Author Topic: EEVblog #673 - Mailbag  (Read 20335 times)

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Online EEVblog

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EEVblog #673 - Mailbag
« on: October 14, 2014, 10:52:22 am »
 

Offline bktemp

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Re: EEVblog #673 - Mailbag
« Reply #1 on: October 14, 2014, 11:50:56 am »
That checkpoint board looks interesting: There seems to be some rf power stuff on the right side. Maybe this board drives those anti-theft protection things found at the exits of department stores or some other long range rfid antennas.
It is probably impossible to make it do something without a lot of other stuff connected to all the connectors, but it could be interesting to probe the outputs.
 

Offline dr.diesel

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Re: EEVblog #673 - Mailbag
« Reply #2 on: October 14, 2014, 12:15:09 pm »
Multi-hour Mailbag episodes are fine with me, love the 2-5min mini teardowns.

Offline coppice

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Re: EEVblog #673 - Mailbag
« Reply #3 on: October 14, 2014, 12:34:04 pm »
Its spring in .au, and for the first time I hear a hum on an eevblog video. Air con, maybe?  :)
 

Online EEVblog

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Re: EEVblog #673 - Mailbag
« Reply #4 on: October 14, 2014, 12:39:24 pm »
Its spring in .au, and for the first time I hear a hum on an eevblog video. Air con, maybe?  :)

Yep, next doors aircon. I turn mine off during shooting.
 

Offline nsayer

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Re: EEVblog #673 - Mailbag
« Reply #5 on: October 14, 2014, 01:10:21 pm »
If anyone's curious, that clock had the "whacky" firmware in it - it ticks once a second, but on a random tenth-of-a-second.
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Offline AmaG

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Re: EEVblog #673 - Mailbag
« Reply #6 on: October 14, 2014, 02:30:32 pm »
I have laying around some solar cells from all stages of the production line. From ingot-chunks (lumps of poly-silicium) over thin sheets of silicium cut with a wire-saw to the finished cell.
If you like, I'll send you a sample of every production state and some with different production errors on it.
The lumps make nice paperweights  ^-^

AmaG
 

Online mikeselectricstuff

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Re: EEVblog #673 - Mailbag
« Reply #7 on: October 14, 2014, 02:56:41 pm »
If anyone's curious, that clock had the "whacky" firmware in it - it ticks once a second, but on a random tenth-of-a-second.

A while ago someone did a much more subtle clock hack - it gradually sped up in the half-hour before lunchtime and slowed down for the next hour!
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Offline Rufus

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Re: EEVblog #673 - Mailbag
« Reply #8 on: October 14, 2014, 03:11:29 pm »
The UT513 at 500v has full scale of 20G and only 10% accuracy up there. The 20G resistor was probably more than 20G or the UT513 thought it was. OL is just a not very good over range indication.

It showed OL on the 10G resistor till the voltage got high enough to produce the minimum measurable current.

 

Offline Rasz

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Re: EEVblog #673 - Mailbag
« Reply #9 on: October 14, 2014, 03:52:49 pm »
Dave you got  set up to fail with that solar cell, it was VERY POORLY packed. You dont pad the shit out of things that might shatter when bend, you pack them in something STURDY first (like a sheet of metal for example,or a plank of wood), not cardboard and bubble wrap :/


That checkpoint board looks interesting: There seems to be some rf power stuff on the right side. Maybe this board drives those anti-theft protection things found at the exits of department stores or some other long range rfid antennas.

I dont think its rf, it looks like Power Over whatever_serial_interfaces_they_used so all the sensors hanging off this thing dont need separate supplies


ps: not long enough!
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Offline Porto

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Re: EEVblog #673 - Mailbag
« Reply #10 on: October 14, 2014, 04:16:39 pm »
Dave, you might consider giving our Hungarian friend a free uRuler for destroying his precious solar panel! ;)
Just to show the world what a great guy you are!  :-DD
 

Offline bktemp

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Re: EEVblog #673 - Mailbag
« Reply #11 on: October 14, 2014, 04:28:15 pm »

I dont think its rf, it looks like Power Over whatever_serial_interfaces_they_used so all the sensors hanging off this thing dont need separate supplies
At least the board transmits something at a higher power level and processes the received signal: On the right side is a frequency jumper and a TXGND label. The parts to the left seem to be a analogue RX chain (GAIN jumper, and some Analog Devices parts, maybe opamps and adc).
Those ferrite parts on the top side look similar to those used in rf power amplifiers (for push-pull amplifiers or differential-single ended conversion).

Dave, maybe you could take some high-res fotos of the part numbers?
 

Offline nsayer

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Re: EEVblog #673 - Mailbag
« Reply #12 on: October 14, 2014, 04:48:28 pm »
If anyone's curious, that clock had the "whacky" firmware in it - it ticks once a second, but on a random tenth-of-a-second.

A while ago someone did a much more subtle clock hack - it gradually sped up in the half-hour before lunchtime and slowed down for the next hour!

One of the available firmwares for mine is one that will run 10% fast for 12 hours, then 10% slow for another 12. Makes the days fly by.

The problem you run into if you want to get much more sophisticated is that the controller has no idea where the actual hands are pointing. All it can do is make the second hand move.
« Last Edit: October 14, 2014, 04:50:05 pm by nsayer »
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Offline uMinded

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Re: EEVblog #673 - Mailbag
« Reply #13 on: October 14, 2014, 06:52:06 pm »
Yes the right hand side is for rf. The board was installed in one of those 6ft anti-theft gates and had two coils wrapped around the gate structure vertically. There where some things dangling off the other side that where chopped off, presumably the checkout scanner and another section of gates.

The controller must be their in-house hammer for every problem as its massivly overpowered for such a task. I added up the blackfin, memory and fpga and was over $200/qty100
 

Offline daqq

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Re: EEVblog #673 - Mailbag
« Reply #14 on: October 14, 2014, 06:56:54 pm »
:D you got a Vetinary clock! Awesome!

As to that resistor, I'm guessing it's rated MUCH higher than 500V - these kinds of resistors were/are used for amongst other things for high voltage dividers. I'd look for the error somewhere else.
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Offline nsayer

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Re: EEVblog #673 - Mailbag
« Reply #15 on: October 14, 2014, 07:16:03 pm »
:D you got a Vetinary clock! Awesome!

Actually, while a Vetinari firmware is available for that controller, that one isn't running it. The Vetinari firmware ticks ostensibly normally most of the time, but actually ticks imperceptibly slow. Once it has "gathered" enough time, it does a special "double tick" to catch up. It winds up doing that approximately every 30 seconds or so (there's random distribution to make it unpredictable).

The firmware Dave got just ticks once a second, but on a random tenth-of-a-second, so it's an arhythmic clock.
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Offline TeaNTronics

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Re: EEVblog #673 - Mailbag
« Reply #16 on: October 14, 2014, 08:37:16 pm »
i liked the video,

i think it better now that it more about opening mails, and less about reviewing them.
so you open the item, do a quick 2 minutes review, and go to the another one.
and if you need to do a full review, you can do it on teardown tuesday.

Also, maybe you can do Mailbag Monday "The Marathon" with 1 hour or so video,
so you can open everything :)

And about the new µRuler, i would like to buy one.
 

Offline Neilm

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Re: EEVblog #673 - Mailbag
« Reply #17 on: October 14, 2014, 08:42:37 pm »
The UT513 at 500v has full scale of 20G and only 10% accuracy up there. The 20G resistor was probably more than 20G or the UT513 thought it was. OL is just a not very good over range indication.

It showed OL on the 10G resistor till the voltage got high enough to produce the minimum measurable current.

A real "Megger" 5kV tester measures about 100G at 500V.

Also, I have seen some Welwyn resistors of about that size that were good for 100G 15kV element voltage (when in oil or potted)
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Offline John_ITIC

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Re: EEVblog #673 - Mailbag
« Reply #18 on: October 14, 2014, 09:46:37 pm »
Mailbag Monday.

Professional USB 2.0 Protocol Analyser:
https://www.kickstarter.com/projects/itic/professional-usb-20-ls-fs-hs-protocol-analyzer-mod
from International Test Instruments:
http://www.internationaltestinstruments.com

Thanks Dave! Yes, the Kickstarter campaign was a flop but I have determined KS is simply the wrong forum for such projects. KS is, of course, all about hobby projects and, since the pledge levels were in the "laptop-price", few hobbyists could help out.

Anyways, the PCIe connector you mentioned is for attachment to a debugging board that allows the FX2 firmware to be downloaded and debugged interactively via serial port (SRAM and RS232 line drivers are on the debug board). Also, the debug board routes out a bunch if LVCMOS FPGA pins to MICTOR connectors that allow me to hook up to my Agilent 16700 Logic Analyzer for deep LA capture. Finally, the ground strips along the edges of the board are something i normally use to avoid ESD damage - better to dischange static electricity into the GND plane than into individual components on the board. The top fill is actually 3V3, not GND, so this is why is it is not connected to the edge GND strips.

By the way, I also have a PCI Express Protocol Analyzer available for sale on ITIC's web site. Ans, a USB 3.0 Protocol analyzers is being designed!

Cheers,
/John.
« Last Edit: October 14, 2014, 09:48:13 pm by John_ITIC »
1480A USB 2.0 LS/FS/HS/OTG 1.3 Protocol Analyzer - $695 USD
2500A PCI Express 1.1 2.5 Gbps Protocol Analyzer - $6,995 USD
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Offline zoltan

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Re: EEVblog #673 - Mailbag
« Reply #19 on: October 14, 2014, 09:52:36 pm »
The CheckPoint stuff is theft protection device used in stores. It must have a 58 kHz RF loop as antenna attached to be able to detect armed RF tags.

And it's sold in millions as it can be found in almost any store these days.


 

Online EEVblog

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Re: EEVblog #673 - Mailbag
« Reply #20 on: October 14, 2014, 10:43:33 pm »
The CheckPoint stuff is theft protection device used in stores.

Ah, right, of course, Guess I should have googled that.
 

Online EEVblog

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Re: EEVblog #673 - Mailbag
« Reply #21 on: October 14, 2014, 10:45:48 pm »
The UT513 at 500v has full scale of 20G and only 10% accuracy up there. The 20G resistor was probably more than 20G or the UT513 thought it was. OL is just a not very good over range indication.

Doh, that explains it.
 

Offline Rufus

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Re: EEVblog #673 - Mailbag
« Reply #22 on: October 14, 2014, 11:58:55 pm »
A real "Megger" 5kV tester measures about 100G at 500V.

PASS will sell you Megger's entry level MIT515 for £1865, they will sell you a UT513A for £189.
 

Offline tombi

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Re: EEVblog #673 - Mailbag
« Reply #23 on: October 15, 2014, 06:48:04 am »
I just happened to be watching Shariar's teardown Calibration etc of a Keithley 220 and that unit appears to contain the same high value wire wound resistors. Skip to around 10:39. I suppose that figures.

 

Offline JackOfVA

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Re: EEVblog #673 - Mailbag
« Reply #24 on: October 15, 2014, 12:19:36 pm »
Re the ferrous battery correction on the Sanwa VOM...

D'arsonval meter movements can have an external magnetic field and hence the meter accuracy can be degraded with nearby magnetic objects.

If you look at old catalogs of panel mount meters, you can sometimes find two versions, one calibrated for non-magnetic panels and one for magnetic panels.  I believe most modern D'arsonval movements are shielded internally, at least the more expensive ones, and hence are suitable for magnetic or non-magnetic panel mount.

If you remember, some dry cells included a steel outer jacket - I think Ray-o-Vac featured that construction in the USA, claiming it reduced damage from leaking cells and I assume you had something similar 'down under."

I believe that Sanwa has intentionally added a ferrous battery holder so that whether a steel jacketed or non-jacketed cell is used, the meter movement always sees the same magnetic environment, with the leakage magnetic field dominated by the ferrous battery holder.

It's possible the battery holder is something more exotic, such as mu-metal, but I suspect it's steel.

It's a nice touch to maintain accuracy where the meter movement is unshielded, or imperfectly shielded.

 


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