EEVblog #661 - Mailbag

[EEVblog]

Mailbag Monday
Negative Feedback T-Shirts:
NOTE: Black shirt coming shortly, bug in Teespring site...
http://teespring.com/negativefeedbackAsh
555 Timer: http://teespring.com/555timer-grey3
Warranty VOID: http://teespring.com/warrantyvoid2





Spoliers & Links:
Programmable Constant Current Dummy Load: http://www.instructables.com/id/Arduino-Programmable-Constant-Current-Power-Resist/
Conrad Retro Radio Kits:
http://www.conrad.com/ce/en/overview/2420100/Retro-Kits
Evoke Flow WIFi Radio OLED Display Repair
MiniDSO Pocket Oscilloscope (a.k.a Seed Studio DSO Quad)
http://minidso.com
Pi Power Raspberry Pit power adapter: https://www.tindie.com/products/nsayer/pi-power/
L293D H-Bridge Motor driver chip: http://www.ti.com/lit/ds/symlink/l293d.pdf
MOSFET: http://www.aosmd.com/pdfs/datasheet/ao3400.pdf
MCP1804 LDO: http://www.microchip.com/wwwproducts/Devices.aspx?product=MCP1804
Silicate rock used in solar cell manufacture

[coppice]

While the dummy load PCB is really excellent for someone's first attempt, you really couldn't see issues? The ground flood is very poor. With the shifting of just a few tracks the ground plane would have flowed between groups of traces, and the ground plane would have been much quieter. In particular, the traces under the big chip have ruined its ground plane.

Don't get me wrong. Hardly anyone does a job as good as this on their first try, but I wouldn't expect good results in EMI/ESD tests without ground plane improvements.

[EEVblog]

While the dummy load PCB is really excellent for someone's first attempt, you really couldn't see issues? The ground flood is very poor.

Unless you flooded the top as well and then via stitched, there isn't a huge amount of improvement to be had there.
Yes, I should have mentioned that.
But it's more than good enough for a dummy load.

[Dave]

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

[coppice]

While the dummy load PCB is really excellent for someone's first attempt, you really couldn't see issues? The ground flood is very poor.

Unless you flooded the top as well and then via stitched, there isn't a huge amount of improvement to be had there.
Yes, I should have mentioned that.
But it's more than good enough for a dummy load.

My guess is the developer is a pretty smart person who has yet to realise the full benefit of continuity in the ground plane. Its easy to see how a few tracks could be moved, which would allow some of those isolated ground areas to join up. Improving the area under the MCU would take more effort. Via stitching is really a last resort you have to use when you can't achieve continuity in a single plane. It takes a lot of vias to stitch the plane together as well as a pretty narrow in-plane trace would.

[calexanian]

I would do a forum give away with the extra DSO, or.... Start collecting an entire set!

[EEVblog]

My guess is the developer is a pretty smart person who has yet to realise the full benefit of continuity in the ground plane. Its easy to see how a few tracks could be moved, which would allow some of those isolated ground areas to join up.

Sure, but it's still a double sided board, so you will never get a good continuous ground plane.
You can fuss around moving traces to get some extra flow and shorten power loop area, but like I said there isn't really a huge amount of improvement to be had here.
Although I haven't looked over every detail of the layout, the only thing that stands out at first glance in that area is one spot under the micro.

[EEVblog]

I would do a forum give away with the extra DSO

Yep, should do!

[chickenHeadKnob]

 A minor nag on the power load PCB. When you have a parallel ganged  array of resisters you should input and output at diagonally opposite corners to equalize resistance/path length. like so:

        high side >---------------------------------------------------------
     res.->               I     I     I     I      ......              I     I     I     I
                             ---------------------------------------------------------->   low side

 The connector was routed to the middle of the array on one side. Those resistors will get hotter.

[EEVblog]

The connector was routed to the middle of the array on one side. Those resistors will get hotter.

I haven't done the calcs, but at 1ohm a pop, I doubt it matters.

[Legit-Design]

Pi Power Raspberry Pit power adapter: https://www.tindie.com/products/nsayer/pi-power/

Pi power here on forum.
https://www.eevblog.com/forum/crowd-funded-projects/pi-power-the-power-supply-the-raspberry-pi-*should*-have-come-with!/

[Rasz]

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.

edit: unless it was send because it is broken

edit2: DSO nano/203 could really use an addon with a panel of physical knobs and buttons. This would elevate it from shitty toy for a beginner to useful status immediately. Or an app displaying virtual buttons/knobs on a 7/10' android tablet.

[vk3yedotcom]

A bit more about the Franzis radio kit is at

It seems to drive a speaker with a 1.5v battery - but at low volume.

Wouldn't be surprised if it's based on the MK484 or similar 1 chip TRF receiver, with a transistor or two for audio amplification.

If the above is correct Jaycar sell those chips and they make a fun project. 

If Sagan does build it I can guarantee, that unlike that digital radio, it will switch on instantly!

[rs20]

Dave, I'm fairly sure you got sent on a tangent by a spelling mistake in the Norway letter -- what you have there is most likely a lump of refined silicon -- pure, solid silica (silicon dioxide) is transparent, also known as fused quartz, and is what the windows of the space shuttles are made of. When mixed with other things to bring the melting point down to a easily manageable level, you have standard window glass. Pure silica is definitely not shiny and metallic.

No, I think what you have there is silicon that's gone through the zone refining process. I'm jealous! All you have to do is sputter on some boron and phosphorus and demonstrate making your own transistor -- Fundamentals Friday demonstration? 

PS/ Let's not forget people who (inconsequentially, to be fair) confuse silicon with silicone...

[dean1066]

Hello,

RTFM indeed!.  The product user guide for the Evoke Flow can be downloaded from here..

http://support.pure.com/au/files.php?s=96235459dedc6db91f07f2815c3e65b7&id=4

You will be able to listen to the Amp-Hour podcast, it is listed in the Pure Connect database.

Cheers

[GreyWoolfe]

Dave, thanks for the extended version of the mailbag.  Fifty minutes of package opening (with the Sicilian toothpick) and discovery goodness.  Beauty!

[rob77]

Dave, I'm fairly sure you got sent on a tangent by a spelling mistake in the Norway letter -- what you have there is most likely a lump of refined silicon -- pure, solid silica (silicon dioxide) is transparent, also known as fused quartz, and is what the windows of the space shuttles are made of. When mixed with other things to bring the melting point down to a easily manageable level, you have standard window glass. Pure silica is definitely not shiny and metallic.

No, I think what you have there is silicon that's gone through the zone refining process. I'm jealous! All you have to do is sputter on some boron and phosphorus and demonstrate making your own transistor -- Fundamentals Friday demonstration? 

+1

definitely a pure metallic silicon most probably not refined to eleven nines for growing wafer grade mono-crystal , but it's definitely metallic silicon.

[tecman]

The piece of silicon you have looks like a sawed then broken piece of a crystal used for wafers, not a mineral rock.  The surfaces are sawed (by appearance).  A standard wafer would be sawed much thinner.  The shiny appearance of the sides are the look of single crystal silicon.

paul

[Kjetil]

what you have there is most likely a lump of refined silicon

Yeah, just my bad for not checking the English name for it properly, here we use Silisium for the stuff, while we use silikon for breast implants etc.. hence the confusion on my end.

I'm jealous! All you have to do is sputter on some boron and phosphorus and demonstrate making your own transistor -- Fundamentals Friday demonstration?

I got more of the stuff  But I was hoping that Dave would do something like that.

The piece of silicon you have looks like a sawed then broken piece of a crystal used for wafers, not a mineral rock.  The surfaces are sawed (by appearance).  A standard wafer would be sawed much thinner.  The shiny appearance of the sides are the look of single crystal silicon.

The piece was from a large slab of silicon that measured approx 10x10x30cm (or thereabouts), and got cut by a diamond saw into very thin wafers, which was then sent somewhere in Asia for further processing. These then ended up as the cells you see in your regular solar panels. This part is the bottom, hence the "rough" surface on one side, and also has the worst quality in the batch. If I remember right the top side was >99.9% Si and the bottom was >98% Si, so you would get varying grades of wafers throughout the slab.


The letter was meant for next weeks mailbag (episode 666), forgot to write that on the front 

[G7PSK]

Norway is or used to be one of the major producers of metallic silicon, (plenty of hydro electric) its made by reducing sand or other silicon oxides using the carbothermic  process using carbon electrodes to heat the sand to 1800 deg C or above the carbon electrodes are consumed to produce CO2 and silicon. So your silicon chips have quite a carbon footprint before they are even made.

[selkathguy]

I'll throw in my two cents that I prefer the close-up format with you behind the camera, at least for the smaller items.  You seem to be changing around the camera to get the close-ups anyway.   I can see using the able for larger items like quadcopter kits or whathaveyou.
 
Not complaining, I'll watch either way just throwing in my vote.

[SeanB]

I had some metallurgical grade silicon from Iscor, used in steel making to improve the final material properties, and it is very different, having lots of blow holes and porosity in it. Electronics grade can be zone refined from that, and that wafer could probably be used as a transistor directly just by using a pair of needles to make point contacts on the surface and use the substrate as base.

The photoamplifier looks like it has a jfet input and a 2 transistor amplifier amplifier as well inside the can. I do have a few old data books with the actual drawings of a lot of transistor dies on it.

[PSR B1257]

Hy Dave,
you missed the second line of the note of the radio-kit. It says (translatet 1:1) "For children under 14 years NOT suited".
I'm afraid Sagan has to wait a little while for this kit (it's accualy a multi-band radio, as it says on the maual) to assemble 

[wilhe_jo]

Little issue with that little DC-Load.... please DO NOT USE IT WHILE YOUR PC IS CONNECTED!

If there are optos or something like this - my fault, but there isn't isolation between your load and the uC it may (so thanks to murphy it will) kill your PC-Mainboard (potential risk of a ground loop!)...

73

[vindoline]

Rs20 is absolutely right. That is a piece of pure elemental silicon (Si). It does not occur like this in nature. It has been refined (most likely from quartz or "sand" as you call it). As it came from a photovoltaic plant, it is obviously photovoltaic "grade."  Very cool.

Dave, I'm fairly sure you got sent on a tangent by a spelling mistake in the Norway letter -- what you have there is most likely a lump of refined silicon -- pure, solid silica (silicon dioxide) is transparent, also known as fused quartz, and is what the windows of the space shuttles are made of. When mixed with other things to bring the melting point down to a easily manageable level, you have standard window glass. Pure silica is definitely not shiny and metallic.

No, I think what you have there is silicon that's gone through the zone refining process. I'm jealous! All you have to do is sputter on some boron and phosphorus and demonstrate making your own transistor -- Fundamentals Friday demonstration? 

PS/ Let's not forget people who (inconsequentially, to be fair) confuse silicon with silicone...