BeanieBots
Moderator
I have a 28X monitoring the case temperature of a 1kW motor. The 28X is housed in an earthed metal case supplied via a switcmode power supply. The DS18B20 has a 2m twisted 3-core flying lead.
About 1 in 3 times, at the point when the motor is energised, the 28X resets, crashes nad has even lost its program. (there is no problem once the motor is running). So far, I have determined that the cause is solely due to noise comming in via the DS18B20 leads.
I have done the following in attempt to stop it.
DS18B20 supplied via 22R.
10uF tant plus 100nF ceramic across DS18B20 rail.
PICAXE pin to DS18B20 via 330R
4k7 pullup on PICAXE side of 330R.
This reduced crash frequency to about 1 in 5.
Adding 1nF between signal and 0v on DS18B20 side of 330R gives about 1 in 8. Increasing to 10nF causes failure to read.
I am currently using 2n2 and suffering about 1 in 10 crashes. Often the PICAXE is OK but the DS18B20 returns 0 until power is cycled.
Does anyone have suggestions on how to suppress this noise problem further? The motor itself is well suppressed, it seems to be the startup surge that is causing the problem. Slow start is not an option.
About 1 in 3 times, at the point when the motor is energised, the 28X resets, crashes nad has even lost its program. (there is no problem once the motor is running). So far, I have determined that the cause is solely due to noise comming in via the DS18B20 leads.
I have done the following in attempt to stop it.
DS18B20 supplied via 22R.
10uF tant plus 100nF ceramic across DS18B20 rail.
PICAXE pin to DS18B20 via 330R
4k7 pullup on PICAXE side of 330R.
This reduced crash frequency to about 1 in 5.
Adding 1nF between signal and 0v on DS18B20 side of 330R gives about 1 in 8. Increasing to 10nF causes failure to read.
I am currently using 2n2 and suffering about 1 in 10 crashes. Often the PICAXE is OK but the DS18B20 returns 0 until power is cycled.
Does anyone have suggestions on how to suppress this noise problem further? The motor itself is well suppressed, it seems to be the startup surge that is causing the problem. Slow start is not an option.