Quote from: stooba on April 13, 2012, 08:07:04 PM
Hey again.
Is there really no one out there who has an OBI110 unit who is willing to take photos of the relay and components that are missing from the current builds?
Seems like there should be some units out there.
Just because people have such units doesn't necessarily mean they want to disassemble them. On the bottom of my OBi110 (which I am sure has a relay) there are no visible screws, and I sure don't want to start prying off feet or punching holes in the label to find them.
However, I am wondering if you aren't going about this the hard/expensive way. Since you seem to know something about electronics, wouldn't it be possible to use a low voltage, low current DPDT relay (with the coil of the relay connected to a "wall wart" transformer) to switch your phone line? I know it would be nicer if it were built into the device, but since it isn't, it just seems like an external relay solution might be cheaper and easier to build than trying to track down a bunch of unknown components.
The way I picture it, such a relay would have eight contacts, two for the coil and six for the DPDT switch. So:
The coil contacts would connect to a low voltage transformer plugged into the electrical supply.
The DPDT switch center contacts would connect to the phone (replacing the PHONE port). You'd probably want to connect these to a standard phone jack so you can plug your phone in.
The DPDT switch normally closed (when no power is applied) contacts would connect to the PSTN line (which would also be connected to the OBi110 LINE port).
The DPDT switch normally open (when no power is applied) contacts would connect to the OBi110 PHONE port.
So, as long as power is available, the phone would connect to the OBi110 PHONE port through the relay's normally open contacts, and when the power drops it would connect to the phone line via the relay's normally closed contacts. If you use a low-current relay with a low-voltage AC coil, and an AC transformer (not DC) you probably don't really need to worry about kickback protection, since there are no rectifiers in the power supply to protect. Of course you
could use a relay that has a coil that matches the local power supply voltage (such as 110 volts in the USA and Canada) but I don't recommend that because then you'd have to be VERY careful to not let the relay coil contacts and the switch contacts come in contact with each other.
With smaller relays it may be a bit difficult to keep the two circuits isolated so that's why I would consider using a "wall wart" to step down the AC voltage, but of course if you have a larger old-style relay that puts plenty of distance between the coil contacts and the switch contacts it might not be such an issue. BUT since I don't know who might be reading this, as a general rule I would say you should NOT use higher voltages (probably anything above about 24 volts) for the relay coil voltage unless you are VERY EXPERIENCED with electrical devices and know the dangers of dealing with the higher voltages (which can include fire or DEATH if you are not careful or don't know what you are doing!).
I really do "get" the desire to not have to use an external relay and to fill in the "missing" components, but sometimes you just gotta be practical and use what you know will work and what is available. In fact I wonder if the reason the relay is missing in the first place is because it was made in Japan and the factory that makes them was damaged in last year's earthquakes, causing a shortage (similar to what happened with hard drives)?
