Hi all
I have been messing around for a year or so with the TH and it's been great. I have a need to put 17 DS18b20s on to one TH but I seem to be having problems with it. The array of DSs work fine on a Uno but I seem to be having no joy on the TH. any suggestions?
Re: 17 DS18B20 on a EmonTH
Power supply problems are the first thing I would look for. You're obviously powering all 18 at the same time, so what happens to the battery voltage and the power rails when they all get turned on? (I'm assuming your Arduino was mains-powered and the sensor array was not switched?)
Re: 17 DS18B20 on a EmonTH
They should only be pulling about 25mW and the board should be good for 150mW yes I know the script has an error where the const int TEMPERATURE_PRECISION = 1; is I have it set to 11 in the script
I seem to be getting data on the first 6 now I added the correct precision
Node: Key Name Process list last updated value
19 1 log 34s ago 31.0
19 2 34s ago 238
19 3 34s ago 265
19 4 34s ago 270
19 5 34s ago 275
19 6 34s ago 275
19 7 34s ago 0.00
Re: 17 DS18B20 on a EmonTH
Checked the voltage today and it holds a good 3.3volts..... I have tried setting it to 9bytes and giving the 750mS to see if we have a time problem...
Re: 17 DS18B20 on a EmonTH
With 17 sensors you may have long wiring lengths.
Multiple 1-wire sensors become quite sensitive to wiring conditions, so it's probably worth checking http://www.maximintegrated.com/en/app-notes/index.mvp/id/148. In particular, you don't want long stubs on a daisy chain of sensors.
Re: 17 DS18B20 on a EmonTH
I have just noticed that if I disconnect all the sensors that I'm still getting a reading from some of the sensors Ok not from the sensors but from something...
19 1 log -3s ago 31.0
19 2 -3s ago 0.00
19 3 -3s ago 0.00
19 4 -3s ago 273
19 5 -3s ago 273
19 6 -3s ago 272
19 7 -3s ago 0.00
19 8 -3s ago 0.00
Re: 17 DS18B20 on a EmonTH
Ok scrap that it was the unit had locked up.... but I'm still stuck on only getting 3 senors to read....
Re: 17 DS18B20 on a EmonTH
As Billt says, the method of wiring is important. You might find that, with a complicated network of sensors, you need an external driver IC as per Maxim's data sheets.
Re: 17 DS18B20 on a EmonTH
It would seem to be a problem with the EmonTH when all of the other parts of the software are running. I can ID and read all of the sensors if I do it as a read of the DS18B20s but when I try and exstend the TH script I only can see the data from the first 3 ext sensors.
Maybe the payload size or max data the RFM12B can send.. I really don't know..
Re: 17 DS18B20 on a EmonTH
I deleted the duplicate post.
There is of course a limit on the message size, it is fully documented, both in JeeLib and in Building Blocks.