Homemade Remote Detonator: The noobie, the Pro and the Chad

Prerequisites:

Reader understand about basic electronic and has > 2 intergers IQ.
i.e; Know what's a battery is, how many toes are there on a hand,  Derivative and Calculus 1

Nah, the last 2 are not required, I'm just fucking with ya.

When I was a kid I always fascinated by the remote detonator in movies. I thought those were the coolest thing ever! And just like this guy I often hold a brick console pretend to detonate a bomb. The difference is, his brick can make things go ka-boom while mine lacks that capability.

In my previous write we learned about low current e-match, combine with a remote detonator and we can make things 💥 from afar. How cool!

As I grown older I've unlocked the skills to made such device from multiple sources of hardware. From modifying toys to solder my own Rx modules. Now I don't have to pretend any more, I can do it for real, yay ⸜(｡˃ ᵕ ˂ )⸝

The Noob

For some reason my neighbor beat the shit out of his son, destroy and throw away all of his toys in the trash. Upon collecting his toys from the bin (now they are mine). A 4 channel RC car got me interested. It reminds me about the first detonator that I made when I was about his age.

Cut open the car and the controller, these are the heart of our project. They operate on the 27MHz frequency (all the cheap chinese toys work on this frequency). You can buy a minimum PCB set like this on Alibaba for like 2$. They might look a bit differ, but works just about the same.

Powered by a single 18650, antenna held in place by a metal nut. 4th button is missing because a piece of PCB broke off.

They works well with 18650 cells. Tx runs on 3 - 5V and Rx 8.4V no problem (2x 18650 in series). For the sake of simplicity, let's use a 9V cell for our diagram, pretend the arduino is the RX board with corresponding wire color

 

Red and black: To battery obviously.
The other 2 pairs control motor1 and motor2. Connect them to your electric match (denoted by the incandescent bulb).
In this configuration, 4 channels can detonate 2 fire crackers.

Let's modify it a bit. Re-arrange the wiring, now we can detonate up to 4 individual fire crackers or whatever device that you like

Switched to LED for a smaller diagram footprint

That's much better. But what if  we need to drive a current larger than that the board can provide, says 2 Ampere? Here's an answer:

 Relay                                                       MOSFET    

Relay: A mechanical switch, but activated by electricity (it has little magnet inside). Rather bulky, make clicky sound during operation.

MOSFET: Works like a solid state switch, no moving part, will get hot under high current. A lot smaller than relay, great for small, stealthy device. Don't let the link scare you, use it is easier than it looks.

Both have a defined activate voltage. i.e; The relay above will only work with U >= 5V. This depend on the model of the relay/MOSFET. Refer datasheet to chose the correct one.

MOSFET wiring example. Do the same with other channels

 The Resistor is important. It acts as a pull down resistor

This is my Rx module, using 2 MOSFET sits on top of each other. I only use 2 channels, the other 2 were reserved.
Everything held together using 3M double side tape. It held up pretty good so far.

Notes the pull down resistor connects signal wires to Ground

These MOSFET work well with low voltage, and can pass high current

This "toy" while cool and bad ass, only suitable to ignite rocket, mini bomb and firecrackers. For more beefy stuffs like HE, safety is a serious concern:

The signal is not encoded. Any toy controller that using the same 27MHz frequency will control your device as well. Boy does it sucks when your RDX block explode when you don't want it to.
You can change the frequency of the Tx and Rx to avoide RF overlapping with other controllers, but I don't trust my life with that shit.

These things only work up to 30 meters, and that's a stretch. I don't want to be within 30m from a detonating HE block.
The 27MHz is also prone to interfere by your skin. Having the antenna near or touch your skin (or a plastic bag) will cause the signal to drop entirely.

The Pro

It's time to upgrade our technology tree. Now we step into UHF radio region. By using these 315/443 MHz Tx/Rx module, our signal can go further, clearer, and you can even encode your signal with 8 bits encoder.

Less chance of signal overlapping + longer distance = less chance you got blown into tiny pieces.

Unlike the toy car, these micro controller modules can only output < 100mA on its pin out. Use a relay or MOSFET to drive the current is a must.

My wiring is a mess, but it's no different than the car toy above. Check the datasheet of your 315/433 Rx module for pin out instruction.

Depend on the vendor/retailer, the Rx module may or may not withstand a voltage higher than 5V. I fried one when trying to connect it directly to a 8.4V power source, thinking it should have an embedded voltage regulator - ah shit it ain't.
Use a voltage regulator like a LM78L05 to avoid all that drama.

Field test with clear line of sight and I was able to control my device up to a distance of 350m! It could be more, but I'm out of space ಠ_ಠ

Antenna plays a crucial role in RF communication. Depend on your module Frequency you need to tune your antenna to the correct length, both for Tx and Rx. This ensure you have the best transmission.

I use the 3rd channel for a little RGB led, so I can find it in thick foliage and low light condition. Can't remember how many time I lost it in the bush.

The CHAD
Surfing on the net and I found some of the most bad ass remote detonator design that I ever see. Despite being goofy and (maybe) impractical, their simplicity blown my mind (and IDK why, but the majority of them are from India)  ¯\_(ツ)_/¯

This guy use gear box from a toy car as a trigger. A crude form of a relay, very slow relay, but it works nevertheless.

Instead of Radio Control device, this guy use Infrared Signal to detonate his firecracker. This was done by modifying a TV box IR receiver, connected it to a relay to pull high current.

This particular design got me interested. Because unlike Radio, Infrared spectrum are often over looked in signal jamming. 

RF jamming can prevent commanded IED from detonating or even jam GPS guided munition.
So I though: Making a remote detonator triggered by IR signal at long distance? The cons that you must have a direct line of sight to the target, rain and fog can affect operational range but less prone to active jamming.

This might be a project I'll have in the future (˵ •̀ ᴗ - ˵ ) ✧