Help needed to find a bright 5V LED wall light

Is there a signal *in the hall* showing whether the gate is open or not Is there mains power for the light?

All the light needs to be is a fairly large LED.

You would be surprised how little power is 'noticeable' especially when flashing

I would suggest getting a camper van light like

You can get LEDs with a built in IC that flash them at approx 1Hz to

Random seller on Ebay for 1.5Hz version

I had a mains to a USB A adapter which I took apart to reveal the very small module inside (made smaller by un-soldering the USB connector). This board, and the series resistor, was fitted in a standard plastic light switch 1 gang back box. A hole was drilled in a 1 gang blanking plate for the LED. In my case I just tapped off the immersion heater switch mains supply to turn the whole system on. In your case you could either switch the mains or the 5V supply.

LEDs have a forward voltage drop Vf. The LED will not light, unless at least Vf is applied to the legs.

A red LED is 1.6V perhaps.

A white LED (which is a blue LED plus a phosphor) is 2.5V (at 10mA). For the high current LEDs (350mA or 700mA) the voltage is closer to 3.5V on those.

The 5V supply has sufficient voltage, to run one LED.

You can see in the example, this budding designer is able to run some amount of loading with his ideas. You can make arrays of LEDs, equip each LED with a resistor, and drive a decent power source into the thing. I have two 4x12 arrays running at 10mA per LED, for 480mA total current (each one using about half a 5V 1A adapter).

The second circuit, with the transistors arranged as a Darlington on the output, the signal driving the Darlington tree is coming off the timing capacitor node. Maybe that is why there are three transistors in the Darlington structure, to lift the threshold voltage to turn on the incandescent light he happens to be using as a load.

You can place a few components, after the NE555, to drive larger loads. You have to know a small amount about electronics, the biasing of transistors, to do some of those tricks (without smoking something and ruining it).

You can use LEDs which are mounted on an alumina substrate for home projects. This takes care of the tricky detail of soldering things directly to the LED. Ordinary soldering can be done to the pads on the alumina substrate.

At that power level, the star substrate gets hot, and should be fastened to a piece of scrap metal for cooling purposes.

Using the smaller LEDs and making an array of LEDs, is a bit better with regard to cooling issues. But it also takes a lot of resistors (which are needed to control and limit current flow). Some suppliers of electronic compoents, charge 20x as much for resistors as other companies, so you don't buy your bulk leaded resistors from boutique stores that charge too much. $0.05 per resistor, $0.20 per small T1 3/4 LED, is enough expense.

Super-high-power LEDs are not eye-safe, so use a diffuser to lessen the risk of eye damage.

The above is not exactly a recipe-grade set of instructions. It's the beginning of an illustration how to proceed, but many details must be worked out. Your first circuit will have one tiny LED and the circuit will not draw a lot of power. You work your way up, scaling and testing as you go, until you learn how to assemble and drive larger loads (as a hobbyist).

Paul

Thanks ... but I graduated in Electronic Engineering in the mid 70s. I was looking for something that looked acceptable to SWMBO when fixed on a wall.

That's interesting, I hadn't thought of looking at campervan stuff. Thanks.

See

Thanks, but I want to be able control frequency and duty cycle, hence using a 555 (plus I have several in the "bits" rack). If I'd thought of this before decorating then it would have made sense to sink a back box and drill a blank plate, but making holes in that area is "not allowed". Hence the search for something surface mount that looks "nice" to female eyes.

The LED lighting industry, has their own ideas of how luminaires should work. That's why the applied voltage choices, might not be ones you are interested in.

There was a section of the legacy lighting industry, that ran small devices at 12V. And that is likely why there are still designs today that run at 12V.

There are a lot of 19V DC adapters for laptops that would be a natural for operating a light source. Yet, you don't see a lot of activity like that in LED arrays.

Some of the one inch square light sources, they run at around 40V or so. And some individual made a comment once (with no justification), that somewhere around 90 VDC would be a good choice (maybe this is the output of an SMPS in the design).

But as for guessing what the industry would or should use, I don't have any reliable crystal ball predictions of what the designers will gravitate to.

All we've got then, is a chance that an item may be available at 12V.

Making one for 5V, is easily do-able by hobbyists, and I don't consider that part of the project to be tough. The last LEDs I bought, small ones, were 100 LEDs for $20, and the packaging (the PCB) for mounting the LEDs, and other odds and ends, cost a lot more for the project than the LEDs did. This is why, hobbyist projects quite easily go over budget.

The luminaires are made for consumers. who either want to wire the device directly to mains (all in one solution), or, there is an adapter provided with the kit which is consistent with the design voltage. The hobbyist market is quite small by comparison. They make colour LED arrays for hobby display purposes, and the people who make those, have lost their shirts on the effort (hard to get rid of stock, if you run off even one batch of those). That's part of the reason there isn't a thriving market driven by hobby voltages. Not enough buyers of the material.

If you could find a luminaire with its own wall adapter, you should be able to run your NE555 circuit off a voltage derived from that source, and switch the light on and off as desired. This is why I was looking at relatively low voltage lights, like <35V, as it's easier to dream up interface circuits that will work at those voltages.

While 5V circuit design will definitely work, you are likely to be designing the whole thing for yourself. I don't consider that a problem. I made my own kitchen LED lighting from scratch (star LEDs), and my own bicycle light (front and back array lights), so I've done this kind of work before. I can't recommend it from a "cheapness" perspective. It doesn't save money to do that. But I am getting my 25,000 hours from the kitchen light. It hasn't blown like the commercial "light bulbs" do. The kitchen light happens to run off 12V, but that's just what I had handy as an adapter to power it.

Paul

I'd say the way to go would be to find something that looks OK e.g. a round battery cabinet light that will be big enough to modify. I have three nightlights which are not wall mounting so wouldn't be of use here, in which I reduced the brightness and increased the light detection sensitivity by resistor changes, and there's plenty of room inside for some small more complex PCB. Most will use two or three AA cells, so removing them will give a bit more space.

What you won't find is one with a built-in beeper, but generally piezo sounders are loud enough to be heard through a plastic case, and if not, an unobtrusive hole at the side or bottom would solve that.

Something that may be of use here or elsewhere is the flexible LED striplight which is cheap and easily available. It generally has sets of three LEDs in series fed from 12V, which can be modified by careful track cutting and different resistors to run on 5V. I have a strip of two groups rewired to run on 5V to plug into a USB socket and light my keyboard on Summer evenings, when I want doors and windows open but without the room lights on to attract insects. Actually, now there seems to be 5V strips available.

The amusing part is that recommended 555 timer pre-dates you. First marketed by Signetics in 1972. I remember them being all new and shiny.

I have never ever used a 555.

They are actually just as expensive as e.g an RP2040 Zero, so far down the pan have Raspberry PI prices gone from China.

That is what I would use.

If any of those USB chargers are USB C type then they might not be limited to 5v and even so a 5V to 12V buck converter module can be found for pennies.

My current LED project was made easier by finding a couple of chunky 40v power bricks in a charity shop. Those were unusual but 20V bricks are pretty common and lots of people have old laptops with them.

The USB supply is a USB-A on a computer. I'm willing to bet that will stick to 5V.

If it's USB2 or 3.0 then definitely. If it's USB 3.1 or later then up to 48V.