Yeah we know it's limited and might not work on our parents.

So, a supplier of 500 ferad capacitors who doesn't have a minimum of 1000 units? That really is the question. The LED, the compressor, the breadboard, all that works. What we need is the right sized capacitor. Sources?

Google These:

Mouser Electronics

Digikey

Onlinecomponents.com

All Electronics Corp

If all else fails, you could order from Fry's electronics if there are no stores near you.

Tip: If you wire two or more capacitors in parallel, their values add. If you place same-value capacitors in series, divide the capacitance value by the number you have in series. Capacitors of different values in series is more complicated. Google: Product over the sum method. This will allow you to combine capacitors to get exactly the value you need.

(March 13, 2017 at 11:35 pm)AFTT47 Wrote: Google These:

Mouser Electronics

Digikey

Onlinecomponents.com

All Electronics Corp

If all else fails, you could order from Fry's electronics if there are no stores near you.

Tip: If you wire two or more capacitors in parallel, their values add. If you place same-value capacitors in series, divide the capacitance value by the number you have in series. Capacitors of different values in series is more complicated. Google: Product over the sum method. This will allow you to combine capacitors to get exactly the value you need.

Thank you!

Jenny, there's been a mistake, you definitely *don't need* a 500 Farad capacitor unless you plan on frying your in-laws Frankenstein style. With a 500 Farad capacitor, you can orbit Arnold Schwarzenegger and it would be the size of a small cow. It makes no sense in the context of an oscillator circuit driving an LED, be it for 40 Mhz or 40 Hz. I'll assume there's another typo and you meant 40 Hz. In that case my gut feeling says you need 40 pico or micro at most depending on the context of the circuit. For 40 Mhz you typically need orders of magnitude less.

Building this thing out of linear components with varying tolerances will only get you close to 40 Hz, but not on it. How close it needs to be is something I doubt you can determine from the study.

(March 13, 2017 at 6:30 pm)Jenny A Wrote: Hi, my husband and I have a project.  Neither of us know much about electronics beyond household wiring.  But we want to build an LED that flashes at 40 megahertz.  

Just realized that several people already said what I said about the frequency most likely being 40 Hz.

You might possibly consider starting with the much easier task of programming a computer to flash a large TV screen at that frequency and see if you can get the folks to stare at it for a few minutes. It would literally take me 10 minutes to make a Windows program that did this.

Flashing a screen with 40 Hz is probably difficult because the refresh rate is quite close to that. If it's 60Hz you will get something very weird if you attempt to flash with 40 hz.

(March 13, 2017 at 7:10 pm)RoadRunner79 Wrote:

(March 13, 2017 at 6:30 pm)Jenny A Wrote: Hi, my husband and I have a project. Neither of us know much about electronics beyond household wiring. But we want to build an LED that flashes at 40 megahertz.

Why? Well we recently heard on Radio Lab about a study in mice in which a 40 megahertz flashing light reversed alzhimerz symptoms in mice. His mother and my step-father are both suffering from dementia. So we'd like to try this out as we can't imagine it could hurt and it will be years before it's cleared to test on people.

We have two small breadboards, 9 volt batteries, and LED's. We've tested with other capacitors, but to get a 40 megahertz flash we need 500 Ferdinand capacitors with at least a 9 volt capacity. I can't buy them locally. On line I keep finding them in quantities of 1000 or so. Any suggestions for where to purchase 10 capacitors or less?

You should be able to get some sort of oscillator/ clock freq. generator to work at that freq. However you would probably need fiber optic grade LED's. looking online though most seem to say 40 HZ...not 40 MHZ

40 HZ also does fall within the brain gamma waves they mentioned.... but so does 60 Hz, which if you have fluorescent lights they are flickering at that rate in the US

Re-read and realized one statement may not have been clear. The 40hz was in regards to the mentions of the study I seen.

Yeah, but a led blinking 40 000 000 times a second.... imperceptible, and one needs small capacitors...

One could make a death ray of sorts with a 500 farad (from Michael Faraday), capacitor. Plus you need alot of current to charge it.

That is why in electronics one uses mostly capacitors in the nano-pico-micro farad range, depends on the application of it