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Power DeWalt 12V laser measure from power supply

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    #1

    Power DeWalt 12V laser measure from power supply

    Hello,
    i got a Dewalt laser measure which uses the 12V batteries to operate. The laser measure is faulty and I want to attempt a repair, never fixed such thing before. You might see a different topic if I fail with the repair
    However I do not have dewalt batteries nor want to buy one for 140EUR as the laser tool might have some chance that it is very hard to repair or unrepairable.
    I want to power it from my PSU.
    The tool has 3 input pins, on the battery it is marked with B-, B+ and ID/TH.
    i want to know what is the third pin exactly and what do I need to do in order to get it going.
    Obviously I have tried just hooking up 12V on + and - but nothing happened. I have read somewhere that the center pin is for thermocouple and a resistor is needed between the pins. On the below image I have added a 47k resistor between + and the center pin. The tool draws few milliamps every second like checking something but it does not turn on.
    I'm open for ideas.
    Attached Files
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    #2
    Re: Power DeWalt 12V laser measure from power supply

    it's faulty - so stop wasting time and look for the fault.
    the sensing is usually only important for the charger so check if the microcontroller / display get voltage and move from that point.
    and check that microswitch - mechanical stuff is less reliable than electronics

    Comment

      #3
      Re: Power DeWalt 12V laser measure from power supply

      And I’ve seen YouTube videos folks repairing them also. YouTube “laser level repair”. There are tons of them.

      Comment

        #4
        Re: Power DeWalt 12V laser measure from power supply

        Originally posted by stj View Post
        it's faulty - so stop wasting time and look for the fault.
        the sensing is usually only important for the charger so check if the microcontroller / display get voltage and move from that point.
        and check that microswitch - mechanical stuff is less reliable than electronics
        Well... I'm unable to measure anything without supplying voltage to it. Without schematic it is also hard to tell where to inject voltage to bypass the microcontroller on the power circuit.
        The laser works with PWM pulses so I need the entire thing powered to probe anything on it. I did the basic looking for shorts and burnt parts thing but its not enough here, 2 out of the 3 lasers are working.
        I found a breakdown for milwaukee batteries and there it does look like it has serial communication to validate power and charge. I would be surprised if it is different with dewalt as there is a microcontroller right at the power circuit.

        I have ordered the PCB of the battery bank from aliexpress, it will hopefully help, tho I need to work for it.
        Last edited by dansity; 10-29-2023, 10:27 AM.

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          #5
          Re: Power DeWalt 12V laser measure from power supply

          Originally posted by CapLeaker View Post
          And I've seen YouTube videos folks repairing them also. YouTube “laser level repair”. There are tons of them.
          I did see them also. Usually it is the tiny wires that are broken or the step up converter. This is not the case here, 2 out of the 3 lasers are working fine. That is why I need to power this somehow.
          Anyway I have ordered the pcb from the battery, that will help me power it.

          Comment

            #6
            Re: Power DeWalt 12V laser measure from power supply

            can you swap the lasers to see if it's the laser or the drive circuit?

            Comment

              #7
              Re: Power DeWalt 12V laser measure from power supply

              https://forum.allaboutcircuits.com/t...id-pin.180775/
              Look at post #4

              Unfortunately I don’t have any Dewalt 12V tools

              Comment

                #8
                Re: Power DeWalt 12V laser measure from power supply

                i think it is optically set I dont want to bother them. i will measure voltage at their butt once I have power sorted out

                Comment

                  #9
                  Re: Power DeWalt 12V laser measure from power supply

                  Originally posted by CapLeaker View Post
                  https://forum.allaboutcircuits.com/t...id-pin.180775/
                  Look at post #4

                  Unfortunately I don't have any Dewalt 12V tools
                  tried this exact thing, if you see the photo in my first comment you will see the resistor soldered on the pin. Unfortunately did not work here. However I have seen the tool work with a battery so it might be something. Thanks for bringing this up

                  Comment

                    #10
                    Re: Power DeWalt 12V laser measure from power supply

                    Maybe try other resistor values. Read this:
                    https://www.sevarg.net/2018/08/19/12...-ryobi-cb120l/

                    Comment

                      #11
                      Re: Power DeWalt 12V laser measure from power supply

                      Originally posted by CapLeaker View Post
                      Maybe try other resistor values. Read this:
                      https://www.sevarg.net/2018/08/19/12...-ryobi-cb120l/
                      The 10k resistor between B- and the center pin did the trick.

                      The laser is on now. I'm not really sure at the moment what is the issue, why one diode is not working. It is working with a 50% duty cycle 7.2V PWM signal.
                      I can measure the PWM on all 3 laser channels so the electronics and the power supply is fine.
                      When I test the 3 laser diodes with diode tester all 3 shows same voltage both ways (1.1V one way 0.7V the other)

                      Any idea how else to test if a diode laser is blown?

                      Comment

                        #12
                        Re: Power DeWalt 12V laser measure from power supply

                        Maybe swap the lasers around and see if the problem transfers.

                        Comment

                          #13
                          Re: Power DeWalt 12V laser measure from power supply

                          what colour are the lasers?

                          Comment

                            #14
                            Re: Power DeWalt 12V laser measure from power supply

                            I got it working. Thanks guys for the help.
                            It is impossible to swap the lasers, they are glued in the factory.
                            It was a weak capacitor on the circuit. However that laser is still weaker than the rest and slightly blinking. I was able to see a tiny circuit on the butt of each laser diode that is full of ceramic capacitors. I suspect those are also toast but it is impossible to service it without damaging the entire construction.
                            So it will be a slightly faulty laser with one diode going on 80%. I can live with it, it will be overkill for my shelf installing kind of home projects anyway. It was a great bank for the buck as this is a pro tool and I got it for change.

                            So I will leave here a checklist for anyone ever coming across a similar faulty DeWalt DCE089G laser meausre

                            -Check the tiny wires going laser diodes. Continuity test does not work, there is some continuity on the circuit so even if the wire is broken it will show resistance. You have to visually examine if any of the tiny wires are broken.
                            -Check the 3 ceramic capacitors on the main power board.
                            -Check the power regulator IC on the main power board, check for warming on shorts
                            -If you have an oscilloscope you can check if each diode gets power. These lasers are working with some power generator kinda hybrid PWM signal to trick you they are brighter (somewhere between 4.2 and 7.2V), it is impossible to see with a multi-meter what is happening exactly.

                            And most importantly: While disassembled use a safety glass as the green laser can output a lot of infra light and can blind you.

                            Some images attached
                            Attached Files

                            Comment

                              #15
                              Re: Power DeWalt 12V laser measure from power supply

                              a lot of green lasers are red or IR with a crystal in front of them that shifts the frequency orf the light!

                              Comment

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