Hi, Mick:

Actually, it can read your voltage, as long as your device's output impedance is less than the 2200 ohms input impedance of the Elk.

The voltage provided by the Elk is 13.8 volts, through a 2200 ohm pullup resistor. If your output driver can overcome this pullup, meaning it has an output impedance less than 2200 ohms, your voltage reading will be correct. Most op-amps or line-drivers would have an output impedance less than 2200 ohms, so if your device can't drive the input, a simple op-amp buffer should be all that is needed.

Of course, I agree that removing the pullup would be a better solution, if it's not an SMD part. That's a Spanky question.

 

[BraveSirRobbin]

http://www.cocoontech.com/index.php?showtopic=6642&hl=analog

http://www.cocoontech.com/index.php?showtopic=4356&hl=analog

http://www.cocoontech.com/index.php?showtopic=4352&hl=analog

http://www.cocoontech.com/index.php?showto...l=surface+mount

 

[znelbok]

I now have the M1 working with my 4-20mA current loop devices.

I removed the pull up resistor and can measure voltages (0-12V), thus making a current loop easy to measure.

Thanks for the help guys

Mick

 

[BraveSirRobbin]

How do you convert the current to voltage? External resistance somewhere?

Glad you got the analog inputs working. So the eight bits is working OK for you? How are you displaying/interfacing the analog readings?

Thanks again for the info.

BSR

 

[znelbok]

How do you convert the current to voltage? External resistance somewhere?

Glad you got the analog inputs working. So the eight bits is working OK for you? How are you displaying/interfacing the analog readings?

Thanks again for the info.

BSR

I have a 620 ohm resistor across the zone inputs - this gives a 0-12.4V range.

The resolution is fine for the type of inputs I am looking at.I would like higher, but its better than nothing. I get what appears to be a 0.5 deg resolution on the test temperature probe I am using. I will put the process meter on it and inject a signal early next week and see how good or bad it really is.

There is no interfacing yet. I use CQC and need Dean to make changes to the driver so that the voltages can be read, but I also need a scaling option as well as a temp of 3.9 volts or a level of 7.5 volts does not really mean that much.

I can see this as a handy option for a lot of people as it now measures external voltages. As mentioned here I would like to see a jumper on the board to change the function of the zone.

Mick

 

[BraveSirRobbin]

Hi Mick;

Thanks for the reply. Can you list the sensors you are using? I'm always interested in what people have found usefull with various sensors such as the ones you mentioned above.

As far as converting to something "readable" I'm sure Dean will accomodate. If he needs ideas, this was actually incorporated into MarkL's Elk HomeSeer plugin (with my suggestion).

The way we did this was come up with a way of entering (via ini entries) the "m" (slope) and "b" (intercept) values for the sensor's slope intercept equation ( y = mx + b ). The result of that equation was then placed in a HomeSeer device, which could then be read or acted on with an event like any other device. It is a real handy feature, though very few people actually use it .

Also, for those reading this thread and playing along at home, THIS guide was written to help incorporate analog type sensors into your home automation system.

Thanks,

BSR

 

[znelbok]

Yeah I need the equation of a straight line as a minimum. I dont think I need a square root function, but I have to check my flow meter

These are the devices I have (they are all industrial).

Vega ultrasonic level transmitter (water tank level)
Yokogawa Pressure transmitter (water pressure)
Fuji mag flow transmitter (house water flow in - this should be a linearised output, but I need to check, if not I need a sqrt function as well as a straight line)
CT that has a 4-20ma output (or voltage if I want - used on pump)

Future plans
Another ultrasonic (cant think of brand) for Dam level (future, needs a radio link as well).
Add another tank with another ultrasonic for water during blackouts.
Grey water tank with ultrasonic level.
Pool temps may be voltage or current.
UV light for water treatment intensity (4-20mA output)

The solar hot water system has two temp sensors that are used to control the circulating pump. As this system has its own voltage supply, I will tap into this and measure the voltage to get the temps of the hot water in the tank and collector (no reason just want to cause I can)

I am a process control engineer so I pick up some of the old gear at work and put them to use here at home - hence they are all industrial in build and quality.

Mick