Monday, July 15, 2013

Installing lights on Traxxas E-Revo VXL

My son really wanted his RC car to have lights "just like on the real cars". The Spektrum SR3300T receiver is a 3 channel receiver and the AUX channel can be used to control lights - so why not? Turning the head and tail lights by flipping the AUX switch on the remote control was an extra feature, I thought would be pretty cool. 
Our design goal was : 2 high-intensity white head lights, 2 red (light red / deep orange) position (tail) lights, 1 red/blue flashing ("dash mounted, "police strobe mode" light) - all switched remotely. 2 dual-step intensity, combined break lights / position lights (deep red color, bright - break, dim - tail) - switched on/off at the model, automatic break signal detection and intensity control.
Parts used: kits - RCL5004E, RCL5090 and miscellaneous connectors, wires, resistors

Front View - head lights - high-intensity cool-white LEDs in chrome "reflector" fixtures providing great level of illumination. The flashing blue/red  strobe light is seen just behind the windshield. This light improves the model's visibility during the twilight hours.

 I made two elongated holes in the Lexan body (using Unibit drill bit) in order to properly align the head lights - parallel to the body, almost level (very slightly tilted forward for maximum illumination of the road ahead of the vehicle). Adjustments were made based on the current suspension settings.

 The head lights wiring harness. The chrome reflector fixtures were glued at the specific angle / position in the elongated openings using hot melt glue. It was a bit tricky to keep them properly oriented while the glue cools down.

 Rear light bar - the black plastic plate with the 6 holes came off the Spektrum DX3S packaging (used to secure the remote control to the cardboard retail box with wire ties. It is the perfect size for the tail light bar. All I need to do is to enlarge 4 of the holes  to accommodate the black plastic bezels and to drill two more mounting holes. The bar is secured to the Revo's wing mount with 3 zip-ties for easy installation/removal.

The outside two LEDs are the dual-intensity, deep red color, tail / brake lights. The inside two LEDs are a second set of tail lights - slightly different red color (deep orange). The LEDs are wired in parallel (on the back side) in two separate pairs and all connections are water-proofed using black UV resistant silicone sealant.

This picture shows the water-proof receiver box with the Spektrum SR3300T receiver mounted, the Y-split wire harness for the dual-servo steering, EBS (electronic break-detection switch) connected in-line with the THR (Throttle) signal going to the ESC (EBS is the clear heat-shrink covered  unit at the top). Pictured also is the RPS (Remote Power Switch) connected between the LED controller and the AUX output of the receiver. It got really tight in the small receiver box but I was able to fit everything inside.

This is my DIY "LED Controller". The RCL5004E comes with a "LED Controller" but it is too bulky and the connector placement didn't work for me. It is not water-resistant too. What they actually call a "LED Controller" in this case is nothing more than a combo of two "power strips" with built-in current limiting resistors.
 I made my own "LED Controller" except I used a single connector, soldered the current-limiting resistors on one side and covered it with silicone and heat-shrink tubing for water-proofing. The wire lead from EBS+RPS plugs in the center of the power strip - left side is RPS controlled for head lights, tail lights and emergency light, the right side is EBS controlled for the dual-intensity brake/tail lights. It could have been even smaller but I left a couple of positions for future expansion and for extra configuration flexibility provided direct power outputs (in case the current limiting takes place at (or near) the LEDs and it is part of the wire harness. In addition, I incorporated two different sets of current limiting resistors with different values per channel - 82 Ohms and 150 Ohms as options for different current (brightness) levels.

The "LED Controller" is positioned between the receiver box and the heatsink of the motor and it is held in place with Velcro. The wire harness for the rear light bar is place in a braided polyamide sleeve. Visible, just in front of the motor between the two servos  is the "emergency light" LED  - it is a special high-intensity dual color (red-blue) fast flashing LED and it is directly plugged in one of the current limited ports of the LED power distributor (on the RPS controlled side).
My goal was to have the wiring look neat - probably this is as good as it will get.

One reason I was trying to avoid the "wire-salad" look is because sometimes, we drive the car with a clear Lexan body that shows off the beautiful vehicle internals (no headlights on the unpainted body).

This is how the complete model looks like. We went with the dark blue/bright yellow color scheme for an improved visibility. The windows were masked as well as the most of the car body, leaving exposed only the areas to be painted blue. Then the yellow paint was applied. All of the painting is done on the under side to protect it from scratches during roll-overs and crashes.

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