Led with integrated shmitt trigger or buffer or mosfet - Page 1
Forum section: electronics / projects

author: Bendba
author_rank: Regular Contributor
timestamp: September 01, 2016, 01:11:39 pm
content: Hi,I had an idea earlier today which seems to be a good idea. So I believe someone else already had it (unless it is a million dollar idea but then I loose it by putting it out there)Are there any sort of 3 legged LED's that would have a Vcc pin, a ground pin and a input/trigger pin with an integrated current limiting, input buffer, and mosfet drive so it can be directly interfaced with a ttl or cmos circuit without a driver chip? (it would be handy for example to display 16 addresses of a microprocessor at full brightness of the LED without frying the chip's output)Plus it could have a high impedance input to have minimal impact on the rest of the circuit.

author: Zero999
author_rank: Super Contributor
timestamp: September 01, 2016, 01:16:22 pm
content: No, I've never seen that, although LEDs are available with built-in resistors and are suitable for direct connection to 5V.http://www.mouser.co.uk/new/kingbright/kingbright-resistor-LEDs/

author: Bendba
author_rank: Regular Contributor
timestamp: September 01, 2016, 01:22:24 pm
content: Quote from: Hero999 on September 01, 2016, 01:16:22 pmI do know about those but they have a very high current demande for any logic ic or even microcontroller when it comes to display more the 4~6 outputs.

author: tszaboo
author_rank: Super Contributor
timestamp: September 01, 2016, 01:35:32 pm
content: Quote from: Bendba on September 01, 2016, 01:11:39 pmThere is your problem. You dont need 20mA for an SMD LED. 1-2 is plenty, just use the right type. If you need "really high current" like 20mA, then just use a pnp transistor, or a not gate. You get 6 not gates, for 24 cents in a 7404. Your custom LEDs will cost more, vendor lock in, compatibility issues, and nobody needs displayed 16 address in any kind of product. There should not be any need for it.

author: MK14
author_rank: Super Contributor
timestamp: September 01, 2016, 01:57:18 pm
content: Quote from: Bendba on September 01, 2016, 01:11:39 pmYou may be able to get them, depending on your definition. As they are somewhat different to how you describe. But the LED (RGB) with built in driver (and other features), is what you get.It would probably be 4, NOT 3 pins. As they like to be connected up in "chains", so 1 pin is ground, 1 is positive power, one is the input and the fourth is the output (to continue the chain).Example:https://www.parallax.com/sites/default/files/downloads/28085-WS2812B-RGB-LED-Datasheet.pdfBecause Led matrix's are increasingly popular, and RGB have dropped in price over the years. That is the configuration they tend to come in.I'm not sure about single colour LEDs, but maybe. Also it is probably a serial signal (presumably a big shift register), not an on-off. But that is because they are meant for many LED applications, so they need to share the rare I/O pins.

author: Bendba
author_rank: Regular Contributor
timestamp: September 01, 2016, 02:28:52 pm
content: Quote from: NANDBlog on September 01, 2016, 01:35:32 pmI'm sorry to have to disagree with you.Maybe a smd led doesn't need that high a current but they also don't give that high a light output either.Regarding the demande and cost, we don't need randomly flashing RGB LED's, or usb dancing dogs thought they get sold by thousands just because some people do actually want them. And if you can fit a 3 channel pwm controller chip in a 5mm LED and sell it for under $0.05/piece, how hard would it be to fit a die with an opamp and a mosfet?That said, you are right, we don't necessarily need that device, but I'm sure if it was out there, sooner people would buy it, at least I would.Quote from: MK14 on September 01, 2016, 01:57:18 pmYes, unfortunately they are serial, though really handy devices, but not quite what I have in mind.

author: Cyberdragon
author_rank: Super Contributor
timestamp: September 02, 2016, 07:22:04 pm
content: They do exist...sort of....There are OLETs except it doesn't seem like anyone has thought to indevidualy package them.EDIT: I have found something that might work. There is something called an LED with integrated driver available from adafruit. And yes, they are available in single color high-intensity.

author: Mechatrommer
author_rank: Super Contributor
timestamp: September 02, 2016, 07:32:06 pm
content: a sot23 transistor, a 0603 resistor, a led and a pot, easily made at home. otherwise you can tell a factory your specification...

author: Bendba
author_rank: Regular Contributor
timestamp: September 13, 2016, 10:02:49 am
content: Quote from: Mechatrommer on September 02, 2016, 07:32:06 pmThat's what I'm doing at the moment, with a sot23 mosfet and a couple of resistors.I just thought having a single component with everything integrated would be nice.Let's say, just for my knowledge, if I wanted to get it manufactured, where should I start?

author: alexanderbrevig
author_rank: Frequent Contributor
timestamp: September 13, 2016, 10:23:11 am
content: I'm only guessing through a quick google, but maybe something like this:http://www.prophotonix.com/products/custom-and-oem-solutions/led-custom-illumination.aspx? Keep us posted on your progress

author: Bendba
author_rank: Regular Contributor
timestamp: September 21, 2016, 12:49:40 pm
content: Hi.It's been a little while.Unfortunately, I can't seem to find an LED with the integrated circuit I want.I contacted a semiconductor manufacturer (triad semiconductor), they gave me a ballpark figure of 75 to 150 thousands dollars to design, produce and package the chip in an LED. At that price, a minimum of 1 million pieces is necessary to make it worthwhile.So, one idea would be to find a lot of people interested in the device and get it done with a crown funding (considering the shipping costs and handling, I'd say it would be needed to sell at least 2 millions of them in packs of at least 1 thousand)I've been looking at a couple of companies producing chips for hobbyists and developers (they share the mask between a few customers). It seem to be possible to get it done for 2 to 5 thousand dollars but not for a big amount of chips. And then comes the issue of assembling the device.I did find a Texas Instrument and NXP single schmitt trigger that is packaged in a SOT-23 (74LVC1G17,) it is basically the chip I want in the LED with a current limiting resistor. I was wondering if contacting them to see if the could package it in an LED instead of a SOT-23 would be a good idea. I mean, the die is already produced anyway, it would just need a different package.

author: Bendba
author_rank: Regular Contributor
timestamp: September 21, 2016, 01:13:09 pm
content: The next crazy idea is to try to kill two birds with one stone and male the device such as-if powered one way, it works as a schmitt trigger buffered LED-if the polarity of the supply is reversed, it work as a pulse on pulse off buffered LED which would bit a handy device for me too (eventually with a reset function so that there is a way to know with certitude what the state of the led is if the driver circuit bugs and has to restart or losses track of the state)I've tried to make a multiplexed LED matrix that sort of works like a flip dot display, which would give me the possibility to drive a very big display with little processing resources. So far, the only good idea I have is to use some latching buffers.

author: MK14
author_rank: Super Contributor
timestamp: September 21, 2016, 01:18:28 pm
content: Why not use a low cost, small surface mount IC constant current LED driver ?A wide range of them are readily available.They allow adjustable brightness, end to end stackable (they can drive e.g. x16 LED's per IC) built in shift registers, and can even have other functionality in some cases, such as built in DC to DC, switch mode voltage converters, for powering the LEDs, efficiently.LED's are amazingly cheap in general, as are most of the driver chips. So trying to sell much more expensive ones, may be problematic.LED's can have many different colours, viewing angles, brightness's, case styles, etc etc. As part of their specification.So if you are selling yours in ONLY one colour, size, package type, brightness level, viewing angle, manufacturer etc etc. You will limit your market size. There are (I think), thousands of different LED's available, narrowing yourself to only one or a few types, is going to be rather limiting.Where are the massive boxes, of million+ LED's going to be stored etc. Things get VERY large, as the quantities go up. Distribution is a big and complicated thing in its own right.If they cost you $0.25 to get made, you may need to sell them (final price) for $0.50 or $0.75 or even a $1.At $1 they would NOT be very popular.x16 would cost $16, where as normal LED's are readily available for a cent or few, and drivers for a lot less than a dollar (especially in quantity) for 16 channels, I believe.

author: MK14
author_rank: Super Contributor
timestamp: September 21, 2016, 04:00:01 pm
content: Quote from: Bendba on September 01, 2016, 01:11:39 pmWhen you use a resistor with a MCU port output pin to drive an LED, the user, (end customer) can choose what brightness level they want, by suitable choice of resistor.E.g. Outdoors needs to be much brighter than indoors.Some people like them bright, some medium, some low level brightness, etc.Your smart LED, does not seem to give the user any choice on brightness level ?If your answer was to be, use PWM, what if the MCU has got only 4 or 6 PWM's and wants to have 8 smart LED's, at a particular brightness level ?If the LED's cost $0.25 to make (I'm NOT 100% sure how much they will be from your posts), adding in some other costs and profit etc.They must surely then be $0.50 each ? (if not more)So if you sell them on a crowd funded website, with say 100 LEDs or 500 LEDs in a pack, the charges would be .....?100 * $0.50 = $50 + postage for 100 smart LED's500 * $0.50 = $250 + postage for 500 smart LED'sSo a $50 pack of x100 smart LED's + postageOr $1/$2/$3 pack of x100 normal LED's + $0.50 resistorstl;drI don't think e.g. $250 for a pack of x500 smart LED's would get many customers. So reaching your apparent goal of 2,000,000 smart LED's may not be practicable.Also LED's use up limited/valuable MCU I/O pins. Sometimes designs have plenty of spare I/O pins, other times, way too few. So using LED serial Driver chips, also means that a few I/O pins can drive as many LED's, e.g. twenty, as you like, all from a few (serial) I/O pins.When using Matrix LED's, this becomes even more important.Final point. It would need, by the sound of it, at least three connections for the LED, power, ground and input. That would mean extra cost as well, for packaging the LED's.There could well be scope/market for some new types of LED's. Because addressable ones (already on the market), which can create easy matrix LED displays, with adjustable RGB colours, and maybe other features. Might be a significant market segment.But just giving a normal LED, a schmitt trigger input, does not seem to make it worth the (probable) MASSIVE increase in cost per LED, (I'm guessing $0.50 or even $1 each, as opposed to existing ones for $0.10 or considerably less, especially in quantity), so I'm skeptical it should be put on the market.Schmitt triggers, are usually used for counting circuits, such as flip-flops, counters, and to help debounce input switches. LED's seems to be a bit of a strange use for Schmitt trigger inputs.

author: Siwastaja
author_rank: Super Contributor
timestamp: September 21, 2016, 07:01:22 pm
content: As the 74LVC1G17 offers the same current most if not practically all microcontrollers and other digital devices driving LEDs typically offer, I really can't see any point in any of this. You are adding completely transparent, unnecessary component in the chain that only costs money and requires you to route extra wires in a PCB, which can be a quite big turn-off for the customers.In case you are driving so many LEDs off one microcontroller that the "total current per port" or "total current per MCU" is becoming a problem (i.e., more than about 5-8 LEDs), you might have a horrible mess to actually route these special LEDs, and you are probably short of IO anyway. You most likely want to use a multichannel LED driver in this case, myriad of those exist, with internal - and ADJUSTABLE - current limiting; or traditional shift registers would do.