I would approach from a manual setting, but auto fill.
if you have a balance beam
put your empty holder on one side (Tare weight)
then ballance to zero
add your 100g weight.
put an optical sensor on the fill side scale.
when the fill side triggers the sensor.
you have a fill.
if you have a 'fork' under the fill bucket and a servo to tip it to empty it, you can have the system repeat.
to change weight, you would have to have the weights for the scale, but that should be very simple.
one start/run/stop switch
one 'filled' sensor (otp-interupter from an old scanner/printer/mouse ?
servo woudl only need to be sized to lift/tip/empty the cup with the load you want.
as a note, for 125g, you could have 25 and dump 5 times.
for 200g, you could full to 100 twice, etc.
since I think you are into the really small weights, this might be easier than trying to get a micro gram weight sensor.
and the beauty is that you might have all the parts needed.
Hi,
I agree with @dave-in-nj, a simple balance beam would mean simple mechanical system that would be quite low in cost and easy to maintain.
To change weight settings you just change the counter weight.
You could have a couple of sensors, one for beam level and another at say 10% before level.
The 10% sensor could be used to slow the feed rate down for accurate final total.
dave-in-nj:
I would approach from a manual setting, but auto fill.
if you have a balance beam
put your empty holder on one side (Tare weight)
then ballance to zero
add your 100g weight.
put an optical sensor on the fill side scale.
when the fill side triggers the sensor.
you have a fill.
if you have a 'fork' under the fill bucket and a servo to tip it to empty it, you can have the system repeat.
to change weight, you would have to have the weights for the scale, but that should be very simple.
one start/run/stop switch
one 'filled' sensor (otp-interupter from an old scanner/printer/mouse ?
servo woudl only need to be sized to lift/tip/empty the cup with the load you want.
as a note, for 125g, you could have 25 and dump 5 times.
for 200g, you could full to 100 twice, etc.
since I think you are into the really small weights, this might be easier than trying to get a micro gram weight sensor.
and the beauty is that you might have all the parts needed.
honestly I still dont understand how the way it works
Is it something like this?
TomGeorge:
Hi,
I agree with @dave-in-nj, a simple balance beam would mean simple mechanical system that would be quite low in cost and easy to maintain.
To change weight settings you just change the counter weight.
You could have a couple of sensors, one for beam level and another at say 10% before level.
The 10% sensor could be used to slow the feed rate down for accurate final total.
if you google water park tipping bucket. you can see a simple design and a simple concept.
if you make one out of a small cup, and add a servo to it, you could dump the cup.
if you mounted that onto a simple scale, then zero it as empty to account for the weigh of the cup and the servo.
when you put your desired weight on the other side, it would move. then you know you are overweight.
use the servo to tip the bucket into your bag, press go and start over again.
Make sure the bucket start moving before the desired weight is reached, as inertia give it some reaction time (so it's got more than needed to start moving) and it takes time for the last seeds to reach the bucket as you close the hopper.
