EEVblog #827 - Mailbag - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: December 07, 2015, 09:57:26 pm
content: More Mailbag Monday.SPOILERS:RemoteBoot Kickstarter:https://www.kickstarter.com/projects/658903329/remoteboot-wifi-remote-management-module-for-pcsDigilent PowerBric:https://www.kickstarter.com/projects/658903329/remoteboot-wifi-remote-management-module-for-pcsArty Artix-7 FPGA Development Boardhttp://www.digilentinc.com/Products/Detail.cfm?NavPath=2,400,1487&Prod=ARTY&CFID=21499368

author: max666
author_rank: Frequent Contributor
timestamp: December 07, 2015, 11:00:23 pm
content: Dave you goofed up the "Digilent PowerBric:"-link, here and on YT.That Elektrosluch 3 thing was more fun than I expected. But € 90.00 is a little steep, if you ask me, for something that simple. Have to build that up my self for fun.

author: Dave Turner
author_rank: Frequent Contributor
timestamp: December 07, 2015, 11:58:56 pm
content: Hi DaveWhat's your beef with the white silk screen? For my sight it is one of the clearest silk screens I've seen. I could easily read everything. Surely clarity is a good thing.RegardsDave

author: CrashO
author_rank: Unknown
timestamp: December 08, 2015, 12:03:48 am
content: Quote from: Dave Turner on December 07, 2015, 11:58:56 pmProbably the same reason I hate them (and black mask) too.It's hard to see the traces.. Seeing easily where traces are going is more valuable to me than crispy clean silkscreen.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: December 08, 2015, 12:12:59 am
content: The remote PC reset thing is a neat idea, but That wifi module isn't going to work well with that solid groundplane behind it.Could also have saved themselves some fiddly soldering by combining the pin headers into a larger one.

author: v8dave
author_rank: Regular Contributor
timestamp: December 08, 2015, 12:18:08 am
content: It's a WHITE soldermask with BLACK silkscreen not white silkscreenFor final boards it's fine but for prototyping I prefer the standard green as you can still see the tracks.

author: hcglitte
author_rank: Regular Contributor
timestamp: December 08, 2015, 12:37:53 am
content: Anyone noticed the ground plane beneath the WiFi module...? If you are reading this Ben, you should remove the ground plane below the antenna and also at some distance to it from the sides.

author: janoc
author_rank: Super Contributor
timestamp: December 08, 2015, 12:40:38 am
content: Dave, that "record player" is actually guts from an old talking doll. My sister had one exactly like that when we were kids - you pushed a button on the back and it said something, depending on the record that was in. You could even get different records for it with songs and what not.

author: v8dave
author_rank: Regular Contributor
timestamp: December 08, 2015, 12:47:58 am
content: Quote from: hcglitte on December 08, 2015, 12:37:53 amI saw that too. The range will be reduced quite a bit if he doesn't remove this around the antenna area.

author: AF6LJ
author_rank: Unknown
timestamp: December 08, 2015, 12:56:31 am
content: Good Stuff from one of the 2%

author: AF6LJ
author_rank: Unknown
timestamp: December 08, 2015, 01:08:36 am
content: Quote from: janoc on December 08, 2015, 12:40:38 amThey use to sell those here as a Bag of Laughs.

author: Dave Turner
author_rank: Frequent Contributor
timestamp: December 08, 2015, 01:17:09 am
content: Ok I see your point regarding the 'hidden' tracks whilst developing a 2 layer prototype.However, for a multilayer board the comment is less relevant as much is hidden internally. Also it strikes me as sour grapes 'cos' it makes it harder to reverse engineer visually.

author: Someone
author_rank: Super Contributor
timestamp: December 08, 2015, 02:22:38 am
content: The EM sniffer is picking up the change in frequency/duty cycle of the camera power supply as its dumping data to the drive/flash, there are big power demands for data writes.

author: kindiana
author_rank: Contributor
timestamp: December 08, 2015, 04:20:17 am
content: Designer of Remoteboot here, the ground plane now has a cutout under the antenna, thank you all for the feedback.

author: tpw_rules
author_rank: Regular Contributor
timestamp: December 08, 2015, 07:33:57 am
content: The Elektrosluch has been known to the telephone industry for a while. The telephone-ish thing is their equivalent. The real tool is the other box, which generates a warbling tone to put on ethernet, telephone wire, etc. This turns the wire into a giant antenna and following the warbling with the pointy phone as the wire snakes in walls and through pipes is super easy. I have a set from my uncle in the trade and it was invaluable trying to label breakers in our ancient house.

author: SteveLy
author_rank: Regular Contributor
timestamp: December 08, 2015, 08:04:08 am
content: The minidisc was one of the best portable recorders in its day. Kind of a Zoom H2n of the late 1990s, early 2000s. I've recorded a few gigs with one and it did a great job when it worked. Sound quality was amazing for a small device (even just with the small external stereo mic that came with it). But the discs (and/or the read/write mechanism) became unreliable after a while and you'd end up with unreadable chunks of data on your recordings, which was most disappointing.That Slovakian RF snoop box is cool.

author: con-f-use
author_rank: Unknown
timestamp: December 08, 2015, 09:07:47 am
content: The maximum output capacity thing could be, because the USB standard only allows 10uF of capacity. I suspect it's an inrush and fuse thing.

author: boffin
author_rank: Unknown
timestamp: December 08, 2015, 10:57:27 am
content: The Bzz Bzz Bzz, isn't the line to the LED, it's the bulk data-write to the SD Card.

author: aveekbh
author_rank: Regular Contributor
timestamp: December 08, 2015, 05:08:28 pm
content: Quote from: boffin on December 08, 2015, 10:57:27 amThe SD clock will be 50 to 100-odd MHz, so it's quite likely that that's what we're hearing. The LED current draw wouldn't likely emit so loudly (pun intended).

author: station240
author_rank: Unknown
timestamp: December 08, 2015, 06:47:48 pm
content: Quote from: mikeselectricstuff on December 08, 2015, 12:12:59 amIf you've seen inside a PC, you'd know the for the wires for the various buttons/leds are on individual 2-3 pin headers. So a single large header is in fact harder to connect into, as you can't get easy grip on the plugs. Also less prone to install mistakes, as you can rewire the various buttons one at a time.My own PC motherboard came with a piggyback header, which you plug all the loose 2-3 pin plugs into, then plug the single large one into the motherboard.I too liked the Elektrosluch 3, though I'm more interested in seeing if it could be used to make a proper EMF compliance tool. I'll have a dig through my inductor pile to see if I have any suitable ones.

author: SeanB
author_rank: Super Contributor
timestamp: December 08, 2015, 07:22:26 pm
content: Just look for any ferrite inductors with open magnetic systems, and anything from around 1mH upwards will work, current capacity not too important. If you can only get PC power supply ones try them, and if no joy simply rewind the core with as many turns of 30 SWG or thinner wire as it can hold.The buzzing on the camera is likely from the data blocks being written to the card, the amplifier demodulating the envelope of the write blocks, demodulating the RF signal.

author: ConKbot
author_rank: Super Contributor
timestamp: December 09, 2015, 06:26:48 am
content: Quote from: SeanB on December 08, 2015, 07:22:26 pmThe amplifier used is a FET input one(more immune to RFI compared to a bipolar input) and it looks like it is being run as a low pass filter. If you really wanted to catch higher frequency RF stuff, throw a RF schottky diode(1N5711 maybe? from a very very brief digikey search) on the input as an envelope detector, and you should be able to pick up even more stuff. With the stereo jack sticking out of the front, and a connector with enough space in the housing, you could perhaps make a plug in module to extend the AM demod range of it.

author: PinheadBE
author_rank: Regular Contributor
timestamp: December 09, 2015, 08:04:42 am
content: Dave, that "bag of laughs", you HAVE to make it work!Why? Because, when you have, you can then turn the small recorded disc on its other side (just like eldery people used to do with their vinyl records, eons ago), and listen what's onthatside.Just get Sagan out of the room first, because it's a bit more.... "adult oriented"....

author: Fungus
author_rank: Super Contributor
timestamp: December 09, 2015, 08:17:58 am
content: Quote from: PinheadBE on December 09, 2015, 08:04:42 amI had one of those bags when I was a kid.Quote from: PinheadBE on December 09, 2015, 08:04:42 amUrban legend? Not gonna happen - the disk only has one side (just look at the disc in the video).

author: fubar.gr
author_rank: Unknown
timestamp: December 09, 2015, 01:59:30 pm
content: That minidisc player is one of the late NetMD models released from 2001 onwards.You could connect it via USB and essentially drag and drop MP3 files into it. In reality it was a bit more complicated than that, the included software would convert the MP3 to ATRAC and then transfer it to the disc, but the whole process was very fast.You could fit 4 CD's worth of play time into a single minidisc at good sound quality, or the equivalent of 8 CDs at OK quality. And minidiscs were tiny, you could fit several in your pocket. Also, would last forever with a single AA battery, more than some modern mp3 players on their internal Li ion battery.All in all, it was one of the best portable music players of the time. There were solid state storage solutions back then, but they were either ridiculously expensive, or they couldn't hold more than a hundred of megabytes worth of music, or they sucked in other areas, such as interface, build quality, battery time, etc.

author: mrkva
author_rank: Unknown
timestamp: December 09, 2015, 08:53:29 pm
content: Hey guys, creator of Elektrosluch here. Hit me up if you have any ideas how the device can be improved. It will always remain open source for future generations!)I am now comparing different opamps, and getting quite different "range" with LME49720. It is slightly lower noise, but also it also catches different signals then OPA2134. To be more exact, it catches frequencies which don't even appear with OPA2134 (I would expect them to be there but maybe lower - as an effecto of LP filtering). Don't really know why. Wonder if anyone has a explanation.

author: open loop
author_rank: Regular Contributor
timestamp: December 09, 2015, 09:35:27 pm
content: The Electroslutch reminds me of what happened when I turned on my ZX Spectrum while the AM radio was on. Didn't the legendary Bill Herd say something about how a computer did not "sound" right during an amp hour because of its interference on an AM radio.Great work on it though would be interested in playing with the circuit myself when I get time.

author: rollatorwieltje
author_rank: Unknown
timestamp: December 09, 2015, 11:36:52 pm
content: Why would you use that Remoteboot thing when you can do the same with Wake on Lan? Many routers have it in their web interface. To my surprise I can even wake up my Macbook via wifi (from sleep mode, didn't try complete power off).

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: December 10, 2015, 12:48:06 am
content: Quote from: mrkva on December 09, 2015, 08:53:29 pmBuilt-in speaker would be the obvious one

author: SeanB
author_rank: Super Contributor
timestamp: December 10, 2015, 04:28:12 am
content: Quote from: rollatorwieltje on December 09, 2015, 11:36:52 pmWOL depends on sending a "magic packet" which is not transmittable out of the LAN. It is an Ethernet packet with the MAC of the card, and not TCP/IP, so will not traverse a router. Enabling a router to respond to WAN commands is not considered a good idea, there you really do want a very good security protocol, otherwise scans will find it and things happen afterwards.Sleep as well ( depending on the actual level) just means the screen is off, and the system is running at the lowest speed the processor can run at, along with all RAM swapped out and most applications not given any processing time, the processor only responding to interrupts and the hard drive being commanded to idle. Low power state, not off.I hope the OP is implementing very good security on the device, as it will either be open to packets via a DMZ on a router, or will be internet visible. Checking the sending side is within an acceptable network block ( reduce the sites that can attack to the IP block of the main user) along with using a good long password or PKI communications are really needed. There are enough vulnerable IOT devices out there already.

author: EEVblog
author_rank: Unknown
timestamp: December 10, 2015, 04:36:56 am
content: Quote from: mikeselectricstuff on December 10, 2015, 12:48:06 am+1

author: bitwelder
author_rank: Super Contributor
timestamp: December 10, 2015, 06:57:13 am
content: Quote from: kindiana on December 08, 2015, 04:20:17 amHow about making a version of the RemoteBoot with a different variant of the ESP8266 (perhaps the ESP-07) that has the antenna connector, so to bring the antenna outside the PC case?

author: rollatorwieltje
author_rank: Unknown
timestamp: December 10, 2015, 08:06:29 am
content: Quote from: SeanB on December 10, 2015, 04:28:12 amDave said he uses a VPN, so I assume he can already securely access his lab network from home. That's how I used it. My router was also a VPN endpoint, so I could open a VPN to it from anywhere, log in on the web interface and send the WoL packet. I used it to wake up a powered off (really off, as in shut down) desktop pc via ethernet.I was just surprised I could also wake my laptop, I thought WoL wasn't supported over wifi.

author: mrkva
author_rank: Unknown
timestamp: December 10, 2015, 06:15:58 pm
content: Quote from: EEVblog on December 10, 2015, 04:36:56 amThanks for the suggestion Dave and Mike! Any suggestions for low-part-count & high fidelity solutions for amp+speaker? I experimented with LM386, but I'd like to go more hi-fi with this one (more like "laptop speaker quality" - i don't expect wonders). Probably some monolithic Class D solution would be optimal for the amp, since battery life is important to me.

author: jancumps
author_rank: Unknown
timestamp: December 10, 2015, 08:25:39 pm
content: The on-board audio can be simple, just a tactical tiny mini speaker. You can always keep the audio-out plug that's already there for the audiophile user

author: Fungus
author_rank: Super Contributor
timestamp: December 10, 2015, 09:36:05 pm
content: Quote from: jancumps on December 10, 2015, 08:25:39 pmI imagine the stereo sound is useful to more than audiophiles...

author: Brumby
author_rank: Unknown
timestamp: December 10, 2015, 09:43:29 pm
content: ... like an EEVblogger.

author: sakujo7
author_rank: Contributor
timestamp: December 17, 2015, 01:13:32 am
content: Quote from: SeanB on December 08, 2015, 07:22:26 pmCan confirm that lower inductors work.I "built" a "poor man's" version by attaching a 470uH wire-wound inductor to a uCurrent (nA range, effectively a x100 amplifier with 10k input impedance). Output directly connected to headphones, though a series pot is a good idea if you value your hearing.

author: mrkva
author_rank: Unknown
timestamp: December 17, 2015, 07:01:05 am
content: From my experience higher values have more sensitivity & different frequency responses. 22mH/33mH seems to be optimal in combo with OPA2134 opamp, but I am also working on bigger hand-made antennas.BTW if anyone builds one, I'd love to see some pics!

author: Seekonk
author_rank: Super Contributor
timestamp: December 17, 2015, 08:12:43 pm
content: That ultrasonic transducer amplifier circuit that was mailed in with questions reminded me of a question on another forum. At least I hope that is this mailbag. That circuit has an interesting property. This other poster wasn't getting the gain that he expected from the resistor combination of the first inverting amplifier. It wasn't the op amp and everything was working as it should. I love simple circuits like this that have a built in feature. Can you guess what it is?

author: ondrejko0102
author_rank: Newbie
timestamp: January 01, 2016, 12:15:30 pm
content: Hi, I am from Slovakia too. Elektrosluch are two words - "Elektro" and "sluch" meaning "Electrical" "hearing" :-)PS: Happy New Year!?

author: harnon
author_rank: Regular Contributor
timestamp: March 22, 2019, 09:36:01 am
content: Just randomly watched this mailbag, @36:22 Dave comes within about 1mm of slicing his finger in half using the Crocodile Dundee knife