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EL7900

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He's posted more often in this user-group than anybody else, and he's not unrepresentative. You may have your own silly ideas about what we ought post here, but nobody else much seems to share them.

John Larkin's behaviour is evidence - if you appreciated what he does, and what many other people who post here regularly do, you wouldn't have been silly enough to claim that this user-group was exclusively about electronics. We all hang out here because we are interested in electronics, but most of us also have lives outside of electronics.

I'm not in conflict with him - I correct his more flagrant mistakes from time to time, and he doesn't like being corrected, and reacts unpleasantly, but I don't see any evidence of a permanent state of war.

-- Bill Sloman, Nijmegen

Reply to
Bill Sloman
Loading thread data ...

--
Marco,

The data sheet states that: "Although finite, the output impedance of
the device is considerably large.", and Table 1 of the data sheet
indicates that the lower the load resistance the more current it can
source before compliance kills it.

Would you do me a favor and measure the output short-circuit current
available from the device, please?

Like this: 

.+5-------+--------+
.         |        |
.        [R]       |
.         |     +--+--+
.       [LED]-->|   Is|---+
.         |     |_    |   |
.         +-----|E    |  [mA]
.         |     +--+--+   |
.         |        |      |
.GND>-----+--------+------+

Thanks,
Reply to
John Fields

That figures.. Your common phrase must be:

"I am never wrong, once I thought I was, but that turned out to be a mistake"

With all your retractable statements, you still managed to make comment on how you correct people, JL in this case.

Who corrects you? Oh wait, I forgot, you're never wrong..

Jamie

Reply to
Jamie

u
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You don't pay much attention, do you. There are things that I knew that turned out not be so, and some of them get exposed here.

It doesn't happen all that often, but it has certainly happened.

It varies. I'm damned if can remember who did it most recently - I had an idea that it was Tim Williams but the search engine doesn't throw up anything.

-- Bill Sloman, Nijmegen

Reply to
Bill Sloman

He is AlwaysWrong, you know.

--

John Larkin                  Highland Technology Inc
www.highlandtechnology.com   jlarkin at highlandtechnology dot com   

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME  analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators
Reply to
John Larkin

No, I am not, and you are doing it again.

Reply to
Chairman Meow

Il 05/09/2012 00:03, John Fields ha scritto:

You drew a led coupled to the photodiode. Do you recommend any kind of led (white, green, etc...)? What's the difference between using a led instead a lamp or sunlight?

Marco

Reply to
Marco Trapanese 

--
It Probably doesn't make much difference, but figure 1 on page 3 of
the data sheet shows peaks in the green and IR.
Reply to
John Fields

Il 05/09/2012 11:26, John Fields ha scritto:

Well, I have only standard green leds (low-power) and they can't drive the device properly.

So I used several light sources: white led, incandescent lamp and halogen lamp. With a supply of +5V the maximum output current measured was about 4 mA no matter how close the light source was. Unfortunately today I can access only to a DMM with 1 mA of resolution.

With a supply of 3.3V I read max 3 mA.

I didn't see any collapse. I'm curious to redo the test with direct sunlight - when possible.

Marco

Reply to
Marco Trapanese

Allow me.

*ahem*

*Whoosh!*

Reply to
JW

--- Good!

That means that with only the low resistance of the milliammeter in the circuit, the voltage dropped across it doesn't run into the Vcc-0.3V compliance limit of the device.

Take a look at Table 1 of the data sheet and you'll notice that for any illumination level there's a maximum value of load resistance allowed, the reason being that if the resistance goes higher, then the output voltage will increase to the point where it exceeds the voltage compliance limit for the device.

You can prove whether that's true or not by doing this test:

Vcc / .+5-------+--------+ . | | . [R] | Vout . | +--+--+ / . [LED]-->| Is|---+----+----+ . | |_ | |5k | | . +-----|E | [POT]-----+--------+------+---------+

Start with the pot at minimum resistance and illuminate the device to get some current - say 3mA - out.

Then slowly rotate the pot and eventually you should get to the point where the collapse you noticed in your circuit is duplicated.

Then, subtract Vout from Vcc, and the difference should be less than allowed by the data sheet specs.

If the collapse happens, then what it means is that your load resistance is too high for the level of illumination being used and you should either decrease the illumination or the load resistance or increase Vcc, or both.

---

--- I'm all ears!

-- JF

Reply to
John Fields 

--
There once was an old dog named Larkin
who everyone's life tried to darken.
but then one fine day,
when he learned how to bray,
was suddenly cured of his barkin'.
Reply to
John Fields

:) Jamie

Reply to
Jamie

Oh boy!

Reply to
JW

Ahhh... Shaddup!

Reply to
JW

you

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It seems to have been Phil Hobbs in the thread "LTC Switcher CAD3 ?" on the 4th June.

I was talking about nanohenries per root turn, which is a mistake I'd been making for years, and I didn't immediately realise that Phil was right when he told me that it should have been Henries per turn squared. It was three in the morning, my time, and I should have gone to bed rather than responding without thinking hard enough about what I was posting.

It was embarrassingly obvious that he was right when I looked at the thread the following morning, and I did post an acknowledgement immediately.

You should have remembered. You chimed in almost immediately, and - as usual - said absolutely nothing that was interesting or useful.

-- Bill Sloman, Nijmegen

Reply to
Bill Sloman

You're no better a poet than you are a circuit designer.

-1

--

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

That's unkind. He's an uninspired circuit designer - from what I've seen - but it's not as bad as his poetry.

Good theme though. Someone with talent might make something of it.

-- Bill Sloman, Nijmegen

Reply to
Bill Sloman

0xFFFFFFFFFFFFFFFF 
--

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

Make that a long long int.

Jamie

Reply to
Jamie

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