Also, here's an abstract about the paper in question: (the paper is behind a pay wall)
http://www.nature.com/nature/journal/v54...20587.html

It's definitely 40Hz not MHz.

This episode of RadioLab is a perfect example of why it is my favorite podcast.

(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.

Might this be a more portable and less difficult solution?

https://codepen.io/kimberleyhansen/full/VmBBoO/

Also, there is research that says that even in advanced patients, the flicker helps, but it needs to be in isolation, and for very long periods of time (days).

Worth a try!

(March 14, 2017 at 2:13 pm)LastPoet Wrote: 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

The Farad is a huge unit. FWIW, if you were to place one hand each on the terminals of a 1 Farad capacitor at anything over 50 Volts potential, you will likely die. The current flow will stop your heart (it'll clench). That voltage could be as low as 30 V if your hands are wet, for better contact.

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(March 14, 2017 at 2:27 pm)SteelCurtain 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.  

Might this be a more portable and less difficult solution?

https://codepen.io/kimberleyhansen/full/VmBBoO/

Also, there is research that says that even in advanced patients, the flicker helps, but it needs to be in isolation, and for very long periods of time (days).

Worth a try!

And it's free! I'm curious what the dosage is. Does one have to sit there staring at this flicker for hours, over several days, or a few minutes several times a day?

(March 14, 2017 at 2:13 pm)LastPoet Wrote: 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

Really?

Hmmmm....

Something to try on neighbours...

(March 14, 2017 at 3:06 pm)Fireball Wrote: And it's free! I'm curious what the dosage is. Does one have to sit there staring at this flicker for hours, over several days, or a few minutes several times a day?

From the paper/video, it seems to be contiguous days of exposure. I am not sure if looking away or taking a short break would disrupt the treatment, though. The only side effect is that even staring at it for a minute or so gives me a bit of vertigo.

More info:

You said hubby said the value you are looking for is 500 nanofarads. That may be so but capacitors are never rated in nanofarads. 500 nanofarad capacitor would be rated as 0.5 microfarads. Make sure that value came from the correct frequency of 40 Hz though. All these prefixes are very important so make sure your units are correct.

Lol on some of these comments about a 500 farad capacitor. Yeah, you would definitely want to be careful with one of those.

(March 14, 2017 at 8:11 pm)AFTT47 Wrote: More info:

You said hubby said the value you are looking for is 500 nanofarads. That may be so but capacitors are never rated in nanofarads.  500 nanofarad capacitor would be rated as 0.5 microfarads. Make sure that value came from the correct frequency of 40 Hz though. All these prefixes are very important so make sure your units are correct.

Lol on some of these comments about a 500 farad capacitor. Yeah, you would definitely want to be careful with one of those.

I worked on a program 30+ years ago that used a gyrotron at about 2 MW for Ion Cyclotron Resonance Heating. I'm pretty sure that the capacitors in the crowbar circuit were less than 500 F. Big-assed inductors, as well! I would do the math, but since I don't recall anything but the approximate power level, I'm not going to spend any time on it.

I also worked on a machine that we performed spin-balancing of spacecraft with. We had two .5 F caps to send all the higher frequency harmonics to ground. There was all kinds of noise in the system, and we just wanted to see the sinusoidal behavior of the teeter-totter mechanism.

I've built a model rocket launcher with 6 of these 630 farad capacitors wired in series. They are only rated at 2.5v so the series string is necessary to get the voltage I need. Capacity of the string is 105 farads at 15V although long-term voltage rating is more realistically about 12V. They are used because they are useful for launching cluster rockets where each ignitor may pull close to 40A albeit only for milliseconds. I charge them by plugging into my vehicle's 12V system and keep the topped up at the launch site with a 45W solar panel. Much lighter than hauling around a big-ass lead-acid battery. They work well. The largest cluster I've launched used 9 motors (and ignitors). Ignition was nearly instant as it would be when using a medium-large lead-acid battery. I calculate I could launch a cluster > 20 with similar performance. It would just take longer to top them back up.

(March 14, 2017 at 10:29 pm)AFTT47 Wrote: I've built a model rocket launcher with 6 of these 630 farad capacitors wired in series. They are only rated at 2.5v so the series string is necessary to get the voltage I need. Capacity of the string is 105 farads at 15V although long-term voltage rating is more realistically about 12V. They are used because they are useful for launching cluster rockets where each ignitor may pull close to 40A albeit only for milliseconds. I charge them by plugging into my vehicle's 12V system and keep the topped up at the launch site with a 45W solar panel. Much lighter than hauling around a big-ass lead-acid battery. They work well. The largest cluster I've launched used 9 motors (and ignitors). Ignition was nearly instant as it would be when using a medium-large lead-acid battery. I calculate I could launch a cluster > 20 with similar performance. It would just take longer to top them back up.

OK, we're getting off topic pretty far here, but I have a launch table that will support 10 model rockets, on which I have launched rockets singly, or drag-race style with a 6-Volt lantern battery, all 10 at once. The battery only lasted for a few hours, though, I will admit.

(March 14, 2017 at 9:44 am)Alex K Wrote: 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.

Yeah that's a good point.  I know some monitors have variable rates-- I used to have some that were 30, 50, 60 something like that.  But I doubt that's the case now.