Thread: "Saw dust bin full" Sensor

Originally Posted by ericks2

Bob....nice job! I have been working with microcontroller based stuff for a few years. These hobby boards are no good in real world applications. When you start using microcontrollers around mains supply and switching mains operated stuff eg. solenoids then filtering of the power supply and isolation of the i/o are required.

ps....i use pic micro's

Yeah, thanks Ericks2, I am aware of this as a problem especially with all those leads flying around all over the place just waiting to pick up signals etc, and even pro gear can suffer from problems outside the box. When I worked in the US on on of our analytical bits of gear we used custom mains powered isolated amplifiers with Peltier cooling to measure DC currents of +/- 10^-14A and occasionally they would shoot up to 10 or 20 times that. Eventually we traced the problem to the use of a RF powered mineral disintegrator in another lab. We were located on 7th floor of the lab and the RF amp was on the second floor. It turned out the Faraday cage around the RF disintegrator was not properly grounded - we also remade the cage around the amps and beefed up the cooling so on a good day we had baselines of ~5x10-15A.

Even though the output of the force sensor is noisier at the MS than at home, the reason the MC stops working is not a force sensor I/O issue as the MC runs fine at the shed on a battery until the battery runs out.

In terms of general mains power quality I've also had 3 different Arduino based dust particle sensors running continuously at the mens shed for weeks at a time with no problems, unless someone turns the mains power or or trips the circuit breaker. However, the Dust bin sensor MC is running on a different mains circuit. I've looked at the mains from that circuit with an oscilloscope but could not see anything but that does not mean that there are spikes or dips that get into the circuit at other times eg when blokes are switching on other HD bits of mains gear.

I once designed a dedicated controller for an Industrial sealing machine. Replaced the existing plc they had in there. From time to time my micro would reset....however i switched multiple valves and controlled a VSD. Took me 80 hours to experiment/redesign the board to cope with any "noise". Good thing about this is that once you solve these issues you use the same design in all your stuff.

Hope you get your issue resolved

Just an idea....if i were to make a "bin full" system myself i might look at using a capacitive proximity sensor. Bob have you looked into this?

Originally Posted by ericks2

Just an idea....if i were to make a "bin full" system myself i might look at using a capacitive proximity sensor. Bob have you looked into this?

Had a brief look - the problem is dust goes and sticks everywhere inside the bin. Might not work too well if a large thin curly shaving happened to trap some air over the sensor. Would have to do some experiments to see how it reacts.

The sensor would sense from outside the bin, through the plastic...