App note: Infrared (IR) Spectroscopy with the SFH 473X – Background & technology

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Infrared spectroscopy by OSRAM and their SFH 473X broadband light emitters. Link here (PDF)

Imagine you can check if the mangos on the market are sweet – without even touching them…

Imagine you can verify if your prescribed medical tablets contain the life-saving compound – or if they are counterfeits…

Imagine you can check the calories of your favorite cheese dish – before eating…

Imagine all this is possible with one fingertip on your smartphone…

The SFH 473X series is precisely designed to support this innovation. This note covers briefly the background of spectroscopy and the case for the SFH 473X series.

Hacked Television Uses No Power In Standby Mode

How much effort do you put into conserving energy throughout your daily routine? Diligence in keeping lights and appliances turned off are great steps, but those selfsame appliances likely still draw power when not in use. Seeing the potential to reduce energy wasted by TVs in standby mode, the [Electrical Energy Management Lab] team out of the University of Bristol have designed a television that uses no power in standby mode.

The feat is accomplished through the use of a chip designed to activate at currents as low as 20 picoamps.  It, and a series of five photodiodes, is mounted in a receiver which attaches to the TV. The receiver picks up the slight infrared pulse from the remote, inducing a slight current in the receiving photodiodes, providing enough power to the chip which in turn flips the switch to turn on the TV. A filter prevents ambient light from activating the receiver, and while the display appears to take a few seconds longer to turn on than an unmodified TV, that seems a fair trade off if you aren’t turning it on and off every few minutes.

While some might shy away from an external receiver, the small circuit could be handily integrated into future TVs. In an energy conscious world, modifications like these can quickly add up.

We featured a similar modification using a light-sensitive diode a few years ago that aimed to reduce the power consumption of a security system. Just be wary of burglars wielding flashlights.

[Thanks for the submission, Bernard!]


Filed under: hardware, home entertainment hacks

This Miniscule IR to HID Keyboard Hides in a Key Cap

Shards of silicon these days, they’re systematically taking what used to be rather complicated and making it dead simple in terms of both hardware and software. Take, for instance, this IR to HID Keyboard module. Plug it into a USB port, point your remote control at it, and you’re sending keyboard commands from across the room.

To do this cheaply and with a small footprint used to be the territory of bit-banging software hacks like V-USB, but recently the low-cost lines of microcontrollers that are anything but low-end have started speaking USB in hardware. It’s a brave new world.

In this case we’re talking about the PIC18F25J50 which is going to ring in at around three bucks in single quantity. The other silicon invited to the party is an IR receiver (which demodulates the 38 kHz carrier signal used by most IR remotes) with a regulator and four passives to round out the circuit. the board is completely single-sided with one jumper (although the IR receiver is through-hole so you don’t quite get out of it without drilling). All of this is squeezed into a space small enough to be covered by a single key cap — a nice touch to finish off the project.

[Suraj] built this as a FLIRC clone — a way to control your home-built HTPC from the sofa. Although we’re still rocking our own HTPC, it hasn’t been used as a front-end for many years. This project caught our attention for a different reason. We want to lay down a challenge for anyone who is attending SuperCon (or not attending and just want to show off their chops).

This is nearly the same chip as you’ll find on the SuperCon badge. That one is a PIC18LF25K50, and the board already has an IR receiver on it. Bring your PIC programmer and port this code from MikroC over to MPLAB X for the sibling that’s on the badge and you’ll get the hacking cred you’ve long deserved.

[via Embedded Lab]


Filed under: Microcontrollers

App note: General overview of IR transmission in free ambient

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Vishay’s general information about IR transmission in free ambient. Link here (PDF)

Free ambient IR data transmission, IR remote control as well as most opto-electronic sensors and light barrier systems work with an optical wavelength between 870 nm and 950 nm. The emitter and detector components are highly efficient in this near IR wavelength band and can be manufactured at low cost.
Data transmission in free space demands high interference immunity of the IR receiving modules. The receiver unit, waiting to receive signals, is bombarded with different optical and electromagnetic noise signals, which are omni-present in the ambient or generated by the electrical appliance itself. All optical sources with an emission spectrum in the reception bandwidth (830 nm to 1100 nm) of the detector can be considered as disturbance sources. These are mainly fluorescent lamps, incandescent lamps and sunlight. Many plasma displays can also produce significant emissions in the optical band of the IR transmission.

App note: Using Vishay infrared receivers in a Wi-Fi environment

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2.4Ghz and 5 Ghz Wi-fi signals can sometimes affect IR receivers, here’s Vishay’s app note about them. Link here (PDF)

In recent years, Wi-Fi connectivity has penetrated most consumer electronic devices used for media reproduction. New TVs, satellite receiver and cable boxes, and streaming devices are more often than not built with Wi-Fi capabilities at multiple frequencies: 2.4 GHz and 5 GHz. Most of these appliances continue to support an infrared (IR)-based remote control link, often even when the device also supports a newer RF-based remote control.
IR remote control receivers are built with highly sensitive wideband input stages and are able to detect signals near the noise level of their circuitry. In noisy environments, such as with both low- and high-frequency electromagnetic interference (EMI), the receiver may be noise-triggered, typically manifesting itself in the form of spurious pulses at its output. Most Vishay IR receiver packages are designed with metal shields to effectively guard the receiver against low-frequency EMI. However, these metal shields have not proven entirely satisfactory against high-frequency EMI in the GHz range used for Wi-Fi.

TV Tuner IR remote with a PIC16F684

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Tahmid built a TV tuner IR remote with a PIC16F684:

I then proceeded to write an IR transmitter using the PIC16F684 (using the MPLAB X IDE and XC8 compiler), following the timing information from the extended NEC protocol. In order to connect all the keys, I connected them in matrix keypad form.
In order to power the remote off 2xAA batteries, it is necessary to use sleep mode – otherwise the battery will be drained extremely quickly. So, in order to detect when a button is pressed, an interrupt is used. After the IR command is sent, the microcontroller goes to sleep. The interrupt wakes up the microcontroller when a button is pressed. Debouncing is achieved using simple software delays. When a button is held down, the NEC command repeat sequence is not sent. Instead, the remote relies on releasing the button and pressing it again.

More details at Tahmid’s blog.

ESP8266 NodeMCU Backdoor uPWM hack for IR signals

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The AnalysIR crew has published an article showing how to achieve accurate PWM for Infrared carrier signals on the ESP8266 NodeMCU:

Quite simple really – just set the baud rate to 10 times the desired Infrared carrier frequency and send a ‘magic’ 8 bit character to achieve the desired duty cycle. Of course we need to take the 1-start bit and 1-stop bit into account plus the 8 bits in each character. Remember that the UART sends the data inverted, so this needs to be taken into account with the characters sent and also in the IR LED driver circuit above, which required 2 transistors instead of the usual one.

More details at AnalysIR blog.

Developing an IR remote and Software controller

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Hardware Hacks has published a new build, a DIY Infrared remote for speaker:

The idea is simple, we capture the IR signal from a remaining speaker remote and record the commands that get transmitted. We did this by connecting up our IR Receiver to the Arduino, the receiver has 3 pins and from left to right GND, +5V, SIGNAL and using the Arduino IRRemote library. Run the Examples > IRRemote > IRrecvDumpv2 example. (see image below with the IR Receiver connected to a Arduino Uno (for prototyping, you can use the Arduino nano, but you’ll have to upload/reset the sketches when testing) If this is running correctly, point the speaker remote at the receiver and press a button – When the IRReceiver gets any data it will flash with the on board red LED, so you know it’s working. Open the Arduino serial monitor and you should see an output of the data it has received.

Project info at Hardware Hacks site.

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