|How to build IR remote controls
explains how to build remote controls for military use that are immune to jammers.
Advantages of optical remote controls :
This receiver is intended to be dug down, at a depth where it is invisible to
Only non-metallic parts above the ground.
A red high power LED in series with a resistor is connected on the front of the box instead of a blasting cap, because this is only a test. And we want to find out how long is the maximum shooting distance.
The shooting range is an abandoned railroad.
Very little leaking is measured from the high voltage circuit to the
The delay time is measured from when connecting voltage to the transmitter circuit
till the receiver relay connects the 95 Volts to the blasting cap.
But this is a test circuit, and the real transmitter has 5.5 mS instead of 5.0 mS between each pulse.
Which means about 125 mS delay time instead of 115 mS.
|Testing results :
The receiver's power consumption is about
8 mA at 5 Volts, which means that AAA size batteries will last about 225 hours.
The delay time is 23 pulses instead of 19 as calculated, but the 6.8 uF +/- 20%
capacitor is also measured to be bigger than average marking.
The charge-up time is not measured but is about a minute. The time it takes to charge up the capacitors to 95 Volts.
Maximum shooting distance is measured to be 235 meters +/- 1%.
But this is a worst case configuration in which a glass bar is used, and a bad
reflecting non-metallic cone, and a small 33.5 mm diameter transmitter lens.
The landscape is often polluted with metallic garbage which means that under normal conditions there is no need to use a non-metallic receiver because the enemy already have too many false alarms. (But a non-metallic optic fibre can be useful if the enemy uses EMP weapons to neutralize electronics.)
The blasting cap can be mounted inside the box if you want to shield it from
EMP-weapons, and connect it to an explosives filled plastic tube through a cable gland.
Optimized for four alkaline batteries.
Make sure to use a BC547C or similar high HFE type at the input stage because the amplification is only 50% if you use a low HFE type like BC547A. Which means about 30 percent shorter shooting distance.
The electrolytic capacitors give protection against ignition caused from glitches in the battery connection, but never trust anything for 100% and you will live a longer life. Always connect the battery before you connect the blasting cap.
The 2.2M resistor at the input is necessary when used in darkness.
Cheap and simple :
The intention of this webpage is to help you build remote controls from electronic
parts easily available in an occupied nation.
Use a 5Volt relay.
How the receiver's sensitivity is affected by daylight-DC and sunshine-DC.
A typical photodiode (LT536) has a sensitivity of 42uA for 1mW/cm2
|Input DC current||Relative AC sensitivity||Relative shooting distance|
|The shooting distance is decreased to 73 percent if the sun is shining
into the photodiode.
It seems like no trouble when using 1-2 photodiodes in parallel.
Current : 2 Ampere, 100uS pulse every
You should put a lens or a simple magnifying glass in front of the LED to
The BDX33 transistor is of the darlington type. See datasheets on the web for more information.
The 47 Ohm resistor is for safety against unintended trigger, and discharges the
1000 uF capacitor in less than 0.25 seconds, because the circuit will emit
pulses of light until the capacitor is fully discharged, even if you don't push the
The battery's internal resistance together with the 2.2 Ohm resistor protects the switch against high current which else limits its length of life. This resistor is not necessary if used with a standard 9V alkaline battery which has a high internal resistance.
Connect to a tiny 9V alkaline.
LED Everlight IR383
The datasheets are always about recommended limits for eternal life, but we don't want
any eternal life, and would rather barbecue the LED in a few minutes if it helps improving
the shooting distance.
My own testing tells that the LED survives more than 2 Ampere electric current. (pulsed
100 uS, dutycycle 2%)
If you use fast high voltage for the blasting caps in the receiver then can you try a "one-shot" timer circuit at perhaps 200 mS, and increase the current to the LED.
The LED has been tested to survive 7 Ampere for 5uS pulses, and 6 Ampere for 20 uS pulses, 9mS pause between every pulse. (Tested in 15 minutes of continuos barbecuing) But my own testing showed that most sources of disturbance and unintended trigger are easier to filter out if you use 100 uS pulses. It's about safety.
|Mass-production of PCBs Printed Circuit Boards
ZIP-file of the transparent OH-sheet above in
full size, 183 kB
Print out the circuit boards on a transparent OH sheet on any printer, for
phototransfer to a circuit board.
My own printer Canon IP4200 can print out photos but not OH borderless, and I
had to resize the BMP minus 3 percent.
Multiple UV-tubes, or move the UV-tube between multiple exposures.
You will need these chemicals. Buy at a paint-shop.
NaOH the same as used for cleaning sewage pipes.
Hydrogen peroxide H2O2 of about 20 % concentration
mixed with HCl and perhaps some water to slow down the reaction.. (If it stinks chlorine
gas then you use too little H2O2, add more.)
Ant then finally remove the remaining photoresist with high concentrated
Top view of the receiver PCB
Top view of transmitter PCB
This little cable is your life insurance.
Solder the wire for improved safety.
And also remember that the photodiode must be 100 percent electrically
Use a shielded cable of high quality, and put the photodiode inside a metal construction that is connected to the shield.
|Atmospheric disturbance :
The atmosphere acts like a lens when it is compressed and decompressed by the whirlwinds up in the sky. And with the sun at the other side it will create a modulated twinkling light that is too fast for your eyes to detect, but is measurable in the receiver.
The question is, how the safety is affected ?
Outdoor testing :
When the sun was shielded away the peaks was at 10mVpp after the 47 nF capacitor.
There is a risk of blowing your head off if increasing the receiver's sensitivity too much.
If you can't avoid the sun shining directly into the photodiode.
But the suns path on the sky is predictable which means that you usually can avoid the
direct sunlight, and then can you increase the sensitivity 15 times to get the same safety
A thumb rule of safety is to increase the transmitter's output power instead of increasing the receiver's sensitivity. You get four times more safety if you use a 60 mm diameter transmitter lens instead of a 30mm diameter lens, and design for 300 meters maximum shooting distance. But perhaps the transmitter becomes too big and bulky for your pocket.
You can win the most safety by limiting the photodiode's view angle, with a tube around the photodiode. If you limit the illuminated landscape area that the photodiode can see to 1 percent then it has become 100 times more safe. And the only thing the photodiode really must see is the transmitter's LED.
The safety can also be improved if you add more filters to the construction.
A tone modulated system compared to the impulse system above, can be made immune to atmospheric disturbance and other sources of twinkling light. It's more safe.
Another risk factor is oscillating plasma in lamps and mobile telephones and displays
As a thumb rule, the blasting cap is the last thing to connect, (or first thing to disconnect).
The rest of this page explains how to increase the shooting distance and safety.
|The picture below explains why you should try to increase the transmitter's output power before trying to increase the receiver's sensitivity.|
How to increase the shooting distance :
|First of all :
The square law of attenuation for propagating light waves.
The measured voltage from the receiver's photodiode is attenuated with the square of the distance away from the transmitter.
At 2 meters the received voltage is 1 / 4 of what you get at 1 meters.
You can use this square law to calculate the maximum shooting distance if you know the received voltage at a specific distance, and if you know the receiver's trigger level.
This is the thumb rule you have to learn :
How to increase the shooting distance :
1 Squeeze out the power from the LED
2 Put a lens in front of the transmitter's LED.
The methods 3,4,5 below are the most safe and useful in combination with a tone
3 Also put a lens in front of the receiver's photodiode.
4 Put a cone in front of the photodiode
5 Connect more photodiodes in parallel in the receiver.
6 Connect more receivers and transmitters in a chain.
7 Use multiple LEDs in parallel and no lens in the transmitter.
Two types of transmitters
Type 1 : One LED and a lens
A lens can increase the distance 5 to 25 times dependent on type of lens.
Lenses can be used to increase the shooting distance for your remote control.
Two parameters describes any convex lens.
The burn width f is the
same as the distance from the center of the lens to the target when you try to ignite fire
from the sunlight.
This is the mathematics you need to know to do your own
Adjusting the focusing of the transmitter lens :
It can be hard to adjust the focusing of the weak LED's lightspot on a screen or target 300 meters away. But if you understand the formula above it becomes easier.
As you can see from the formula, the 1/a is almost equal to zero for
targets very far away, which means that 1/b is almost equal to 1/f.
What's the diameter of the projected light spot ?
Lenses for receivers
It's the aiming accuracy that limits the usable burn width of the lens.
Conical amplifiers and optical fibers
The light is concentrated to the output end of the cone, but with increasing angles.
If you use the cone together with an optical fiber.
Sooner or later the number of bounces will reach a limit where the angle becomes greater than 90 degrees and the light is reflected back to the transmitter. There is a limit to the effective length of the cone.
Testing a cone and a BP104 photodiode :
Cones and 2mm fiber tested together
The yellow field is below the +/- 13 degree limit described above.
And in theory the best cone angle is perhaps somewhere below the critical angle if you count on aiming inaccuracy. But I leave this for future experiments to find the truth.
It seems like the cone angle is more critical or important when used together with a fiber.
Optical fibers tested
The advantage of optical fibers is that you can make the receiver invisible to radar
since there are no visible metallic parts. And also immune to impulse weapons that are
used to neutralize electronics. (including unshielded electric blasting caps). And also
immune to EMP from nukes.
The manufacturer of a 2mm diameter fiber says that the damping is 500dB/km
By measuring the signal strength for two different lengths of this fiber can I
calculate that :
But there is a mismatch between the 2mm fiber diameter and the size of the sensitive chip (2.2 x 2.2 mm) of the BP104 photodiode that damps the signal. And when testing with a 5.3 mm diameter plastic PMMA glass bar instead, the voltage is about 1.66 times higher than for the 2 mm diameter fiber.
Corrected approximative formula :
Received Voltage = 0.67 * e -0.00181*Length
Length in millimeters
For zero length the damping is 0.67 which means that about 33 percent of the light is lost somewhere. By reflection when passing through the end surfaces of the fiber, and leaking light at the bends.
For a typical 400 mm length PMMA glass bar about 70 percent of the voltage is lost
because of the glass bar.
With a 2mm fiber of the same length, the shooting distance is decreased to 35 - 40 percent because of mismatch between the fiber and the photodiode.
A 5mm diameter PMMA glass bar cost about $2 per meter.
|Optical components :
For the receiver :
Use types with daylight filter if you use IR-light. That will lower unwanted signals to
The photo receiving components becomes faster with higher voltage across.
Photodiodes are the best, and phototransistors are piece of shit, but still useful if you haven't got anything else.
Photodiodes work well in any light condition, while phototransistors will give you
trouble in extreme light conditions.
What happens in extreme sunlight ?
What happens in extreme darkness ?
Even if a receiver works well in extreme sunlight,
you should always try to shield away the sunlight for safety reasons.
Piece of shit, or not ?
Testing to build a receiver from a computer mouse.
Let's build a roadside potato
A black painted (inside) U-shaped aluminum plate and a sheet of glass and a wood stick is glued together.And then cover with polystyrene. Paint the potato and it looks like a stone. Ready to be planted at the roadside to kill the enemy.
Potato testing results:
The potato is half dead and useless until I connect electric current to
the internal LED.
In the computer mouse I took the phototransistors from, there is two slow
phototransistors at each saw wheel, but also an extremely slow phototransistor at the
finger wheel. And perhaps finger wheel transistors are too slow to be used at 100 uS
pulse width ?
89 uA DC current through the phototransistor when the potato is directed
at clouds in the sky.
Any closer to the sun and the current rises quickly.
5Volts across the serial resistor when directed at the sun, (saturated and paralyzed transistor.)
But usually there is a filter included in the receiver which means higher
This potato was never tested together with the receiver circuit on this
page because it is not dimensioned for the higher sensitivity of a phototransistor.
Suggested improvements :
Use asphalt or anything similar to make a watertight seal around the
Some tested IR photodiodes
With black filter against visible light.
|Photodiode||Daylight||Directed at sun||Relative shooting distance|
|LT536||54uA DC||269uA DC||1|
|Measured from single devices.
Note the last one which is a black LED-shaped photodiode with a built in lens focusing in a narrower 40 instead of 120 degree beam. Which gives 30% longer shooting distance. But also higher DC when aimed at the sun.
Translation of the table above
into absolute shooting distance:
As described earlier it's possible to extend the shooting distance with a bigger transmitter lens, or multiple photodiodes in parallel or a lens or cone in the receiver in front of the photodiode.
You can buy photodiodes or take them from TV sets or other remote controlled equipment.
Some high power IR LEDs
|950||ELD-950-525||160mW/Sr 100mA||20||2A10uS||Roithner Lasertechnik|
|940||L-7104F3BT||70mW/Sr 50mA||34||1.2A 10uS||Kingbright|
|950||ACULED VHL IR2||390mW 700mA
|855||ACULED VHL IR1||880mW 700mA
|IR LEDs are available in wavelengths between 700 and 7000 nm. But
880nm and 940nm are the most used because of the sensitivity peaks for these wavelengths
in the photodiodes. See the picture below.
The shortest wavelength types (880 nm) are visible to your eyes in darkness like a glowing cigarette.
Use 940nm if you want light that is invisible to the enemy's eyes.
But IR light is visible to the enemy's TV cameras, and also visible in ordinary digital cameras.
Daylight filter :
Links to LEDs and datasheets
http://www.roithner-laser.com LEDs from 7.0 um IR to UV
You can buy IR LEDs or take them from TV remote controls or other remote controlled
If you limit the view angle to 10 degrees instead of 120 degrees then the daylight DC is 1% of it's original value. ( 0.2 mA instead of 20 mA for a phototransistor )
And the received signal voltage from unwanted wide angle light from jammers or lamps or atmospheric disturbance is also decreased to 1/100 of it's original amplitude.
For more safety and in order to lower the DC-current, can you put a black painted tube around the photodiode or phototransistor. The tube will limit the view angle, and shield away lamps and sunlight that can cause unintentional ignition, or too much DC-current which limits the battery lifetime. Always shield with aluminum foil against electric noise.
The longer tube the more safe, but it also means you must aim it more precisely the longer the tube.
Use non-glossy black paint from a marker pen to paint the inside of the tube, to damp reflected light.
Whenever a car drives near a fence it creates impulses from its lights.
"The receiver circuit on this page did not ignite from a double fluorescent tube lamp 2*36W at 1.2 meters when tested." That's high power 100 Hz at close range, and sharp impulses every 10mS.
A mosquito which moves its transparent wings at 700Hz creates 1.4mS wide
The most important source of disturbance are lamps, at 100 - 120 Hz.
The ordinary 60 Watts lamps you use at home are filled with gas, which means that they contain a light emitting plasma. The glowing wire itself won't emit frequencies above kHz, but the plasma can emit oscillating light at high power and at high frequencies.
I have measured frequencies up to 160 000 Hz at high power from these lamps.
A torch can have gas filled lamps. Never use a torch (electric lamp) when planting
How to become more safe ?
1 Shield away any unnecessary light from the receiver's photodiodes, for example by
twisting a painted black paper around the photodiode. Never let any light from the sun or
lamps hit the photodiode.
2 Use two receivers in parallel and of different type, with the relays connected in series.
3 Make the receiver less sensitive and increase the output power from the transmitter.
4 Tell innocent people to keep away.
5 First plant the photodiode and then keep away from it and don't touch it
anymore, then connect the battery and at last the blasting cap. Do in inverse order when
6 Never walk in front of the photodiode and don't kick up sand and dust.
7 Electronic circuits can have energy stored in capacitors which means that they still can emit light or connect a relay even if the battery is disconnected.
8 Someone else can have planted a receiver, don't play with the trigger.
9 Turn off your cordless telephone before you start working, and never use any kind of lamps or electronic displays.
10 Protect against moisture, paint the circuit board at both sides.
11 Shield against electric disturbance, use a metal box, shield the entire photodiode
with layers of aluminum foil and plastic tubes. The aluminum foil must be connected to the
wires shield, and connected to ground on the circuit board. The box must be
connected to the same ground.
12 Never connect to the same battery as other types of equipment. For example a car battery.
13 Always test new equipment for a while to see if it is safe to use.
14 Multiple cascaded simple RC filter stages is often a better solution than more complicated filter designs because they will not ring like a bell when receiving impulses from the enemy's impulse weapons or other sources of disturbance. Use non ringing filter designs.
15 You can improve the safety by only using the receiver sensitivity that is really
There is always an arms race.
Using a microprocessor to increase the safety level.
A single chip microprocessor cost $2 and you can program them at home if you buy a
programmer for $30 - $300 that you connect to a PC.
You must change the construction to use pulse distance codes and measure the time
between each pulse.
Power FET transistors
Use color filters and colored LEDs.
Interference filters can also be used to damp broad band disturbance from lamps and atmospheric disturbance about 27 times. And improve the safety.
Perhaps it's possible to use a simple CD as a filter, because it acts like a interference mirror that deflects light with an angle proportional to its wavelength. This is for homebuilt filters in occupied nations.
Use a tone modulated system.
The description of tone modulated systems will be updated in the future.
|If you want faster ignition
Because that makes it easier to hit those fast moving vehicles.
Then you must use higher Voltage.
The delay time = K / Voltage2
It's square function.
The solution is obviously a charged up high voltage capacitor.
Comparing different solutions
Below are some calculated relative delay times.
|Alkaline batteries :
67 batteries in series
67 * Ri = 10 Ohm
Voltage = 100.5 Volts
Cost = $45
Delay time = 58
The internal resistance is too high, which causes the long delay time.
|Lead batteries :
8 batteries in series
8 * Ri = 0.4 Ohm
Voltage = 102.4 Volts
Cost = $100
Delay time = 4.7
Cost too much.
Low impedance 470 uF
Ri = 0.040 Ohm
Voltage = 100 Volts
Cost = $2
Delay time = 4
50 times cheaper.
Low impedance 100 uF
Ri = 0.040 Ohm
Voltage = 200 Volts
Cost = $2
Delay time = 1
4 times faster at the same cost.
The fastest and cheapest solution is to use an electrolytic capacitor.
And use an electronic circuit to generate high voltage from a few alkaline batteries as shown below.
The circuit below is also used in photo flashes, which explains why some bomb makers take the circuit from a photo flash instead of building their own circuit.
Simple 5Volts to 90 Volts DC to DC converter .
The electric high voltage energy is stored in the electrolytic capacitor at the output.
The 56 Ohm resistor is necessary against crazy oscillation.
The resistors at the output is used to select the voltage that turns of the circuit.
This circuit is almost foolproof. If it doesn't oscillate then you have probably connected the wires from the feedback coil wrong. But that's easy to fix.
You must shield the circuit against leaking power that can activate the receiver
And you must also shield against leaking radio power that the enemy can use to
find the circuit.
What size of capacitor to use ?
Don't use too big capacitor because it means shorter battery life, because of leakage current in the electrolytic capacitor.
The stored energy = 0.5 * Capacitance * Voltage 2
Which tells us that you get only 25% energy if you charge up your capacitors to 50 V instead of 100 V. Use as high voltage as possible.
A capacitor of 1000 uF (=0.001000 F) has a stored energy of 5 Joule at 100 Volts
Toys for men
Foldable homebuilt IR-remote control
The modular and foldable design makes it easy to change to a lens of bigger or smaller size if necessary. And helps to hide the transmitter in the pockets.
This transmitter was built only for evaluation.
If you are planning to attack vehicles on a road, then perhaps a simpler
construction is better.
A simple and cheap watertight electrically shielded recloseable
box with good electric connection.
Use it in combination with cable glands.
IED jammers have made all radio types of remote controls useless
The radio jammers are standard military equipment. Search for "ied jammer",
Advantages of optical remote controls :
Why is an optical system better than a radio system :
Since the resistance's transmitter is located at least 20 times further away from the
receiver than the enemy's jammer, it can be estimated that the resistance's transmitter
must emit 160 000 times more radio power to generate the same signal strength in the
The immunity against jammers can be improved further with tone selective systems, or narrow band color filters, or microprocessors and pulse distance coding.
Calculation about immunity against jammers :
* 1 - 4 times because some light will be absorbed or lost out in space instead of being reflected.
* 100 - 1000 times because the enemy does not know where
the transmitter is located and the jammer must emit its light in a wider beam compared to
Mean value of about 4 * 100 * 2 * 500 = 400 000 times more power must be emitted from the jammer compared to the transmitter. And since the transmitter's LED consumes 3 Volts * 2 Ampere with a dutycycle of 1.8 percent = 108 mWatts can we estimate that the jammer must consume about 43 kWatts. That's not portable or possible to install on every military vehicle, which means that the only solution is special jammer vehicles.
The receiver becomes more immune to jammers if you aim it in
a direction where no close objects are in the view angle. See the picture below.
Why use remote controls ?
An electric cable is detectable with airborne radar
that can penetrate the ground to a depth that is equal to the wavelength used by the
radar. If the enemy can see a cable then they also know that there is a bomb. You should
not give the enemy those lines on the radar screen that point out the cables and bombs.
It's about becoming more effective.
What to connect to your IR remote control
No more foot patrols for the enemy
Screws and nuts are probably the cheapest projectiles to fill up the grenade with.
If you have no high explosives
If you read the US military's own statistics then you will find that EFP is 6
times more effective than the big bombs at killing US troops and vehicles.
EFP is also useful against fortified buildings.
The shape of the dish decides what happens.
The jet is a special case in which there is no lasting projectile.
First some proof of the fact that EFP is easy to build at home and
that EFPs don't have to be circular or machined with precision in iran.
Patent : 6606951 EFP antiarmour mine
A possible easier way to build EFPs
The resistance consist of amateurs which most of them are unskilled in
using tools or shaping EFP liners. Which means that if a a weapon need to much work then
noone will build it.
You can't find circular dish shaped liners ready to use anywhere, you
can't buy them.
The clothes-pin shaped EFP from patent 4649828 tells us that there might be an easier way to build EFPs.
Simplified Improvised Multiple EFP SIM-EFP
At shorter roadside bomb distance there is no need for any aerostable cone tailed projectiles, which means that the liner can be simplified.
A SIM-EFP is built of simple cut and bent steel bars.
A SIM-EFP is a construction that fits in between the linear cutting charge and the
A simplified EFP has a thicker liner and thicker explosives layer.
Impact angle and penetration in armor
No trouble with timing differences anymore
The SIM-EFP is by it's construction optimized for killing armored vehicles.
When the production of EFPs becomes too easy, then it will become the standard weapon instead of a rarely used special weapon. And that will improve the resistance's striking power and killing efficiency and force the enemy to abandon the roads.
EFPs are 6 times more effective than the big bombs at killing the enemy.
Try evaluate the design below, because it is so powerful that it will change the battlefield if it works.
Heavy tank killer ?
With this it's too easy to build a weapon launching a projectile half a meter in length. The penetration in armor is almost the same as the projectile length, which means that it can penetrate a heavy battle tank like Abrams or Merkava from a side attack.
It's flat design also makes it easier to hide in the terrain.
See the picture below that shows a circular and a flat EFP side by side.
It's easier to create a long rod projectile from a flat EFP design compared to a
circular EFP design.
With this design you are not limited to attacking the heaviest tanks from the top or bottom anymore. You can kill them from a side attack.
Circular EFPs of that size are difficult to build. Which means
that if you want a homebuilt heavy tank penetrator then you must abandon circular EFPs and
try a flat EFP design.
If you got nothing else then take a railroad track. Send it like a projectile through the enemy's tanks.
Flat EFPs are only useful at short and medium roadside bomb distance because they are not aerostable.
The flat EFP design is also an argument for redesigning nuclear powerplants because
it's easy to build at home a weapon launching a projectile straight through a nuclear
Explosives for the EFPs
You can take the explosives from military grenades and bombs.
ANFO Ammonium Nitrate Fuel Oil or fertilizer bombs.
The enemy can use metal detectors and high frequency impulse mine seekers to find bombs under the road, and you must use construction matter that is hard to detect, like wood or stone. Some plastic matter is visible while others are invisible.
Since the remote control is visible on the metal detector you must use a explosives
filled plastic tube of about 10 meters length between the receiver and the bomb.
Two approaches :
As you can read on wikipedia and in the newspapers, most armored military vehicles are
instable and causes traffic accidents. And the military must send their drivers to a
driving school for heavy instable armored vehicles.
All you have to do to cause traffic accidents is to blow up holes in front of the vehicle, or make the vehicle jump and bounce down from a mountain or hillside.
New military vehicles are instable
Put the men inside an elevator or armored car and also throw in some bench-vises
It doesn't matter how much armor the elevator or vehicle has.
And it isn't necessary to penetrate the armor, just shake and bake.
Remote controlled RPGs
RPGs are an alternative to EFPs
Point weapons like big bombs are easily disarmed while line Weapons like RPG and EFP are immune to the enemy's countermeasures.
The remote controlled RPG and EFP can't be disarmed as easy as the big bombs, because
they are standoff weapons that can be launched alongside the road to kill disarming
vehicles and robots from far away.
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