EEVblog #661 - Mailbag

[T3sl4co1l]

Some more comments on that opto device, it could be a TIA with a simple circuit, for example I built this once upon a time:



So, a 4N35 with excellent linearity and much improved speed (~1us t_r).  This uses four additional transistors, and takes advantage of the photodiode actually being in a phototransistor, so it's kind of cheating.  But the same general idea could be used with only three transistors, for somewhat poorer performance, which might be balanced against the size of the photodiode, or other requirements for that particular device.

In short, after a little more study, I wouldn't be afraid to put voltage on that sensor and see what it does.  Got any high speed light sources to test step response?

Tim

[eV1Te]

I was laughing so hard when Dave was talking about rocks and minerals while holding silicon in his hand  Dave gets most things right but those few times when he goes on and on with something completely wrong is just pure humor.

By the way, why do people call it metallic silicon? It is a semiconductor and is not metallic unless doped very heavily (hence not pure silicon any more), but maybe the terminology is different in different countries?



 

[T3sl4co1l]

It's shiny, and easier to say than "semimetallic" or whatever.

It's still true, if referring to the luster.  Galena for example is described as having a metallic or submetallic luster.

Tim

[rob77]

I was laughing so hard when Dave was talking about rocks and minerals while holding silicon in his hand  Dave gets most things right but those few times when he goes on and on with something completely wrong is just pure humor.

By the way, why do people call it metallic silicon? It is a semiconductor and is not metallic unless doped very heavily (hence not pure silicon any more), but maybe the terminology is different in different countries?

i was not laughing - i rather rushed to the forum to tell him it's silicon and not the ore i never laugh at someone who is wrong - it can (and actually does) happen to all of us
and actually Dave knows very well how a silicon wafer looks like - he made a very nice video showing a lot of silicon IC manufacturing stuff.  and let's be realistic - the highly polished wafers with the epitaxial layer of silicon are looking way different (color, surface) than the roughly cut silicon - so no wonder if someone makes a wrong assumption (supported by incorrect wording in a letter).

and why metallic ? probably because it looks like metal and most probably because silicon is a metalloid by definition

[eV1Te]

i was not laughing - i rather rushed to the forum to tell him it's silicon and not the ore i never laugh at someone who is wrong - it can (and actually does) happen to all of us
and actually Dave knows very well how a silicon wafer looks like - he made a very nice video showing a lot of silicon IC manufacturing stuff.  and let's be realistic - the highly polished wafers with the epitaxial layer of silicon are looking way different (color, surface) than the roughly cut silicon - so no wonder if someone makes a wrong assumption (supported by incorrect wording in a letter).

and why metallic ? probably because it looks like metal and most probably because silicon is a metalloid by definition

I agree that it is bad to laugh at someones mistakes, but it I was not laughing to the fact that he was wrong, but to the suspense when he continued, and took the time to look up how silica was made into silicon, how it would be different from sand and if silica was mined in Norway.  Dave is great, I do not blame him, he should be honored that even his mistakes are amusing and attracts viewers!
 
I work as a researcher within material science and just because of my personal interest in the subject, I had to look up the properties of silicon. Interestingly it does not have a metallic luster/reflections, it behaves as a dielectric material with very high absorption.

For example metals does not polarize light when reflected of its surface, but glass/plastic and silicon does. Light can not penetrate metals, it is reflected if its top surface, but in silicon it can penetrate into the material (used in solar panels) and if thin enough it can go through, similarly to that of a highly colored glass object.

Wikipedia:
There is no standard definition of a metalloid, nor is there complete agreement as to which elements are appropriately classified as such.

[wigman27]

Hi all!

A big thanks to Dave for putting my PCB on the mailbag! I'm really happy you like it!

Thanks very much for the feedback from everyone here and a big thanks again to everyone who has helped me!

This certainly is my second ever PCB and I had made a few improvements from rev A and everything works quite well! One thing I would improve in the next one is the opamp, not too happy with the offset of the LM324 but apart from that I'm pretty happy!

Thanks for the comments on my ground plane, I can certainly see what you're talking about and will definatley try and improve that in my future designs!

I think Dave must of accidentally forgot to include the links in the description of the video so here they are

http://www.instructables.com/id/Arduino-Programmable-Constant-Current-Power-Resist

www.youtube.com/playlist?list=PLzlqY1PgCfF6wMwhryeSO72kd-sh6Fgyo

https://github.com/wigman27/Arduino-Programmable-Constant-Current-Power-Resistance-Load

https://www.eevblog.com/forum/oshw/arduino-programmable-constant-current-power-resistance-load/

I'm nearly out of spare boards but if there is enough interest I will re-run it. The gerbers are also on my GitHub.

Thanks again Dave! Love the blog as always!

[nsayer]

That PiPower board could use some thicker traces. It's not like there were space limitations there.

I could be wrong, but I thought 25 mil for the main current path was sufficient. The traces are fairly short. I wanted to insure good coverage of the groundplane as well. I even put a couple extra vias to make the ground path closer (since the groundplane on the bottom is much less interrupted) for the diode anode, input and output filter cap junctions.

[miguelvp]

The raw pure silicon that the Avogadro project uses cost 1 million Euros, after making the perfect sphere for the new reference kilogram, it probably cost around 3 million dollars according to popular science.

[Dave]

I could be wrong, but I thought 25 mil for the main current path was sufficient. The traces are fairly short. I wanted to insure good coverage of the groundplane as well. I even put a couple extra vias to make the ground path closer (since the groundplane on the bottom is much less interrupted) for the diode anode, input and output filter cap junctions.

AFAIK you normally give it as much copper as you can. Check out your chip's datasheet and look at the example PCB layout (page 16). There are huge copper polygons there.

[FrankBuss]

I would do a forum give away with the extra DSO

good idea, its a shitty scope for someone with a 100MHz box on the bench, but great tool for a beginner.

Is it this scope?

http://www.seeedstudio.com/depot/DSO-Nano-v3-p-1358.html?cPath=63_65

200 kHz analog bandwidth and 1 Msps is really just a toy for beginners. If you have a PC and don't need a display, this looks very good:

http://parts.arrow.com/item/detail/arrow-development-tools/bescopebundle

50 MHz analog bandwidth, 250 Msps and (kind of) a FPGA development kit integrated, for $50. Even with $38 shipping cost to Germany it is a great deal.

[miguelvp]

Damn, I already have a BeMicro CV but I guess I have to get this as well, curse you!!!!
The BeMicro CV by itself cost me $50 a back in May.

[nsayer]

I could be wrong, but I thought 25 mil for the main current path was sufficient. The traces are fairly short. I wanted to insure good coverage of the groundplane as well. I even put a couple extra vias to make the ground path closer (since the groundplane on the bottom is much less interrupted) for the diode anode, input and output filter cap junctions.

AFAIK you normally give it as much copper as you can. Check out your chip's datasheet and look at the example PCB layout (page 16). There are huge copper polygons there.

Well, Si non confectus, non reficiat.

[miguelvp]

Damn, I already have a BeMicro CV but I guess I have to get this as well, curse you!!!!
The BeMicro CV by itself cost me $50 a back in May.

For what is worth, shipping and taxes where $12.25 to the states, so $38 doesn't sound like much.
And of course Thank You instead of cursing you

Other things to know about the BeMicro CV FPGA dev kit is that if you can find it (actually I did) you can get the BeUSB 3.0 evaluation board with the EZ-USB FX3 superspeed 3.0 device controller for $99 that attaches to to the custom connector of the BeMicro CV or the original BeMicro.
https://parts.arrow.com/item/detail/arrow-development-tools/beusb3.0

A bit pricey for me since I'm not doing anything with USB 3.0 anyways.

Also you can buy the InterPoser (adapter that allows you to connect Analog Devices dev boards to the BeMicro) for $50 more.

http://components.arrow.com/part/detail/NEG50150698S8959040N1911

More details here
http://www.arrownac.com/solutions/adi_interposer/

Edit: click on ADI Evaluation Boards to see what boards are available (all kinds of DAC, ADC, DDS, PLL, Wave Generators, etc.. goodness), also you'll find reference designs and the links to purchase it all of course

http://wiki.analog.com/resources/alliances/altera

[FrankBuss]

Yeah, sometimes marketing creates interesting prices I found it because I got an ad eMail, promoting this: http://parts.arrow.com/item/detail/arrow-development-tools/bescope First I thought $45 is a nice price for such a scope, but then I read in the fine prints of the datasheet, that you need the BeMicro CV, too. And no link from this page to the bundle page of course. Luckily I found it with some Google searching. Looks like the usual in big companies, the right hand doesn't know what the left hand is doing.

[miguelvp]

That interposer connector is really expensive for being just a connector, but  boy does it open a lot of analog devices possibilities!

Not sure about the 6GHz and around that frequency boards I would think the FPGA couldn't cope with that but maybe.

[hikariuk]

The thingamabob is a Sith insignia.

[RupertGo]

I have to rant about that Pure Evoke Flow wireless... I mean, by all that is unholy and misbegotten, look at that bloody interface! Scroll bars! Incomprehensible menu items! Lag and asynchronous messages and god knows what else hidden away in there!

And did I mention the SCROLL BARS! This is 2014! I'd be ashamed to have produced something that crapulous in 1984.

There is zero or less excuse for this sort of thing these days. Look at the sort of standard one-man-and-his-dachshund outfits are producing for free smartphone apps, while Pure are shoving this sort of manure out. No wonder DAB is dying the death of a dingo in a liquidiser with this sort of teenage Science Fair bollockry being flogged to the confused masses.

RTFM? I have hundreds of apps on my mobile, which is itself a brain-blowingly complex and capable info-tool, and I haven't had to RTFM (even if there was an FM) for any of this. And you sbould have to for a bloody radio? As that little analogue kit shows - you turn one knob to get the noise, and another to choose which noise you want. Posh version - add a band switch.  Not this crackling heap of robo-vom.

Jeez.

[Rasz]

good idea, its a shitty scope for someone with a 100MHz box on the bench, but great tool for a beginner.

Is it this scope?

http://www.seeedstudio.com/depot/DSO-Nano-v3-p-1358.html?cPath=63_65

200 kHz analog bandwidth and 1 Msps is really just a toy for beginners.

no, its 203/dso quad
50MHz or something analog bw

[rs20]

I have to rant about that Pure Evoke Flow wireless... I mean, by all that is unholy and misbegotten, look at that bloody interface! Scroll bars! Incomprehensible menu items! Lag and asynchronous messages and god knows what else hidden away in there!

And did I mention the SCROLL BARS! This is 2014! I'd be ashamed to have produced something that crapulous in 1984.

There is zero or less excuse for this sort of thing these days. Look at the sort of standard one-man-and-his-dachshund outfits are producing for free smartphone apps, while Pure are shoving this sort of manure out. No wonder DAB is dying the death of a dingo in a liquidiser with this sort of teenage Science Fair bollockry being flogged to the confused masses.

RTFM? I have hundreds of apps on my mobile, which is itself a brain-blowingly complex and capable info-tool, and I haven't had to RTFM (even if there was an FM) for any of this. And you sbould have to for a bloody radio? As that little analogue kit shows - you turn one knob to get the noise, and another to choose which noise you want. Posh version - add a band switch.  Not this crackling heap of robo-vom.

Jeez.

Except your phone has a powerful CPU and GPU that makes even face-palmingly poorly written routines run seemingly instantaneously, multiple cores, millions of colour pixels, a OS and software development kit with all the GUI and threading groundwork done for you, and a touch screen. I agree that the interface was on the radio was poor, but saying that the average person who can make a useable app could do a better job here is just completely ridiculous.

[Rasz]

I have to rant about that Pure Evoke Flow wireless... I mean, by all that is unholy and misbegotten, look at that bloody interface! Scroll bars! Incomprehensible menu items! Lag and asynchronous messages and god knows what else hidden away in there!

And did I mention the SCROLL BARS! This is 2014! I'd be ashamed to have produced something that crapulous in 1984.

There is zero or less excuse for this sort of thing these days. Look at the sort of standard one-man-and-his-dachshund outfits are producing for free smartphone apps, while Pure are shoving this sort of manure out. No wonder DAB is dying the death of a dingo in a liquidiser with this sort of teenage Science Fair bollockry being flogged to the confused masses.

RTFM? I have hundreds of apps on my mobile, which is itself a brain-blowingly complex and capable info-tool, and I haven't had to RTFM (even if there was an FM) for any of this. And you sbould have to for a bloody radio? As that little analogue kit shows - you turn one knob to get the noise, and another to choose which noise you want. Posh version - add a band switch.  Not this crackling heap of robo-vom.

Jeez.

Except your phone has a powerful CPU and GPU that makes even face-palmingly poorly written routines run seemingly instantaneously, multiple cores, millions of colour pixels, a OS and software development kit with all the GUI and threading groundwork done for you, and a touch screen.

all than and phone is still CHEAPER
if you really want networked radio get cheap chinese tablet, or second hand android phone, not this piece of crap evoke whatever

[Paul Moir]

no, its 203/dso quad
50MHz or something analog bw

Unfortunately not even close to this.  They botched the analog frontend leading to a huge dip between about 1MHz and something like 7.  Some hacked it to get a pretty good rolloff -3db@10MHz.  But still it's fundamentally flawed in a few ways.

Really it was a huge disappointment.  One wonders what could have happened if they had involved the community at the design stage.

Gory details:
http://www.seeedstudio.com/forum/viewtopic.php?f=26&t=1944

[RupertGo]

Who says you have to use a slow CPU and a dumb display? These are being presented and sold, often, as premium products: I know there's not the same economy of scale as with smartphones, but the disparity is far too wide to make any sense.

If there's no economic way to make a digital radio with a decent interface, then there's no economic way to make a digital radio.

[rs20]

Who says you have to use a slow CPU and a dumb display? These are being presented and sold, often, as premium products: I know there's not the same economy of scale as with smartphones, but the disparity is far too wide to make any sense.

If there's no economic way to make a digital radio with a decent interface, then there's no economic way to make a digital radio.

I'm not necessarily defending the quality of the Evoke, I'm just saying that a comparison to single-man phone apps is the height of irrelevance. I'd hazard to guess that whatever hardware is in there is capable of operating in a snappy and intuitive way; it's just the software that sucks. Just like it would if a single-man app writer tried to write it.

all than and phone is still CHEAPER

Yes, economies of scale are amazing.

if you really want networked radio get cheap chinese tablet, or second hand android phone, not this piece of crap evoke whatever

Great, no AM, no FM, crap speakers, looks weird on the table-top. I agree with you, I don't want one of these either, but I can't help but feel that you're missing the point of this thing. Something to do with style or fashion or something weird like that.

[Rasz]

no, its 203/dso quad
50MHz or something analog bw

Unfortunately not even close to this.  They botched the analog frontend leading to a huge dip between about 1MHz and something like 7.  Some hacked it to get a pretty good rolloff -3db@10MHz.  But still it's fundamentally flawed in a few ways.

Really it was a huge disappointment.  One wonders what could have happened if they had involved the community at the design stage.

Gory details:
http://www.seeedstudio.com/forum/viewtopic.php?f=26&t=1944

doh, never mind then

another alternative might be labtool based on LPC4370 (ARM M4 with 80MHz 12bit ADC buildin)
http://www.lpcware.com/content/project/Mixed-Signal-Logic-Analyzer-Oscilloscope-Lab-Tool-Solution
http://www.embeddedartists.com/products/app/labtool.php

~$150
software is pure shit tho, as always

how is the software for BESCOPE?

btw Chris was looking for cheap scope for his course, BESCOPE might be it (fpga as added bonus).

[FrankBuss]

how is the software for BESCOPE?

It looks very basic, like something someone hacked with LabVIEW in some hours, see page 16 of the datasheet, but should be sufficient as a basic scope. There is a link in the datasheet where you can download the software, with the note "TBD" and of course the page doesn't exists and I can't find a download link on the shop page either. I hope when I get it that it comes with a CD with the software, but all this doesn't inspiring confidence. Well, I guess you get what you pay for. Someone should hack the PicoScope software to use it with the BeScope