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U85 laser rangefinder modules

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iliasam edited this page Aug 23, 2022 · 6 revisions

Currently (2021/22) two types of modern laser tape measure modules are exists: U85A and U85B:
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PCB of the module is marked as 85A/85B.
Another side:
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It looks like that 85A version is designed to be powered from Li-ion battery with 3.7-4.2V, and MCU of this module is powered by linear 3.3V LDO.
Otherwise, 85B is designed to be powered from two AAA batteries, so it have step-up DC converter that produce 3.5V - to power MCU.
Firmware is the same for both types of modules.

Notice that pervious version of such modules is exists: 81B, but I can't guaranty that my firmware will work well at 81B hardware.
Module size: 41x17x7mm, Weight: ~4g
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Specific attribute of such modules: they have rectangular lens at the photodiode!

You can see some information about reverse engineering this module here:
https://github.com/iliasam/Laser_tape_reverse_engineering/tree/master/PCB_photos/module_U85
I do not draw schematic at this time.

Firmware (including HEX files) is placed here: https://github.com/iliasam/Laser_tape_reverse_engineering/tree/master/Code/CortexM0

Pinout:
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Current changes of hardware and firmware (comparing to 701/703A modules) (10/2021):

  • U85 modules are more sensitive at shorter distances (< 30 cm). Sensitivity of older bigger modules dropped significantly when object was close to rangefinder module.
  • Firmware is not controlling beeper (it was used in calibration in prev. modules)
  • External buttons are not used, calibration could be started only by UART command.
  • You don't need to short pins (7-8) at PCB to get module enabled, just connect "PWRON" pin to power source pin.

Where to find such modules?

X-40 laser tape measure: looks like older X-40 but have 85B installed. It have only 6 screws in its case (not 7 (with 1 hidden) as in older versions).
Notice to the form of photodiode lens!
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Such module should contain 85A module: https://www.aliexpress.com/item/1005001394260306.html
Notice: according to information from https://www.hackster.io, this seller sell devices with round photodiode lens, which are not 85x!
Price is 22$
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D30 laser tape measure, proved that it contains 85A module:
Shop link: https://aliexpress.ru/item/1005001772064136.htm
Price is 14$.
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