Author Topic: EEVblog #813 - Mailbag  (Read 16285 times)

0 Members and 1 Guest are viewing this topic.

Offline EEVblog

  • Administrator
  • *****
  • Posts: 29891
  • Country: au
    • EEVblog
EEVblog #813 - Mailbag
« on: November 03, 2015, 04:58:50 am »
Bumber Mailbag.
Guest appearance by Sagan



SPOILERS:
Sinclair / Thandar SC110 10MHz portable analog CRT oscilloscope form the 1980's!
Makerbeam by Chartup: https://www.chartup.com/index.php?cPath=1_2
A mystery device from a Police auction from Rossin Corporation
10MHz TCXO reference clock generator: http://www.bloguetronica.com/2015/08/gerador-de-relogio-gr10m.html
AST3TQ TCXO datasheet: http://www.abracon.com/Oscillators/AST3TQ.pdf
CC2541 Bluetooth microcontroller datasheet: http://www.ti.com/lit/ds/symlink/cc2541.pdf
Fitbit ripoff teardown
MMA955L Motion sensing pedometer datasheet: http://www.freescale.com/products/sensors/intelligent-sensors-and-sensor-hubs/motion-sensing-pedometer-platform:MMA9555L
Harbour Freight Cen-Tech multimeter teardown!

 

Offline crispy_tofu

  • Super Contributor
  • ***
  • Posts: 1124
  • Country: au
Re: EEVblog #813 - Mailbag
« Reply #1 on: November 03, 2015, 06:07:40 am »
Those Thandar/Sinclair SC110s (also called Thurlby SC110) show up on eBay once in a while for about US $50, some of them are even RS branded!  :-+
http://www.ebay.com/itm/Vintage-RS-SC110A-Thandar-Portable-Oscilloscope-/221840075629
Manual: http://www.kevinchant.com/uploads/7/1/0/8/7108231/thurlby_sc110-instruction-manual.pdf

And that cheapo multimeter is really similar to the DT-830, there are a lot of rebrands (there's a lot of them, some don't have transistor tester, backlight, etc.). They use the ICL7106 IC in these meters  ;) There's one at Jaycar (Digitech, $10) and one at Dick Smith (Digitor, in a shiny silvery plastic for $22).
There's even one that's UL listed, in case someone wasn't sure about the quality  :-DD
(Interestingly, it has CAT I on the front, unlike the Harbour Freight meter)
« Last Edit: November 03, 2015, 06:37:54 am by crispy_tofu »
 

Offline tec5c

  • Frequent Contributor
  • **
  • Posts: 422
  • Country: au
Re: EEVblog #813 - Mailbag
« Reply #2 on: November 03, 2015, 06:15:54 am »
Is it just me or does Sagan sound a tad British?
 

Offline EEVblog

  • Administrator
  • *****
  • Posts: 29891
  • Country: au
    • EEVblog
Re: EEVblog #813 - Mailbag
« Reply #3 on: November 03, 2015, 06:55:09 am »
There's even one that's UL listed, in case someone wasn't sure about the quality  :-DD

Just like the Batteriser is UL tested!  :-DD
 

Offline Dr Bob

  • Contributor
  • Posts: 6
  • Country: us
Re: EEVblog #813 - Mailbag
« Reply #4 on: November 03, 2015, 07:59:20 am »
The mystery sensor looks a bit like this patent from the same time frame:

http://www.google.com/patents/US4468658

dB
 

Offline Dr Bob

  • Contributor
  • Posts: 6
  • Country: us
Re: EEVblog #813 - Mailbag
« Reply #5 on: November 03, 2015, 08:03:42 am »
The first thing to do with those Harbor Fright meters is to delete the included battery before it leaks all over the place. I have a few of these meters that I've received for free at HF. They are handy to toss in a glove box or tool kit to have about for a bit of quick troubleshooting.

dB
 

Offline jwm_

  • Frequent Contributor
  • **
  • Posts: 317
  • Country: us
    • Not A Number
Re: EEVblog #813 - Mailbag
« Reply #6 on: November 03, 2015, 08:15:05 am »
The first thing to do with those Harbor Fright meters is to delete the included battery before it leaks all over the place. I have a few of these meters that I've received for free at HF. They are handy to toss in a glove box or tool kit to have about for a bit of quick troubleshooting.

dB

The battery isn't even alkaline, it is heavy duty meaning carbon-zinc construction. At least you can pull out some nice inanimate carbon rods from the batteries. They can save the day in a pinch.

Offline mrkva

  • Supporter
  • ****
  • Posts: 70
Re: EEVblog #813 - Mailbag
« Reply #7 on: November 03, 2015, 08:30:04 am »
Dave, I've sent you an item in August from Slovakia - did it arrive? Cardboard box, around 15x15x5 cm I have a tracking number, but all I get is that it left Slovakia.
 

Offline vk3yedotcom

  • Frequent Contributor
  • **
  • Posts: 535
  • Country: au
    • vk3ye dot com (radio articles and projects)
Re: EEVblog #813 - Mailbag
« Reply #8 on: November 03, 2015, 08:32:36 am »
My very wild guess for that sensor thing is a window microphone that could activate a tape recorder when someone talks. 

Or maybe it could be pointed at a mirror and detect any small movement due to talking?

Colin Mitchell might know ;)
If you're into amateur radio you might enjoy my books. Choice of 6. Electronic or paperback. Details here: http://home.alphalink.com.au/~parkerp/vk3yebooks.htm
 

Offline SteveLy

  • Regular Contributor
  • *
  • Posts: 220
  • Country: au
Re: EEVblog #813 - Mailbag
« Reply #9 on: November 03, 2015, 10:06:44 am »
Child labour - done right.
 

Offline EEVblog

  • Administrator
  • *****
  • Posts: 29891
  • Country: au
    • EEVblog
Re: EEVblog #813 - Mailbag
« Reply #10 on: November 03, 2015, 11:06:58 am »
Is it just me or does Sagan sound a tad British?

Probably Pepper Pig & Mr Maker!
 

Offline Deathwish

  • Supporter
  • ****
  • Posts: 1426
  • Country: wales
Re: EEVblog #813 - Mailbag
« Reply #11 on: November 03, 2015, 12:00:13 pm »
The mystery sensor looks a bit like this patent from the same time frame:

http://www.google.com/patents/US4468658

dB

Differential pyrolectic sensor ?
Electrons are typically male, always looking for any hole to get into.
trying to strangle someone who talks out of their rectal cavity will fail, they can still breath.
God hates North Wales, he has put my home address on the blacklist of all couriers with instructions to divert all parcels.
 

Offline Deathwish

  • Supporter
  • ****
  • Posts: 1426
  • Country: wales
Re: EEVblog #813 - Mailbag
« Reply #12 on: November 03, 2015, 12:05:19 pm »
Having watched Sagan take the nut driver from dad's hands and listened to him articulate himself I can only say this to him.

Dont worry mate, it wont be long before you can park dad in his wicker chair on wheels in the corner and watch him as he drools when you take over the show.  :-DD
Electrons are typically male, always looking for any hole to get into.
trying to strangle someone who talks out of their rectal cavity will fail, they can still breath.
God hates North Wales, he has put my home address on the blacklist of all couriers with instructions to divert all parcels.
 

Online mikerj

  • Super Contributor
  • ***
  • Posts: 2152
  • Country: gb
Re: EEVblog #813 - Mailbag
« Reply #13 on: November 03, 2015, 12:35:31 pm »
The first thing to do with those Harbor Fright meters is to delete the included battery before it leaks all over the place.

How do you delete a battery?  I never use cheapo included batteries in anything I actually care about keeping.
 

Offline WN1X

  • Supporter
  • ****
  • Posts: 75
  • Country: us
Re: EEVblog #813 - Mailbag
« Reply #14 on: November 03, 2015, 01:32:59 pm »
(Interestingly, it has CAT I on the front, unlike the Harbour Freight meter)

I love how the Cen-Tech meter is marked as being Cat II rated  :-DD
- Jim
 

Online Fungus

  • Super Contributor
  • ***
  • Posts: 10103
  • Country: 00
Re: EEVblog #813 - Mailbag
« Reply #15 on: November 03, 2015, 02:49:15 pm »
Don't complain, your meter has a fuse in it!

When I did my teardown video there were no fuses at all in either of mine.

...and an on/off switch! Luxury!!


PS: Yes, they're pretty damn accurate, rugged, too!


I want to know why they bother with the transistor tester. It's totally useless and costs them money.  You'd think that would be the first thing to go when they look at the build cost. :-//
« Last Edit: November 03, 2015, 02:58:15 pm by Fungus »
 

Offline max666

  • Frequent Contributor
  • **
  • Posts: 367
  • Country: at
Re: EEVblog #813 - Mailbag
« Reply #16 on: November 03, 2015, 03:53:15 pm »
...
PS: Yes, they're pretty damn accurate, rugged, too!
...

Some bloke having a swim with his meter. Where have I seen this method for testing multimeters before? 
 

Offline djQUAN

  • Frequent Contributor
  • **
  • Posts: 252
  • Country: ph
    • My DIY website
Re: EEVblog #813 - Mailbag
« Reply #17 on: November 03, 2015, 04:17:51 pm »
AFAIK Cen-Tech is the HF brand for their tools or something like that.

The multimeter PCB is not actually routed. It is cut (stamped?) with a cutter and die. Have a look at the PCB edges and they are kind of frayed, not the clean, smooth edge you get when they are milled.

It costs more to make the cutter but only a one time cost. Then cutting the PCBs is just stamping them out like cookie cutters.

The entire PCB outline is cut including the slots, large and odd shaped holes in just one step.

We did this where I used to work. The prototypes are done as we are all familiar with using milling and drills but once the PCB shape is finalized, the mass produced product will use the cookie cutter thing. I forgot what they call it in the industry.
 

Offline free_electron

  • Super Contributor
  • ***
  • Posts: 7234
  • Country: us
    • SiliconValleyGarage
Professional Electron Wrangler.
Any comments, or points of view expressed, are my own and not endorsed , induced or compensated by my employer(s).
 

Offline Towger

  • Super Contributor
  • ***
  • Posts: 1554
  • Country: ie
Re: EEVblog #813 - Mailbag
« Reply #19 on: November 03, 2015, 06:06:15 pm »
Those multimeters cannot be too dangerous.  My father managed to blow the tips off his probes, trying to measure the voltage across an immersion element...
He lived to tell the tail, but he still thinks there was something wrong with the meter, rather than 'user error'...
 

Offline woox2k

  • Regular Contributor
  • *
  • Posts: 54
  • Country: ee
Re: EEVblog #813 - Mailbag
« Reply #20 on: November 03, 2015, 07:18:56 pm »
You can't argue the fact that these free multimeters are great value for money. They still are reasonably accurate for everyday use. I agree that these shouldnt be used as a mains testers but for <50v everyday measurements they are fine.

About the safety, i own similar looking unbranded and even unfused meter. I once foolishly tried to measure a car battery when probes were in 10A plug... :palm: Needles to say i am still here to tell the story because apparently those "patented safety probe leads" acted as a fuse and the lead just broke in the middle instantly, i barely even saw the sparks coming off the battery terminals  :-DMM I still use that meter sometimes, with new cheap probes.
 

Offline Ampere

  • Regular Contributor
  • *
  • Posts: 73
  • Country: us
Re: EEVblog #813 - Mailbag
« Reply #21 on: November 03, 2015, 07:47:18 pm »
I have a few of those Harbor Freight meters. I keep one in my trunk. I wouldn't use them to measure any amount of current, but they're still quite useful to keep around for voltage or resistance measurements.
 

Offline Christe4nM

  • Supporter
  • ****
  • Posts: 241
  • Country: nl
Re: EEVblog #813 - Mailbag
« Reply #22 on: November 03, 2015, 08:28:42 pm »
That intro with EEVblog junior mark 1 is a keeper!  :)  I instantly gave a tumbs up before watching the rest of it.

About that multimeter; how about a high voltage test? It's been too long since we saw something being blown up  >:D
 

Offline Don Hills

  • Regular Contributor
  • *
  • Posts: 159
Re: EEVblog #813 - Mailbag
« Reply #23 on: November 03, 2015, 09:43:56 pm »
The battery isn't even alkaline, it is heavy duty meaning carbon-zinc construction. At least you can pull out some nice inanimate carbon rods from the batteries. They can save the day in a pinch.

Have you seen any carbon-zinc 9v batteries with cylindrical cells inside? All the ones I've seen have a stack of "pancake" cells inside.
 

Offline wojteks

  • Newbie
  • Posts: 3
  • Country: pl
Re: EEVblog #813 - Mailbag
« Reply #24 on: November 03, 2015, 11:07:24 pm »
On the topic of oldschool miniature CRO's - my recent eBay score:
https://www.eevblog.com/forum/testgear/oldschool-1972-polish-oscilloscope-ebay-score/
 

Offline Don Hills

  • Regular Contributor
  • *
  • Posts: 159
Re: EEVblog #813 - Mailbag
« Reply #25 on: November 04, 2015, 12:07:41 am »
On the subject of the Thandar scope:
The blue wire wrap winding on the transformer is almost certainly the filament power winding for the directly heated CRT tube.
 

Offline jnissen

  • Regular Contributor
  • *
  • Posts: 61
Re: EEVblog #813 - Mailbag
« Reply #26 on: November 04, 2015, 01:46:23 am »
(Interestingly, it has CAT I on the front, unlike the Harbour Freight meter)

I love how the Cen-Tech meter is marked as being Cat II rated  :-DD

Just depends on your definition of CAT! Meow!
 

Offline gordo51

  • Contributor
  • Posts: 10
Re: EEVblog #813 - Mailbag
« Reply #27 on: November 04, 2015, 02:07:53 am »
I can see it will not be too long before Dave2 is laid off and Sagan takes over. Pretty clever and articulate for a 4 year old.
One problem I have had with cheap multimeters is that they do not have a Lo Batt indicator. I was tearing my hair out once checking something with a cheap meter, Radio Shack I think, and finally concluded the meter was wrong. Turned out the 9v battery was way low. No cheap meters any more, just Fluke or Tektronix.
 

Offline crispy_tofu

  • Super Contributor
  • ***
  • Posts: 1124
  • Country: au
Re: EEVblog #813 - Mailbag
« Reply #28 on: November 04, 2015, 02:16:10 am »
One problem I have had with cheap multimeters is that they do not have a Lo Batt indicator.
I'm pretty sure the DT830 has a battery indicator on the bottom left of the LCD, but those multimeters tend to drift a lot when the battery is low, exactly what you describe.  :-+
 

Offline Alexei.Polkhanov

  • Frequent Contributor
  • **
  • Posts: 683
  • Country: ca
Re: EEVblog #813 - Mailbag
« Reply #29 on: November 04, 2015, 03:53:23 am »
 

Offline djQUAN

  • Frequent Contributor
  • **
  • Posts: 252
  • Country: ph
    • My DIY website
Re: EEVblog #813 - Mailbag
« Reply #30 on: November 04, 2015, 04:12:53 am »
I have seen a glass breakage detector with an internal lithium coin battery.

The battery runs the circuitry and the two wires are simply a normally open contact (open collector).

Maybe that is the case with the cell inside the intrusion detector.
 

Offline bills

  • Frequent Contributor
  • **
  • Posts: 350
  • Country: us
Re: EEVblog #813 - Mailbag
« Reply #31 on: November 04, 2015, 05:49:18 am »
What ever the battery is for it is no doubt dead by now,so it's purpose is moot. 
Never argue with idiots. They drag you down to their level and beat you with experience.
 

Offline AmmoJammo

  • Frequent Contributor
  • **
  • Posts: 782
  • Country: 00
Re: EEVblog #813 - Mailbag
« Reply #32 on: November 04, 2015, 08:30:06 am »
Is it just me or does Sagan sound a tad British?

Probably Pepper Pig & Mr Maker!

LMAO! I knew that when I heard him speak!  :-DD

Don't let him park his car on a 50 degree slope like Peppa Pig does though!
« Last Edit: November 04, 2015, 09:22:26 am by AmmoJammo »
 

Offline bookaboo

  • Frequent Contributor
  • **
  • Posts: 604
  • Country: ie
Re: EEVblog #813 - Mailbag
« Reply #33 on: November 04, 2015, 11:23:12 am »
Is it just me or does Sagan sound a tad British?

Probably Pepper Pig & Mr Maker!

Was thinking exactly that, we have the same problem here. The word generally used (slang if you want to call it that)  for mother here was "mammy", now all the 5 year olds including mine refer in an oxbridge tone to their "mum".
 

Offline f4eru

  • Frequent Contributor
  • **
  • Posts: 552
Re: EEVblog #813 - Mailbag
« Reply #34 on: November 04, 2015, 12:35:03 pm »
(Interestingly, it has CAT I on the front, unlike the Harbour Freight meter)

I love how the Cen-Tech meter is marked as being Cat II rated  :-DD

Just depends on your definition of CAT! Meow!

Probably it can hold the weight of two stacked cats.
 

Offline kfitch42

  • Frequent Contributor
  • **
  • Posts: 300
  • Country: us
Re: EEVblog #813 - Mailbag
« Reply #35 on: November 04, 2015, 03:24:58 pm »
Hearing about Kindergarten orientation, then watching Sagan play with those Makerbeam thingys made me think about what will happen the first time he gets a homework assignment along the lines of "Using common household object build a diorama of your community."

I suspect Sagan might end up leaving a wake of "reactive rules" as he progresses through school. The year after him will have lots asterisks on their assignments like "* High voltage power supplies and nixie tubes are NOT common household objects."
 

Offline Towger

  • Super Contributor
  • ***
  • Posts: 1554
  • Country: ie
Re: EEVblog #813 - Mailbag
« Reply #36 on: November 04, 2015, 03:35:51 pm »
Was thinking exactly that, we have the same problem here. The word generally used (slang if you want to call it that)  for mother here was "mammy", now all the 5 year olds including mine refer in an oxbridge tone to their "mum".

That depends on the area you are from. We never said mammy, my 5 year old says mummy and the 8 and 9 have progressed to 'Mother', in a posh accent...
 

Offline Stonent

  • Super Contributor
  • ***
  • Posts: 3824
  • Country: us
Re: EEVblog #813 - Mailbag
« Reply #37 on: November 04, 2015, 05:00:37 pm »
We can't have Sagan getting a British accent, we need to start him watching old episodes of Mr. Wizard and we can Americanize him.

Heathkit Hero 1 Mini Teardown:



Sounds like Hero has a Votrax SC01 accent.
« Last Edit: November 04, 2015, 05:06:25 pm by Stonent »
The larger the government, the smaller the citizen.
 

Online SeanB

  • Super Contributor
  • ***
  • Posts: 15118
  • Country: za
Re: EEVblog #813 - Mailbag
« Reply #38 on: November 04, 2015, 05:33:46 pm »
Thandar/TTI/whatevertheyarenow made a whole range of test equipment in that same case, all using the same front panel switches and knobs. The scope was the one, and there was a function generator as well. All battery powered.

I still have a SC110A I got in school many years ago. It worked well for many years till it finally died. I should look to see if I can fix it some day, as I can now get the manual online for it. IIRC it was a $200 scope, my dad bought it in Hong Kong on a business trip to Japan when he went to Toyoda to see the Toyota works. Still have a paper picture of Mt Fujii on the wall, apparently they are collectors pieces now. He went on a tour there with Toyota, and this was one of the places he visited and this was a gift.
 

Offline apis

  • Super Contributor
  • ***
  • Posts: 1668
  • Country: se
  • Hobbyist
Re: EEVblog #813 - Mailbag
« Reply #39 on: November 04, 2015, 11:46:55 pm »
I got a couple DT830 from ebay for 1$ including shipping (each), what surprised me was that there are different versions, some crappier than others. They probably use the same chip but circuitboard and the cases were different, one didn't even have a trimmer pot.

And wrt the alcohol tester, Iv'e seen a teardown of a alcohol tester that works, it had an air pump so it could sample a known volume of air and the sensor had to be calibrated regularly. That one from ebay must have had some very nice sensor in it, or maybe not. ::)
 

Offline bookaboo

  • Frequent Contributor
  • **
  • Posts: 604
  • Country: ie
Re: EEVblog #813 - Mailbag
« Reply #40 on: November 05, 2015, 10:31:13 am »
Was thinking exactly that, we have the same problem here. The word generally used (slang if you want to call it that)  for mother here was "mammy", now all the 5 year olds including mine refer in an oxbridge tone to their "mum".

That depends on the area you are from. We never said mammy, my 5 year old says mummy and the 8 and 9 have progressed to 'Mother', in a posh accent...

Im in the north west, I always thought Mammy was standard across the board? Im thinking south Dublin the exception. Certainly never heard "mother" or "mum" until recently :)
 

Offline Robomeds

  • Frequent Contributor
  • **
  • Posts: 391
  • Country: us
Re: EEVblog #813 - Mailbag
« Reply #41 on: November 05, 2015, 03:36:59 pm »
There are many many different 830 meter designs.  The HF ones seem to be the cheapest (price and construction).  But even the HF meters vary quite a bit.  Just from threads around here...
https://www.eevblog.com/forum/reviews/harbor-freight-cen-tech-90899-small-teardown/msg181243/#msg181243
https://www.eevblog.com/forum/reviews/harbor-freight-cen-tech-90899-small-teardown/msg181264/#msg181264

Non HF versions
https://www.eevblog.com/forum/testgear/world's-cheapest-multimeter-teardown/

I've wounder if the meter in question was adjusted before being sent to Dave.  I've tested perhaps 6 or 7 of these things against other meters (Fluke 87-3 and 87-5, not true calibration equipment) and found none out of spec and most within a few counts.  That does speak well of the IC used in the things.  Currently I have I think 5 of them.  3 in the pile, one in each car.  The local school was throwing them out (maybe someone pointed out the near total lack of safety circuitry) so I picked them up as give aways and back of the car meters.  I see them as better than nothing if you know their safety limits.  Never my first choice. 
 

Offline bloguetronica

  • Frequent Contributor
  • **
  • Banned!
  • Posts: 354
  • Country: pt
Re: EEVblog #813 - Mailbag
« Reply #42 on: November 07, 2015, 06:52:12 pm »
Dave, first of all I want to thank you for the excellent review you've made on the GR10M board I've sent you.

You did point some valid aspects, some of which I can't implement due to the nature of the project and the enclosure used of it, which is an Hammond 1455D601. I guess where won't be space for holes (nor need to) or BNC connectors. I know the SMB connectors are not very durable, but the other option would be to go for SMA, which is even worse IMHO. However, the voltage rating idea printed on the silkscreen is a nice feature that I've already implemented on my next project, and all thanks to you.

I'm worried about the state of your board, since F1 seems chipped to me. I could swear the board seemed to be fine when I sent it to you. Since I never wished to sent you something that is broken (or got broken during transportation), I can send you a replacement polyfuse. Please, could you confirm if F1 is damaged? Thanks in advance.
 

Offline twice11

  • Contributor
  • Posts: 30
  • Country: de
Re: EEVblog #813 - Mailbag
« Reply #43 on: November 08, 2015, 01:37:06 pm »
I'm pretty sure the DT830 has a battery indicator on the bottom left of the LCD, but those multimeters tend to drift a lot when the battery is low, exactly what you describe.  :-+

Actually, the 7106-based 9V multimeters are quite good at handling low battery. The configuration is basically a zener diode for the reference voltage which is tapped by the pot together with fixed resistors to produce 100mV. Typically the LCD gets unreadable before the values get inaccurate (only exception: on a weak battery, the current drive in ohms range may fail early, producing garbage readings, even if the leads are open-circuit).

I really got bitten by a much higher-priced 3.75 digit autoranging multimeter that displayed "-3.785 V" or something like that in auto-range volts with -7V applied. When manually switchted into the 40V range, display was OK. Obvisously with the low battery the output common mode range of the input ampliefier (the 7106 don't even have such a thing!) was exceeded before the output voltage was low enough to trigger the range switch. The "lo batt" indicator of that meter was *NOT* turned on at that point. Utter fail! (I fail to remember the brand or model, though. The case was yellow...)
 

Offline Poe

  • Regular Contributor
  • *
  • Posts: 209
Re: EEVblog #813 - Mailbag
« Reply #44 on: December 31, 2017, 07:54:50 pm »
Sorry for bumping an old thread, but I wanted to add some points regarding the cheap meter.

The small/large PCB arrangement not only improved PCB area usage, but also reduced the main board's copper weight to half ounce or less.  The small board appears to be 2 or 3 ounce copper for the current shunt.

Not that they needed that thick copper, the probe wires have fewer than five strands of 30AWG wire!  I had one with only three strands in each wire.   10A results in 5 to 8W of heat before the wires melt.

V-score is cheaper than routing, but even that would be too expensive.  Both of these boards are punched, including the plated through holes.


 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf