[SOLVED] AD2USB Causing OC on keypads

[los93sol]

I've had my AD2USB installed and working for about a year now with no issues. Recently we took a power hit, but I believe the panel held on the backup battery and the server the AD2USB is connected to is on it's own UPS so it did not lose power either. However, both of my physical keypads, one at address 17 (6150RF), the other at address 18 (6150), displayed OC which seems to indicate open circuit, or failure to communicate with the panel.

Okay, no big deal, I go down to the utility closet and completely power down the panel and back up....the issue persists. I did notice that the AD2USB works flawlessly despite the other keypads showing OC. Okay, so the troubleshooting saga begins. I disconnect all keypads and add them back one at a time. First I added the 6150RF and power on....all good there, then the 6150, all good there. Finally I added the AD2USB and boom, the other keypads show OC, but oddly, the AD2USB is working fine. At this point I have all 3 keypads connected so I'm thinking to myself, alright, there must be an address conflict here somewhere. I validated the addresses at the physical keypads first, then on the AD2USB, the AD2USB is on address 19, with the 6150 on address 18, and the 6150RF on address 17, exactly how I suspected. I'm now stumped and hoping someone here has some idea what I can look at next.

[mathewss]

It is Zapped.

If you want to unsolder the broken part it is not needed for Ademco panels Q1 as I recall has failed. Or you can send it back and I can repair it for you. The next generation we are building fixes this problem with lightning strikes by adding a fuse in front of Q1 and a EMI circuit in front of everything.


Re
Sean M

[los93sol]

Just to be sure I understand correctly, the problem is a failed component on the AD2USB, but it is a component that is not required for normal operation with my panel so I can just desolder the component at Q1. Would that be the case even though the AD2USB always sees messages from the panel and can even send keypresses without issue?

[mathewss]

Yep its not needed for the Ademco bus.

I will admit I never tested sending data on the bus when this part fails. I could see how it "may" work with this part failed but keypads would be unhappy with the faulted part. Q1 is a FET and when fets fail they tend to fail in a closed circuit. This drains the voltage on the DO line causing the keypads to think they are not connected to the panel.

Looking at the part if you see it looks damaged and cooked thats a good sign but they can fail and not even look like anything is wrong.

Re
Sean M

[los93sol]

Just a quick sanity check, I opened up my AD2USB but I do not see Q1 anywhere, but I do see Q2 in the corner of the board next to the panel inputs, and I see C1 almost directly behind the panel inputs. I sat with it under the scope for about 15 minutes going over and over the board, but I may just be overlooking it. Any other clue as to what vicinity of the board I should be searching?

[mathewss]

Sorry my bad. It is Q2. Its right next to the green terminal block at the edge of the board.

Re
Sean M

[los93sol]

Thanks for verifying that, I'm going to run back to the shop now and desolder it from the board. I will report back how it goes. Thanks for your prompt responses, your customer service is outstanding!!!

[mathewss]

ad2usb24.png

Here is the new AD2USB design. I am currently preparing for a production run of the new design I have been testing for the past six months. This redesign incorporates the improvements we put into the last Ad2Serial and the new Ad2Pi boards including a chip designed to protect from high voltage ESD and lightning strikes and the added fuse to protect Q1. Video of me testing in our lab with a zapper can be found on our facebook page. I also changed out the FTDI chip for a smaller one with fewer features but just as much performance. This extra room allowed me to add the galvanic isolation. Now the computer and the alarm panel can exist on totally different ground planes. I also added ESD protection directly to the new USB chip to protect it from ESD from the USB side.

Probably about 30 days out before we will start shipping. We are currently out of AD2USB but you can still get them from a few of our suppliers.

Re
Sean M

[los93sol]

You were correct! Pulled that FET off the board, re-installed, and everything came right up! Thanks for the assist in reviving my alarm panel!

I've been seeing references to AD2Pi but haven't looked at it yet, I'll have to go browse the shop to see what it's all about, sounds interesting though!