On 1/9/07, Michael Weber <[EMAIL PROTECTED]> wrote:
I have some problems running a PID-Temperature Controller. It works fine
most of the time, but tends to crash with varying frequency (months to
hours).
So yesterday, I changed from the old python module to the ownet interface
(but still use the old v2.4.1 owserver binary) and encountered the
following error (obviously during the read of a temperature sensor)
ValueError: negative buffersize in recv
The program is very simple: It reads the temperature every minute,
calculates the updated P, and I gains and the correction terms from those.
If the term is 0 or 1, the heater is turned off or on, if it is inbetween,
the heater is put into PWM mode. Most of the writing I encapsulated in
"try." already, but since yesterday I know that the problem seems to be
(also?)the temperature reading.
Any suggestions? Since the first implementation of this regulator, I
rewired the bus using CAT5 cables, and I removed all the "star"-parts from
the topology. Cable length is less than 50m, the connection is done via a
MOXA port server, a serial-to-1wire converter including a filter.
Well, you've changed only one thing, and that changed from working to
non-working? My thought is that either the 2.4.1 owserver tcp protocol was
slightly different, or that there is an error in ownet.py
If it is easy to test a current version of owserver, that would simplify the
analysis. In 2.4.1 there were no owserver protocol clients besides the
owserver library so the protocol wasn't as well tested for bad field values.
A 1-wire PWM module? Very interesting.
Electrical problems on the 1-wire bus should not give protocol errors.
owserver should filter them out.
The circuits we use are available at
http://www.aip.de/People/wbittner/1wire/index.html
Sorry, only in German:
"Spannungseinspeisung am Master Kabel auch hier!" is the serial-ow
converter
"Temperatursensor für Daisy Chain Verkabelung mit RJ12 Anschluß für
Sensoren" is the Temperature sensor
"PWM Modul für Heizungsregelung" is the PWM-heater module
Dr. Michael WeberAstrophysikalisches Institut Potsdam
An der Sternwarte 16
D-14482 Potsdam
Tel: 0331 7499 351
Fax: 0331 7499 200
email: [EMAIL PROTECTED]
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