connecting a 50m laser range finder module to arduino

Hi All,

I want to build my own laser range finder to, finally, make a 3D scanner over larger ranges and to scan large objects (boats).

On Aliexpress, I bought a 0.02-50 m laser module with serial communication (TTL). The package comes with a so-called ‘manual’ in English, but it makes no sense to me. I basically have no clue how to connect the thing to an Arduino, while that should be possible according to the supplier (at least, it was in the description).

I hope that maybe some of you more experienced people out there would have some suggestions? Do not worry about any safety considerations, I have experience with laser and put safety first!

Here is a description of the system:
model: HI50
measuring accuracy: +/- 1 mm
measurement time: 0.3-2 s
typical accuracy: 0.02-50 m
laser class: II
voltage: 2-3V (120-300mA)
laser type 635 nm, <1 mW
communication interface: serial communication TTL, 19.2K, baud rate parity bit: no parity, data bits 8

The physical package contains 2 units: the laser module, and a ‘USB-to-TTL’ thingi that looks a bit like a datastick. This USB ‘stick’ has 6 connections: 5V, VCC, 3V3, TXD, RXD and GND. The VCC and 3V3 connectors are linked by a jumper.

In the quite challenging manual, it says that the laser module should be connected to 3V power (that is correctly indicated), but also to ‘TX’ and ‘RX’. Do you think it would be the intention to connect these two with wires to the USB stick (TXD and RXD)?

I do not understand the connection to an Arduino board at the moment as the USB connection would not fit to aan Arduino?

Any comments are welcome to help me further.

Kind regards

Schermafdruk 2019-12-21 18.26.30.png

Please post a link to the manual.

You could avoid these difficulties by buying the Lidar Lite V3, which is Arduino compatible, comes with an excellent manual and is well worth the price.

See this remarkable 3D ranging scanner video demonstrating its capabilities.

I had a look indeed to the Lidar v3 option, but thought ir was a bit too expensive not to justify a try with a cheap alternative. And there I am... I will include some pics of the manual. It is not too much.

Here are pictures of the manual.

The ranging module itself appears to be directly compatible with a 3.3V Arduino. Use AltSoftSerial to control it at 19200 Baud. Use a 3.3V to 5V level shifter for RX, TX with 5V Arduinos.

You might need to use a separate power supply for the ranging module as the 3.3V output of a standard Arduino cannot handle the current draw. Don't forget to connect all the grounds.

The "USB stick" is probably a com port TTL serial adapter for a PC, as the first sheet shows the ranging module being controlled by a PC terminal program. This link shows the ranging module for sale without the USB adapter.

Keep us posted!

First image: your first challenge is that this thing apparently needs 2-3V input, that's a rather unusual voltage, more common is 3.3V but that's too high. Maybe it's designed to work with AA batteries? Though when fresh an alkaline battery is about 1.6V so 2x alkaline would be slightly out of spec already. 2x NiCd would work wonders.

You'll have to get an appropriate regulator for this thing - one that produces 2.0-3.0V. So that would exclude 3.3V output of an Arduino, however the supplied USB/TTL adapter suggests 3.3V is actually fine for this device.

Second image: "open" and "close" is Chinglish for "switch on" and "switch off".

Third image: that should be pretty clear.

Fourth image: lovely error messages... Description is rather useless. It does use the word "VBAT" suggesting the makers indeed expect to run the thing off batteries.

The PCB is apparently designed to be used with connectors; which you apparently don't have. That's going to require some careful soldering. Remember to properly shift the Rx/Tx levels (sensor Tx to Arduino Rx doesn't need this if you operate the device at 3.3V; the Arduino Tx to sensor Rx needs a voltage divider), and connect sensor Rx to Arduino Tx and the other way around.

(edit) The link in #4 gives a working voltage of DC2V - 3.2 V, which is exactly what you can expect from 2x alkaline. 3.3V is out of spec but so close it's very likely just fine. Chinese specs are usually not that accurate...