Today we are taking a look inside another automotive device, more specifically the Kapsch OBU-4041 (On-Board Unit). At first glance, it is an inconspicuous box with a single button, mounted on the windscreen of a truck. Its purpose is to interface with electronic toll collection systems. On the front, there is a single button which, when pressed for a long time, is used to select the number of axles; a short press shows the current setting. The separate numbers 2, 3 and 4 are illuminated by LEDs. Correct selection is the responsibility of the driver. The specific method of use is well illustrated by a sticker on the device itself:
A separate issue is the passage through the toll station. Communication is via an antenna mounted on a gantry above the toll road section. The driver is informed of correct toll collection by an audible signal. The device can operate in two modes: pre-pay and post-pay, depending on the contract concluded. A single beep indicates correct toll collection, two beeps indicate a low pre-pay account balance or low battery, and four beeps indicate that the toll has not been paid. If the toll is not collected, the system automatically takes a picture of the vehicle and sends it to the highway patrol after verification.
Time to look inside. I thought it was the screws in the corner, but they look more like rivets. I broke out the housing.
The board is simple - battery, buzzer, one IC with a quartz resonator, the aforementioned button, and, well, LEDs - interestingly, each with a transistor.
The battery used is a Tadiran 3.6V lithium battery, doesn't look replaceable at all. Presumably the whole thing needs so little power that it is disposable.
The main controller is 68535 09899 D2L899 1225 I couldn't find any information about it, maybe someone reading will have better luck?
The most interesting thing is from the other side - it looks like we have microwave antennas here:
In summary, the Kapsch OBU-4041 is a very simple device for its application. Inside there is a single integrated circuit with a quartz resonator, a few discrete components, a buzzer, a button and LEDs to indicate the operating status. All the logic and operation of the device has thus been condensed to an absolute minimum, which suits its one specific task well. Probably the most interesting thing turned out to be the antennas. It's a pity I don't have access to the receiver, because then it would also be possible to see what further processes the requests - some kind of microcontroller, an SBC with GSM?
So much for my part in this topic, if anyone is able to add more, please feel free to do so. By the way, I can recommend a related topic about the transmitter from Car Sharing .
Do you use this type of module?
Cool? Ranking DIY Helpful post? Buy me a coffee.
