How to add precise amounts of ingredients in my beverage making robot? [closed]

Question

I am currently in the process of making a robot that can make a cup of tea, when It receives the command to do so. The general idea is as follows:

• checks if saucepan is placed
• checks if milk is available
• checks if tea leaves are available
• Hot plate is turned on using a relay
• Pours milk from the refrigerated container using a pump
• Drops tea leaves and sugar into saucepan
• Waits a set amount of time during which tea is mixed(not sure how)
• Chai is pumped from saucepan into cup, or is left in saucepan.
• Hot plate relay is turned off and user is notified through blynk or IFTT

I have figured out how to go about most of the steps, but I cant seem to find a reliable way to add the desired amounts of sugar and tea. I have thought of a few ways:

1. Using a screw conveyer powered by a simple servo moter. I found this CAD model which i could replicate The Thingiverse link

2. Using plastic bottles filled with sugar or tea leaves. The opening of the bottle could be opened or closed with a servo moter, allowing the sugar or tea leaves to drop into the saucepan. This video shows what i mean, The video

With both possibilities the issue is how I would control the amount of ingredients. I want to choose the amount in tea spoons to add. How would I be able to add the exact desired amount? With the milk i thought i would first calculate the rate in L/M of my pump then turn on the pump for exactly the required amount of time in code. Please let me know if you think is a good way to go about it and if you have any idea how i could control amount of substance added and how.

Answer 1

You could have a spoon (or spoons) attached to a belt or chain in a loop. Sort of like an old-style grain elevator scoop conveyor. But instead of a continuous chain of buckets, have a discrete number of teaspoons (maybe even just one), with enough distance between spoons for your controller to count and stop the motion when done.

I haven't found a compelling way to sketch this without using animation, so I'll try with mere words.

Consider making the spoon handles parallel to the belt surface, such that they are remain parallel to the roller axis. The spoon has to travel below the surface of the sugar in order to scoop some up. Ideally it would disturb only the sugar it will lift — pushing anything else around is wasted energy. So you would want to minimize the distance the bowl travels while under the surface. If you were to use an actual spoon, you wouldn't want its bowl sticking way out like a paddle -- which it would if the handle were perpendicular to the belt surface. That also suggests that the radius of the lower belt roller should be as small as feasible.

Also consider what happens at the top of its circuit. I picture the spoon bowl(s) sticking off the edge of the belt. That way, it can dump its load into a chute. But if the bowl hugs the belt, it can only spill onto itself.

One supposes even the milk could be measured by similarly traveling cups.

There is something satisfying about controlling teaspoons of stuff by counting spoons instead of counting seconds. Easier? That depends. Does "easier" override other considerations? That depends too. Pumping sugar is harder than pumping milk. Scooping milk seems harder than pouring or pumping it, but it just might share engineering with the sugar scoop machinery.

Answer 2

I find the idea of the screw conveyer quite promising. I would use a self-made scale to weigh this. For example, a strain gauge with a sort of bowl fixed on it. Put this self-made scale on a 90 degrees servo to enable pouring into the mug of tea (or water at this stage). Then have both the tea screw and the sugar screw pouring on the scale.

For how it works:

• Pour sugar on the scale using the sugar screw, until the controller detects the desired weight of sugar.
• Pour the scale content (sugar) into the mug.
• Repeat with the tea.

More generally, I would use the same thing for all ingredients. You could also weigh the amount of water/milk you add.

Hope it helps!