The days when you could park your car on a supermarket parking lot for days are already over. While many operators monitor the parking time with parking discs, other retail chains are already one step further: Sensors report the inspectors automatically by app, where they have a speeding ticket for exceeding the "Free parking time" can distribute. But are the Verpetzer so reliable that operators can take the risk to demand without further review 30 euros and thus annoy customers? In the test of a Bosch parking lot sensor, we show which different sensor concepts exist and what their advantages and disadvantages are. Among other things, we have learned that even self-learning sensors can have their defiance phase.
Both Bosch and competitors use LoRa technology for data transmission. LoRa stands for Long Range and is a wireless, proprietary transmission technology that uses a special modulation method (chirp spread spectrum). The process is very energy efficient, allowing sensors to operate for several years without battery replacement. In sparsely populated areas can be bridged up to 50 kilometers between transmitter and receiver. In the city, the range is reduced by the development to a few kilometers, but thanks to good penetration also underground sensors, for example in the subway, can be achieved.
The whole works without license costs, because LoRa operates on the free ISM frequency bands 433 MHz and 868 MHz. However, the transmission time on the ISM bands is limited to 1 percent in order not to overload the frequencies. This corresponds to an occupancy of 36 seconds in one hour.
Simple gateway for hobbyists
Another advantage: the special receivers, known as LoRaWAN gateways, are already available at low cost. For our test, we have used the self-assembly manual, which we described in December 2018. With the help of a Raspberry Pi, a so-called concentrator board and an antenna, a gateway can be assembled for a price of 130 euros. On the net, there are matching housings for printing on a 3D printer. All we have to do is adjust the back wall and add an intermediate plate. However, our housing is only suitable for indoor use. A visual contact with the sensor is required. There is no reception in a room on the opposite side of the building.
Although it is also possible to use a Raspberry Pi 3 as a LoRa server. However, we have linked the gateway to The Things Network (TTN). The Dutch initiative now has almost 10,000 gateways in 147 countries. Thus, their number has almost doubled in the past year. TTN's Fair Access Policy, however, only allows 30 seconds of transmission per day.
Pilot projects by Bosch and Siemens failed
Originally the parking lot sensors have been developed to be one "intelligent parking search" to enable. While Bosch and Siemens more or less failed with pilot projects in Stuttgart and Berlin, startups such as Smart City System from Nuremberg have brought successful products to market. The Stuttgart-based company Park & Control uses its parking pilot. The Düsseldorf-based company Safe Place relies on sensors from Smart City System and the Scottish provider Smart Parking.
The Stuttgart-based engineering group initially had the sensors for its April 2016 largely announced "active parking space management" used. The decision to reinstate the project after a year and a half of testing was not very flattering for Bosch. Although the insufficient detection rate of the sensors is supposed to have been responsible for stopping the project, the devices are now marketed separately.
However, that is in need of explanation. What has Bosch improved on the sensors, why was the business model changed and why should the failed sensor convince?