Slot Car Corner - Making a Controller Adapter

Slot Car Corner

Adding an XLR Connector to Your Controller

by Steve Sawtelle.

Note: Click on any of the thumbnails throughout the article to see a larger image (Use Browser "Back" Button to Return)

XLR: The Ultimate Controller Connector?

I'm very fortunate to be part of a very active slot car club (Shoreline Model Raceways). The club races every Wednesday night, organizes informal races and practice sessions as member's schedules permit and gets together 2-3 times a year to race with the H.O.S.T. club as well. Virtually every track we race and practice on has driver's stations with traditional 3 post, commercial style hookups. It is a rare race when at least one racer doesn't hookup their controller wrong. Keep in mind we're not talking about just the rookies - some club members have been racing for 20-25 years or more!!! In most cases, the mistake is caught quickly; however, occasionally a controller will require repair or a circuit breaker will need to be reset. Of course, other racers take every opportunity to "remind" the offender about the proper way to hookup their controller ("Gee, look at this!! The alligator clips have these little colored rubber protectors and the colors match those on the posts they are supposed to get hooked up to!! What will they think of next?").

For some time, club members have been discussing better ways to connect controllers. There have been several suggestions such as standard 3 prong electrical plugs, quick disconnects of various types such as those used for trailers and XLR connectors. After some research and further discussion, Shoreline Model Raceways adopted XLR connectors as a club standard (we've still retained the 3 post hookups as well). XLR connectors offer several significant advantages over the traditional 3 post setup and other connectors. First, XLR connectors are virtually foolproof. Because of the XLR connector configuration, there is only one way a male and female XLR connector can be mated (see accompanying picture). Second, when fully seated the male XLR connector attached to the controller cannot accidentally disconnect (like alligator clips are prone to do from time-to-time...) from the driver's station. Third, when changing lanes between heats, it literally takes about one second to disconnect the XLR connector and another second to reconnect it to the driver's station for the next lane you will be racing in. Fourth, XLR connectors are relatively inexpensive. Finally, XLR connectors are easy to attach to slot car controllers. Unlike plug connectors, they have large solder pots which makes it easy to connect the controller wires even if you only have modest soldering skills.. With all of these advantages, XLR connectors might just be the ultimate connector for 1/32 slot car controllers.

This is the first in a series of three (3) how-to articles about XLR connectors. In this article, detailed step-by-step instructions will show you how to attach an XLR connector to your controller. The second article, entitled "Adding An XLR Connector to Your Driver Stations", provides detailed instructions to easily add a panel mount XLR jack to your existing driver stations. The third and final article in the series, entitled "Making A Controller Adapter - XLR to Alligator Clips", will describe how to fashion a simple adapter to convert a controller with an XLR connector to alligator clips for use with traditional 3 post style driver's stations. The adapter takes up very little room and is a useful addition to your track or slot box.

Before Starting - What Is Your Standard?

Before proceeding with step-by-step instructions, there is one prerequisite to cover off. If you belong to a club planning to use XLR connectors or race at other tracks which offer XLR connections, you will need to wire the 3 connectors according to an agreed upon standard. The Shoreline Model Raceways club I belong to adopted a standard which was already in use by the HSARC club in the greater Houston, TX area. The accompanying picture shows which controller wire will be connected (soldered) to which XLR connector "pin". If you look very closely, you will see the pin numbers embossed in the plastic next to each solder pot.

Step-by-Step Instructions

The picture to the left shows the basic components needed to attach an XLR connector to your controller. To complete this project, you'll need a soldering iron (with stand and cleaning sponge), rosin core solder, rosin flux, a wire cutter/stripper and a clamp or vise. Always wear safety glasses and follow all manufacturer's instructions and safety guidelines when using tools. For the pictures accompanying this article, I used a Professor Motor controller; however, the same basic steps apply to virtually any other brand of controller you might use.

Note: You can purchase a high-quality XLR connector like the one shown (excluding the controller...) from the Online Store.

The first step is to label the existing controller wires so you know the color (white, black, and red) associated with each. If you have a controller with white, black and red wires and/or colored protective boots, this is very easy to do. A short length of painters tape works well - write each wire color on the corresponding piece of tape as shown and skip to the next step.

If you have a plug-style connector like the one shown (1/4" or mini-style are most common) and the controller wires are not white, black and red you can use a multi-meter to quickly determine which wire is which. Where the 3 wires exit the plug leading to the controller, strip away a small amount of wire insulation (do NOT cut through the wire at this point) about 1/2" from the plug. Strip away enough insulation so you can easily make contact with the wire using one of your multi-meter probes. Now take a closer look at the plug in the accompanying picture. Notice the plug has 3 distinct sections or bands. The labels indicate the corresponding wire color for each band. Turn on your multi-meter and set it to measure resistance (typically denoted by the ohm symbol - if not sure, consult the user manual). Touch one multi-meter probe to the outermost (tip) band being careful it does not touch the other 2 bands. Now use the other multi-meter probe to touch each wire where you stripped away a small amount of insulation. When the second probe touches the wire connected to the plug tip, it completes ("closes") an electrical circuit - the meter display will read zero ohms. When the second probe touches the other 2 wires, the circuit is "open" - the meter will read infinite resistance (different meters indicate this in various ways - check your manual if necessary). The wire with zero resistance is your "red" wire (refer to the picture). Use a piece of tape to label the wire. Now move the first probe to the middle band of the plug. Use the second probe to touch the remaining 2 wires - the one reading zero ohms is your "black" wire. Take a piece of tape and label the wire. The remaining wire is your "white" wire - you can check with your meter to be sure (touch the first probe to the innermost band on the plug). Label the wire and take a minute to double check your findings before proceeding.

Once you have labeled the controller wires, you can remove the existing connector(s) from your controller. The controller used for this article had individual alligator clips; however, your controller might have a plug or some other sort of connector.

When removing the existing connector(s), make sure all 3 controller wires are exactly the same length as shown.

Use a pair of wire strippers to remove about 1/4" of insulation from the end of each wire as shown.

The next step is to prepare each wire end for soldering. Depending on the gauge wire used for your controller, you may have to use the wire strippers to reduce the diameter of the wire strands slightly (by cutting away some of the outer wire strands) so it will slip easily into the solder pots on the XLR connector. Test fit by twisting the wire strands together tightly as shown and test fitting into the solder pots. Use the wire strippers to reduce the overall diameter slightly if necessary. This is an iterative process - take your time.

Now use your soldering iron to "tin" the end of each wire. Tinning the wires will make soldering the wires into the solder pots on the XLR connector much easier. Make sure the wire strands are twisted together tightly. Apply some liquid flux to the end of each wire. Make sure your soldering iron tip is clean and apply a small drop of solder to the tip. Touch the tip to the bare wire - the solder should "flow" from the soldering iron tip to the wire as shown.

Slide the 3 wires through the protective boot as shown. Don't forget to do this as there is no other way to get the boot over the wires once the wires are soldered to the pots in the next several steps.

Soldering the wires to the solder pots will be MUCH easier if you have both hands free. A quick release clamp like the one shown will hold the plastic fitting which houses the solder pots securely while you position and solder each wire.

Apply liquid flux to the inside of each solder pot and the tinned ends of each wire before soldering. Refer to the diagram, small pin numbers embossed on the connector fitting next to each solder pot and the tape labels you attached to each wire to ensure the correct wire is soldered to each pot.

If you sized the diameter of the wire tip correctly in a previous step, the solder pot will hold the tinned wire tip in place with little or no additional support. Make sure you soldering iron is cleaned and tinned - carefully touch the tip to the seam between the solder pot and wire. Once the solder starts to flow, wait a couple of seconds and remove the soldering iron. Repeat for the remaining 2 wires.

The connector should look something like this once all 3 wires have been soldered to the solder pots.

While not required, I like to wrap a small piece of electrical tape around the solder pots to prevent an accidental short circuit. Most electrical tape is about 3/4" wide - trim it to about 1/2" wide and use a piece about 2" long.

Place the sleeve over the 3 wires as shown - make sure to orient it as shown. The "U" shaped cutout in the sleeve (1) must be aligned with the tab (2) before sliding the sleeve over the plastic fitting. The sleeve will prevent the wires from shifting and serves as a strain relief once the XLR connector is fully assembled.

Slide the sleeve all the way up and over the plastic fitting which houses the 3 pins and solder pots. Make sure the "U" shaped cutout is positioned over the tab as shown.

Now slide the plastic fitting and sleeve inside the metal XLR connector housing. The inside of the metal housing has alignment channels which prevent the fitting/sleeve from being inserted incorrectly. Note the relationship of the "U" shaped cutout and tab with the small rectangular slot at the far end of the metal housing. You may have to wiggle the fitting/sleeve slightly to align it properly with the channels inside the housing.

Once aligned, push the fitting/sleeve as far up into the metal housing as it will go.

Now slide the outer plastic housing (you did remember to slip the wires through it previously, right?) toward the metal housing and carefully thread it onto the metal housing. Use caution not to cross-thread the plastic housing and damage the threads. Make sure the plastic housing is nice and snug - hand tighten only to prevent damage to the housing!

Congratulations! You've successfully attached the XLR connector to your controller! The finished connector should look like the one shown.

The XLR connector is now ready for use. You won't believe how easy/convenient these connectors are to use!

Summary

This is a relatively easy do-it-yourself project that just about anyone can complete in less than 30 minutes. Once you try XLR connectors, you'll never want to use conventional controller connectors again!

Remember to check out the other XLR-related articles in this series listed below: