[Sergei Sharonov]

in reply to: Doppler Radar Reading Low Speeds #357

There are a few possibilities:

1. If your radar still reads low speeds (3-25mph), even in the absence of a valid target, it may be a result of a noisy environment. Radar picks up motion. Trees sway under wind, compressor/fan blades rotate, plasma oscillates inside fluorescent light bulb, system enclosure may vibrate due the wind or mechanical moving parts, rain droplets fall towards the radar, etc. Sometimes noise source is of electrical nature. Radar is designed to detect minuscule amounts of the RF power. If your system has a strong source of RF power such as cell modem, WiFi or Bluetooth located close to the radar it is possible to overload the radar and cause it to malfunction. The first order of business is to identify the source of the noise. Take the radar out of the enclosure and point it in some other direction. Did spurious readings go away? Then there are a few things you may try to do to mitigate the problem: move radar away from noise source, dampen enclosure vibrations, block radar view of the noise source, move RF antennas away from the radar, when acceptable increase minimum detectable speed of the radar to that above the speed produced by the noise source.
2. If your radar reads speeds that appear to be only somewhat lower that expected but generally are in the right ballpark it is likely due to the well-known cosine effect. The radar measures radial component of the speed (e.g. speed towards the radar) but not the tangential component of the speed. If the vehicle moves exactly towards the radar, we will read exact speed. However when the vehicle is passing the radar (e.g. the radar points at the side of the vehicle) cosine effect will result in a lower reading. All radars, even police radars, are affected by cosine effect. The only thing you may do about it is try to correct for it for a known geometry of the installation.
3. Your radar is configured to report speed in mph but you expect kph. Configure the radar to use correct units.

[Sergei Sharonov]

in reply to: How do I connect Doppler radar to the network? #343

In order to connect our Doppler radar to the network one must use a device called “terminal server”. Terminal server converts serial port into the Ethernet port. Many such devices are available on the marketplace and range in price from $80 to over $500. We have tested three terminal servers to work well with our radars.

1. ES-551 from Brainboxes
   Advantages: DIN rail form factor (if you need that), robust galvanic isolation, full industrial temperature range (-40°C to +80°C), convenient removable terminal blocks.
   Disadvantages: higher price (~$300), may need to be upgraded to the latest firmware to achieve maximum throughput.
2. USR-N520 from USR IOT
   Advantages: low price(~$90), dual serial ports allow connection to two radars, full industrial temperature range (-40°C to +85°C)
3. NPort 5150A from Moxa
   Advantages: small form factor, reasonable price (~$130), wide temperature range (-40 to 75°C)

[Author]

Posts