Topic: Looking for schematic for TexasWeatherInstruments WLS-8000 power supply

[DaleReid]

I've picked up a working Texas Weather Instruments WLS-8000 unit, minus sensors and power supply/wall wart.

I've got stuff to make most of the sensors work, and have a PS from another type of TWI station that power the unit just fine.

However, there is a 12 v gelcel onboard that apparently powers this unit during loss of wall power, and I'm not sure what the power supply looks like.

There is a red and black wire that goes to the boards pretty straight forward.  There is a common ground with the battery on board, and a three wire attachment through a Molex, red/green/black that goes to the wall wart.

I'm sure that the supply just furnishes power to the station over red and black, and the green (which goes to the + side of the battery) is fed with a charging/trickle current when local power is present.

I'm not sure how the wall wart flips to a power-out mode.  Is there a steering diode that is biased during normal power that now feeds from the green wire over to the red when local power outage occurs?

I'm hoping someone here has one of these and can tell me what the layout is so I can make use of the backup power if local ever goes out.  Doesn't happen often but would be nice to use all the functions of the station.

I checked with TWI a few months ago when I got this and they wanted $80 plus shipping for the wall wart.  I should be able to wire it up myself for considerably less if I knew the layout, since my wife isn't so sure that $80 plus shipping is vital for the few times the power fails.  You know how that goes.

Any thoughts?  Anyone have one of these and can take a look at what is on the power supply end?

Dale

[DanS]

Hi Dale, from your description I envision one possibility. The wall wart feeds the circuitry and battery through a resistor and 2 diodes. The resistor is for keeping a charge for the battery. D1 is the main power to the circuitry during normal operation. When AC drops then the battery powers the circuit through D2. Just one possibility.

Nice find by the way, the WLS-8000 that is.

[DaleReid]

Thanks, I've never seen one before, and really like the construction of the couple three 25s that I have.

This thing weighs a ton with the battery in it, and looks sort of industrial with the rack mount handles.  Sort of like the hi end amps for stereo when I was a kid.  I like the green LEDs so it can be read across the room.  Wired is still OK with me for the location, and once I get all the sensors attached I'm going to be happy.

This looks very doable, and maybe I can take one of my 'extra' wall warts and breadboard the diagram up you furnished.  I'll see what sort of charging draw I can get figured out for the resister value to keep a nearly drained battery not taking too much out of the wall wart and whip this up.  Nice diagram, thank you very much for the thought you put into it.  I was trying to cypher in just one resister and must have been too tired to see the obvious.  Again, my sincere thanks.  The members of this board have always been helpful and polite.

Dale

[DanS]

I'm not sure what wall-wart you're going to use and its capabilities but once you plug in all the numbers to get your resistor value you will want to keep the trickle charge so you float around 13.6v. Too much more above that and you run the chance of the battery gassing and that not only ruins the battery but plays heck with the circuitry. Good luck, sounds like a neat project you have with interfacing all the sensors.