Page 60 - EE Times Europe Magazine | February 2020

58 EE|Times EUROPE
Let’s Cook Arrosticini Using Open-Source Hardware

meat extends down roughly half of the skewer are available in small diameters
length, and the skewers are positioned on the suitable for robotic applications.
stove with the bare wood extending over The motor has a diameter of
the edge, allowing the cook to turn them so 30 mm and is characterized by
that the meat cooks evenly on all four sides high dynamics and high torque. It
(Figure 2). After defrosting and before grilling is available in two lengths, each in
the meat, the cook would dry it with absor- a standard version and a high-
bent paper and wait for its temperature to torque version, with a maximum
reach approximately room temperature. nominal torque up to 110 mNm at
The average grilling time is about 1 to 2 75 W. In all versions, the new EC-i
minutes per side (related to the temperature 30 motors can be expanded with
of the coals and the relative distance from the encoders, gearboxes, servo con-
arrosticini). trollers, or positioning controllers.
The DC Motor Control Shield
DESIGN from Infi neon Technologies is one
The project must include temperature sensors of the fi rst high-current motor
to control the temperature of both the arrosti- control boards compatible with
cini and the coals. The optimum temperature Figure 4: n neon’s M Boot it Arduino as well as with Infi neon’s
of the meat will determine the degree of XMC1100 Boot Kit, based on the
cooking, so it will be necessary to assess the BTN8982TA IC. The DC Motor
difference in temperature during the design tion, a defective temperature variation Control Shield can drive two unidirectional DC
phase. The hardware structure comprises: should reduce the speed of the motor so motors (half-bridge confi guration) or one bidi-
1. an Arduino board 2 that the cooking remains optimal. rectional DC motor ( -bridge confi guration). A
2. temperature sensors The temperature sensors used are PT100 PWM can control the BTN8982TA NovalithIC
3. a display to show the temperature of the sensors, which commonly fi nd application half-bridges via the IN Pin (Figure 4).
coals and the arrosticini. The two tem- in industry settings such as laboratories for The arrosticini in our project can be
peratures must be different the operator measuring temperature during work sessions. connected to a motorized system to rotate
must keep the coals under control so The nominal resistance of these sensors is them 90° every 1 to 2 minutes. Once the 360°
that the temperature is the same as the established by the IEC 751 standard and is rotation is complete, an arrosticino must be
starting temperature. 100 in a temperature condition equal to removed from the coals. The taste of the meat
4. a fan to ensure uniform heating and, 0°C. The use of thermal resistance in the depends on the temperature of the coals,
therefore, uniform cooking. In this case, PT100 allows it to operate in a broader tem-
the model described above will pres- perature range, between –200°C and 850°C, Automating the grilling
ent a coeffi cient to multiply that takes with excellent accuracy and interchangeabil-
ventilation into account. According to the ity, stably and durably (Figure 3). process with a sensor system
programming, the fan can be switched on Conditioning is accomplished via the
where necessary, i.e., when the tempera- MAX31865, an easy-to-use resistance-digital and motor control will yield
ture difference between the coals and the converter optimized for platinum resistance perfect arrosticini.
meat begins to deviate. temperature detectors (RTDs) such as the
5. an I C display to indicate the tempera- PT100. An external resistor sets the sensitivity
2
ture and control text on the cooking of for the RTD used, and a precision delta-sigma which can vary widely (900°C can be reached Fast, Compact and Foolproof
the meat ADC converts the ratio of RTD resistance to inside the coals, at a distance of 10 to 20 cm,
6. two stepper or DC motors — one to turn reference resistance into digital form. Arduino whereas in the fornacella, they reach tempera- Inhouse PCB Prototoyping
the arrosticini and the other to slide makes this easily manageable through the tures of 1 0 C to 00 C) bringing the meat The new LPKF ProtoLaser ST impresses with its
them off the grill. The speed of these two libraries that can be implemented in the inte- to a temperature of approximately 150°C
motors must be synchronized. In addi- grated development environment (IDE). starts the so-called Maillard reaction — the compact design and easy operation. Find out more:
Brushless DC (BLDC) motors chemical reaction that gives browned meat its www.lpkf.com/protolaser_st
offer high effi ciency, but above all, distinctive fl avor and aroma.
excellent torque and speed values Calibration will be required to coordinate
that suit a broad range of applica- the movement of each arrosticino with the
tions. The design of a brushless DC temperature of the grill and of the arrosticino
motor aims to optimize the torque, itself, together with the movement of the slid-
or the amount of rotational force, ing mechanism that will transfer the cooked
which is related to the magnet and meat to the plate. The slides can be removed,
coil winding. The greater the num- and the operator must take care to remove
ber of pole pairs in the magnet, the them once the cooking time has passed.
greater the motor torque. 3 Therefore, the software will have to provide
Portescap’s Ultra EC platform temperature reading/setup and display func-
offers a range of brushless motor tions a grid temperature control algorithm
families to target different torque evaluating deviations within 5% of the origi-
and speed requirements. The parent nal temperature and control alarms, such as Embedded World: 25 – 27 February, Hall 3, Booth 249
company’s patented coil minimizes an LED and/or a buzzer module.
Figure 3: Arduino and PT100 sensors with condi- iron losses to maximize effi ciency. Cooking on the grill will still present the
tioning circuit Maxon’s EC-i brushless motors practical problem of keeping the temperature

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