1-wire DS18B20 change resolution

[gjniewenhuijse]

Is it possible to change the resolution from a 1-wire DS18B20 to 12 bits with a LogicMachine, like in this topic:
http://www.homautomation.org/2015/11/17/...1112-bits/

And i like to change the send delta to a lower value, now the range starts with 0.2

[admin]

You can read 12-bit result via a script but there's no big point in doing that. Even though theoretical resolution is better the resulting value won't be stable due to how the measurement works. The better approach is to do over-sampling by averaging the resulting values over a specific period of time.

[gjniewenhuijse]

You can read 12-bit result via a script but there's no big point in doing that. Even though theoretical resolution is better the resulting value won't be stable due to how the measurement works. The better approach is to do over-sampling by averaging the resulting values over a specific period of time.

Oke, but i like to have my values with 0,1 precision.
With a arduino and the same type sensor i can do this (theoretical ), but connected to the LM4 it gives strange results: see attached picture.

[buuuudzik]

You can read 12-bit result via a script but there's no big point in doing that. Even though theoretical resolution is better the resulting value won't be stable due to how the measurement works. The better approach is to do over-sampling by averaging the resulting values over a specific period of time.

Oke, but i like to have my values with 0,1 precision.
With a arduino and the same type sensor i can do this, but connected to the LM4 it gives strange results: see attached picture.

You can add an event-based script which repeat this value with custom precision or you can use custom values for visualisation if this is only for visualisation purposes.

[gjniewenhuijse]

Oke, i can do a reading and custom precision with:

Code:

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require('ow') value = ow.readfile('SENSORID', 'temperature', true) -- third argument will force a new conversion log( round(value,1) )

I know its theoretical, but can i change the precision by lm4 or do i need to connect them to a arduino and execute the following code:

Code:

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ds.search(addr); // address on 1wire bus if (addr[0] == DS18B20)     // check we are really using a DS18B20 {    ds.reset();             // rest 1-Wire    ds.select(addr);        // select DS18B20    ds.write(0x4E);         // write on scratchPad    ds.write(0x00);         // User byte 0 - Unused    ds.write(0x00);         // User byte 1 - Unused    ds.write(0x7F);         // set up en 12 bits (0x7F)    ds.reset();             // reset 1-Wire    ds.select(addr);        // select DS18B20       ds.write(0x48);         // copy scratchpad to EEPROM, next reboot it has the new precision    delay(15);              // wait for end of write }

[admin]

You don't need to change the precision, reading "temperature" property will read the 12-bit value, by default LM uses 10-bit value ("temperature10" property).

[gjniewenhuijse]

You don't need to change the precision, reading "temperature" property will read the 12-bit value, by default LM uses 10-bit value ("temperature10" property).

perfect.. thanks

[gjniewenhuijse]

something like this?

resident script every 60 seconds:

Code:

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-- better to save the last 5 readings and avg them and then write to bus require('ow') require('user.nit_measurements') -- second argument temperature10 (10-bit value) -- third argument will force a new conversion readValue = ow.readfile('28.690E0A070000', 'temperature', true) -- measure last 5 readings mValue = measValue (5, readValue) log (round(mValue,1))

user_library nit_measurement:

Code:

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avgMax = 5 function measValue (iMax,iValue)   -- init value array   if not measCount then     if iMax then       avgMax = iMax     end       measCount = 0     measValues = {}       for i=1,avgMax do         measValues[i] = iValue       end   end   measCount = measCount + 1   -- set values   for i=avgMax,2,-1 do     measValues[i] = measValues[i-1]   end   measValues[1] = iValue   --log(measValues)      -- reset counter   if (measCount == avgMax) then     measCount = 0   end      rValue = 0   for i=1,avgMax do     rValue = rValue + measValues[i]   end   rValue = rValue / avgMax   return rValue end

[admin]

Here's a function you can use to calculate the average, this version will keep last count values and will returnt the average for every insert:

Code:

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function avg(store, count, value)   local sum = 0   -- add new value as first (newest) store element   table.insert(store, 1, value)   -- remove old elements, until store size is correct   while #store > count do     table.remove(store)   end   -- calucate value sum   for _, value in ipairs(store) do     sum = sum + value   end   -- get average value   return sum / #store end

And here's how you can use it:

Code:

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if not store then   require('ow')   -- load avg function here   store = {} end value = ow.readfile('28.690E0A070000', 'temperature', true) avgvalue = avg(store, 5, value)

You can add an extra counter in your resident script if you want to send a new value for each X samples.

[gjniewenhuijse]

great!