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]
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]
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]
ReturnZero published a stroboscope build:
At its heart, a stroboscope is just a rectangular wave generator hooked up to a light source. I wanted a few extra features to make it nice to use:
Ability to set flash rate by either frequency or RPM
Set duty cycle of output without affecting flash rate
– 2×16 for displaying RPM, frequency and duty (one per line, so one will be hidden at any time)
Rotary encoder (with button) for main interface
– When button is not pressed, knob will increase/decrease the value of the selected digit
– When button is pressed, rotating knob will scroll through display digits
Buttons for quickly halfing/doubling thirding/trebling the flash rate
– This is useful for checking that you haven’t hit on a multiple of the rotation rate
Nice beefy output stage for switch big sets of LEDs
DIY stroboscope – [Link]
Spacewrench over at Dorkbotpdx writes:
I had some spare 4-digit 7-segment LED displays and some AT90USB82s, and I’d always intended to do something with them. This was probably the easiest thing! It’s just the AT90 driving the display, with a(t least) 4 wires controlling it: Vcc, GND, MOSI and SCK. (I haven’t written the code yet, but my plan is to make the display accepts characters via SPI and then spends the rest of the time displaying them).
The board has footprints for a 16MHz crystal and USB connector, so you could make it a USB-enabled 7-segment display as well. I stuffed those parts on my test board, but I’m not sure whether the USB actually works. You can power the display from USB, at least, although the video shows it being powered over SPI (which is the same connection I use to flash code).
Standalone SPI 7-segment display – [Link]
by Boris Landoni @ open-electronics.org:
Since when white light emitting high brightness LED are available, the handover from traditional lighting bulbs to the solid-state lighting has become irreversible: LEDs have an efficiency (expressed in lumens/watt) higher than that of almost all the traditional lamps (except, at the moment, the large sodium vapor lamps used for street lighting, unusable in closed environments for the high power required and the chromatic aberration they produce) at a cost that is today less prohibitive than it was a few year ago. They are indeed very sturdy and have a very acceptable ratio of luminous flux and size.
The perfect Remote, Programmable, Controller for interactive LED strips – [Link]
by BABU TA @ edn.com:
This flasher/beacon circuit can be employed as a distress signal on highways, a direction pointer for parking lots, hospitals, and hotels, etc. The circuit uses a power LED, and provides more light than a typical incandescent lamp flasher. Use of a 6V or 12V SLA lantern battery makes the circuit portable.
HB-LED flashing beacon repurposes switching regulator – [Link]