Slot Car Corner - Making a Controller Adapter

Slot Car Corner

Making a Controller Adapter - Alligator Clips to XLR

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Introduction

This is the fourth article in a four part series about XLR connectors. The first article, entitled "Adding An XLR Connector to Your Controller", began by discussing the many advantages an XLR connector offers when used with 1/32 slot car controllers. The article then went on to provide detailed step-by-step instructions to replace your existing controller connector(s) with an XLR connector. The second article, entitled "Adding An XLR Connector to Your Driver Stations", provides illustrated step-by step instructions which show you how to add an XLR jack to your driver stations. The third article, entitled “Making a Controller Adapter – XLR to Alligator Clips”, showed how to fabricate an adapter to convert an XLR controller connector to 3 alligator clips which can be connected to any driver's station with traditional 3 post hookups. This article describes how to make an adapter like the one shown so you can use a controller with alligator clips on tracks with driver’s stations which include an XLR jack. If your track has XLR jacks, you might want to have a couple of these adapters on hand for visitors or if you host races.

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 adapter 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 right shows the basic components needed to fabricate the controller adapter.

You will need:

Three (3) pieces of wire about 8" long each. Hookup wire will work (though it is usually a bit stiff); however, high strand silicone wire works much better (due to its "limpness").
Inline XLR male connector
Three (3) 6-32 x 1-1/4" brass machine screws
Three (3) step down butt connectors (12-10 to 14-16)
Heat shrink - one (1) piece each black, white and red cut to length (about 1/2" to 3/4" longer than the butt connectors
Heat shrink - three (3) pieces about 3/8" long each

To assemble the adapter, you'll need the following tools and materials:

A soldering iron rated at 25W or more (with stand and cleaning sponge)
Rosin core solder
Rosin flux
Wire cutter/stripper
A small clamp or vise,
A pair of "helping hands" (soldering aid).

CAUTION: Always wear safety glasses and follow all manufacturer's instructions and safety guidelines when using tools.

Note: The components shown are available in kit form in the Online Store. If you prefer, pre-assembled adapters are also available for purchase.

If you plan to use wire with colored insulation (1 wire each - black, white, red), you can skip this step. Otherwise, you'll need to designate which of the wires will be "black", "white" and "red". It will be very important to know which wire is which later in the fabrication process. In the accompanying picture, I've used small pieces of colored electrical tape for this purpose.

Start by stripping about 1/4" of sheathing from one end of all 3 wires as shown.

Twist one of the bare wire ends together tightly and check to see it will fit into a solder pot on the XLR fitting. If the wire diameter is too large, you will need to decrease the diameter by removing some of the outer wire strands using a pair of wire strippers. Be careful not to remove too much - check for fit frequently.

Now use your soldering iron to "tin" the end of each wire. Make sure the bare 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 for just a couple of seconds - the solder should "flow" from the soldering iron tip to the wire.

One end of each wire should now be tinned. Here is a close-up of the tinned wire ends.

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. Be careful not to overtighten the clamp or you could damage the plastic fitting.

Before soldering each wire, apply some liquid flux to the solder pot (see picture) and the tinned end of the wire.

Recall the pinout configuration our club uses is 1 - black; 2 - white and 3 - red. You can solder the wires to the corresponding solder pots in any order - I started with the black wire (pot #1). The tinned end of the black wire was inserted into the solder pot labeled "1" and soldered. Repeat for the remaining two wires. If desired, you can then reposition the fitting in the clamp to facilitate soldering the next wire.

Once all three (3) wires have been soldered to the fitting, it should look something like this.

Now slide some small pieces of heat shrink down over each wire and cover the solder pots as shown. This is a precaution to prevent a short circuit should a the "bare" solder pots come in contact with one another (this is very unlikely; however, this step only take a few seconds for an added measure of insurance).

Use a heat gun (or hair dryer) to complete installation of the heat shrink.

Position the strain relief (if your XLR connector includes one) around the wires and solder pots as shown. Once the XLR is completely assembled, the strain relief will prevent the wires from being "bent" (where they attach to the solder pots) or pulled out of the solder pots.

Ensure the small metal tab on the plastic XLR fitting aligns with the rounded notch in the strain relief as shown.

Slide the outer XLR housing over the plastic fitting and strain relief as shown.

Now slide the plastic fitting and sleeve inside the metal XLR connector housing. The inside of the metal housing has an alignment keyway which prevents the fitting/sleeve from being inserted incorrectly. Note the relationship of the "U" shaped cutout and tab with the release lever on the metal housing. You may have to wiggle the fitting/sleeve slightly to align it properly with the keyway inside the housing.

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

Slide the female portion of the outer XLR cover over the free ends of the three wires and position as shown. Carefully thread the plastic cover onto the metal housing taking care not to cross-thread or over-tighten (hand tighten only...).

The completed XLR connector should look like the picture to the right. Depending on the wire gauge you are using, it may not be possible to thread the plastic cover all the way onto the metal housing. This is OK - again, hand tighten only!

Use a pair of wire cutters to trim the wires so they are all the same length.

Next, use a pair of wire strippers to remove about 3/8" of sheathing from the end of each wire as shown.

Tin the wire ends as described earlier.

Slide the wire end into the end of the step-down butt connector with the "small" opening. The step down butt connector will have a "stop" inside at the halfway point. Be sure the wire insulation fits up against the end of the butt connector. The wire shown in the picture is too long (note the tinned wire showing where the wire fits into the connector). Trim the length of the tinned wire if necessary for a proper fit.

Cut the heads off the 6-32 x 1-1/4" brass machine screws using your favorite cutting tool. Because the brass is relatively soft, I use a pair of lineman's pliers.

Here is one of the brass screws after the head has been removed. The 6-32 diameter screw fits perfectly "inside" most alligator clips.

Flux the inside of the step-down butt connector. Make sure to flux both ends.

Flux the end of the brass screw which you just cut. Don't worry if it is rough - we'll "hide" it in the next step.

Insert the end of the brass screw which was cut into the 12-10 end of the step-down butt connector. The "finished" end of the brass screw should be visible - it will be inserted into the controller alligator clip when in actual use.

Insert the tinned end of a wire into the 14-16 end of the step-down butt connector.

Use a pair of "helping hands" (available at many electronic and hobby stores) to hold the assembled components together for soldering. This will leave both of your hands free to solder the components together. Be sure the wire and brass screw are inserted as far as possible into each end of the butt connector.

The wire, butt connector and brass screw dissipate a LOT of heat - be patient and let the soldering iron heat the joint properly. Notice the opening in the middle of these butt connectors - it is perfect for feeding solder into the joint. In addition to the center opening, apply a small amount of solder where the brass screw enters the butt connector.

Let the soldered components cool thoroughly before handling. The three brass screw connectors should look something like this after soldering.

Use heat shrink to insulate the brass screw connectors at shown. The heat shrink serves a couple of purposes - first to identify which alligator clip to connect, and second, to prevent the connectors from touching each other and creating a short circuit when in use.

Your controller adapter is now complete and ready for use!!

When using the adapter, be sure to attach the alligator clips properly. The accompanying picture shows the WRONG way to make the connection.

Here's the CORRECT way to connect the adapter to an alligator clip. Insert the adapter "post" straight INTO (up inside) the alligator clip.

Be sure to insert the adapter as far as it will go inside the alligator clip. Check to see the protective boot on the alligator clips is pushed up toward the end of the alligator clips as far as it will go. A rubber band or piece of tape can be used to keep the protective boot from sliding off.

This picture shows the adapter connected to a controller with alligator clips.

You can easily adapt the steps described in this article to fabricate other controller adapters as well. The accompanying picture shows an example with a 1/4" TRS (tip, ring, sleeve or stereo) plug instead of an XLR connector.

Summary

There you have it!! The finished adapter extends the functionality of your controller and is a great addition to your track or slot box.

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

"Adding An XLR Connector to Your Controller"
"Adding An XLR Connector to Your Driver Stations"
“Making a Controller Adapter – XLR to Alligator Clips”