EEVblog #964 - Mailbag - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: January 17, 2017, 06:48:59 am
content: SPOILERS:Educational kits fromhttp://tronclub.com/Electro-permanent magnet for UAV's and drones from NicaDronehttp://nicadrone.com/index.php?id_product=13&controller=productCisco VOIP phone teardown1980's GE Cordeless phone teardownOpen source USB charger:http://www.bloguetronica.com/2016/12/modulo-carregador-usb-ucharge-rev-1.htmlSTM32 Development board:https://www.tindie.com/products/maxtch/arduino-compatible-stm32f103c-development-board/Max Chan is for hire:https://en.maxchan.info/

author: Kelbit
author_rank: Regular Contributor
timestamp: January 17, 2017, 07:22:51 am
content: Is that the new EEVBlog meter we're seeing? Looking forward to the the full video on it.

author: Brumby
author_rank: Unknown
timestamp: January 17, 2017, 08:59:37 am
content: That electro-permanent magnet is very neat.

author: elgonzo
author_rank: Unknown
timestamp: January 17, 2017, 09:20:53 am
content: You look for something that will enthuse your young one for mechanical engineering? Get an educational IKEA furniture kit.You are interested in wood-working, but aren't sure whether you should invest much in tools or whether your interest will last longer? Why not start with a reasonable priced educational IKEA furniture kit?You just want to build some cool thing? Want to share it or gift it to friends?Something convenient, a gift that keeps on giving? Get an educational IKEA furniture kit.I love these kits. They are sooo educational...In all seriousness, many of these kits teach as much about electronics (or programming, for that matter) as IKEA furniture teaches about mechanical engineering and "wood"working...

author: loomx
author_rank: Newbie
timestamp: January 17, 2017, 09:26:34 am
content: @Dave:Regarding the LowZ-Mode on the BM235: I noticed this "error" myself and got in contact with the German distributor Marco (Welectron.com). He told me that he got in touch with Brymen and this is the intended behaviour (and has been through all firmware versions). For whatever reason, they don't include that in the specifications. He mentioned that they didn't know if this might be changed in the future or if Brymen might just change the specs.Marco provided me with the test report attached.I should have reported that earlier (and possibly prevented that return) but at least this mailbag gave me a reason to register on the forum . Sorry about that

author: McBryce
author_rank: Super Contributor
timestamp: January 17, 2017, 12:00:30 pm
content: The "upside down button" design on the Cisco phone is quite common for this type of application. It avoids the button being damaged by people slamming the phone or beating on the button with their finger (as is very common). The pressure on the button can only come from the spring so it's always the same and the expected lifetime can be guaranteed. The hairpin spring ensures that the spring can't get over or under extended over its lifetime.McBryce.

author: technix
author_rank: Super Contributor
timestamp: January 17, 2017, 01:18:45 pm
content: Thanks for starring my item, although it took an exceptionally long time... (I will just keep marking my packages with the words "From Shanghai With Love" so you can tell my packages from Chinese Ebay items)I have got a Arduino-likecore ready but there are still problems not sorted out. Schematics are available for those who are brave enough to explore though.

author: iaeen
author_rank: Regular Contributor
timestamp: January 17, 2017, 02:37:01 pm
content: Normal service is resumed, WooHoo!The force is strong with the tronclub kits. I'm seriously considering signing up... Thanks for sharing!Also looking forward to seeing the "super secret" multimeter come out of hiding. You're killing us with all these teases.

author: Fungus
author_rank: Super Contributor
timestamp: January 17, 2017, 04:33:14 pm
content: Quote from: McBryce on January 17, 2017, 12:00:30 pmWhy do people do that? Is it just hollywood or do people do it in real life when the connection is lost? There's absolutely no way it will reconnect you or fix anything.With practice you can bang on the 'hook' switch to dial the number. Just bang it N times quickly/rhythmically to dial the number N, eg. bang it twice to dial a '2'. Pause between each number.The reason it works is because that's how those old mechanical dial phones dialed the numbers. The dial would simply make/break the switch contact N times as it returned from number N. You're just emulating that.It's quite easy with a bit of practice and totally defeats those old dial locks, leaving no trace.Edit: Aren't you supposed to put the lock on the number '1'? Putting it on '0' achieves nothing - you can still turn the dial.

author: slicendice
author_rank: Frequent Contributor
timestamp: January 17, 2017, 05:26:29 pm
content: That Tron-Club kit subscription looks really nice. And as you said, it's bargain.On their site they claim you'll get over 252 circuits per year to keep you occupied. That is AWESOME!Think I might start subscribing for both kits and build circuits with my kids.Hope Tron-Club will become successful and stay in business for a long time.

author: nctnico
author_rank: Super Contributor
timestamp: January 17, 2017, 05:28:47 pm
content: Just a remark about the Cisco phone teardown and the comments about the copper pattern on the PCB: having an even pattern distribution on a PCB is still important nowadays. Some manufacturers (like Eurocircuits) will break your balls if you have large empty (=no copper) spaces on a design because it will make it harder for them to produce the PCB reliably. See:http://www.eurocircuits.com/Plating-index

author: sleemanj
author_rank: Super Contributor
timestamp: January 17, 2017, 06:37:44 pm
content: Quote from: Fungus on January 17, 2017, 04:33:14 pmAn interesting fact, here in New Zealand the order of numbers on a pulse dial phone was reversed, to dial 1, there were 9 pulses! There is no real conclusive answer as to why that happened, various opinions range from protecting local manufacture, to iust "that's just what the guy in charge decided on the day".I remember i first learned about this oddity when I bought my first modem and there was a note about pulse dial (ATDP) in NZ, i don't remember how it was worked around in the modem now since by that time we had been tone dialling for a few years, push button phones having been installed at home to much amazement in, i think, 1988, maybe 89

author: capt bullshot
author_rank: Super Contributor
timestamp: January 17, 2017, 07:07:59 pm
content: Quote from: Fungus on January 17, 2017, 04:33:14 pmYes, but you can't dial "0", which keeps you from long distance calls. In former times local calls were kind of flat (pay per call, not per seconds), but long distance calls were really expensive (like pay per every 20 sec or 40 sec)

author: Fungus
author_rank: Super Contributor
timestamp: January 17, 2017, 07:19:59 pm
content: Quote from: sleemanj on January 17, 2017, 06:37:44 pmWeirdosIn theory they have to keep the exchanges backwards-compatible forever so it will still work. I haven't got a phone here to try it but I did it about six months ago as a party trick.nb. I actually know why they bash on the hook in the movies. In the very old days the operators had lights on their consoles and it made the light flash to get their attention. The operator would then connect to your line and you could talk to them...)Quote from: sleemanj on January 17, 2017, 06:37:44 pmYes, modems would have been fun. You'd have to do math on the number to be able to dial it.

author: Fungus
author_rank: Super Contributor
timestamp: January 17, 2017, 07:23:04 pm
content: Quote from: capt bullshot on January 17, 2017, 07:07:59 pmYou'd have to put it in the '9' for that.

author: PeterL
author_rank: Regular Contributor
timestamp: January 17, 2017, 09:40:17 pm
content: @25:00If you order a pcb at eurocircuits, you can preview your order in their 'PCB visualizer'. On their they show you a simulation of the copper plating, and also calculate a 'Copper Plating Index'. It shows you if you can expect trouble with regards to the plating.And nowadays you won't run into trouble fast, but I have had a few boards that were oversized for mechanical reasons, on which this plating index was to low.Anyway, if you want to learn more about copper plating this tool if really helpful.

author: slicendice
author_rank: Frequent Contributor
timestamp: January 17, 2017, 09:44:02 pm
content: Quote from: Fungus on January 17, 2017, 07:23:04 pm00358 is the number to dial if calling to Finland, I don't see any 9 in there..besides that lock makes sure the whole dial won't move at all. If it'd move then it'd be possible to call anywhere anyways.

author: Fungus
author_rank: Super Contributor
timestamp: January 17, 2017, 09:59:53 pm
content: Quote from: slicendice on January 17, 2017, 09:44:02 pm00358 is the number to dial if calling to Finland, I don't see any 9 in there..besides that lock makes sure the whole dial won't move at all. If it'd move then it'd be possible to call anywhere anyways.Does this image help? The important part is the metal bit which your finger hits when you turn the dial.(which is actually a totally brilliant design BTW. Whoever thought of that is a genius)

author: Zbig
author_rank: Frequent Contributor
timestamp: January 17, 2017, 10:01:56 pm
content: Quote from: Fungus on January 17, 2017, 07:19:59 pmI always wondered why there was a button on landline phones that generated brief "on hook" - "of hook" pulse and was labelled "Flash". Didn't seem to do anything useful yet pretty much every keypad-based phone around here had one. Finally, the mystery is solved! ThanksBTW, regarding slamming of the "hook" contact - we had Siemens sets in our office few years ago that had optical (IR-based) sensor; no moving parts at all. It was rather funny watching people swirling their fingers around the headset cavity when they were trying to break the connection in order to make a new one without actually putting the headset down and back up again. Looked kind of like they were stirring an invisible cup of tea with their fingers.EDIT:After jogging my memory a little, now I remember those "Flash" buttons weren't really that useless, after all. At least on some exchanges over here, they were used, in sequence with DTMF keys, for functions like switching to waiting call and such. At least now I know the origin of the "Flash" label.

author: Co6aka
author_rank: Unknown
timestamp: January 17, 2017, 10:44:35 pm
content: Hey Dave, you actually pronounced it right!!!"Nee-ka-ra-gyou-wah"Have a hear here:

author: Cerebus
author_rank: Super Contributor
timestamp: January 18, 2017, 02:11:49 am
content: Yeah, that Cisco 7961. The hook switch is known, possibly even notorious, for being 'sticky' after the phone has been in service for a while. Phone rings, you grab the handset and the phone carries on ringing.One reason for having the hook switch engineered the way that it is that they needed a PCB at that point anyway. On that board there's a LED used as the 'message waiting' light. The LED connects to a light pipe in the cradle that shines onto another light pipe that goes all the way through the top of the handset. It actually works really well and is easy to spot.There's, I suspect, quite a lot of DSP goodness hidden inside the Cisco branded chip and a fair bit of CPU grunt as it has to have the horsepower to run end-user 'enterprise' Java applications on the phone on top of all the basic IP phone stuff. The phone's firmware package, if unzipped, contains separate firmware for the DSP. The DSP side of things is used to handle the various voice, and in other models in the range, video codecs and to run the genuinely excellent hands-free capability of the phone. From memory the CPU is a MIPS 32 implementation. Oh and there's a 2 port ethernet switch built in as well so that your PC and phone can share a single wall socket.

author: boffin
author_rank: Unknown
timestamp: January 18, 2017, 02:42:06 am
content: Is it wrong that I made a bowl of popcorn to watch mailbag ?Do I need to join a support group?

author: Brumby
author_rank: Unknown
timestamp: January 18, 2017, 02:51:47 am
content: Not at all.Just make a bit extra next time and share it around...

author: Brumby
author_rank: Unknown
timestamp: January 18, 2017, 02:56:20 am
content: Quote from: Fungus on January 17, 2017, 04:33:14 pmYes - with pulse dialing it doesn't take much to learn how to do it - and reliably. Never had to use it on "locked" phones though. I just did it so I knew I could.

author: EEVblog
author_rank: Unknown
timestamp: January 18, 2017, 03:06:07 am
content: Quote from: loomx on January 17, 2017, 09:26:34 amThanks.Manual now updated.

author: EEVblog
author_rank: Unknown
timestamp: January 18, 2017, 03:09:19 am
content: Quote from: nctnico on January 17, 2017, 05:28:47 pmThanksNever had a manufacturer complain about this before.Incredibly common to have little copper on your outer layers when you are using internal ground planes.

author: kalleboo
author_rank: Regular Contributor
timestamp: January 18, 2017, 04:03:43 am
content: Quote from: sleemanj on January 17, 2017, 06:37:44 pmSweden also has a slightly "modified" pulse-dialing system. It's not reversed, but the 0 is before 1 rather than after 9. So 0 is one click and 1 is two clicks (and so on).

author: Dave
author_rank: Super Contributor
timestamp: January 18, 2017, 04:11:56 am
content: To demagnetise a ferromagnetic material, you need to repetitively drag it through progressively smaller hysteresis loops (see image).The flux inside the magnetic circuit goes through zero many times during that process, therefore the metal that is stuck to it gets released and grabbed again multiple times, making the noise as it repetitively bangs against the magnet.F*cking magnets, how do they work?

author: McBryce
author_rank: Super Contributor
timestamp: January 18, 2017, 09:00:16 am
content: Quote from: Fungus on January 17, 2017, 04:33:14 pmThe answer is in the picture you included, if it was on 1 you couldn't call the emergency services "999" in the UK. Putting it on 0 means you can only call local numbers or the emergency services.I don't think the "banging out the number trick" works in Germany since they went to digital telephone exchanges, the new exchanges only react to DTMF dial tones.McBryce.

author: Fungus
author_rank: Super Contributor
timestamp: January 18, 2017, 09:15:34 am
content: Quote from: McBryce on January 18, 2017, 09:00:16 amI never thought of that.But still, putting it in the zero only works psychologically. You can still dial a '0' but you turn the dial using the lock instead of putting your finger in the zero hole.Quote from: McBryce on January 18, 2017, 09:00:16 amIt should still work. It has to be backwards compatible with old telephones.(Unless they forced everybody to change their phone, which is possible I guess)

author: Terrius
author_rank: Contributor
timestamp: January 18, 2017, 09:44:18 am
content: I look forward to the exploding capacitor video! Though I think a small portion of the "fun" might be lost in not being there to experience the smell! No better smell (hmm or perhaps nothing more awful) than old electronics burning!That Tronclub thing is really cool, Does anyone know if they will only send the items once per month? or if once you finish one project you can pay for the next month and get them to send the next kit?

author: McBryce
author_rank: Super Contributor
timestamp: January 18, 2017, 11:41:10 am
content: Quote from: Fungus on January 18, 2017, 09:15:34 amNope, the lock stopped it from going far enough. It hit that metal hook thing, so it dialed a 9 instead of a 0 if you dialed with the lock on.The exchanges aren't backwards compatible. As far as I can remember they announced at some stage that the old phones wouldn't work anymore. At the time you only had the choice of Deutsche Telekom as service provider and the phone itself was part of the contract, so you could go in and swap it for a new one.McBryce.

author: bktemp
author_rank: Super Contributor
timestamp: January 18, 2017, 11:52:38 am
content: Quote from: McBryce on January 18, 2017, 11:41:10 amIf you still have the old analogue phone line and haven't upgraded to ISDN or DSL, the old pulse dial phone should still work. I know somebody who used one until last year.

author: Zbig
author_rank: Frequent Contributor
timestamp: January 18, 2017, 12:04:30 pm
content: Quote from: McBryce on January 18, 2017, 11:41:10 amThey are - to some extent - or at least they could be, if needed. I'm not sure if that's still the case in Poland (don't have a landline), but you could still use pulse dialing alongside DTMF here for ridiculously long into 21th century. Might or might not be related to low average wages and inability and/or unwillingness to get a new phone (you bought your own on the open market here) for considerable part of the userbase.

author: Fungus
author_rank: Super Contributor
timestamp: January 18, 2017, 12:16:28 pm
content: Quote from: McBryce on January 18, 2017, 11:41:10 amI haven't got one to try but I find hard to believe it wouldn't dial a zero if you turned the dial until the lock touches the metal hook. The lock only prevents a couple of mm of travel at the most. That's no worse than holding your finger at the wrong angle.

author: McBryce
author_rank: Super Contributor
timestamp: January 18, 2017, 01:57:40 pm
content: Quote from: bktemp on January 18, 2017, 11:52:38 amI think it may depend on where you live too. I don't think it's possible to have an analogue line anymore in Cologne.@Fungus: That is enough to stop the 0 from working, or at least it was with the phone we had at home when I was a kidIt's only about a 4 or 5mm difference, but it hangs over the number 9 hole and definitely didn't let you get a zero. My father had pretty fat fingers and regularly dialed wrong numbers because of it. My girlfriend of the time lived relatively near to us, but we were at the county border and she had a different area code.McBryce.

author: twice11
author_rank: Contributor
timestamp: January 18, 2017, 10:07:56 pm
content: Quote from: Terrius on January 18, 2017, 09:44:18 amThese Rifa capacitors are known as "Knallfrosch" ("firecracker") in German vintage HiFi forums. Most HiFi enthusiasts don't share the excitement about them exploding, though.

author: bluetopia
author_rank: Newbie
timestamp: January 19, 2017, 03:14:56 am
content: I've signed up for TronClub, I've been wanting to get back into electronics again. (Also Hello everyone!)When I heard they were based out of Canada, I assumed that they'd be pulling the same trick that my VOIP provider does; primarily operates in Canada, but charges everything in USD. But as it turns out, it was $25 CDN for me. Score!The only thing I'm not particularly happy with is the fact you can't set up both the beginner/advanced subscriptions easily on the site. Couldn't figure out how, and I wanted to get the microcontroller starter kit as well. But at least they will let you swap between the two series without issue; you receive whatever your next kit is in the chosen series, and they keep track of which kits you've received, so you shouldn't receive the same kit twice.Once I get my first kit, I'll be flipping it to get the first micro kit as well.

author: Fungus
author_rank: Super Contributor
timestamp: January 19, 2017, 09:34:23 am
content: Quote from: McBryce on January 18, 2017, 01:57:40 pmI would have expected the switch point to be a bit further back (for people like your father). Maybe it varies between phones. I don't have any to test so I bow to experience.

author: McBryce
author_rank: Super Contributor
timestamp: January 19, 2017, 11:51:31 am
content: I must ask my father if he still has that old phone. It would make a quick but interesting teardown. Maybe I could convert it to DTMF to use as a cool retro device.McBryce.

author: bktemp
author_rank: Super Contributor
timestamp: January 19, 2017, 12:18:24 pm
content: Quote from: McBryce on January 19, 2017, 11:51:31 amIf the teardown is too quick, try understanding how everything works (the schematic should be available for most phones, because there aren't many different models). A lot of clever engineering went in designing those old phones to make them simple and reliable.

author: McBryce
author_rank: Super Contributor
timestamp: January 19, 2017, 01:23:40 pm
content: I doubt it contained anything more than switches and a bell. It looked something like this.I'll be back home (Ireland) in a few weeks and go looking.McBryce.

author: bktemp
author_rank: Super Contributor
timestamp: January 19, 2017, 01:42:25 pm
content: It is a bit more complicated than just a switch:http://macao.communications.museum/eng/exhibition/secondfloor/MoreInfo/2_6_1_DTMF.htmlhttp://www.britishtelephones.com/dial1.htm

author: McBryce
author_rank: Super Contributor
timestamp: January 19, 2017, 03:04:17 pm
content: Quote from: bktemp on January 19, 2017, 01:42:25 pmCool, that will make an interesting teardown (if I can find it).McBryce.

author: rrinker
author_rank: Super Contributor
timestamp: January 20, 2017, 01:46:14 am
content: I have that exact model Cisco phone on my desk at work. Yes, we still use old crap. About half of them got stuck buttons, those were replaced by new models. The ones that never got stuck, pretty much never will. Yes, they are super slow to boot up - the processor is really too slow to run all that java overhead garbage. Once running it's generally fine but you really can see the screen refresh when you do something that calls up info on it.

author: nctnico
author_rank: Super Contributor
timestamp: January 25, 2017, 03:12:27 am
content: Quote from: McBryce on January 19, 2017, 11:51:31 amHere is a reverse teardown from James May 'The Reassembler':

author: crashputer
author_rank: Newbie
timestamp: January 31, 2017, 05:42:22 am
content: Quote from: slicendice on January 17, 2017, 09:44:02 pmI don't know how other countries built their telecom systems, but in America it was entirely possible to dial the phone on old-style analog systems, even with the lock installed. The tapping seen in classic movies is the same as dialing the rotor -- tapping the receiver 10 times would dial the operator, or you could tap a complete telephone number by using the corresponding number of taps with about a second pause between numbers.Edit: Apparently 20 people already answered this before I did, and more, haha.