Tv remote jamer

[Integrator741]

Hello, I am planning to build a TV remote jammer using this circuit:

but before I do that, I want to learn how to analyze it and how to do any calculations before I buy any components.

I was wondering maybe someone can enlighten me and tell me all about it. I believe it shouldn't be heck of a problem for guys like you here !

Thanks

 

[(*steve*)]

It's probably easier to stick a piece of opaque tape over the sensor on the TV.

I'm not sure there are any calculations to perform.

 

[duke37]

You can get much information on the 555 on the net. It is cofigured here as an oscillator with the frequency set by charging and discharging C1.

The output is pin 3 and this changes from 0V to 9V. When it is low, current is passed through the two diodes so giving about 1.2V at the base of the transistor. The transistor will then pass current but beacause of the base/emitter drop there will be 0.6V across R5.
This will define the current through the leds.

I looked up the transistor and it seems to be a common type but not common. Almost any pnp transistor would do.

The 555 has quite a powerful output and can drive the fets directly in series with a resistance , in fact, the current to drive the transistor is more than the current in the fets.

Where did you get the circuit from?

You can do the calculations.
Voltage = current * resistance (V = I*R)
Rearrange this equation if you want current or resistance from the other two variables.

 

[Fish4Fun]

IR remote detectors in general use a 35-45kHz carrier frequency, When a signal in this frequency range is "detected" the output goes low, when it is absent, the output is high. Most detectors are designed to "reject" inputs of less than ~10 pulses of the carrier frequency. This implies that the maximum baud rate is ~4kbps. There are numerous serial communications protocols utilized by various MFGs to prevent in-inadvertent control of devices other than the targeted device, so It is difficult for me to imagine why one would want to design/build a device to intentionally disable all IR remote functionality in a room. That being said, as Steve suggested, if I wanted to disable a particular device's IR remote functionality, I would almost certainly use a piece of tape. If the purpose of the jammer is to prevent other people in the room from changing the channel, I would suggest a social engineering approach,,,either remove yourself from the room with the annoying people, or ask the annoying people to remove themselves from the room.

As far as the circuit goes, as long as the frequency is ~40kHz, it should effectively disable all IR remote functionality to devices with a detector within line of sight of the transmitter. I don't see any reason you couldn't drive most IR LEDs directly with a 555.

Fish

Fish

 

[Integrator741]

Thank you for the replay!

My first question would be, what is the purpose of those two diodes in series? I understand that they will create voltage drop of 1.4V (0.7V each) so that means base voltage of the transistor is 9-1.4=7.6V? Because I red the 555 timer pin out and it says that pin 3 output stays at VCC and it says that it can source up to 200ma (by the way how would you calculate the current from pin 3?) is that correct?

And then resistors R1 and R2? What are they doing?

Thank you and sorry for my lack of knowledge!

 

[Integrator741]

IR remote detectors in general use a 35-45kHz carrier frequency, When a signal in this frequency range is "detected" the output goes low, when it is absent, the output is high. Most detectors are designed to "reject" inputs of less than ~10 pulses of the carrier frequency. This implies that the maximum baud rate is ~4kbps. There are numerous serial communications protocols utilized by various MFGs to prevent in-inadvertent control of devices other than the targeted device, so It is difficult for me to imagine why one would want to design/build a device to intentionally disable all IR remote functionality in a room. That being said, as Steve suggested, if I wanted to disable a particular device's IR remote functionality, I would almost certainly use a piece of tape. If the purpose of the jammer is to prevent other people in the room from changing the channel, I would suggest a social engineering approach,,,either remove yourself from the room with the annoying people, or ask the annoying people to remove themselves from the room.

As far as the circuit goes, as long as the frequency is ~40kHz, it should effectively disable all IR remote functionality to devices with a detector within line of sight of the transmitter. I don't see any reason you couldn't drive most IR LEDs directly with a 555.

Fish

Fish

how about the range of this device? Say 3m radius? More or less??
and i reckon that this device wouldn't be able to block for example PS3 wireless remote controller right?

 

[Fish4Fun]

Range would depend a lot on the IR output level, how closely the jammer frequency matches the detector's frequency, how sensitive the detector is, how good the detector's noise rejection is and how directly the IR jammer is pointed at the detector, so in general, I would SWAG 2m > <10m.

I know almost nothing about Playstations; however, I believe they would almost have to use RF in order to allow more than 1 wireless controller to operate, so, no, your IR jammer should have no affect on an RF receiver. I feel confident someone here will know considerably more about the PS3 controllers than I.

FWIW, a small uController could reduce your part's count and has the potential to be far more versatile, and perhaps even more power efficient (not that either approach would be particularly power hungry. )

Fish

 

[duke37]

Why should I answer your questions if you will not answer mine?

You can get details of the 555, use Wikimedia "555 timer i.c." "ASTABLE".
R1, R2 and R4 set the duty cycle and frequency of the output.

The base voltage of the transistor should be looked at relative to the 9V (it is pnp). The two diode voltage drops will be about 1.2 or 1.4V. There will be a loss of one diode drop in the transistor so that there will be 0.7V across R5. You can now calculate the current from the equation I gave.

The advantage of the diode/transistor circuit is that the current stays constant even when the battery voltage drops.

The range will depend on the led current, it is very low in this circuit.

We are all ignorant in certain areas and, if not too pig headed, never stop learning.

 

[Integrator741]

Why should I answer your questions if you will not answer mine?

You can get details of the 555, use Wikimedia "555 timer i.c." "ASTABLE".
R1, R2 and R4 set the duty cycle and frequency of the output.

The base voltage of the transistor should be looked at relative to the 9V (it is pnp). The two diode voltage drops will be about 1.2 or 1.4V. There will be a loss of one diode drop in the transistor so that there will be 0.7V across R5. You can now calculate the current from the equation I gave.

The advantage of the diode/transistor circuit is that the current stays constant even when the battery voltage drops.

The range will depend on the led current, it is very low in this circuit.

We are all ignorant in certain areas and, if not too pig headed, never stop learning.

Thank you, you helped me a lot!

Excuse my lack of concentration and attention - I got this circuit from a fella at "Instructables" website http://www.instructables.com/id/TV-Remote-Jammer!/

 

[Integrator741]

Range would depend a lot on the IR output level, how closely the jammer frequency matches the detector's frequency, how sensitive the detector is, how good the detector's noise rejection is and how directly the IR jammer is pointed at the detector, so in general, I would SWAG 2m > <10m.

I know almost nothing about Playstations; however, I believe they would almost have to use RF in order to allow more than 1 wireless controller to operate, so, no, your IR jammer should have no affect on an RF receiver. I feel confident someone here will know considerably more about the PS3 controllers than I.

FWIW, a small uController could reduce your part's count and has the potential to be far more versatile, and perhaps even more power efficient (not that either approach would be particularly power hungry. )

Fish

Thank you