LMS Heating

This application note descirbes how the heating of a LMS outdoor scanner is working.

There are two heating boards in the device: bottom and top. They work independently. The upper heating board will switch on at the temperature below 10°C. The lower heating board will switch on at the temperature below 0°C. The controller of the heating is programmed to turn off if the temperature gets higher than 10°C. The device is not starting operation below internal temperature 0°C. If the heater is turned on it will anyway on for min. 3 sec., than it checks the temperatures again. During that time the heating is working, so the controller will not react very sensitive to temperature up and down turnes.

The internal heater can not be operated when the LMS1xx is not switched on.
The heating reacts only on temperature, not on humidity or something else.

If the internal temperature of the device is > 0°C, the device starts working. If the temperature sinks below 0°C during runtime, the device remains running anyway.
For the heating a separate power supply is necessary, or rather, the power supply for the heating is not the same as the one for the scanner, they are separated.
As wind has an influence to temperatures, the wind speed is specified with 0m/s for -30°C, tolerance is up to 0,5 m/s. Every speed higher than this, removes the warmth from the scanner and cools the device down, so the boot up time gets higher.
There are two heatings in the sensor, one in the top and one in the bottom of the sensor, but they are turned on and off the same time.

(tested with a standard LMS111 device)
   0°C: 0:30 min
-10°C: 1:33 min
-20°C: 4:24 min
-30°C: 9:11 min

Colder than -30°C: The device never starts running as the device is specified only down to -30°C.

For the heating, a ripple of the supply voltage would only cause a variation of the heating power, but for the electronic it is no problem. That is why the ripple is not specified especially for the heating.
The voltage for the heating has just to always over 20V to reach the specified heating power, that means, U_b = 22,2V or higher.

Valid for all variants of LMS511 and LMS531.

Background:
The LMS5xx has one heater on the motor board, dedicated especially for the motor. There is another heater board around the rotating mirror, close to the front window.  Both heaters can only be switched on or off (no regulation in between), but the switching on/off may happen at different timing. The rule when each of these heatings is switched on, is handled by the internal heating controller, depending on the specification of the components which need to be heated.
The heating will be switched on automatically if it is too cold to turn on the motor. When the device is heated up sufficiently for starting the motor, the motor/mirror will switch on to circulate the air inside of the device. Once it is warm enough inside, the measurement starts (laser will be turned on), the device becomes "Device Ready".
There are several temperature sensors on the PCBs in the device, and the value given in SOPAS is not the result of one of the sensors, but a weighted average of several sensors.
As there are only internal temperature sensors and no external ones, the heating strategy can only use these internal values and not the real outside temperatures.
As wind has an influence to temperatures, the wind speed is specified with 0m/s for -30°C, tolerance is up to 0,5 m/s. Every speed higher than this, removes the warmth from the scanner and cools the device down, so the boot up time gets longer.

Consider the LMS5 as a device which does automatically regulate it's temperatures when used within the specified outside temperature range and connected to sufficient power supply (77W). When sufficiently power is connected, don't bother about the heater strategy.

Remark! LMS2xx vs. LMS5
For correct operation of LMS511/LMS531, the power supply needs to be connected to the sensor (heating controller) as well as to the heating (heater elements itself).
Difference to old LMS2xx: with LMS2xx it was possible only to power up the heating. The heating controls the switching on / off on its own.
This is not given anymore with LMS1xx and LMS5xx!


Strategy:

• The heating is switched ON if the internal temperature of all temperature sensors is below 5°C
• The heating switches OFF when one internal sensor is above 50°C.
• The heating switches OFF when all internal sensors are above 10°C.
• When the sensor boots up and it is too cold, the heating is switched ON for 3h at minimum to remove possible icing on the device.
  This interval can only be interrupted by:
  -- When one temperature sensor reaches max. specified temp., heating switches OFF, e.g. to protect laser from overheating.
  -- Power-off-on of the device. Then the heating process starts again.

The heating itself has no peak in the bootup voltage, because the heating consists just of resistors.
 

Valid for LMS511/531 without wind. Approxiumate values.

See attachment "boot-up-times-lms5.xlsx"

• See related article "Heating does not switch on, power supply seems to be sufficient"
• Correct dimensioning of cables:
  see attachment 2022-03-23-dimensioning-of-cables.xlsx"

In the Service Level a commissioning test is available.
With this test you could also check the heating (only outdoor LMS5xx).

To switch on the heating, the LMS5xx (OD) needs as min. 17,4V.
(needed also for commissioning test, if not directly red).
The current will be switched on for 10 sec. (current about 2A)

The power supply for the heating is only for the heating itself. The control of the heating is done by the sensor. So if the sensor is running, also the control of the heating is working. That causes, that the sensor must be powered on for running the heating. The heating will not run by it self.
The sensor turns the heating on or off, but there is no other regulation.
If the power supply for the heating has not the full value, than just the heating is not that strong and fast enough. Only if the power of the heating is below the specified minimum, that the heating will not turn on. As long as the power supply of the heating is in the specified range, the heating will work more or less strong, depending on the supplied power.
If the voltage for the heater is lower than specified (<20V), than the behavior of the heater remains normal (point of switching on and off) but it cannot reach the necessary temperature, or not the full temperature.
It is like the device is specified for not so low temperatures.
This is valid for LMS1xx and LMS5xx

After the device boots up in a cold environment, the internal heating system is activated.

If the telegram sEN LMDscandata 1 is sent to the device, it responds with sEA LMDscandata 1. However, no measurement data will be transmitted until the device has reached the required internal temperature and completed the boot process.

Once the device is sufficiently heated and fully operational, it begins sending sSN LMDscandata <payload> telegrams according to its configuration.

Data stream sample:

<STX>sEN LMDscandata 1<ETX>
<STX>sEA LMDscandata 1<ETX>
<STX>sSN LMDscandata 0 1 145A22E 0 0 0 2 1E2F5495 1E2F9B1F 0 0 3F 0 0 1388 168 0 1 DIST1 40000000 00000000 FFFF3CB0 1388 3 8D 8E 95 0 0 0 0 0 0<ETX>
<STX>sSN LMDscandata 0 1 145A22E 0 0 1 3 1E2FA264 1E2FE8C3 0 0 3F 0 0 1388 168 0 1 DIST1 40000000 00000000 FFFF3CB0 1388 3 9D A2 A2 0 0 0 0 0 0<ETX>
<STX>sSN LMDscandata 0 1 145A22E 0 0 2 4 1E2FF050 1E3036D9 0 0 3F 0 0 1388 168 0 1 DIST1 40000000 00000000 FFFF3CB0 1388 3 A1 A2 A5 0 0 0 0 0 0<ETX>
<STX>sSN LMDscandata 0 1 145A22E 0 0 3 5 1E303E82 1E30852C 0 0 3F 0 0 1388 168 0 1 DIST1 40000000 00000000 FFFF3CB0 1388 3 A2 A4 A2 0 0 0 0 0 0<ETX>
<STX>sSN LMDscandata 0 1 145A22E 0 0 4 6 1E308CFD 1E30D3B8 0 0 3F 0 0 1388 168 0 1 DIST1 40000000 00000000 FFFF3CB0 1388 3 A3 A4 A0 0 0 0 0 0 0<ETX>
<STX>sSN LMDscandata 0 1 145A22E 0 0 5 7 1E30DB77 1E312207 0 0 3F 0 0 1388 168 0 1 DIST1 40000000 00000000 FFFF3CB0 1388 3 A4 A3 A3 0 0 0 0 0 0<ETX>
<STX>sSN LMDscandata 0 1 145A22E 0 0 6 8 1E31299A 1E317022 0 0 3F 0 0 1388 168 0 1 DIST1 40000000 00000000 FFFF3CB0 1388 3 A3 A3 A2 0 0 0 0 0 0<ETX>
<STX>sSN LMDscandata 0 1 145A22E 0 0 7 9 1E3177EA 1E31BEA4 0 0 3F 0 0 1388 168 0 1 DIST1 40000000 00000000 FFFF3CB0 1388 3 9A A4 AB 0 0 0 0 0 0<ETX>
<STX>sSN LMDscandata 0 1 145A22E 0 0 8 A 1E31C673 1E320D0A 0 0 3F 0 0 1388 168 0 1 DIST1 40000000 00000000 FFFF3CB0 1388 3 9F A0 A2 0 0 0 0 0 0<ETX>
<STX>sSN LMDscandata 0 1 145A22E 0 0 9 B 1E3214AC 1E325AF1 0 0 3F 0 0 1388 168 0 1 DIST1 40000000 00000000 FFFF3CB0 1388 3 A2 A1 A6 0 0 0 0 0 0<ETX>
<STX>sSN LMDscandata 0 1 145A22E 0 0 A C 1E32627A 1E32A8F8 0 0 3F 0 0 1388 168 0 1 DIST1 40000000 00000000 FFFF3CB0 1388 3 A4 A4 A7 0 0 0 0 0 0<ETX>
<STX>sSN LMDscandata 0 1 145A22E 0 0 B D 1E32B079 1E32F6C8 0 0 3F 0 0 1388 168 0 1 DIST1 40000000 00000000 FFFF3CB0 1388 3 A6 A5 A4 0 0 0 0 0 0<ETX>
<STX>sSN LMDscandata 0 1 145A22E 0 0 C E 1E32FEC0 1E33456E 0 0 3F 0 0 1388 168 0 1 DIST1 40000000 00000000 FFFF3CB0 1388 3 A2 A6 A4 0 0 0 0 0 0<ETX>
<STX>sSN LMDscandata 0 1 145A22E 0 0 D F 1E334D47 1E3393D4 0 0 3F 0 0 1388 168 0 1 DIST1 40000000 00000000 FFFF3CB0 1388 3 9E A3 A1 0 0 0 0 0 0<ETX>
<STX>sSN LMDscandata 0 1 145A22E 0 0 E 10 1E339B9D 1E33E206 0 0 3F 0 0 1388 168 0 1 DIST1 40000000 00000000 FFFF3CB0 1388 3 9D A0 A8 0 0 0 0 0 0<ETX>
<STX>sSN LMDscandata 0 1 145A22E 0 0 F 11 1E33E985 1E342FEB 0 0 3F 0 0 1388 168 0 1 DIST1 40000000 00000000 FFFF3CB0 1388 3 A1 A4 A3 0 0 0 0 0 0<ETX>