SubscribeMiniaturization in all areas of technology demands that sensor technology continuously develops ever smaller sensors.
In doing this, however, no one wants to forgo the advantageous properties of today’s best sensing features. Now the MINOS Series from Baumer introduces ultra-miniature optical sensors, with full adjustability in all sensing styles. The flagship of the MINOS line is the world’s smallest diffuse sensor with electronically adjustable background suppression.
Increasing complexity, higher levels of integration, and continuous miniaturization of many components in the machine-building, electronics and entertainment industries drives the need for ever more compact and complex production lines. These precise and rapid assembly, conveyor, and combination processes make great demands on the “eyes of the machine”; the sensors.
Baumer electric has accepted this challenge and developed a complete line of extremely miniaturized sensors that fully meet the rigorous demands of industrial-application suitability, adjustability, and short reaction times.
For example, the MINOS family now presents a diffuse sensor series with adjustable background suppression and previously nearly unimaginable properties. The decreasing amount of space in industrial machinery also place demand on connections. Often, a sensor will not fit because, simply, the cable, connection or optics, are facing the wrong direction. To combat this, the MINOS line offers both rear and bottom-exit cables and connectors as well as straight-line and angled optics. The sensors are easily mounted in any location, using a readily available M3 screw.
In order to develop units in the MINOS Series at this level of compactness without losing sight of the market demands, Baumer Electric product designers gave equal consideration to the optical requirements, user friendliness, mounting variations, and the technical properties during the development stage.
The following specifications prove their success:
- Ultra-compact housing design (8.0 x 10.8 x 16.2 mm);
- Adjustable sensing distance / sensitivity using teach-in procedures;
- Teach-in possible via an integrated key or an external teach input;
- Programmable light / dark operation;
- Algorithm to suppress reciprocal optical influence between sensors;
- Two housing versions to optimize mounting with an M3 screw.
What made this tiny wonder possible was, to some extent, new and innovative solutions in both development and manufacturing. With these developments, the lenses were optimized for the shortest possible focal length and then integrated in the front cover. The small number of manufacturing components such as the PCB holder, optics carrier and cable strain relief simultaneously serve as the housing and are finally connected and sealed at the end of the manufacturing process using an extrusion technique.
A Complete Family
In order to have the right sensor type for every application, the entire family is available; from diffuse sensors, diffuse sensors with background suppression, retro-reflective sensors with polarizing filter, to through beam sensors. Among these, it is the world’s smallest diffuse sensor with background suppression that stands in the spotlight.
Background Suppression with Diode Line
The great advantage of the diffuse sensor with background suppression lies in the fact that, regardless of the target’s colour, the sensing distance between the object and the background can be precisely adjusted. For the MINOS, we were able to call on our vast experience with laser distance sensors. The foundation of this background suppression, like our distance measuring lasers, consists of the triangulation principle in conjunction with a diode line.
The receiver optics reflects emitted beam from the target back onto the receiver element, with the location of the reflection on the diode line depending on the distance to the target from the sensor, not on the object’s surface reflectivity or colour. A microcontroller then allows the position of the reflection on the diode line to be read with pixel-level accuracy. In contrast to the PSD receiver that is currently extensively employed, this process permits colour independence equal to that found in mechanically adjustable background suppression.
Electronic Adjustment
The microcontroller can be used to adjust the transition from background to sensing area pixel-by-pixel. This is achieved with a built-in button or by means of an external teach input, if the sensor is no longer accessible after installation. The sensing range can be adjusted from 10 mm to 60 mm, with a maximum resolution in the area of < 0.3 mm.
Two teach-in procedures are available to the user: a static or a dynamic teach-in process.
Static teaching allows both the operating point as well as light/dark operation (based on the teaching sequence) to be determined by learning two measuring positions that are then saved. It is not the learned measuring positions that are stored as operating points, but instead, an optimal operating point that lies somewhere between these positions! The entire process requires only a press of abutton at each position; a green LED indicates that the teach-in process was successfully completed and the positions have been stored.
Dynamic teach-in is particularly suited where moving targets or difficult to position parts are involved. In this mode, the sensor constantly evaluates the receiving signal. When the process is concluded by pressing the button, the sensor defines the operating point on the basis of the saved measured values. Light/dark operation can be switched shortly thereafter, also via the Teach-in button.
Naturally, both teach-in procedures can also be undertaken in the same manner using an external teach line.
A certain amount of insecurity often exists on the part of the user with regard to teachable sensors because, in contrast to the use of an adjusting screw, adjustments with a button lack a manual “feel” and therefore offer no feedback. With the MINOS line, the integrated intelligence ensures that the teachable sensor does not permit any critical states, outside of the sensor’s optimum operating ranges. With screw-adjusted sensors, an operator can easily exceed the sensor’s optimum settings.
In practice, this can lead to uncertain operating behavior and can result in significant problems for the customer during practical application. In this regard, the teachable sensor offers increased security in every application.
Diffuse Sensors and Retro-Reflective Sensors
The MINOS line also includes a diffuse sensor (sensing distance: 150 mm), a through beam sensor (nominal range: 2.5 m), and a retro-reflective sensor with polarizing filter (nominal range: 600 mm). Naturally, the sensitivity of all of these sensors can also be adjusted by means of a teach-in procedure. Thanks to polarizing filters, the retro-reflective sensor is also able to easily detect very shiny or reflective objects. And, by reducing sensitivity, even semi-transparent objects can be detected.
Suppression of Reciprocal Optical Influences
The diffuse sensor, the diffuse sensor with background suppression, and the retro-reflective sensor all have an algorithm to suppress reciprocal optical influence between two sensors. This allows sensors to be mounted very close to one another without their influencing each other and possibly causing false triggers. This is a property which is extremely significant for situations such as those described above where there is frequently a high sensor density within an extremely limited amount of space. Despite increased signal processing times, response and release times of < 0.5 ms are still ensured.
Installation Advantages Through Two Housing Versions
Tight spaces and small installation systems often require system components – such as sensors – that are very small and that have been space-optimized down to the last detail. In these cases, the attempt to employ miniature sensors can fail because of cable and optic orientations.
This requirement was also taken into account in the design of the two cable orientation variants. If sensors with plug connections are desired, both housing versions are also available with mating connectors. For quick and simple installation, the MINOFIX mounting kit with an ingenious, integrated cable pass-through is also available.
The Little Guys Are Coming
It is obvious that the demand for small, compact sensors with outstanding characteristics will continue to increase. With its MINOS Series, Baumer electric has once again raised the bar on the miniaturization of optical sensors. For the first time, a complete line of miniature sensors with adjustable sensing distance is available, whereby the modular design also permits sensors which meet special – and frequently very high – demands on the part of customers, for example, in the packaging industry or in automatic handling systems for the electronics, clock making, or machine-building industries.