41–50 of 135 posts
I just ordered two of these, and they will arrive on Tuesday. Makes me sad because I'm imagining a Raspberry Pi 2.1 release in the near future now...
A xenon tube is a spark gap. If there's anything in this world noisier than a spark gap, I don't know what it is. I think the first radio transmitters were spark gaps. The energy flies thru the air, and is coupled onto the power line. The power supply doesn't cope well with the oscillations, and hiccups. I see the notes about U16 being photosensitive, but if it is a black epoxy like most IC's, I'm not buying that lig…
A light flash is an EMP. Radio waves are light. They also, unless they are very short, pass easily through blue-tack. When they get that short they are basically becoming infra-red anyway. Then we have a wide range through the visible spectrum, up through UV, that blue-tack stops, until we start getting towards x-rays and blue-tack starts to become transparent again. This is caused by an electromagnetic pulse, but of…
The EMP is generated by the lamp/flashing circuit, which is essentially acting like a small (but not atomic) dipole antenna excited by a pulse. Therefore it has a distinctive cut-off frequency, probably in the 10s of Mhz range but I'm not sure exactly (something like this: [1]). This pulse is picked up by wires that act as antenna, and you get RF interference.
The Xenon flash has also a distinct spectrum, but it's essentially contained in the visible light range (in a log-frequency spectral density plot) [2], which is what you want with a lamp! This emission is absorbed by the semiconductor material by exciting bandgaps: displacing electrons causing voltage spikes.
[1] http://www.rfcafe.com/references/electrical/ew-radar-handboo...
[2] http://www.ushio.co.jp/images/en/products/list/lamp/lamp_07_...
A xenon tube is a spark gap. If there's anything in this world noisier than a spark gap, I don't know what it is. I think the first radio transmitters were spark gaps. The energy flies thru the air, and is coupled onto the power line. The power supply doesn't cope well with the oscillations, and hiccups. I see the notes about U16 being photosensitive, but if it is a black epoxy like most IC's, I'm not buying that lig…
A light flash is an EMP. Radio waves are light. They also, unless they are very short, pass easily through blue-tack. When they get that short they are basically becoming infra-red anyway. Then we have a wide range through the visible spectrum, up through UV, that blue-tack stops, until we start getting towards x-rays and blue-tack starts to become transparent again. This is caused by an electromagnetic pulse, but of…
You should probably just admit your error here -- it's light, not radio waves, causing the effect. Sure, they're part of a common spectrum, but your statement "radio waves are light" is obviously false. It's a bit like saying "red is blue".
Edit: I misread the above, lotsofmangos was talking about wavelengths coming from the radio site of the spectrum rather than light, so he didn't get it backwards. The rest of this post stands.
Earlier quoted context omitted.
A light flash is an EMP. Radio waves are light. They also, unless they are very short, pass easily through blue-tack. When they get that short they are basically becoming infra-red anyway. Then we have a wide range through the visible spectrum, up through UV, that blue-tack stops, until we start getting towards x-rays and blue-tack starts to become transparent again. This is caused by an electromagnetic pulse, but of…
To the downvoters of the above comment: if it's technically incorrect, say so. I don't know if it is or not, but it's certainly not an offensively worded comment. When you downvote rather than respond, you are actually spreading ignorance. A downvote is an effort to mute. A half-muted incorrect technical comment will encourage far more ignorance than a properly corrected, visible one. Don't encourage ignorance.
Earlier quoted context omitted.
A light flash is an EMP. Radio waves are light. They also, unless they are very short, pass easily through blue-tack. When they get that short they are basically becoming infra-red anyway. Then we have a wide range through the visible spectrum, up through UV, that blue-tack stops, until we start getting towards x-rays and blue-tack starts to become transparent again. This is caused by an electromagnetic pulse, but of…
To the downvoters of the above comment: if it's technically incorrect, say so. I don't know if it is or not, but it's certainly not an offensively worded comment. When you downvote rather than respond, you are actually spreading ignorance. A downvote is an effort to mute. A half-muted incorrect technical comment will encourage far more ignorance than a properly corrected, visible one. Don't encourage ignorance.
A xenon tube is a spark gap. If there's anything in this world noisier than a spark gap, I don't know what it is. I think the first radio transmitters were spark gaps. The energy flies thru the air, and is coupled onto the power line. The power supply doesn't cope well with the oscillations, and hiccups. I see the notes about U16 being photosensitive, but if it is a black epoxy like most IC's, I'm not buying that lig…
Earlier quoted context omitted.
A light flash is an EMP. Radio waves are light. They also, unless they are very short, pass easily through blue-tack. When they get that short they are basically becoming infra-red anyway. Then we have a wide range through the visible spectrum, up through UV, that blue-tack stops, until we start getting towards x-rays and blue-tack starts to become transparent again. This is caused by an electromagnetic pulse, but of…
"When they get that short they are basically becoming infra-red anyway." You mean UV. You got your spectrum backwards. You should probably just admit your error here -- it's light, not radio waves, causing the effect. Sure, they're part of a common spectrum, but your statement "radio waves are light" is obviously false. It's a bit like saying "red is blue". Edit: I misread the above, lotsofmangos was talking about wa…
Oh neat, I just reproed it with a Pi 2 and a Canon Speedlight flash. I'll put my scope on the power lines and see what's happening when you flash the board. Sounds like from the thread one of the power ICs is photo sensitive. edit: Wow yeah, here's a look at the 3.3V power line when you flash the board, it drops almost down to 0V and then wildly fluctuates for about 100 nanoseconds: http://imgur.com/hG86pRy edit 2: A…
You've got the gear set up... would you mind terribly repeating the experiment but blocking the light with cardboard or something?
