by Martin Jagelka , Martin Daricek & Martin Donoval :
Continuous monitoring of heart activity permits measurement of heart rate variability (HRV), a basic parameter of heart health and other diseases.
This Design Idea is a new design of pulse oximetry that excels in its simplicity and functionality. Due to its capabilities, it can be used as a standalone device, able to monitor heart rate and oxygen saturation.
The core of the system is composed of the ultra-bright red LED (KA-3528SURC), infrared LED (VSMB3940X01-GS08), and a photodiode (VBP104SR) sensitive to both wavelengths of light at the same level.
Simple pulse oximetry for wearable monitor - [Link]
by Jose Daniel Herrera:
Here I present another project based on a addressable LEDs strip, based on WS2812b leds.
It consists of an ‘electronic’ candle, which lets you select set colors, adjust the intensity, and have different effects like rainbow, fade and fire. The project arose from the purchase of an IKEA lantern model BORBY … the idea was to replace a candle of considerable size, for something more … modern.
Candle with remote control and Arduino Pro Mini - [Link]
by Marian Stofka:
Standard optocoupler speed is limited mainly by the relatively slow response of the phototransistor. This Design Idea adds components to the LED drive side to speed things up.
R1 is the original LED resistor, as used before the extra circuitry was added. Here however, its value can be higher, as the turn-on speed is determined mainly by the added circuit. You can thus save power, and also drive the LED with a less powerful driver.
Optocoupler speed-up also reduces power consumption - [Link]
Elmars Ositis has been working on a simple constant current driver:
In my previous post, I slapped together a quick LED lighting solution for my workbench… but it is truly a hack. What I really want to do is make a simple constant current driver, so the power LEDs can be used in other projects. One of those projects is an LED swimming pool light. It needs to be running at maximum brightness and low cost.
After much digging and testing, I found a simple circuit using a power FET, an OP Amp and 0.5 ohm resistor.
This simple circuit accepts a VCC up to 32v (limited by the Op-Amp). The 78L05 regulator provides a stable 5v reference and R1 is a potentiometer serving as a voltage divider, with the output on pin 2 serving as a reference voltage for the basic LM358 Op-Amp.
Simple constant current driver for a high power LED - [Link]
Enhance the power supply capabilities of the PICkit with this external 3.3V/5V supply. The standard supply in the PICkit will only supply 1.8-5V and 30 mA when using the USB connection, while this external supply is selectable between 3.3V/5V, and the LM317 regulator can supply 1.5A. This can be handy if you have more than a few LEDs in your project. The input voltage can vary quite a bit, but must be greater than 6.5V to achieve 5V out. The input capacitor must also be rated for your input V if you choose to use higher V
PICkit Project Power Supply - [Link]
Just wanting to share one of my latest projects, made possible by DirtyPCBs. I got a lot of good boards (actually 2 designs) and saved 25$ using this service. Very nice.
It’s a simple thing, just a micro (ATmega168) + a bunch of WS2812B LEDs. Main purpose: more colours
It’s meant to fit nicely into IKEA Samtid lamps, runs with 5V DC and takes up to 2.75A. The control module is removable, so one doesn’t have to rip the lamp apart every time you change code. I used microMaTch connectors, as they’re somewhat low profile, at least compared to standard headers, and provide quite good mechanical support.
IKEA Samtid mood-light upgrade - [Link]
Pulse-controlled dimmers of lighting – Finder series 15 offer an elegant solution of lighting dimming controlled by a single switch.
Possibility to control level of lighting is beneficial at least from two reasons – saving of energy and naturally – we don´t need always a full intensity of lighting. At watching of media-projector presentation, TV, illumination of corridors, … it´s often desirable only to reach only a minimum level of illumination (but not a total darkness). Light dimmers are for a long period used for these purposes, usually based on a phase regulation.
Solution from company Finder is exceptional in a fact, that it´s usable with almost every light source – for example incandescent bulbs, 230V halogen bulbs powered by a toroidal or EI transformer, dimmable CFL lamps, as well as LED bulbs. The essence of Finder 15 series dimmers versatility is in the possibility to choose a method of a phase regulation – on the beginning of the sinusoid, or on its end (leading/ trailing edge – the difference is illustrated on the attached picture). The first method is generally suitable for electronic transformers for halogen bulbs and LEDs, the second method is better for classic transformers for low voltage bulbs, for 230V CFL and for 230V LED lamps.
As it uses to be, control of such dimmers is maximally simple – by a short push of a control button (switch) the relay (output) will switch on or switch-off. By a longer holding the button presses, we can change the light intensity from minimum to maximum and vice versa. Finder 15 series dimmers also enable to work in a mode with a switched on memory (after a repeated switch on, the last used level of intensity will be set) or without a memory (after switching on, the maximum intensity will be set). An above standard benefit is a possibility to adjust a minimum light intensity by a potentiometer, what´s important mainly at electronic transformers to avoid a possible blinking at very low intensities and it´s also at classic incandescent bulbs, as their efficiency drops down rapidly at very low intensities (duty cycles).
All 3 produced types are available directly from our stock:
18.104.22.168.0404 – assembly to installation boxes, linear dimming (also available types with dimming in 10 incremental steps)
22.214.171.124.0500 – assembly to boxes or on a panel, linear dimming
126.96.36.199.0000 – DIN rail assembly, linear dimming
Available are various versions, detailed information and a comprehensive table about possibilities of usage of particular types will give you the Finder 15 datasheet.
One impulse is able to set intensity of luminance - [Link]
Here’s a proximity-sensing LEDs project by Will_W_76. He writes a complete step-by-step instructions:
So how does this all work? What makes it proximity-sensing? Remember in the explanation above that the photo-transistor acts like a switch. So when the photo-transistor is off, no current is flowing across it to our blue LED and the LED is off as well. Now look at the other side of our circuit. That’s where the IR LED is connected, and it is connected such that it is always on and emitting 880nm infrared waves. Remember that I also mentioned the photo-transistor is set to respond best to wavelengths of 880nm? That’s how the proximity-sensing works! When an object (such as your hand) goes over this little “cluster”, IR light of 880nm is emitted from the IR LED. This light reflects off of your hand and back to the circuit. When the photo-transistor picks it up, it turns on allowing current to flow through from the source to our blue LED lighting it up!
Proximity sensing LEDs - [Link]
by Deddieslab :
I have a couple of front door LED lights which I would like to switch on automatically during the evening/night. The two conventional methods that are commonly available had their disadvantages:
A timer switch is the easiest and cheapest solution, but doesn’t take into account day light savings. Besides that, in Einhoven, the Netherlands where I live in december the sun sets around 16:30 while in June it doesn’t get dark before 22:00. A simple timer doesn’t take that into account either.
Since you only want the lights on when it gets dark, instead of time you can also use a light sensor to distinguish day and night. You have these front door lights that have this built in. The problem that I had with these devices is that they start bouncing (‘flickering’) around sunset/sunrise. They constantly turn on/off which causes damage to the LED lights I was using. This cost me already several expensive led lights.
Frontdoor light switch based on local sunset/sunrise - [Link]