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Temperature sensors - DS18B20
Posted: Mon Oct 08, 2012 9:26 pm
by tentacles
So I got some temp sensor chips, DS18B20, to integrate into my LED fixtures. I was testing a couple with the Reef Angel but it doesn't seem to recognize them. I looked up the pinout on the schematic (and checked with a meter) and tried several chips.
Originally I wanted to use them in a two-wire configuration but I don't think the RA supports this, as it made the included temp sensor (plugged into port 1) say ERROR.
Re: Temperature sensors - DS18B20
Posted: Mon Oct 08, 2012 9:28 pm
by rimai
Make sure you reboot the controller to pick up the new sensor.
It only scans the OneWire bus at boot.
Re: Temperature sensors - DS18B20
Posted: Mon Oct 08, 2012 9:49 pm
by tentacles
rimai wrote:Make sure you reboot the controller to pick up the new sensor.
It only scans the OneWire bus at boot.
Ah, thanks! I will try that - is the one-wire configuration known to work with the RA?
Also, it's a bit off topic, but the temp sensor that came with my RA is reading 94 F - and there's just no way it's anywhere near there. Bad sensor?
Re: Temperature sensors - DS18B20
Posted: Mon Oct 08, 2012 9:51 pm
by rimai
yes. the temp sensors are ds18b20 encased in a ss sheath
Re: Temperature sensors - DS18B20
Posted: Tue Oct 09, 2012 10:29 am
by tentacles
Thanks again, rimai - that's certainly what I thought based on the product page. What I meant by one wire configuration is using the sensor in parasitic mode where only two wires are run to the sensor (power is fed on the data line).
based on the time of your post, I'd guess you didn't see my edit, I am getting high readings (94F) from the sensor that came with my RA. Also, I used the wizard to program it (inputting the values in code) and I can't change the clock on the unit. My plan is to reprogram but enter my values manually into the unit to solve that, but the temperature thing has me stumped. Is there a calibration or something, although my understanding was the 1WS chips feed a binary value for temperature.
Re: Temperature sensors - DS18B20
Posted: Tue Oct 09, 2012 10:46 am
by rimai
You may be able to use parasitic mode, but I've never tested it.
The pull up may not be strong enough and you may need to add another pull-up at the end of the cable where your sensor will be located.
The sensor may be bad if it is reading that high. They are factory calibrated and output the value as it is with the current temperature. There is no need to offset or calibrate it.
To change the clock, you can use any of the remote apps or add this to your setup()