Alix1d with Batt backup work in progress

[oliverb]

I am having another attempt to batt backup my Meteohub (now in an ALIX 1d) and my WMR928.

I have fitted my ALIX1d board in a MINI ITX case.
This case is much larger than the standard case and should allow for the backup battery and PSU.

It also has USB ports etc at the front under a flip down panel along with LEDs for power and CF card activity. These LEDs would have been nice on the standard case.

I also have a micro USB keyboard and LCD monitor connection that fits in my dual input monitor.

I have to cut some major bits off the case and move it around to accommodate my battery. There are batteries that will fit without major case mods but as I already have the battery I am stuck with it.

I plan to add an LCD batt voltage monitor in the front panel as well as a charge indicator LED.

Battery backed up power for my WMR928 weather station will also come out the back panel. I am trying to find out if my WMR928 will the the 13.5v output direct or I will have to regulate it down to 12volts. I have posted a question to Oregon tech support as I don't fancy wrecking my WMR928 experimenting.

I have already tried the ALIX1d with 15.5v and 13.5v with no problems. The manual states 16v is the max input so I knew this was safe to try.

This is very much a work in progress and some if not all the parts are bound to change. I would welcome any comments or suggestions.

See images for proposed installation.



Brett.

[oliverb]

.......and side view.

[oliverb]

sort of "artists impression" of batt meter under front panel mesh.

Also shows USB,audio and firewire connections under front flap.

[oliverb]

In case anyone is following this thread.
I have had a reply from Oregon tech support on running the WMR928 on voltages greater than 12v.

Their reply was basically we only recommend using the supplied mains adapter.

I have therefore decided to add a 12v variable regulator to supply power to my WMR928 weather station. I will in fact run it at around 11.5v so as to allow the regulator to run off the 12v battery during mains power fail. I have used a low voltage dropout regulator to keep the power consumption as low as possible. At some point below 12volt the WMR928 will go into battery backup mode and stop sending data. I am hoping it 11.5volts will not trigger it.

I have built the battery charge and backup circuit and modified the case to fit extra switches and the voltmeter. I have added a switch so that the volmeter can monitor the battery charge and discharge along with the weather station voltage output.

The circuit is on test at present with dummy loads. I will prob run the ALIX-1d board with a dummy load in place of my weather station Fri to give it proper test. I want to test it until the battery runs flat then turn on the mains to check how much current is drawn by the battery at full charge rate.

I am still waiting for my voltmeter to arrive before giving it a long term test. I hope to have the new system up and running for January.

[skyewright]

In case anyone is following this thread.

There's me at least, and I doubt I'm the only one.

All very interesting.Thanks.

[oliverb]

Update. I have had to extend the USB cable that connects to the front panel of my new case as the supplied cable was just too short.

I have now installed the ALIX-1D board in the new case and powered it up. The board consumes 300mA when on. Note this is without the load from my WMR928 weather station. My power meter is showing between 8 to 11 watts at the mains plug.

I have tried unplugging the mains power and the battery backup steps in without a glitch.

The next step is to connect my weather station to the 11.5v jack at the back of my new case and see how it runs. I can then to a battery test to make sure the 11.5volts is maintained to my weather station right down to 12volts from the battery.

I am using a 7ah battery at present as my 18ah was just too big. A 12ah will fit in perfectly but I will wait until the system is working before making the outlay.

[oliverb]

I have now connected my WMR928 weather station to my new case to run some tests.
Setup as follows.
My old meteohub is still running through my NSLU2. This is taking data from my WMR928. Power from the WMR928 is from my new ALIX-1d case rear power connection at 11.5volts. I can confirm the WMP928 runs fine at this voltage.

Without the WMR928 connected the ALIX-1d was drawing 300mA. With the WMR928 connected it now draws 333mA. When you use the touch screen on the WMR928 it goes upto 440mA mainly due to the back light.

The WMR928 used to consume just under 2watts with no back light on and my ALIX-1d system now shows 10.5 watts including the WMR928.

Disconnecting the main has no effect on the ALIX-1d or WMR928.

[oliverb]

I have now tried a battery run for 5 hours. The battery voltage on load was 12.000volts after 5 hours. The WMR928 ran perfectly throughout the test. The LDO regulator providing the 11.5volts to the WMR928 should keep running until the battery voltage drops to 0.25v above this level.

Again on restoration of mains power the WMR928 weather station and ALIX-1d continued working. The current drawn from the PSU went up to 1amp as the battery charge current was quite high. This soon dropped as the battery became charged.

My PSU is rated at 4amps so has plenty in reserve for battery charging on top of normal meteohub operation.

Power fail monitoring
I have a couple of spare temp sensors so may use one as a meteohub mains fail monitor. If I strap it to the very hot PSU I can see when the mains fails as the PSU will cool rapidly. Or maybe I could also power the sensor from my PSU and set an email alert if the sensor looses power?

Is there anyway of setting temperature alerts for example if a sensors temperature goes too low?

Edit. Have now set WMR928 voltage to 11volts and it still works. This means my weather station will now work with the standby battery down to 11.25volts.

[oliverb]

I have made a few mods to my design. I have moved the main battery fuse to a position under the front flap. This way I can power down the system without taking the cover off the case.

I have also added battery terminals to the back of the case so I can now use my larger 18ah battery. This will be hidden away behind my PC. The ideal battery would be a 12ah as it will fit inside my case and would give a run time of around 12 hours.

I have also fitted a preset resistor under the front flap so the battery charge voltage can be set and checked off the voltmeter when it arrives.

Finally I have fitted a probe from one of my spare Oregon sensors to the heat sink of the power supply. I have set this in Meteohub as PSU so I can keep an eye on my system from my mobile phone.

I get lots of power cuts where I live so I can use a Meteohub graph over the year to see when and how long they were.
See example graph from Meteohub below.

[admin]

very interesting project.

If you want to monitor voltages of the battery or loding/unloading currents you could even connect a labjack u3 unit to your Meteohub. That way meteohub can monitor voltages of the power supply by itself.

[oliverb]

Thanks for that, looks very interesting. It it easy to setup with Meteohub?

Brett.

[admin]

its plug and play. Labjack can be selected on "weather station" page as one of the weather stations.

HV variant might fit best as it can directly handle voltages up to 20V on the HV pins. As you already have a shunt in the power support lines to reduce voltage (at least I understood your post that way) you can measure voltage reduction happening at the shunt and ohm's rules will give you the current. Meteohub can do that math by means of calibration factors. When shunt is not bound to gnd, you can use U3's feature to measure voltage differences by using two reference inputs that don't need to be gnd-ed.

[oliverb]

Thanks again. Looks very easy to setup. I use a "hacked" switch mode PSU and a LDO regulator to get my voltages. See diagram. I could prob use a shunt from an ammeter to get the charge/discharge voltages for meteohub to convert.

I will post a better diagram with some notes when I get it all working.

Brett.

[oliverb]

A quick preview of my working Meteohub with ALIX-1d and full battery backup.

I will get some more pics and full info up ASAP.

[oliverb]

I have just posted some images to the site below showing my completed server with battery backup. I have also added a short description and a circuit diagram of the charger and battery backup circuit.
http://www.brettoliver.org.uk/Weatherserver