making a light flicker
You mean 40 to 50 times a second? If so that is faster than you can see the flashes
Gray said:
You mean 40 to 50 times a second? If so that is faster than you can see the flashes
Yes but it’s for medical, so it still works, like binaural beats, just visual
Gray said:
You mean 40 to 50 times a second? If so that is faster than you can see the flashes
Yes but it’s for medical, so it still works, like binaural beats, just visual
How pronounced of a flicker? Are we talking full on-off at 40 or 50hz, or just more-light-less-light? Every LED will use a rectifier into a cap which results in a ripple on the input voltage, but better ones will manage that through proper regulation and using a proper driver, whereas shitty ones will let a significant amount of flicker go through. Incandescent lights will always let through quite a bit of 60hz and a bit of 120hz off mains in the US, but not, like, full on-off, because they’re not going to heat and cool that quickly, and they produce light through heating the element. I actually can’t quite remember if fluorescent lights will go on-off at 60hz, I assume not, but also they flicker like a motherfucker as soon as they’re not happy about something, so uh I guess I should google it to remind myself… mmm
What are you trying to accomplish here? Are you trying to strobe something at 40 or 50hz?
@Rory
Probably on off is best, but I think more and less light would work as well. Yes, I am looking to make a light strobe at 40hz, or even better would be 40,47, 49. It’s for medical so has to be accurate
@Valen
Are you trying to illuminate an object or are you trying to stimulate something in the eye-brain path or are you doing something else entirely?
How custom vs off the shelf do you want this to be? How jank va productized can the setup be (ie, is this for a lab experiment, or does it need to be deployed in hospital rooms?)
The absolute simplest solution for me based on what I know would be to hook up a function generator to a simple circuit that goes: power - resistor - LED - NFET (gate is tied to the function generator) - ground. Then the function generator is set to square wave at 47.00 hz at 50% duty cycle and any decent one will get you within a very small delta, ie, low jitter as a percentage of period/frequency. Then you can easily change to a different frequency as desired.
If strobing for illumination you will want to decrease the duty cycle as low as you can to get the shortest “on” time possible. Think of how a camera flash works. High speed to freeze motion, and usually that means lower total energy spent because it’s flashing for less time. Also why flashes are sometimes called strobes!
(Why not use a xenon tube for this? Because at 47.00 hz this thing will probably overheat very quickly unless you only do it for a short time or work hard to dissipate heat. Also, using 400 to 3000v makes for a different system design.)
If I wanted to make this a permanent fixture, rather than a lab tool, I would put a 555 timer onto it. Until you find that it is insufficient, it’s a trivial solution for a proof of concept. To make it better would mean using both a better square wave (clock) generator, and using an LED driver instead of the trivial circuit.
If you needed it to be brighter, I would look at bare " ultrabright " LEDs which run up to several watts. I say bare to mean you would want to avoid buying commercial products that do things like adding big caps to smooth out the light and reduce ripple - if you want to strobe you want very sharp on and off, which will require a different circuit than one specifically designed to avoid a 60hz flicker.
But I am making a lot of guesses as to what you’re doing, what your knowledge base is, etc.
@Rory
It is to stimulate eye/brain so could just be flickering I suppose. My goal would be to get something to work, then make a bigger batch of them. I was even wondering who to ask to know this stuff because I have a basic idea of the principal (flick a light switch on and off 40x/second lol) but that’s about it
I’ve read about oscilloscopes, but that it just for figuring out the frequency (for spinny machine parts etc) then somehow they make a light to strobe at that frequency to make the machine part seem “still”
@Valen
So an oscilloscope’s job is, at its most basic, to put an electrical signal on a screen or other display, along with a voltage scale and a time scale. That alone is enough to do the job, but of course modern ones have way more features - like, for example, they’ll make a repetitive signal (like a square wave) line up to be visible in live view, and also tell you the measured period and frequency without you having to math it out yourself.
A signal generator is the thing that will make a square wave. Or a triangle, or a sine, or sawtooth, or other patterns. They’re lab bench tools, not production tools (in most cases.)
A strobe is what would let you “freeze motion” on a mechanical spinny device if you align the strobe frequency with the angular velocity of said mechanical part.
A clock in electrical engineering parlance is a square wave with a 50% duty cycle. So when you read “feed it a clock” that means “connect the output of something generating a square wave into it.”
Strobes in ye olde days would generally have been done by firing xenon tubes or other relatively complex things. LEDs have not obviated that entirely but for your use case, an LED is the right answer because it is, effectively, instant-on instant-off. So all you need to do is feed a 40hz signal into an LED, or in the case of it being bright enough that the signal / clock generator cannot drive enough current, you do the circuit I described above.
What’s your budget for this?
Here’s what I would build, again, from my background in EE. Maybe there’s something out there that already does this, so you should google for something like “adjustable frequency LED strobe” … see if you can buy one rather than building one.
Regulated DC voltage supply
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resistor
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LED
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N-MOSFET drain -----
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|<------ gate ------ signal generator
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N-MOSFET source -----
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Ground
So for example if you get one signal generator and one adjustable power supply: set the power supply to (eg) 5.00 volts, signal generator to 47.00 hz square wave, an LED will usually drop ~2 volts, which means you have 3 volts that need to be dropped by the resistor. A basic LED can usually be driven at up to 50mA or so before it starts being a problem, and V = IR, so 3 = 0.050 x R, so R = 3 / 0.050 = 60 ohms.
P = IV so power dissipated in the resistor is 0.050 * 3 = 150mW, so you should get a 1/4 watt resistor.
Put this together in a breadboard and you have a proof of concept.
I am assuming a lot here - I am assuming you’re a student with access to borrow these things, or a few hundred dollar budget. If you’re doing this at home, you will want to go for cheap little versions of the above, which can probably be had for $20-30 for the voltage supply and signal generator. Since you’re not doing anything too interesting for this, the shitty little tools will do the job fine, versus the big fancy bench tools. That would be ~$100 to get started if you went that route.
@Rory
I do construction, so no idea how to actually physically do it 
but I can think of how it would be
Budget doesn’t matter too much as if we can get this to work. My mom who is an optometrist wants something like this and other people also want this, so then I would sell it- basically I’m just trying to make a prototype to see if it even works
@Valen
Ah okay, here’s what I would do then:
- Look up and buy an Arduino starter kit (with LEDs).
- Go through some online tutorials about programming it and running basic projects. It will be easier than building circuits from scratch for a first prototype.
- Program it to output 40 Hz, 47 Hz, etc., to blink LEDs.
It will make a simple platform for testing, and if the effect works well, you can consider consulting with electrical engineers for more specialized production designs.