LED across input zone

[apostolakisl]

I ran a test using the LED previously described. I connected it directly across the zone terminals for a zone on an M1XIN zone expander. The zone is defined as normally open, non-alarm.

Before connecting the LED, Elk RP showed...

Status: Normal
State: Open (+)
Volts: 14.0

After connecting the LED, Elk RP showed...

Status: Violated
State: EOLR (=)
Volts: 5.2

I left the LED connected for a couple of minutes. It didn't heat up at all that I could tell by touch.

If I were to put this into use, there would be a N/O relay involved. The LED would be wired in series with the relay. So, I would wire one of the M1XIN zone's terminals to one contact on the relay. The other relay contact would be wired to one of the LED leads. The other LED lead would be wired to the other M1XIN zone's terminals (keeping in mind the polarity of the LED).

So is Elk RP trying to tell me this is okay? Why is it showing the state as "EOLR (=)" when I have the zone defined as normally open? Is it because the LED isn't letting all the voltage thru like a simple contact closure would, so it thinks there is an EOLR present?

Thanks,
Ira

I just looked at your original question and realized we weren't exactly answering it.

Since elk posted "eolr (=)" with 5.2 volts, Elk is interpreting that as within its range of eolr protected zones. Probably somewhere in the specs section of the manual it will tell you what the exact range is that defines how elk interprets the value. If 5.2 is right on the cusp of being defined as "short", then you probably will want to tweak things with other resistors, but I bet it isn't.

Basically, elk has three ways it can interpret the status at each zone: short, open, eolr. The status screen in elk rp reports both the raw data (volts) and what it thinks of that data (short, open, eolr).

How elk responds to those three states is a different matter all together and is defined by you when you setup the zone. If the zone previously worked like you wanted as a nc zone, then adding the led means you change it to eol supervised. Elk programs will now respond to the +/-5.2 v the same as the responded before to +/-13.8v.

 

[Sandpiper]

I ran a test using the LED previously described. I connected it directly across the zone terminals for a zone on an M1XIN zone expander. The zone is defined as normally open, non-alarm.

Before connecting the LED, Elk RP showed...

Status: Normal
State: Open (+)
Volts: 14.0

After connecting the LED, Elk RP showed...

Status: Violated
State: EOLR (=)
Volts: 5.2

I left the LED connected for a couple of minutes. It didn't heat up at all that I could tell by touch.

If I were to put this into use, there would be a N/O relay involved. The LED would be wired in series with the relay. So, I would wire one of the M1XIN zone's terminals to one contact on the relay. The other relay contact would be wired to one of the LED leads. The other LED lead would be wired to the other M1XIN zone's terminals (keeping in mind the polarity of the LED).

So is Elk RP trying to tell me this is okay? Why is it showing the state as "EOLR (=)" when I have the zone defined as normally open? Is it because the LED isn't letting all the voltage thru like a simple contact closure would, so it thinks there is an EOLR present?

Thanks,
Ira

From this information, I can calculate that the LED/resistor combination appears to the M1 to be a 1.3K resistor. If you add 900 ohms or say a 1K resistor in series with it, the combination of LED/resistor plus another 1K resistor will be within tolerance for a standard 2K EOL resistor.

You can then configure the zone to be an EOLR type zone. Put the combination of resistors and LED in series with the contact. The LED will light when the zone is secure, and will go off when it is not secure.

Of course, with the extra resistance in series, the LED will not be as bright, but I expect it will be OK.

 

[Del91574]

I agree that using an M1XOV or M1XOVR would be a good way to do this, but that would require two boards at close to $100/board (I have more than eight zones), take up space in the can (which is already crowded), use quite a few of the maximum 208 outputs, and take an additional two rules per zone. I'm not sure it's worth the additional costs (monetary and otherwise) for this particular objective.

Another approach would be to change out the SPDT relays that act as "sensors" for the M1G zones to DPDT relays and use the additional set of contacts with a 12Vdc power supply daisy-chained to each of the relays to power the LED's.

Ira

So you're using a SPDT relay connected to the zone valve to sense voltage and then provide a dry contact to the Elk to perform an event, that's what I'm gathering. A DPDT relay would cut down on the programming in the Elk at about the same cost of adding a relay board. You're really coming that close to maxing the outputs on the M1? How many inputs are you driving and want to monitor?

The onboard triggers should drive an LED indicator fine, and depending on your KP's, if you ran enough conductors, you have an output that could be picked up there as well.

As another option you can get a M1RB straight to the panel that would fire 8 dry contacts each for half the price of a M1XOVR or you could cascade a M1XOVR into a M1RB. I'm not sure about how many lines you're anticipating in Rules for each output to eat up, but I can only see a single rule to turn a indicator on or off based on state.

The 5.2V will be seen as a fault irregardless, technically a trouble condition as far as the zone is concerned, because it is not close enough to an EOLR voltage value for any state, basically seen as a high resistance fault vs. the EOLR voltage value, so you'd either need to find a LED with a different current limiting resistor or play the ohm's law game to get back into the appropriate voltage range for the EOLR.

 

[apostolakisl]

The 5.2V will be seen as a fault irregardless, technically a trouble condition as far as the zone is concerned, because it is not close enough to an EOLR voltage value for any state, basically seen as a high resistance fault vs. the EOLR voltage value, so you'd either need to find a LED with a different current limiting resistor or play the ohm's law game to get back into the appropriate voltage range for the EOLR.

Is this for sure true? What is the acceptable range for a secure eolr protected zone? If the elk status screen is reporting "EOLR(=)" under "state" shouldn't that mean that it is interpreting 5.2v as an acceptable number? "EOLR (=)" is exactly what my elk reports under "state" for all of my normally operating zones. Admittedly, they are all between 7.0 and 7.4 volts.


If not, adding another resistor in series will bump up the voltage seen by the Elk. Sandpiper seems to have done the math and it is certainly pretty fast and brainless to throw a 1000 ohm resistor in series with the led.

 

[Ira]

From this information, I can calculate that the LED/resistor combination appears to the M1 to be a 1.3K resistor. If you add 900 ohms or say a 1K resistor in series with it, the combination of LED/resistor plus another 1K resistor will be within tolerance for a standard 2K EOL resistor.

You can then configure the zone to be an EOLR type zone. Put the combination of resistors and LED in series with the contact. The LED will light when the zone is secure, and will go off when it is not secure.

Of course, with the extra resistance in series, the LED will not be as bright, but I expect it will be OK.

Can you explain how you calculated this?

Thanks,
Ira

 

[BraveSirRobbin]

Is this LED one with a built in limiting current limiting resistor? If so, that is probably a correct assumption of about 1K on the resistor value inside it? If you add another 1K resistor as suggested below, it should be (and behave the same) as an EOL terminated zone I'd imagine.

 

[Ira]

Here is the link to the cut sheet for the LED's I have. The actual LED is part number 559-0203-007F (green, 12Vdc, 14" wire leads). The cut sheet says it has an integral resistor but it doesn't say how many ohms resistance it has.

I still don't understand how you get to a 1K resistor value (for the integral resister) from the test I ran.

Ira

 

[Ira]

In the M1G installation manual, page 7, section 1.4 (Control Wiring), it says "a nonviolated EOL zone will measures approx. 7.0 VDC". But in the box/table below that statement, it says for a zone resistance of 2.2k Ohms, the approximate range of zone voltage is 4.0 - 8.8 volts. So it looks like the M1G sees the LED as a viable EOLR.

Ira

 

[BraveSirRobbin]

Well if you have 12 volts across the LED and it draws 13 milliamps (per that spec sheet you linked) without anything else added to the circuit, it would account for a resistance of:

V = I * R

R = V / I = 12 / .013 = 923 ohms (or about 1K ohm).

I didn't read through this entire thread in detail, but if you want an LED indicator and the Elk is having trouble registering the correct value of the zone I would probably try setting the zone as EOL, adding another 1K resistor in series, and see what happens. Of course, I haven't tested this, thought about it a whole lot, or recommend this method, so in case anything happens, well....

You can also help with the trouble shooting by bench testing, having some small jumper cables for shorting resistors, zones and all, and looking at the panel voltage status on the Elk software.

 

[Spanky]

I know this sounds weird, but...

I have some LED's with the following characteristics...

Forward voltage: 12V
Forward current: 13mA

If I want a cheap, easy, external indicator of a zone's status (i.e., the LED mounted externally), can I connect one of these to the zone's terminals on the M1G input zone expander board? If I can do so withoug affecting the M1G, what would happen with the LED when the zone is open and when it is closed if the zone is defined as normally open? Does the opposite occur if the zone is defined as normally closed?

Thanks,
Ira

IRA,
In a word NO. You can not put the LED across the input loop. The LED you have probably has a current limiting resistor in series with it to be able to handle 12VDC. Without a current limiting resistor a LED will blow around 2VDC.

The current drive on the M1's input loops are through a 2K ohm resistor and if using an EOL resistor of 2.2K there is about 3 milliamps of current available. If the voltage on the EOL loop drops below 4 volts or goes above 9 volts, the zone will become violated.

It is easy to write a Rule to monitor all the zones or a single zone status and output the status on one of the J16 outputs to drive your 12V LED.

WHENEVER Zone X becomes not secure
THEN turn on output X

WHENEVER Zone X becomes secure
THEN turn off output X

 

[apostolakisl]

IRA,
In a word NO. You can not put the LED across the input loop. The LED you have probably has a current limiting resistor in series with it to be able to handle 12VDC. Without a current limiting resistor a LED will blow around 2VDC.

The current drive on the M1's input loops are through a 2K ohm resistor and if using an EOL resistor of 2.2K there is about 3 milliamps of current available. If the voltage on the EOL loop drops below 4 volts or goes above 9 volts, the zone will become violated.

It is easy to write a Rule to monitor all the zones or a single zone status and output the status on one of the J16 outputs to drive your 12V LED.

WHENEVER Zone X becomes not secure
THEN turn on output X

WHENEVER Zone X becomes secure
THEN turn off output X

Except he is getting a lit led and 5.2 volts at the panel. So, at least this particular led, is not current limiting enough to drop voltage into zone violated territory.

Would I be correct to say that there is no possible way an led could damage the Elk? Seeing as an led is a passive device without capacitance I can't conceive of any way it could damage the board.