Thread: "Saw dust bin full" Sensor

Originally Posted by doug3030

I wonder if that would work for some of the blokes at the Mens' Shed too?

Sometimes there's the odd member that turns up for coffee and chat and to tell everyone else how to do what they are doing - could work for them.

Soldering iron breakdown yesterday but managed to just get this finished to the point where it can be tested.

The alarm is just a low wattage Blue LED flashing light from Altronics for $15 in the shed we'll use something more substantial like a revolving light of some kind.
The clamp was put on to provide a bit of pressure so the the reading would show more than just zero.
The "8in 06" means the Bin has ~6kg of sawdust in it
When the Bin load exceeds a threshold set by the black knob the alarm and flashing light go off.

IMG_2423p.jpg

Originally Posted by BobL

When the Bin load exceeds a threshold set by the black knob the alarm and flashing light go off.

Conversation between two people in BobL's mens shed in about 12 month's time:

a: "Whats that noise? Why is that light flashing?"

b: "Don't worry about it, you just turn the black knob here clockwise until it stops!"

Cheers

Doug

Originally Posted by doug3030

Conversation between two people in BobL's mens shed in about 12 month's time:

a: "Whats that noise? Why is that light flashing?"

b: "Don't worry about it, you just turn the black knob here clockwise until it stops!"

Turning the knob alone wont actually do it - a switch has t be flipped before turning the knob and I doubt they will remember to do both.
Besides, most of them will probably be too scared to touch it, they are very suspicious about the things I make - that's probably why she don't use the dust extraction..

Originally Posted by BobL

Soldering iron breakdown yesterday but managed to just get this finished to the point where it can be tested.

The alarm is just a low wattage Blue LED flashing light from Altronics for $15 in the shed we'll use something more substantial like a revolving light of some kind.
The clamp was put on to provide a bit of pressure so the the reading would show more than just zero.
The "8in 06" means the Bin has ~6kg of sawdust in it
When the Bin load exceeds a threshold set by the black knob the alarm and flashing light go off.

IMG_2423p.jpg

Well Bob you have got it working, could you now provide a list of parts used and the source code for the Arduino Uno?
The BMS is keen to fit it our DE, so we can stop the overflows that we are getting.

Arie.

Originally Posted by BobL

Sorry am not making these for sale but the details and micro controller software will be freely available to anyone that wants it.

Once you have it all working Bob, I can convert your design on Eagle Cad if you like so it can be made as an Arduino shield for those that want to make their own. Then upload the BOM, Gerber files and 'how to' to order PCB from Itead studio or similar on here if there is enough interest. Depending on your circuit, it could be reduced down to Arduino pro mini or similar to reduce the shield size/cost.

Originally Posted by maxxsinner

Once you have it all working Bob, I can convert your design on Eagle Cad if you like so it can be made as an Arduino shield for those that want to make their own. Then upload the BOM, Gerber files and 'how to' to order PCB from Itead studio or similar on here if there is enough interest. Depending on your circuit, it could be reduced down to Arduino pro mini or similar to reduce the shield size/cost.

Thanks for the offer.

Even though it looks like it, I'm not sure a dedicated shield is warranted as it's not that complicated. Mine is a bit more complex than it needs to be because I built my own relay trigger circuit. The remaining minor complexity is the voltage divider and trim pot but a standard 2 relay Arduino Shield would probably cover those things.

I did the final costing and got reimbursed from the mens shed and it turned out to be more expensive ($78) than I first thought because I purchased the flashing light, relay and alarm locally. If I had bought these on-line it would have been ~$55.

Bob,
Where did you source the force sensor from?
What value pots did you use for trim and comparison?

Regards,
Arie.

Originally Posted by Breezy

Bob,
Where did you source the force sensor from?
What value pots did you use for trim and comparison?

Regards,
Arie.

The force sensor I used was
50kg RFP-611 Thin Film Pressure Sensor Force Sensor 26x26x107mm For Arduino
The unloaded resistance is about 1/2 MΩ and 50 kg is about 76 kΩ.
If you decide to go with these I have couple of spares you can use if you don't want to wait for slow eBay shipping from china to get going with your project and you can replace mine with yours when yours arrives.

I added a 200 kΩ resistor in series with the sensor and originally had a 250 kΩ trim pot in parallel with the 200kΩ resistor but it's not needed - I have never adjust the trim pot because its easier to just accept the read out for what it is rather than trying to get it to accurately measure the weight.

With 5V fron the Arduino fed across the sensor and 200kΩ resistor, the V across the sensor worked out to be = load weight in kg)(^(-0.359)
In the end it worked out that ~40 on the LED display with the sensor set on the edge of the bin means the bin is 3/4 full which is when we change it. I could recalibrate it to get a more reliable wt reading but there have been other problems to try and sort out

Since I built ours I have seen these much cheaper load cells.
DIY 50Kg Body Load Cell Weighing Sensor Resistance strain Half-bridge OriginalGN | eBay
The blurb says these are 1kΩ - I don't know what the fully loaded R is but it might be too low for an Arduino analog port and additional doodads might be required.

As I said above we have another problem as follows.
When the Arduino MC and the force sensor were run direct from the PC or a USB adapter the force sensor readout varied about +/- 2%
However the siren is much louder on 12V so I decided to power the Arduino board with a 12V mains adapter but then the read out of the force sensor wanders around ~ +/- 25%
I reduced that by some smoothing in the program but it was often setting off the alarms earlier than necessary.

At first I though it might have been a ripple in the output of the 12V adapter but it did the same with the 12V from a very stable/steady power supply.
I also another Arduino board but it did the same.

The quickest solution turned out to be to power the Arduino via a 5V USB adapter ($3 on eBay), and then use a separate 12V adapter to power the strobe and the siren.
I only found this out on Friday and all this has been why I haven't posted the parts list and code.
I''l do that in the next few days.

I will be ordering the other parts from China so there will be a delay regardless.
I'm not that interested in exact weight just the ability to trigger when the bin reaches a certain percentage full. I'll play with the coding to display percentage.
Thanks for the heads up on the power supply problem, I was originally going to power the Arduino using 24v from the VFD but that is limited to 200mA, not too sure how much power the Arduino, buzzer, relays, etc would draw, so was going use a separate 12v. The reason behind this is that the current setup didn't include a no power interlock, so if the alarm system isn't turned on the VFD still operates, defeating the purpose of the alarm.

Originally Posted by Breezy

I will be ordering the other parts from China so there will be a delay regardless.
I'm not that interested in exact weight just the ability to trigger when the bin reaches a certain percentage full. I'll play with the coding to display percentage.

Yeah that's good idea. I would be easy to read the sensor V output with the bin full and then work things back from there

Thanks for the heads up on the power supply problem, I was originally going to power the Arduino using 24v from the VFD but that is limited to 200mA, not too sure how much power the Arduino, buzzer, relays, etc would draw, so was going use a separate 12v.

My setup draws a max of 120 mA, but 24V would be too much for any Arduino I can think of anyway. I think the Mega Arduino is supposed to be able to cope with 20V as an input is probably the max. I don't like driving them at close to their max V anyway. The Dust bin full sensor is not the first time strange things have happened in this regard


Cheers

Originally Posted by BobL

The quickest solution turned out to be to power the Arduino via a 5V USB adapter ($3 on eBay), and then use a separate 12V adapter to power the strobe and the siren.

This worked at home but not at the shed. The Mains supply at the mens shed has something twitchy on it that even gets past a USB adapter. I have mangled to get around this problem temporarily by using USB battery in between the USB mains adapter and the Arduino box. I want to analyse the shed power supply before looking for a more compact solution.

Originally Posted by BobL

This worked at home but not at the shed. The Mains supply at the mens shed has something twitchy on it that even gets past a USB adapter. I have mangled to get around this problem temporarily by using USB battery in between the USB mains adapter and the Arduino box. I want to analyse the shed power supply before looking for a more compact solution.

Have you solved this problem?
I found that I couldn't get steady readings at the BMS and went for a software solution, by using a rolling average of ten readings taken at one second intervals.
But our biggest problem is the collection bin is lifted up off the floor by the compression of 1200mm flexible drop pipe. How much it is lifted is dependent on the static pressure, we hope by replacing a part of it with solid 150mm PVC pipe will reduce the amount of lift.
Arie.


Sent from my iPad using Tapatalk

Originally Posted by Breezy

Have you solved this problem?
I found that I couldn't get steady readings at the BMS and went for a software solution, by using a rolling average of ten readings taken at one second intervals.

Yep that's what I did but we are still having power probs at the MS. It works fine at home, but still turns itself off every now and then at the mens shed. Powering it with a Li-ion battery works as long as the battery is charged. I tried powering it with the Li-ion battery and having the battery plugged into the mains to keep it charged but that doesn't work - the unit stays off when the power off. I have ordered a mini Li-ion UPS for it to see what that does.

But our biggest problem is the collection bin is lifted up off the floor by the compression of 1200mm flexible drop pipe. How much it is lifted is dependent on the static pressure, we hope by replacing a part of it with solid 150mm PVC pipe will reduce the amount of lift.

Our piece of PVC is only 150 mm long but we still have a similar problem in that the readings when the bin is near empty are a bit of a guess but once the full size wheelie gets past about 25% full it's not a prob.