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We are building a large car that will drive at around 30mph and I am responsible for figuring out a way to detect if someone's in front of it. We just want it to beep if that's the case. We have been using the HC-SR04 ultrasonic sensor but it is very useless because it has poor range. The problem with the HC-SR04 is that it isn't long ranged and that if the car were driving at 30mph, it would be very hard to stop it by the time it detects something in front of it. What can I do about this? are there any alternative options?

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marked as duplicate by PeterJ, gbulmer, JRE, Daniel Grillo, Ricardo Jan 13 '16 at 16:21

This question was marked as an exact duplicate of an existing question.

  • \$\begingroup\$ Please read the help center to learn how to ask good questions that get good answers. This community doesn't normally give 'shopping advice', or answer vague questions, so your question may get closed. One way to make your question a better fit for this community is to add the results of your analysis and research to the question, to show you have done some work, and are willing to make some effort to get an answer. Also be more specific, so that we can give a proper engineering-quality answer. For example, how far ahead of the vehicle must it detect obstacles? \$\endgroup\$ – gbulmer Jan 13 '16 at 0:57
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    \$\begingroup\$ "oh no, not again" \$\endgroup\$ – Brian Drummond Jan 13 '16 at 1:09
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Sure there are options, but you're not going to like them. The two primary approaches are optical and radar. An optical sensor can be either active or passive. Active optical is generally LADAR, while passive can use a pair of cameras with image processing software to triangulate on an obstacle to find range. Radar can be any of a number of wavelengths from fairly longwave to microwave.

Optical systems have the drawback that they need clean optics, and dust and mud will degrade performance. Radars are typically much more dirt-resistant. However, they usually need larger antennas and have worse spatial resolution.

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