Home > Articles

Hacking Your LEGO Mindstorms EV3 Kit: Connections

  • Print
  • + Share This
Mindstorms’ components use wires to link the power and data of modules together. This chapter from Hacking Your LEGO Mindstorms EV3 Kit explores what’s up with those Mindstorms wires and demonstrates how to hack them into different configurations.
This chapter is from the book

Mindstorms’ components consist of modules linked together. The motors connect to the Intelligent Brick but not directly—they use wires to link the power and data of both modules together. Those linkages are themselves fascinating. This chapter explores what’s up with those Mindstorms wires and demonstrates how to hack them into different configurations. Then, I describe some of the common methods Mindstorms hackers employ to control and connect components without using wires.

Mindstorms Wires Explained

Let’s begin by exploring all the nitty-gritty details of the standard Mindstorms wire. LEGO uses semiproprietary wires in its Mindstorms variants. I call them semiproprietary because they’re just a standard configuration (known in the business as RJ12) but with the tab off to one side, as shown in Figure 3.1. You literally could use RJ12s if those tabs were off-center. Since LEGO has seen fit to do it this way, however, we have to use our creativity to overcome this inconvenience.

FIGURE 3.1

FIGURE 3.1 Mindstorms cables’ off-center tabs are all that differentiate them from RJ12s.

First, however, let’s check out what you get in the EV3 set:

  • Four—250mm/10-inch
  • Two—350mm/13.75-inch
  • One—500mm/20-inch

So to recap, the EV3 set includes four short cords, one long cord, and two in the middle. The cords can be swapped end-to-end and can be used with everything from motors to sensors. They’re truly universal in the Mindstorms world, meaning you only have to worry about length when you grab a wire.

Not surprisingly, these three sizes aren’t good for everyone, so some established suppliers have come up with different wire sets:

  • HiTechnic’s NXT Extended Connector Cable Set (P/M NWS1000) includes six cables, ranging in length from 120mm (4.7-inch) to 900mm (35.4-inch). You can buy the set at hitechnic.com.
  • Mindsensors’ Flexi-Cable pack (P/N FLEX-Nx) includes four cables: 200mm, 350mm, and 500mm just like regular LEGO cables. However, Mindsensors’ cables have thinner and more flexible insulation, allowing them to move around and bend more readily than LEGO’s stiffer wires. You can buy the Flexi-Cables at mindsensors.com.

Inside the Mindstorms Wire

So, what’s going on inside that black plastic insulation? It turns out there are six smaller wires inside, as shown in Figure 3.2.

  1. The blue wire is the SDA (serial data) wire, one-half of a two-wire data transfer protocol called I^2C. EV3 can transmit sensor data and commands through the I^2C bus.
  2. Yellow is the SCL (serial clock) wire, the other half of the protocol.
  3. Green is power, typically delivering either 3.3 or 5V from the EV3’s battery pack. You can use this wire to power electronic circuitry and add-on modules.
  4. Red is ground. Creating a circuit with the power pin and this ground yields 5V.
  5. Black is also ground. A circuit with this ground and the power pin yields 3.3V.
  6. White is analog, transmitting analog sensor signals back to the EV3 Intelligent Brick.

    FIGURE 3.2

    FIGURE 3.2 The Mindstorms wire actually consists of six smaller wires.

Knowing the purpose of each wire helps you hack them, and it never hurts to understand what’s going on under the insulation.

Hacking Mindstorms Wires

Not unexpectedly, LEGO hackers have explored the wires and created their own variants to suit the needs of their projects. The following are a sampling of techniques you could employ.

Changing the Length of a Mindstorms Wire

This is an obvious one. How do you change the length of a Mindstorms wire? The following takes you through the steps, with Figure 3.3 guiding you along the process.

  1. Make a shorter wire: Cut the plug off one end, making sure to leave yourself a couple of inches of wire, and trim the remaining length down to the size you want. To make a longer wire, cut an end off two wires, so that their combined length equals the size you want.
  2. Carefully remove the outer black insulation and pull apart the six inner wires.
  3. Solder together each wire to its same-colored mate on the other side. (If you need to polish up your soldering skills, there’s a helpful how-to here: http://mightyohm.com/files/soldercomic/FullSolderComic_EN.pdf.)
  4. Insulate the individual wires with heat-shrink tubing, such as SparkFun P/N 9353. Then the combined wires should get a larger piece of tubing to keep them in check.
FIGURE 3.3

FIGURE 3.3 To alter a Mindstorms wire, just cut it apart and solder it back together.

Using a Breakout Board

Another way to access the inner workings of a Mindstorms wire is to use a breakout board. These are little circuit boards with Mindstorms-compatible plugs on them, allowing you to break out the six inner wires as separate pins.

A couple of variants are floating around; I like the Bricktronics Breakout Board, selling for only $4 from wayneandlayne.com. In Figure 3.4 I demonstrate how to light up an LED, connecting from the power pin to the red ground (5V) with a 470-ohm resistor protecting the LED from too much voltage.

FIGURE 3.4

FIGURE 3.4 To access the inner wires individually, use a breakout board.

Breadboard-to-PF Hybrid Wire

PF refers to Power Functions, a mostly compatible motorized set put out by LEGO and marketed alongside Mindstorms. In fact, the beams and other building elements in the EV3 set are identical to the parts sold with PF sets, making the two remarkably compatible. Not completely, however, because there is no way to control PF’s awesome DC motors using your EV3 brick. Two of PF’s four wires are 9V and GND, and the other two control the speed of the motor.

You still need a way to trigger the voltage—the 9V the Power Functions motors are expecting is more than the EV3 brick can handle. In Chapter 5, “Hacking LEGO II: Alternate Microcontrollers,” I show you how to use an Arduino microcontroller that not only can control those great PF motors, but also Mindstorms servos as well.

In the meantime, here’s how to make your own hybrid wire:

  1. Cut off one end of a Power Functions extension cable (LEGO P/N 8886). It has a male end and a female end, with the male end looking like a regular 2x2 LEGO brick, and the female end looking like the underside of a similar brick, allowing you to attach them together just like they were regular bricks.
  2. Strip the four individual wires on the female end. They consist of Power, Control 1, Control 2, and Ground. Solder each wire to a male header pin (SparkFun P/N 12693) or a Molex plug like you see in Figure 3.5, which you can crimp on yourself, or buy a pigtail such as the SparkFun P/N 9920. Use heat shrink to cover all conductive surfaces.

    FIGURE 3.5

    FIGURE 3.5 A cable that connects LEGO’s proprietary PF connector to a breadboard.

  • + Share This
  • 🔖 Save To Your Account

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.

Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020