Kill Switch Relay Mod (Headshot Trigger)
A safer, more reliable way to implement the Death Racer headshot kill switch using a relay.
Overview
This page outlines a reliable relay-based solution for implementing the classic headshot kill switch used in Death Racer battles. When the racer figure's head is knocked off, a switch is released, triggering a shutdown of the RC receiver and rendering the vehicle inoperable — the battle is over.
🎯 Gameplay Objective: Knock off the opponent’s head to kill their vehicle.
The "head = kill" mechanic is standard in Death Racer builds. However, the typical method — routing battery power directly through a mechanical switch — has proven unreliable and prone to burnout, especially with 15–20 amp toggle switches.
This guide introduces the relay mod fix, as discussed in theory by Jeremy (M86 Toys) on LeeMerie3D’s May 20, 2025 stream, and will be implemented in upcoming streams using this documentation.
The Problem with Direct Power Switching
Builders often run the main battery voltage directly through the switch
Most toggle or magnetic switches used are rated 15–20 amps, under rated for the potential amp load.
Death Racer power setups can spike higher, leading to switch failure, overheating, or fire risk. Spikes can happen when resistance is applied to motors driving the death racer.
This puts the entire receiver system at risk and leads to inconsistent kills
The Solution: Relay-Controlled Kill Switch
Instead of routing full power through a switch, this method uses a low-power switch to control a relay, which handles the high current load.
How It Works:
A normally-open switch is placed under the Death Racer’s head
When the head is attached, the switch closes and activates the relay
The relay connects the battery to the RC receiver
When the head is knocked off, the switch opens → the relay cuts power → the vehicle dies
⚠️ This isolates the mechanical switch from the full battery current and dramatically increases reliability and safety
Featured on Stream
Jeremy (LeeMerie3D) explained this fix on LeeMerie3D’s livestream – May 20, 2025 (13:37 mark). Watch the live comments by "MalaMaker" explaining this addition.
Parts List
1x Relay module (DC 12V automotive relay, 40amp recommended)
1x Normally-open switch (original switch designated for the death racers)
Wire, connectors, heat shrink
Wiring Concept
Battery (+) ───> Relay ───> RC Receiver (+)
▲
Battery (+) ───> NO Switch (Head-Mounted) ───> Battery (-)Switch is closed when head is on — relay stays active — receiver has power
Switch is open when head is knocked off — relay cuts — vehicle is dead
Mounting Tips
Mount the switch in a way that the figure’s head holds it closed
Use a press-fit, snap-in, or magnet-based head that reliably pops off on impact
Secure the relay in a protected spot near the battery
Safety Benefits
Keeps high current off fragile switches
Prevents melted switches or mid-match failures
Increases reliability and reproducibility of kills
Makes builds tournament-ready
In Development
The final wiring demo, mounting technique, and live test of this relay-based system will be featured in an upcoming LeeMerie3D stream. This wiki page will be updated with:
Video tutorials
STL relay mounts
Printable wiring diagrams
Troubleshooting guide
Want to Help?
If you’ve built this mod successfully or have refinements, consider contributing back to this page or submitting photos, diagrams, or footage of your working rig!
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