Custom Voltage in a Laptop

Collapse
X
Collapse
+ More Options
Posts
 
  • Time
  • Show
Clear All
new posts
  • caspian
    Badcaps Legend
    • Oct 2015
    • 1589
    • Laptop

    #1

    Custom Voltage in a Laptop

    Dear Forum members,

    I need to create a custom voltage of 3.8v in a laptop to drive the CPU fan.
    It is not available in laptops and I have to create it. I can think of a simple voltage divider depicted in the photo.
    but I have doubt that the voltage divider may consume extra power from the +5v_Run rail and make this rail burn after a while.
    the fan consumes 0.16A when the input voltage is 3.8v.
    the laptop is an ordinary 90W laptop called Dell Inspiron 1564.
    the fan has no PWM input and the original FAN Driving Circuit on the mainboard is defective.

    So I have got the questions that:

    - Is it possible that this voltage divider damage something on the mainboard?
    - Is such voltage divider suitable to create a custom voltage in a laptop?
    - If not so, what kind of circuit does suite this purpose such that it can be easily made on the mainboard?
    - What values should be selected for R1 and R2 such the voltage divider consumes very low power?

    Thanks
    Attached Files
    Last edited by caspian; 04-07-2019, 03:44 AM.
  • piernov
    Super Moderator
    • Jan 2016
    • 4435
    • France

    #2
    Re: Custom Voltage in a Laptop

    Unfortunaltey a voltage divider will not work in this case. You're trying to drive an inductive load that'll be drawing a fair amount of current especially at startup.
    If you only want a constant voltage with no control over it (which isn't really the best idea for a laptop fan), you can simply use a voltage regulator. An LDO (like an 1117) can do the job, it'll also require a couple of capacitors and a resistor or 2 to set the output voltage.
    You could also connect it directly to the 3.3V rail, it'll run a bit slower.
    Anyway, you're better off fixing the fan circuit on the motherboard.
    OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

    Comment

    • ktmmotocross
      Boardkiller
      • Feb 2014
      • 3558
      • slovakia

      #3
      Re: Custom Voltage in a Laptop

      if u dont have fan circuit, 3.3V rail is good for that purpose

      Comment

      • peste
        Super Moderator
        • Dec 2016
        • 12274
        • ROMANIA

        #4
        Re: Custom Voltage in a Laptop

        you can use that

        https://fr.aliexpress.com/af/buck%25...wCP=y&jump=afs

        but better fix the problem on the motherboard
        Last edited by peste; 04-07-2019, 07:02 AM.
        Due to a lack of donations, server free space at a critical level, and possible closure of Bios Requests all donations are welcome, click:

        >>>>> https://www.badcaps.net/index.php?pageid=donate1 <<<<<

        Every donation made will go towards server fees and maintenance costs.

        Comment

        • caspian
          Badcaps Legend
          • Oct 2015
          • 1589
          • Laptop

          #5
          Re: Custom Voltage in a Laptop

          Dear ktmmotocross,
          I have tested 3.3v, but the fan spins at a low rate using 3.3v.

          Dear peste,
          the buck converter modules are really interesting to use in sensitive parts of mainboards. Since it is just a FAN, I thought a simple voltage regulator might be enough.

          If I use high resistance values for R1 and R2 in the kilo ohm range, does this voltage regulator burn the +5v_Run rail?
          Last edited by caspian; 04-07-2019, 08:30 AM.

          Comment

          • peste
            Super Moderator
            • Dec 2016
            • 12274
            • ROMANIA

            #6
            Re: Custom Voltage in a Laptop

            I do not think it will burn, because I see on the schema that the fan is powered by the 5v voltage, but you never know ... here ... you can make a test if you want ... but I do not think it will be stable ... in order to be more stable instead of R2 it should be a zener diode .. but for that should be other calculations ... another problem is that the fan will turn around all the time .. to fix it safely motherboard .. but if you want to play ... it's ok ..
            Attached Files
            Due to a lack of donations, server free space at a critical level, and possible closure of Bios Requests all donations are welcome, click:

            >>>>> https://www.badcaps.net/index.php?pageid=donate1 <<<<<

            Every donation made will go towards server fees and maintenance costs.

            Comment

            • caspian
              Badcaps Legend
              • Oct 2015
              • 1589
              • Laptop

              #7
              Re: Custom Voltage in a Laptop

              thank you. I will try it. The laptop owner said: no matter if the fan spins continuously.

              Comment

              • ktmmotocross
                Boardkiller
                • Feb 2014
                • 3558
                • slovakia

                #8
                Re: Custom Voltage in a Laptop

                download electrodroid or another app for calculating all this circuits.

                is good current on that fan? fan i have here tells 0.4A
                Last edited by ktmmotocross; 04-07-2019, 12:47 PM.

                Comment

                • ala_borbe
                  aka Donald
                  • Apr 2011
                  • 1625
                  • Malta

                  #9
                  Re: Custom Voltage in a Laptop

                  take 5v from usb and put two zener diodes in series (or three if it spins to fast)... every diode makes ~0.7v voltage drop

                  works like a charm... done 500 times at least
                  Im Back... sort of...

                  Comment

                  • mcplslg123
                    Badcaps Legend
                    • Jun 2015
                    • 7262
                    • india

                    #10
                    Re: Custom Voltage in a Laptop

                    Originally posted by ala_borbe
                    take 5v from usb and put two zener diodes in series (or three if it spins to fast)... every diode makes ~0.7v voltage drop

                    works like a charm... done 500 times at least
                    I too follow ala borbe's method and in some cases taking load directly from 3.3V rail.

                    Comment

                    • String2016
                      Badcaps Legend
                      • Nov 2015
                      • 2229
                      • philippines

                      #11
                      Re: Custom Voltage in a Laptop

                      @Alaborbe what type of zener diode to use please

                      Comment

                      • caspian
                        Badcaps Legend
                        • Oct 2015
                        • 1589
                        • Laptop

                        #12
                        Re: Custom Voltage in a Laptop

                        I searched the net about using Zener diodes for voltage regulation. and I found out many things are involved in such a circuit. For example, Voltage and Power properties of the Zener diode and R_Load which is the resistance of the load. they say a resistor is required between the voltage source and the Zener diode to restrict the current passing the Zener diode.
                        that means lots of calculations are required.

                        Comment

                        • caspian
                          Badcaps Legend
                          • Oct 2015
                          • 1589
                          • Laptop

                          #13
                          Re: Custom Voltage in a Laptop

                          the other thing which is important is R_Load. Ideally, the output of the voltage regulator should not depend on R_Load. there are two kinds of R_Load: one when the load component is on and the other when the load component is off.
                          Thus, the calculations get complicated a bit. I am not an Electronics expert. So I cannot do these calculations for Zener Diodes.
                          Last edited by caspian; 04-08-2019, 11:28 AM.

                          Comment

                          • ala_borbe
                            aka Donald
                            • Apr 2011
                            • 1625
                            • Malta

                            #14
                            Re: Custom Voltage in a Laptop

                            Originally posted by Mulong2019
                            @Alaborbe what type of zener diode to use please
                            1n4007
                            cheapest available
                            https://components101.com/1n4007-diode
                            Im Back... sort of...

                            Comment

                            • caspian
                              Badcaps Legend
                              • Oct 2015
                              • 1589
                              • Laptop

                              #15
                              Re: Custom Voltage in a Laptop

                              I discovered that the circuit of Post#1 is not correct.
                              How should the two serial Zener diodes be used so that the output voltage does not depend on R_load?

                              Comment

                              • peste
                                Super Moderator
                                • Dec 2016
                                • 12274
                                • ROMANIA

                                #16
                                Re: Custom Voltage in a Laptop

                                Do not complicate yourself, what ala_borbe said in post # 9, is the simplest.
                                Due to a lack of donations, server free space at a critical level, and possible closure of Bios Requests all donations are welcome, click:

                                >>>>> https://www.badcaps.net/index.php?pageid=donate1 <<<<<

                                Every donation made will go towards server fees and maintenance costs.

                                Comment

                                • caspian
                                  Badcaps Legend
                                  • Oct 2015
                                  • 1589
                                  • Laptop

                                  #17
                                  Re: Custom Voltage in a Laptop

                                  That is right. Thank you.

                                  Comment

                                  Related Topics

                                  Collapse

                                  • Document Archive
                                    Microsoft Surface Laptop 3 13.5-inch i5/8GB/256GB SSD Laptop Platinum Notebook Specification for Upgrade or Repair
                                    by Document Archive
                                    This specification for the Microsoft Surface Laptop 3 13.5-inch i5/8GB/256GB SSD Laptop Platinum Notebook can be useful for upgrading or repairing a laptop that is not working. As a community we are working through our specifications to add valuable data like the Surface Laptop 3 13.5-inch i5/8GB/256GB SSD Laptop Platinum boardview and Surface Laptop 3 13.5-inch i5/8GB/256GB SSD Laptop Platinum schematic. Our users have donated over 1 million documents which are being added to the site. This page will be updated soon with additional information. Alternatively you can request additional help from...
                                    09-06-2024, 09:30 PM
                                  • Document Archive
                                    Microsoft Surface Laptop Surface Laptop 2 Notebook 2 Specification for Upgrade or Repair
                                    by Document Archive
                                    This specification for the Microsoft Surface Laptop Surface Laptop 2 Notebook can be useful for upgrading or repairing a laptop that is not working. As a community we are working through our specifications to add valuable data like the Surface Laptop 2 boardview and Surface Laptop 2 schematic. Our users have donated over 1 million documents which are being added to the site. This page will be updated soon with additional information. Alternatively you can request additional help from our users directly on the relevant badcaps forum. Please note that we offer no warranties that any specification,...
                                    09-06-2024, 08:47 AM
                                  • RdeveLabs
                                    MSI GF63 THIN 11UCX (MS-16R6) LAPTOP WON'T TURN ON AFTER RESTARTING
                                    by RdeveLabs
                                    To all the members here...

                                    Let me tell you a little bit about what happened to my laptop (MSI GF63 THIN 11UCX model: MS-16R6) that “maybe” you know how to solve this problem.

                                    So before this problem happened, my laptop was running smoothly. When I wanted to restart my laptop, it looked fine at first. But after I waited for this restart process to take a long time, until finally I panicked (because the restart process did not finish plus the laptop screen only showed a black screen), I immediately pressed and held the power button to force the laptop to turn off. But...
                                    05-05-2025, 04:59 AM
                                  • Document Archive
                                    Microsoft Surface Laptop Surface Laptop 4 Notebook 4 Specification for Upgrade or Repair
                                    by Document Archive
                                    This specification for the Microsoft Surface Laptop Surface Laptop 4 Notebook can be useful for upgrading or repairing a laptop that is not working. As a community we are working through our specifications to add valuable data like the Surface Laptop 4 boardview and Surface Laptop 4 schematic. Our users have donated over 1 million documents which are being added to the site. This page will be updated soon with additional information. Alternatively you can request additional help from our users directly on the relevant badcaps forum. Please note that we offer no warranties that any specification,...
                                    09-07-2024, 06:11 AM
                                  • Document Archive
                                    Microsoft Surface Laptop Surface Laptop Go 2 Notebook Go 2 Specification for Upgrade or Repair
                                    by Document Archive
                                    This specification for the Microsoft Surface Laptop Surface Laptop Go 2 Notebook can be useful for upgrading or repairing a laptop that is not working. As a community we are working through our specifications to add valuable data like the Surface Laptop Go 2 boardview and Surface Laptop Go 2 schematic. Our users have donated over 1 million documents which are being added to the site. This page will be updated soon with additional information. Alternatively you can request additional help from our users directly on the relevant badcaps forum. Please note that we offer no warranties that any specification,...
                                    09-07-2024, 06:11 AM
                                  • Loading...
                                  • No more items.
                                  Working...