Answers.Body: <p>I apologize if this is an obvious answer, or better suited to <a href="https://electronics.stackexchange.com/">https://electronics.stackexchange.com/</a>, but:</p>
  <p>You can use an inexpensive 12V→9V step-down DC/DC transformer. There's plenty of different options, but I picked a couple of available transformers in order to let you have a rough idea of their size:</p>
  <p><a href="https://i.sstatic.net/wiPprbWY.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/wiPprbWY.png" alt="example step-down DC/DC transformer, in plastic case" /></a></p>
  <p><a href="https://i.sstatic.net/mvRKfrDs.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/mvRKfrDs.png" alt="example step-down DC/DC transformer, in circuit board form factor" /></a></p>
  <p>The connection is straightforward - terminals marked &quot;in&quot; or &quot;12V&quot; go to the 12V power supply, and terminals marked &quot;out&quot; or &quot;9V&quot; go to the 9V motor.</p>
  <p>Let me also quote from <a href="https://electronics.stackexchange.com/questions/448650/">https://electronics.stackexchange.com/questions/448650/</a> :</p>
  <blockquote>
  <p>The speed of a brushed DC motor is roughly proportional to the voltage applied, given the same countertorque.</p>
  <p>There's a reason that motor is designed for 6V only. DC brushed motors are very forgiving, even the commutator and the bearing should stand 1.5 times the design speed for a long time.</p>
  <p><strong>But the gears don't.</strong></p>
  <p>It's most likely a plastic gearbox. Running it at overspeed will destroy the innermost gear very quickly. Don't do it.</p>
  </blockquote>
  <p>Which means: do <strong>not</strong> connect your 9V monorail motor directly to a 12V power source. It will most probably run fine, but the gears made out of 30-years-old plastic will disintegrate.</p>
  <p>See also <a href="https://electronics.stackexchange.com/questions/104749">https://electronics.stackexchange.com/questions/104749</a> and <a href="https://electronics.stackexchange.com/questions/112000/">https://electronics.stackexchange.com/questions/112000/</a> - there's no further considerations to attaching a DC motor to a step-down buck transformer.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2024-09-25T12:20:32.027Z
Answers.Text: The information in your links is very helpful.  Having repaired a few Lego motors I know they do contain a plastic gearbox.  If it is the speed as opposed to the voltage that causes any damage then I would think that a 12V supply on a 75% PWM duty cycle brings us back to the operating tolerance of the gearbox (unless the on/off nature of PWM causes any additional stress?).  The first article from which you quote mentions a 150% tolerance for the motor itself.  Here 12V/9V = 133% so we are within that.
Answers.UserDisplayName: RickyBoy
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2024-09-25T12:21:33.917Z
Answers.Text: I read somewhere that Lego motors are in fact rated 12V but I can't find the article.  If anyone knows of it, I think it would be a valuable addition to this thread.
Answers.UserDisplayName: RickyBoy
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2024-09-25T12:23:38.027Z
Answers.Text: Finally, to shed light on the reason for considering 12V, it is simply that MN21 batteries (including holder) fit within a 2-stud space, so are particulary appealing where space is at a premium.  Whether they can supply sufficient current to operate the motor is yet to be established.
Answers.UserDisplayName: RickyBoy
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2024-09-27T16:12:02.590Z
Answers.Text: I guess your follow-up question about PWM is better suited to electronics.stackexchange.
Answers.UserDisplayName: IvanSanchez
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Answers.LastEditDate: 2024-09-25T09:06:38.407Z
Answers.UserDisplayName: IvanSanchez
Body: <p>Does anyone know if the monorail motor (part 2684c01a/b) can be powered by a 12V supply?</p>
  <p>There is this well-known article titled &quot;<a href="https://www.philohome.com/motors/motorcomp.htm" rel="nofollow noreferrer">LEGO® 9V Technic Motors compared characteristics</a>&quot; which provides information for many (if not all) of the other motors from Lego - and this supports what I have found in tests with the Power Functions M, L and XL motors, being that 12V is handled fine. However, it does not include results for the monorail motor.</p>
  <p>The monorail motor is a much rarer and more expensive part than other Lego motors, thereby one I would really hate to damage, so I wondered if anyone had any knowledge on the subject before I start potentially damaging tests.</p>
  
Tags: <motor><electronics><monorail>
Title: Can monorail motor (2684c01a/b) be powered at 12V?
UserDisplayName: RickyBoy
ThreadText: # Can monorail motor (2684c01a/b) be powered at 12V?
  
  (Asked by: username_0 on 2024-09-23)
  
  Does anyone know if the monorail motor (part 2684c01a/b) can be powered by a 12V supply?
  
  There is this well-known article titled "[LEGO® 9V Technic Motors compared characteristics](https://www.philohome.com/motors/motorcomp.htm)" which provides information for many (if not all) of the other motors from Lego - and this supports what I have found in tests with the Power Functions M, L and XL motors, being that 12V is handled fine. However, it does not include results for the monorail motor.
  
  The monorail motor is a much rarer and more expensive part than other Lego motors, thereby one I would really hate to damage, so I wondered if anyone had any knowledge on the subject before I start potentially damaging tests.
  
  **Tags:** motor, electronics, monorail
  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_1 on 2024-09-24. Score: 4
  
  I apologize if this is an obvious answer, or better suited to <https://electronics.stackexchange.com/>, but:
  
  You can use an inexpensive 12V→9V step-down DC/DC transformer. There's plenty of different options, but I picked a couple of available transformers in order to let you have a rough idea of their size:
  
  [![example step-down DC/DC transformer, in plastic case](https://i.sstatic.net/wiPprbWY.png)](https://i.sstatic.net/wiPprbWY.png)
  
  [![example step-down DC/DC transformer, in circuit board form factor](https://i.sstatic.net/mvRKfrDs.png)](https://i.sstatic.net/mvRKfrDs.png)
  
  The connection is straightforward - terminals marked "in" or "12V" go to the 12V power supply, and terminals marked "out" or "9V" go to the 9V motor.
  
  Let me also quote from <https://electronics.stackexchange.com/questions/448650/> :
  
  > The speed of a brushed DC motor is roughly proportional to the voltage applied, given the same countertorque.
  >
  > There's a reason that motor is designed for 6V only. DC brushed motors are very forgiving, even the commutator and the bearing should stand 1.5 times the design speed for a long time.
  >
  > **But the gears don't.**
  >
  > It's most likely a plastic gearbox. Running it at overspeed will destroy the innermost gear very quickly. Don't do it.
  
  Which means: do **not** connect your 9V monorail motor directly to a 12V power source. It will most probably run fine, but the gears made out of 30-years-old plastic will disintegrate.
  
  See also <https://electronics.stackexchange.com/questions/104749> and <https://electronics.stackexchange.com/questions/112000/> - there's no further considerations to attaching a DC motor to a step-down buck transformer.
  
  > **Comments:**
  > **username_0**: The information in your links is very helpful.  Having repaired a few Lego motors I know they do contain a plastic gearbox.  If it is the speed as opposed to the voltage that causes any damage then I would think that a 12V supply on a 75% PWM duty cycle brings us back to the operating tolerance of the gearbox (unless the on/off nature of PWM causes any additional stress?).  The first article from which you quote mentions a 150% tolerance for the motor itself.  Here 12V/9V = 133% so we are within that.  
  > **username_0**: I read somewhere that Lego motors are in fact rated 12V but I can't find the article.  If anyone knows of it, I think it would be a valuable addition to this thread.  
  > **username_0**: Finally, to shed light on the reason for considering 12V, it is simply that MN21 batteries (including holder) fit within a 2-stud space, so are particulary appealing where space is at a premium.  Whether they can supply sufficient current to operate the motor is yet to be established.  
  > **username_1**: I guess your follow-up question about PWM is better suited to electronics.stackexchange.  
  
  ---
  
  