High power leds seem to require much more resistance from components? ex. mosfets etc?
]How should I calculate the requirements of ledstrip? Only information I had was 500mA per 1m
IC555 with sine wave
drives a mosfet which is connected to ~12v
Can I use somehow the same DC 12V with the IC555 also?
for the 3W rgb leds: Arduino or some other (attiny?) microcontroller
controlling 3 mosfets which are connected to power of (??volts) and the 3 colors (RGB) and times 2 (2 different 3W rgb leds for the lamp)
Not really. You NEED to drive a led with current, not voltage. A led strip had resistors on it to do this job (a resistor is a crude version of a current source when connected to a stable voltage). But a high power led is just that, you need to add the current source. And for high powers a resistor isn't a very good current source. It would be very wasteful and you would need a pretty big (physical big) resistor to do the job. Easier to grab a (switch mode) led driverI bed it also said 12V. Combined with 500mA/m isn't that enough?Why a sine wave? That would be a pretty pore choise. Try PWM You can't drive the mosfet or led strip with AC, you need DC. Also easier to get a n-channel mosfet en place it between the led strip and GNDA 555 can handle 12V so I see no reason why not. Why do you want a 555 for the led strip and a micro controller for the high power led?Like I said, you need a current source. This can be made out of transistors but depending on the supply voltage this would be very wasteful and would require big heat sinks. If you want to drive them from 12V as well you would use 3/4 of the current as heat and only 1/4 for the led.Depending in the led you have (does it have a common for the RGB or has each color it's own 2 connections) you need 3 or 6 drivers.
A sine wave to create a fade effect, isn't that what's used? The sine wave would go to a mosfet (N channel IIRC) and through that, the gate would go periodically from low to high to low? Creating the fade effect.
they heat up quite a lot when I did the fade example from the Arduino GUI editor. Is this normal?
For led strip I wanted 555 because it seemed cheapter / easier to set up ? And I only needed fade for the strip, where as I would like to have more options for the 3W RGBs.
I have several 12V PSUs with different amperages, highest is 6A IIRC. How to know which should I choose?
I was thinking of making the led drivers by myself, but from all what I've found on the internet, they would need high wattage resistors and some other stuff?
The idea would be to drive them through arduino, either with WIFI, bluetooth, RF, etc, so no physical (potentiometer).
Also, can I somehow affect how much leds draw power? The strip seems to draw 20mA per color per 2 leds from 12V PSU, which seems a waste, wouldn't it be better to pass like ~5V and let them drain their 20mA's from that?
No, it's not. Although you could dim a led in a linear way with a mosfet it's wasteful and not that easy. The easy way is to use PWM. You modulate the fade in the duty cycle of a fast on off pulse. Turning fully on and fully of the led very quick. You could modulate a sinus but that's not the prettiest dimming. For easy dimming with an Arduino, see my GitHub link in the foot note.
You have to be a bit more specific.- Which leds and mosfet?- Which program exactly?- How did you connect it? (Photo of hand drawing will do, please NO Fritzing breadboard view or a photo of the setup)- What exactly is powering it all?
Mm, cheaper maybe. Although a Aduino clone will only set you back $1,50. But easier, mm. Just plane dimming isn't that hard with a 555 but also fading it makes it a lot harder.
One that can at least supply as much current as the strip or led can draw. For the strip that's apperently 500mA/m. So a half a amp for each meter you use.
If you do it lineair/simple then yeah, you will produce quite a bit of heat. So I can recommand to use a ready made switch mode led driver. They are pretty cheap (in China), less then a dollar.
If you're new to Arduino (aka embedded programming and programming in general) I would drop all the wireless stuff for now. First get a a decent basic knowledge of programming and get the led to fade and dim and whatever you want. Then add the wireless.
Ahhh, you didn't tell us it's a RGB strip And no, it's not a wast add all. 3 leds are in series which adds to around 10V. So only 2V (for a combined 12V) over the resistor (on the strip, as current source) so each resistor wastes 2v x 20mA = 40mW versus the useful 10V x 20mA = 200mW of light.
serie:mA * parallel:count(20mA*3) * 11 // 3 = r,g,b colors and 11 = count of parallel systems in the end project piece
And if you want to dim them you PWM them. With a 50% duty cycle of the PWM they only use 50% of the power. But not, dimmed to 50% duty cycle will NOT look like 50% to our eyes. It will just look a little bit less bright. That's why gamma correction is used if you want to dim linear to our eyes.
This is quite crude picture, still learning some schematics.
Yeah, gonna receive also ATTinys so either or. Just thought 555 would be a nice change and not all about programming.
Should I always calculate the minimum and use that, or should I aim a little higher?
(I don't know if eBay links are allowed, so I will just post specs/images/names)
...also many many more items which I didn't list here (for around $300-400, not quite sure what to order so I ordered everything. I have an oscilloscope, variable bench PSU, multimeter, many components etc)
Didn't order 5W kit because there wasn't really a good pack of them and not sure which resistor I need yet.
I tried to calculate with some calculators, got some different results, and some of them suggestion even 7W+ resistors?
Yeah, I will definitely want to do the fading first before adding wirelessness in the project.I have some experience in programming, working in the field for x years and soon graduating bachlor of CS
So dumb question, the strip says 'cut here' or something, and I have cut there. In this small piece it uses the above mentioned 20mA per color. This is a series connection right? And the strip is consists of these in parallel? So the total mA used is something like:
Thanks a bunch, I think I understood wrong the 555, sine, astable, mosfet combination. I thought sending a sine wave to mosfet (gate?) would be same as sending PWM but this doesn't seem to be the case.
Sorry, that's not going to work. Did you Google it
First of all, you draw a BJT, not a MOSFET.Second, the layout isn't going to work. The mosfet needs to connect between GND and the cathode side of the led. And keep in mind this only works for the strip because the high power led needs an extra driver.
Calculating the minimum is a good thing. Aiming a little higher is a good thing. Any overhead doesn't hurt, the current isn't forced. A 10mA led (with limiting resistor!) connected to a 10A supply will still just draw 10A as long as the voltage is right. But especially with China stuff with bad specs that little extra might be a safe bet.
Why the resistors? Switch mode led driver would be more usefull.
If you still try to use resistors for the high power leds then 7W+ doesn't surprise me. That's probably correct. That's why I said a resistor is a pore choice for a high power led.
Do you have a link to the led?
Experience in programming is indeed a pro. Also in C++? But keep one thing in mind, a micro controller has limited memory so don't piss it away. People that used to program computers usually are spoiled and just put anything in memory because it might be easy. If you do that on a micro you run out of memory pretty quick.
Sine is a linear thing. PWM and the default 555 configurations are all switching. They are on or off, "nothing" in between. That makes it efficient and easy.But nice you dim the leds you can still shape the fade curve. What you use for that is up to you, can be a sin, but a gamma corrected curve gives you a linear fade for our eyes. This shape is then modulated in the PWM (translated to fast on of switching). Have a look at PWM modulation.
Made it by myself, I guess not the best one.
Oh, okay this I didn't know. So the point of the driver is ... not sure.. ?
Good to know ! Thanks
A 10mA led (with limiting resistor!) connected to a 10A supply will still just draw 10mA as long as the voltage is right.
Hmm, not sure what's switch mode led driver? Something that doesn't use resistors? I need to find out, haven't heard of that. Everything I've read about leds and changing their color includes 1 or more resistors
I also purchased this, not sure what it is but it has led in the namehttp://www.ebay.com/itm/181846888859?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
Oh, you can limit it in other ways, I didn't know this. I thought you'd need an X ohm resistor and after that you can (ex. with potentiometer) change the strength.
12v --> potentiometer [or arduino] --> resistor --> led --> groundand the resistor should be so, that the led gets it's required current, and after that you can dim with the potentiometer or other
I'll add all the parts I think are needed for the project/s in the end of this post
Pretty much everything else but C++ but I think I can get on it pretty quickly. And about memory usage, I have always been quite nifty and exact with what I use But lets see how everything turns out!
So I can't run my output of 555 to mosfet? Which would turn the mosfets gate (or something) on / off?
I thought I could change the duty cycle of astable mode of 555 which would result in some kind of fade. Not sure how to make the change of the duty cycle though.
It's an understatement because it will simply not work
Which you need depends on the LED you have. These are just some example I found quickly so looking further may not hurt. I think all these three are based on the PT4115 chip which is a very popular chip.
Making it fade on it's own, without the pot, that's the challenge. Not impossible, not super duper hard. But if you're thinking about using an Arduino anyway I would say this is the time to let the (super duper cool) 555 go.First isn't available anymore :/
Seems a little bit like cheating usin ATTiny or arduino for a simple task, but I don't understand electronics yet so well for me to estimate the difficulty of "simple" tasks.
And does the "crazy" heat come from the PWM?
I googled a more accurate picture:
Very interesting chip, I need to investigate this further.I took a closer look at my nearby electronics shops, and they don't have this chip.Can you sugggest some other chip or should I order this from farther away?
Also, would this kind of switch mode led driver be hard to create? I googled / saw some pics and they seem quite straight forward?
... That leaves the additional 3V for the mosfet @ 400mA. Which produces 3V x 400mA = 1,2W in the mosfet!
Sorry, I can't. I rarely come in a real shop to buy stuff like this. Local stores just don't stock what I want an ask ridiculous prices. If they would sell more China stuff at a reasonable price (because yes, I'm willing to pay a bit more if I can get it NOW) I would go there more often (and I think they would have a lot more costumers). But I'm just not willing to pay €7,- for a PIR or something. Or €10,- for a small project box. I do like a couple of shops in my country but they are not close so I'll order online.
Designing switch mode led drivers (and switch mode converters in general) is kind of a black art on it's own. So many things to think about when designing a PCB with a chip like that. Mainly because of the switch frequency in the MHz gives you all sort of extra worries. So for the price I'll just order them from china.
These day's I would not call it cheating to use a ATTiny to fade a ledstrip. I would call it old school if you did it with 555's and I would call it cheating if you used a 32-bit micro or a Raspberry Pi
Let me see if I understood correctly.
But I will order these/+ic from china probably now. Do you have preferences over alibaba or ebay? Or some other?
I do have an oscilloscope so would that help me?
Let me see if I understood correctly.So, the mosfet heats up because of the higher voltage supply, and not the PWM.And because with the "linear" PWM the current goes quickly up and down, this creates the heat; in the cases where it's not 0% or 100%? Or does 0% mean that it heats up even more? Or maybe not. I think the rapid change of PWM? I do have an oscilloscope so would that help me?