Answers.Body: <p>The LEGO Power Functions connectors have 4 standard designations regardless of the usage:</p>
  
  <ul>
  <li>9V power</li>
  <li>"0V" Ground</li>
  <li>C1 "control 1"</li>
  <li>C2 "control 2"</li>
  </ul>
  
  <p>It seems for motors that the <a href="http://www.philohome.com/pf/pf.htm" rel="noreferrer">9V and Ground are unused</a>.  The C1 and C2 are used in combination to pick the motor direction.  If C1 is providing power and C2 is providing ground then the motor goes forward.  If C2 is providing power and C1 is ground then it goes backwards.</p>
  
  <p><img src="https://i.sstatic.net/rHbT7.gif" alt="power function motor diagram"></p>
  
  <p>The dashed lines are unused at that stage in the flow.</p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2017-12-11T15:57:26.333Z
Answers.Text: To drive two motors in opposite directions at the same time from one output of the remote unit all I need to do is to reverse C1 and C2 on one of the connectors?
Answers.UserDisplayName: Quorneng
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2017-12-11T16:04:50.947Z
Answers.Text: That sounds reasonable.
Answers.UserDisplayName: chicks
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2017-12-19T09:21:52.667Z
Answers.Text: If you're using the standard battery box, and no remote, that is the difference between the two on switch positions
Answers.UserDisplayName: Rowland Shaw
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2023-12-05T22:06:03.090Z
Answers.Text: It's strange that they chose to do the reversal by adding 2 more lines rather than just reversing the polarity of the power. It means there has to be logic in the motors as well as any switches you add to the chain.
Answers.UserDisplayName: John Stock
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2017-12-11T14:28:46.833Z
Answers.LastActivityDate: 2017-12-12T20:18:16.823Z
Answers.LastEditDate: 2017-12-12T20:18:16.823Z
Answers.UserDisplayName: chicks
Body: <p>Does anyone know what the wires do?</p>
  
  <p>If the Power Functions train motors are simple DC only 2 wires would be needed or is it more complex than that?</p>
  
Tags: <trains><power-functions><electronics>
Title: Why are there 4 wires leading to the Power Functions LEGO train motor?
UserDisplayName: Quorneng
ThreadText: # Why are there 4 wires leading to the Power Functions LEGO train motor?
  
  (Asked by: username_0 on 2017-12-11)
  
  Does anyone know what the wires do?
  
  If the Power Functions train motors are simple DC only 2 wires would be needed or is it more complex than that?
  
  **Tags:** trains, power-functions, electronics
  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_1 on 2017-12-11. Score: 11
  
  The LEGO Power Functions connectors have 4 standard designations regardless of the usage:
  
  * 9V power
  * "0V" Ground
  * C1 "control 1"
  * C2 "control 2"
  
  It seems for motors that the [9V and Ground are unused](http://www.philohome.com/pf/pf.htm). The C1 and C2 are used in combination to pick the motor direction. If C1 is providing power and C2 is providing ground then the motor goes forward. If C2 is providing power and C1 is ground then it goes backwards.
  
  ![power function motor diagram](https://i.sstatic.net/rHbT7.gif)
  
  The dashed lines are unused at that stage in the flow.
  
  > **Comments:**
  > **username_0**: To drive two motors in opposite directions at the same time from one output of the remote unit all I need to do is to reverse C1 and C2 on one of the connectors?  
  > **username_1**: That sounds reasonable.  
  > **username_2**: If you're using the standard battery box, and no remote, that is the difference between the two on switch positions  
  > **username_3**: It's strange that they chose to do the reversal by adding 2 more lines rather than just reversing the polarity of the power. It means there has to be logic in the motors as well as any switches you add to the chain.  
  
  ---
  
  