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led's

ltage,

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n confrontation.)

ome spare time while the attendees were doing stuff. So I took along a set up to measure the Johnson noise of a light bulb with a DC current going thr ough it. (The measruements were a bit of a pain, I had to abandon the indu ctor I was using as a bias element and go with a simple resistor...anyway t hat's not important.)

I took that ratio to be the resistance of the bulb. And then I assumed tha t the bulb would be making Johnson noise given by v^2 = 4kTR*BW. Where I 'd see more noise because of increased temperature of the bulb.

urrent

er

ave the

son noise

bulb with a current source is asking for trouble. IMHO)

ed up magnetic noise big time. (I already knew this, but sometimes I need my face rubbed into something a few times till I remember.)

res the bias resistance was much smaller than the DC bulb resistance and it shunted most of the noise to ground.

robably)

s dE/dI

econd maybe 10mS at the fastest. So only at low frequency is that going to be an issue.

sting to

shake out of it. Better might be to suspend it. I would sometimes see a bunch of low frequency 'crude'. Which I assumed was adjacent filament loop s bumping into each other. But there were long periods of relative quite. (I also could filter out the LF stuff.)

Grin, there's not that much gas inside the bulb. It really wasn't too bad .

George H.

d pickup local magnetic field interference. (Mostly from the room lights, which I couldn't turn off because those in the workshop would have objected .) The pickup would increase at higher bulb currents.. which still has me a bit confused. So before I try this again I need some big torodial induc tors and some mu metal to shield the bulb.

? (Should I be thinking in terms of damping or energy?)

Reply to
George Herold
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Yeah the workshop was at a university.. not my comfy lab.

Why what? Why try again? why a big toroid?, why shield the bulb?

Well there are other 'kinds' of electrical resistance.. but I agree electron scattering is the most common.

But if we stick to light bulbs, then there is a question of the DC resistance vs the dynamical resistance.

For instance if I was to use a bulb as part of small signal RC low pass filter. (The bulb is the R) Then I think it will be the dynamical resistance (dV/dI)

Well sure, even without the turns it has inductance and capacitance.

George H.

Reply to
George Herold

You can still buy light bulbs from Newark.

George H.

Reply to
George Herold

Flashlight bulbs are pretty much extinct in the UK - there may still be a few long established independent bicycle shops that carry a small assortment of dynamo bulbs.

As for household lightbulbs; I think anything over 60W has been banned and anything lower is thin on the ground.

They have introduced halogen capsules enclosed in a regular glass bulb with a standard (for UK) bayonet cap - the highest I've seen is 70W, but that is probably as bright as the 100W filament most people would buy given the choice.

LED house lights are starting to appear in supermarkets - but as yet are some way short of matching CFLs.

Reply to
Ian Field

formatting link

Reply to
Ian Field 

--
Regardless of what's happening in the UK, your statement:  

"Last time I checked - the only way you can buy a flashlight bulb is 
buy a flashlight with one in it." 

is wrong, yes?
Reply to
John Fields

Newark lists 957 incandescent bulbs, isn't element 14 in europe?

formatting link

George H.

Reply to
George Herold

Never heard of it, so maybe not in the UK or only in cities.

Reply to
Ian Field

Element 14 was called farnell. They are at least in the UK, Germany, Austria and the Netherlands. I do not know if they have connections with Newark.

Draw back is that as private person you can not buy there, atleast not in Austria and Germany. It took me a long time to get a Raspberry pi.

Reply to
tuinkabouter

Wow, that stinks. So where do you get electronics?

George H.

Reply to
George Herold

From time to time I used to order a package from Farnell - usually 75% stuff just to make the minimum order to get the bits I want.

Funnily enough I never looked there for bulbs.

Reply to
Ian Field

You seem to assume that a single shot always takes out every enemy resource, so advertising your location is no big deal.

Ha!

Can you prove that mathematically?

--

John Larkin         Highland Technology, Inc 

jlarkin at highlandtechnology dot com 
http://www.highlandtechnology.com 

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom laser drivers and controllers 
Photonics and fiberoptic TTL data links 
VME thermocouple, LVDT, synchro   acquisition and simulation
Reply to
John Larkin

You expected better from that dumbass!!!

Reply to
Ian Field

There are radar systems that track incoming rounds and fire on the enemy guns even before the enemy rounds hit the ground. It wouldn't at all surprise me if an M1 tank can put a cannon round on a sniper's muzzle flash in a second or two, before the sniper's round even bounces off the tank.

But anyone who knows so much about Ohm's Law is probably an expert on military matters, too.

--

John Larkin         Highland Technology, Inc 

jlarkin at highlandtechnology dot com 
http://www.highlandtechnology.com 

Precision electronic instrumentation 
Picosecond-resolution Digital Delay and Pulse generators 
Custom laser drivers and controllers 
Photonics and fiberoptic TTL data links 
VME thermocouple, LVDT, synchro   acquisition and simulation
Reply to
John Larkin

As an NRA certified instructor I must advise against putting any obstruction in front of the muzzle. As far as accuracy, just a small nick in the crown at those distances will lead your bullet wide astray. Just sayin" Tom

Reply to
Tom Biasi

I got the idea from a comedy duo of DJs who had a show on BBC R1 (Mark & Lard).

Last I heard, they got kicked off R1 and moved to R2.

Reply to
Ian Field 

--
Or maybe it sneaked in when you weren't watching?
Reply to
John Fields

Still are. Premier Farnell, PLC.

They are at least in the UK, Germany,

Farnell have owned Newark for more than ten years.

Their instruments division (now gone) used to own Wayne Kerr.

Alan Farnell started the company selling components to UK radio repair shops, out of a suitcase.

--
"Design is the reverse of analysis" 
                   (R.D. Middlebrook)
Reply to
Fred Abse

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