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Saturday 22 January 2011

1-wire PSU

I've had flakey 5V power in my greenhouse for some time now.  I've tried various wall-warts of differing ampage but no go.   Finally I pulled power directly from the computer PSU this helped but it was still slightly below 5V  (4.86V).

So i built a 12V to 5V 3A convertor using LM7805 regulators in parallel.  Circuit diagram below.
Big thank you to Colin @ g1gsw with the help designing this.

Now, it is much better with 5.28V in the greenhouse (measured by a ds2438 Smart Battery Monitor).

Circuit diagram:

Friday 14 January 2011

New soil temperature sensors

Due to the very cold weather we had in December, -15C and below, my soil temperature sensors didn't hold up.

The sealant i used (brown frame sealant) deteriorated in cold - which is bad for anyone using it to keep their windows in !

So now i have set the sensors in the same 7mm dia. copper pipe, but only used 50mm long pieces.  Hopefully the HMA (Hot melt adhesive) - more commony know as hot glue gun stuff - will keep the water out.

Initial testing showed the sensors reading 35C and 37C while the glue cooled. :)

Now i have to come up with a method to connect the sensors back to the cable i removed them from - last time it was all one piece.

Thursday 6 January 2011

owfs errors : BUS_select_subbranch

I've been getting errors on owfs for some time now, but after reading the doco and discovering the error stats, i thought i would look into it more.

$ grep -v " 0" /var/1wire/bus.0/interface/statistics/*error*
/var/1wire/bus.0/interface/statistics/errors:         359
/var/1wire/bus.0/interface/statistics/select_errors:         359

turning on debug on owfs with "--error_print 1 --error_level 5"

Then you get to see things like this:

Jan  6 14:00:37 ubuntu OWFS[32423]:   DEBUG: ow_select.c:BUS_select_subbranch(178) Selecting subbranch 1F 8F 67 05 00 00 00 B6
Jan  6 14:00:37 ubuntu OWFS[32423]:   DEBUG: ow_bus_data.c:BUS_send_data(38) Response doesn't match data sent

but this doesnt tell me what branch is at fault main/aux

So i edited the following file in the source code and recompiled

Wednesday 5 January 2011

WeatherSnoop to mySQL

I've placed the code for the script i wrote for a friend (g1gsw) on googlecode in case anyone else wants a copy.

It reads the WeatherSnoop (v2) XML and places it into a mySQL database.

1-wire, long runs and owfs

My 1-wire MicroLAN has a long run using BT cable (the stuff that comes into your house from the pole outside) it's not the most capable and CAT5 is better if you can use it, but mine runs through my flowerbeds into my greehouse, so it needed to be semi-amoured.

Long runs need slightly different 1-wire slew rates or you get lots of errors and devices drop off your LAN :(

Maxim Application Note 148 states:

Testing with long and short bus lines has shown that the optimum timings for all networks are as follows:

Pulldown Slew Rate: 1.37V/μs
Write One Low Time: 11μs
Data Sample Offset/Recovery: 10μs

So with owfs how do you do that with your Maxim USB dongle...?

Saturday 1 January 2011

RJ11 1-wire hubs

I have a number of 1-wire hubs.  I've made my own rather than buy them.