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Hello all!
I wanted to introduce you my last MOC. This is a Lego appliance to cook
soft-boiled eggs powered by an RCX.
You can find pictures, video, NQC codes, CAD files and documentation (in English
and French) on my BrickShelf folder:
http://www.brickshelf.com/cgi-bin/gallery.cgi?f=112398
Description:
The Egglift is mainly composed of four elements:
- A metallic perforated non-Lego® basket where you lay the eggs. The basket, made of metallic wires, is fairly small and can contain 2 eggs maximum.
- A winch that contain a motor to pull up or down the basket through a string and also a light sensor to detect the position of the basket. (in red)
- A Lego® RCX to pilot the basket through the winch and a 180 seconds temporization (adjustable). (in yellow-grey)
- Finally, a Lego® structure where the three above elements are graft. (in blue)
Instructions of operation:
- Fill up a pan with water, and place over a cook top.
- Place the Egglift (with its basket in up position) above the pan, in a way that when the basket is in down position, it fully goes in the pan.
- Place one or two eggs into the basket.
- Turn on the cook top.
- Push the button “Run” of the RCX.
That’s all for the human operations: the Egglift will automatically detect when
the water reached its boiling point. The basket will then automatically drop
down until it is fully submerged in the boiling water. After three minutes, the
basket is automatically pulled up and an alarm rings, warning you the boiled
eggs are ready. Just pick them up and enjoy!
Detecting the position of the basket:
To obtain a reliable cooking system, it is relatively important the lower (and
less importantly the upper) position of the basket remains constant and precise:
the eggs have to be fully submerged in the boiling water for a safe cooking.
The choice of a temporization in the program (turn on the winch for 5 seconds
before turning it off) would have not been well suited for this application.
Because of inaccuracies in the motor, in the gear train and the weight variation
of the eggs, to basket would have not returned to the same place every time.
The position of the basket can be detected with a light sensor aimed at the
black-and-white circle on the left stuck to a 40-tooth wheel.
This wheel has 24 divisions, alternatively black-and-white. When the motor that
control the basket is on, the light sensor counts how many divisions had passed
by, thus letting know the RCX a fairly accurate representation of the position
of the basket.
This method is not too accurate, but it is accurate enough for this type of
application.
Detecting when the water reached its boiling point:
A Lego® temperature sensor (ref# 9755) is connected to the RCX. The drawback of
this sensor is its range: it only works at temperatures between -20oC and 70oC
(-4oF to 158oF). That’s a long way from the water boiling point 100oC.
Thus, the Lego® temperature sensor had to be relocated to a spot where it reach
its maximum range (approximately 70oC) when at the same time, the water reach
100oC.
Typically, it is approximately one Inch (35mm) above the water level.
The use of a DCP Microdevelopments® ProTemp sensor (ref# D10047) dipped inside
the pan would most likely get round this major drawback.
Cooking time selection:
Even if Egglift’s primary function is to cook boiled eggs, it can also cook
soft-boiled and hard-boiled eggs!
Actually, a cooking time selection button is conveniently placed next to the
RCX. Each press on the button selects cooking times.
<humor>
Estimated cost:
If the Egglift had to be mass product (I’m still looking forward any potential
investors who might be interested for a joint venture), its production costs
would be roughly $ 190.00 USD. (This is only including raw materials and not
including assembly costs).
This is very competitive compared to other Steam Egg Cooker on the market whish
retail for around $ 25.00 USD.
The Egglift is more aimed at wealthy “connoisseur” customers who want to cook
their boiled eggs “à l’ancienne” but with a touch of modernity.
Advantage of the Egglift:
The Egglift features countless advantages over other competitor steam egg
cooker:
- It is cheap.
- It is compact.
- It is convenient.
- It can be conveniently stored.
- It can cook eggs in large quantity (two at a time) for large family.
- It is dishwasher safe (after removal of the RCX, the motor and the sensors).
- It will not break up the look of most “gourmet” kitchen.
</humor>
Bon Appetit!!
Acknowledgment:
- The black-and-white wheel light sensor is an original idea from Benjamin Erwin in his excellent book “Creative Projects with Lego® MindstormsTM”.
- Thanks to Freelug Member Richard “Vauban” for his help and advices.
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