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CADDX NX8E system - looking for detailed info on expansion boards

JimLS

Aug 16, 2012
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Having some intermittent trouble with NX-320 remote power supply and NX216E expansion board set up as second partition. Had been working fine for almost 2 years. input zones openings don't show up (always ready even with doors open) and reports expansion power issue but all voltages measure fine. Down to tracing the circuit to try and figure out how they sense voltage (if that is even what causes this fault). Since the system is no longer made I am reluctant to buy used boards not knowing exactly what the issue is. Have substituted a different NX216 and still had issues. Might be the keypad also.

Another question is on my NX1448E keypad I am not able to set the partition. Manual states this is optional so apparently mine don't have that option. If I buy other keypads how do I tell if they have this option as I need it for second partition. Existing second partition keypad is NX148E which has ability to be set for other partitions but I could try to replace it.
 

ChosunOne

Jun 20, 2010
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I have about 40 years experience working with almost all the major brands of professional-grade alarm systems, but by some quirk of fate, I rarely came across this particular brand. Apparently, few dealers in my area used it, although it was a popular brand nationwide. I wouldn't have any qualms troubleshooting your system in person with Installation and programming manuals on hand, but to troubleshoot remotely by proxy, you need someone who's experienced with this particular model.
Incidentally, schematics for all these devices are not available---alarm device manufacturers keep their cards close to their chests and don't encourage diy-ers.

I recommend you try this site, https://www.doityourself.com/forum/electronic-home-security-systems-alarms-devices-87/
where you will find professionals familiar with your system.
 

JimLS

Aug 16, 2012
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I know the company doesn't give out schematics. I design other electronic products and we don't let any of that sort of documentation out either. But was thinking there might be a few that had delved into the details and might have put the info on the net. It happens all the time for various tech items but I haven't found a thing on this.

Already went through some with the monitoring company remotely - they were very helpful but the system started working. Now that I put the remote boards back at the far end of a 250' cable they aren't working even though that's well within the length specs for the boards. Will give the doityourself.com site a try.
 

kellys_eye

Jun 25, 2010
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Now that I put the remote boards back at the far end of a 250' cable they aren't working even though that's well within the length specs for the boards.
I doubt there is a propriatory tx/rx protocol involved (all assumption here - no familiarity with these systems at all) so do you know what is used? RS232/485 etc? Can you 'scope the signal and determine the bus voltages and see if there is either an imbalance or loss on one side?
 

JimLS

Aug 16, 2012
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Aug 16, 2012
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I doubt there is a propriatory tx/rx protocol involved (all assumption here - no familiarity with these systems at all) so do you know what is used? RS232/485 etc? Can you 'scope the signal and determine the bus voltages and see if there is either an imbalance or loss on one side?
I took a quick look at the bus signal at the main panel. Well formed pulses with no ringing. Didn't have time to get into the details of bits times and such like but will take another look. I could borrow a better scope from work that has decoding built in if it is a standard type signal. The expander has an 18 pin microchip micro on it - I can see part of the logo not covered by the label. I hesitated to pull the label to see the full part number but no real reason why not - any warranty or such like is long gone. Might have a standard part number or might be custom labeled. Can't get at the programming of course but it would help to know what pins do what internally.

If I end up having to pay someone to trouble shoot the system I may as well just buy a new system and install it myself like I did this one 20 years ago. They are likely to tell me that anyway and then I would have the expense of a new system plus their fees.
 

kellys_eye

Jun 25, 2010
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The expander has an 18 pin microchip micro on it
What about peripheral devices? It would be highly unusual for a high speed data (serial) bus to exit directly from a microchip for tx/rx without some form of buffering (where the transmission signal levels are 'added'). Lightning can cause many issues unless screened cable is unsed (unlikely) and a dodgy/destroyed bus-interface is easily replaced unlike a pre-programmed (mask?) micro. Given there is a data stream coming OUT of the micro I doubt the issue lies within - nor is the protocol likely to be wrong.
 

JimLS

Aug 16, 2012
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There isn't much in the way of buffering - there are a couple transistors on the board that likely do that but I haven't traced them out yet. There are 2 MC14051 analog multiplexers for the 16 zone inputs. This board is downstream of a NX320 remote power supply that has optical isolators for the comms bus and the cable has surge protectors on both ends where the cable comes into the buildings. I have replaced the zone board and get the same issues so doubt the board is zapped by surges. The NX320 can be accessed for programming so seems to be working. The bus is one line that is bidirectional so hard to tell input from output. It is also a continuous stream so hard to know how to interpret the data stream. I suppose if I could find it was UART serial data I could check for repeating patterns.
 

kellys_eye

Jun 25, 2010
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It is also a continuous stream so hard to know how to interpret the data stream. I suppose if I could find it was UART serial data I could check for repeating patterns.
Seriously doubt it's going to be a 'data' issue - still most likely to be something in the 'physical' signal path. The transistors that buffer the line for example.....or even the optical isolators (LED failure is a 'thing').
 

JimLS

Aug 16, 2012
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Seriously doubt it's going to be a 'data' issue - still most likely to be something in the 'physical' signal path. The transistors that buffer the line for example.....or even the optical isolators (LED failure is a 'thing').
Yep! Last night put a scope on it and the between building cable signals look good. The recreated local data signal is bad. Signal doesn't always stay low when it should. Am tracing out the circuit now. I work with opto couplers and design similar circuits so it should be easy once I get it traced out.
 

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JimLS

Aug 16, 2012
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In addition to the comms circuit issue I found the gates of the FETs for switched power outputs on the NX320 have 25V on them when the max rating is 20 and they usually are run at 15! Determined I don't really need the NX320 for the remote box and just removed it from the circuit. Connected the comms bus directly to the NX216 board and it supplies 12V and data to the board, keypad and sensors there.
 

ChosunOne

Jun 20, 2010
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Determined I don't really need the NX320 for the remote box and just removed it from the circuit. Connected the comms bus directly to the NX216 board and it supplies 12V and data to the board, keypad and sensors there.
Jim, how did you determine you don't really need the NX320? Usually when there's an auxiliary power supply installed, it's because there are too many auxiliary devices for the Control Panel, the NX8E, to handle. Somewhere on the wiring diagram inside the Control Panel cabinet door, there should be information on the maximum current that the NX320 can sustainably supply.

As I said before, I'm not familiar with that model, but here's something I know about almost all alarm system models: The max current supply from the CP (Control Panel) often looks low-balled, but it isn't. It can supply more than the max value for short periods, or as long as it doesn't have to do anything extra---like sound the siren or make a phone/cellular/net call. in the event of an overloaded pwr output, the extra current needed for alarm responses will often pull down the voltage on the CPU to the extent that it can't process signals properly. Sometimes a User find he can't shut the system down with his Code, because the CPU (the NX8E) can't process the keypad signals---the siren is wailing and the User cant' shut it off without powering down the CP, both transformer and battery. The trouble is similar to having a weak battery: Results are unpredictable.

BTW, we often call the CP battery a "standby battery", but it's more than that: The CP's 12V SLA battery supplies the extra current needed during alarm conditions, and the Panel can't be relied on to work properly without it. It's designed to work with a battery in normal operation mode, not just if line power goes out. That's also why your extra power supply, the NX-320, had its own "backup" battery ( I assume it did. It should have.)

Now it's possible that your system doesn't really need the extra power supply. I've seen systems that had extra stuff they didn't really need. But I recommend you test it through an alarm simulation or two to see if everything works without the additional PS.
 

JimLS

Aug 16, 2012
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Jim, how did you determine you don't really need the NX320? Usually when there's an auxiliary power supply installed, it's because there are too many auxiliary devices for the Control Panel, the NX8E, to handle. Somewhere on the wiring diagram inside the Control Panel cabinet door, there should be information on the maximum current that the NX320 can sustainably supply.

As I said before, I'm not familiar with that model, but here's something I know about almost all alarm system models: The max current supply from the CP (Control Panel) often looks low-balled, but it isn't. It can supply more than the max value for short periods, or as long as it doesn't have to do anything extra---like sound the siren or make a phone/cellular/net call. in the event of an overloaded pwr output, the extra current needed for alarm responses will often pull down the voltage on the CPU to the extent that it can't process signals properly. Sometimes a User find he can't shut the system down with his Code, because the CPU (the NX8E) can't process the keypad signals---the siren is wailing and the User cant' shut it off without powering down the CP, both transformer and battery. The trouble is similar to having a weak battery: Results are unpredictable.

BTW, we often call the CP battery a "standby battery", but it's more than that: The CP's 12V SLA battery supplies the extra current needed during alarm conditions, and the Panel can't be relied on to work properly without it. It's designed to work with a battery in normal operation mode, not just if line power goes out. That's also why your extra power supply, the NX-320, had its own "backup" battery ( I assume it did. It should have.)

Now it's possible that your system doesn't really need the extra power supply. I've seen systems that had extra stuff they didn't really need. But I recommend you test it through an alarm simulation or two to see if everything works without the additional PS.
The NX320 was used when I added another building as partition 2 so the main motivation was the remote location not loading. That allows a battery, siren, etc in the building. But the buildings are beside one another so it doesn't really need another siren. My initial determination that I didn't need the NX320 was simply that the system worked without it (and didn't work with it because of issues in the NX320) but I just ran through the loading totals and am well below the panel rating for current draw. And I have tested in alarm (several times) with no issues.
 
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