EEVblog #513 - Mailbag

[alm]

It looks like there are some hand-drawn polarity indicators on the board, indicating where the tab should be, though in a non-standard way, so I can easily see how one might miss those.

I think everyone working with ribbon cables and non boxed headers will have plugged in the ribbon cable wrong, either upside down or offset by 1 pin, at some point. Usually no magic smoke escapes, fortunately.

[c4757p]

I think everyone working with ribbon cables and non boxed headers will have plugged in the ribbon cable wrong, either upside down or offset by 1 pin, at some point. Usually no magic smoke escapes, fortunately.

My very first PC was a junk IBM PC-XT. I remember that having a lot of open headers, and either some of them actually completely lacked a polarity indicator, or I never managed to find it. I reversed cables in that thing numerous times. It took it just fine, though. It's something I always try to keep in mind when designing connections now - they should always be able to survive a reversed cable. Often, that can be achieved with a bit of care in choosing the pinout, without adding any reverse protection components or anything. Even if they are shrouded, some plugs and receptacles are made just poorly enough to mate backwards with very little extra force.

I've never plugged them in offset, though. The trick to that is to hold the plug on both ends with a finger extending past the bottom, so your finger will hit any pins that are off to the side. It's a good habit to get into. Doesn't work so well with flush connectors like on the end of an IDE hard drive, but it works for standard headers with space around them.

I always take it as a sign of quality design when a device can survive a fool mucking about on the inside.

[Zbig]

Exactly, that was my experience with PC ATA interface as well - the telltale sign was the drive activity LED being constantly on but besides that - no damage done. The thing with my design was that by messing it up this particular way, I not as much got it 180 degrees wrong but rather "inside-out", which just happened to cause +5V and GND being swapped. If I remember the post-mortem correctly, it turned out some buffers/level shifters actually passed this reversed polarity voltage all the way to the COG LCD driver.

[alm]

A simple crowbar across the rails would probably also have saved it. Now the LED driver with the hole in it effectively acted as an expensive crowbar diode. But yes, designing the connector so it survives reversing is good practice. Not that I would blame people building a one-off (few-off?) as a hobby for not going through that much trouble, you can't expect them to pay attention to every detail like a big manufacturer like Rigol .

[c4757p]

I pay attention to all the details...

...by swearing at them when they blow up my circuit.

[crisr]

This was a good mailbag episode! Not only great stuff, but good timing as well! Too bad about the burnt BTTF clock, though...

[Stonent]

I think that Dave should somehow mount the time circuits in his car, no matter what the model and just do a drive around video.

[staxquad]

don't know how good Belgian beers are?

they are the BEST (and if they find a great one from another country, they adopt it, like Gordon’s Highland Scotch Ale ABV: 8.5 % which the Scots don't drink anymore, they're into lager piss now)

Westmalle, a Trappist Ale; Duvel, beguiling  , usually available in Ontario; Kwak with licorice  (got maybe 6 left of those), nice glass;  Timmermans, Liefmans, Belle Vue, Jacobins, St Louis, all  Krieks, (cherry), (I was fond of Liefman's cassis until they discontinued it); Hoegaarten White and Forbidden Fruit (coriander); Delirium tremens (desperate to try); lots of Doubles and Tripples; Palm Speciale (a Michael Jackson favorite, no not that one, the other one); and the others I've not had the pleasure.

honorable mention for greats not in the postcard: Rodenbach, Rochefort, Orval, St. Bernardus, Chimay, La Trappe and maybe another 500 others

I wait for du Boucanier 6 packs every Christmas just for the Red Ale (easy to get Belgian beer in Toronto, not so easy in the sticks, they bring in a few at Christmas time, the rest of the year, none, damn fascist LCBO )

[jancumps]

La Trappe is Dutch.

[Mike S]

I remember seeing a case of Duvel at a fancy beer store with a price tag of $90 and always wanted to know what it tastes like.

[Hypernova]

Regarding the dodgy decimal on jmedved's board, since I used the same ones in my oven controller I am guessing that he figured that since he didn't need it he didn't connect it. These particular LCDs need to be driven with AC at 4Hz so charges were being coupled to that floating segment via their Common.

As for why the ranges go up to amps there are alarming numbers of USB implementations where the 5V supply is just connected directly to the 5V rail of the PSU so that port will happily deliver several amps. I have an old ASUS laptop that have no trouble powering a external 2.5" drive rated for 1A originally meant for laptop internal use.

[free_electron]

the best is missing : westvleteren. it has won the title of best beer in the world multiple years ...

it is still made by the monks according to a recepy predating the world war ...
production is so limited you have to call a special phone number to make reservations. when youi go buy it they write down your phone number and licence plate. you can only buy once every few months ... and limited in quantity.
simply because the brewery is small and the beer needs aging ... they can't produce more.  the monastery is a non-profit ...

http://en.wikipedia.org/wiki/Westvleteren_Brewery

[Medo]

Regarding the dodgy decimal on jmedved's board, ..

Dodgy decimal has since been fixed in gerbers. Anyone grabbing them now should have no issue.

[nitro2k01]

Ah, you've finally equipped the biological project with dual thumb technology!

[mickpah]

Mailbag galore.
Dave screws up and releases the magic smoke on the best mailbag item ever. Turns a light bulb on with his mobile phone, and goes underwater in a submarine.
And a cameo appearance by everyone's favorite.
http://shackspace.de/
http://lightdream.com.au/
http://www.avbotz.com/
http://jmedved.com/usbamps

cheer up Dave - try this http://ldd.lego.com/en-us/   Lego CAD !!! - so good to be a dad.

[rollatorwieltje]

cheer up Dave - try this http://ldd.lego.com/en-us/   Lego CAD !!! - so good to be a dad.

Too bad Lego removed the link to the Pick-A-Brick store. I have designed several things with LDD, but it's a bit of a gamble what colors are available. Really annoying when you selected some bricks and they turn out to be unavailable....

[iloveelectronics]

Too bad Lego removed the link to the Pick-A-Brick store. I have designed several things with LDD, but it's a bit of a gamble what colors are available. Really annoying when you selected some bricks and they turn out to be unavailable....

Have you tried bricklink.com?

[rollatorwieltje]

Too bad Lego removed the link to the Pick-A-Brick store. I have designed several things with LDD, but it's a bit of a gamble what colors are available. Really annoying when you selected some bricks and they turn out to be unavailable....

Have you tried bricklink.com?

I know, I just thought it was a nice feature to be able to design and order your model directly from Lego. I guess it was too expensive (you even received a custom box).

Which, on a side note, would be a great feature for PCB design tools. Having a parts list that's synchronized with the availability of Digikey / Element14. Saves the mindless browsing though those sites looking for part numbers that are in stock.

[NickS]

This just popped in to my inbox: http://dx.com/p/usb-av-usb-power-current-voltage-tester-translucent-blue-silver-235090
USB power meter for $6.40 delivered. Arguably not as good but I found the timing interesting.

[FrankBuss]

This just popped in to my inbox: http://dx.com/p/usb-av-usb-power-current-voltage-tester-translucent-blue-silver-235090
USB power meter for $6.40 delivered. Arguably not as good but I found the timing interesting.

Looks interesting. I checked http://jmedved.com/usbamps , but looks like he doesn't sell it. I was thinking about to ask him, if maybe a Kickstarter project would be a good idea, but you can't compete with such a low price, at least not if it doesn't have some added value (any ideas?). Good for my USB device development.

[Medo]

Looks interesting. I checked http://jmedved.com/usbamps , but looks like he doesn't sell it. I was thinking about to ask him, if maybe a Kickstarter project would be a good idea, but you can't compete with such a low price, at least not if it doesn't have some added value (any ideas?). Good for my USB device development.

There is no chance of selling UsbAmps at such a low price - $6.40 (with delivery) cannot even cover parts...

UsbAmps is only worth it if you build it yourself.

[Bored@Work]

This just popped in to my inbox: http://dx.com/p/usb-av-usb-power-current-voltage-tester-translucent-blue-silver-235090
USB power meter for $6.40 delivered. Arguably not as good but I found the timing interesting.

And you get them for half on eBay.

http://www.ebay.com/sch/i.html?_nkw=usb+voltage+tester

I have a few of them from different sellers. They use a Holtek HT 46R064B OTP http://www.holtek.com.tw/english/docum/uc/46r06x.htm chip. Soldering quality is not great and the enclosures of mine seem to fall apart after some usage. But that could well because of the abuse they face by some colleagues who like to borrow them. I have started to give them away on occasions, they make nice giveaways for geeks.

[FrankBuss]

This just popped in to my inbox: http://dx.com/p/usb-av-usb-power-current-voltage-tester-translucent-blue-silver-235090
USB power meter for $6.40 delivered. Arguably not as good but I found the timing interesting.

I ordered one and this is how it looks like. I could open it, was just snapped together and not glued:



Fits nicely at my USB port at my TFT monitor, but if you have just ports at your PC, you might need an USB extension cable, too.

It shows the current for 10 seconds, then the voltage for 4 seconds and so on. Some measurements:

display	measured
5.12V	5.130V
0.02A	33mA
0.08A	93mA
0.16A	170mA
0.30A	305mA

As you can see, not useful for low current measurements.

The SO16 IC is a HT46R064, a cheap microcontroller. Unfortunately OTP, so I can't improve the firmware unless I solder a PIC or something similar. Would be better if it would display the current all the time and with 3 decimal places. The voltage is right anyway, if you don't draw too much current

[Napalm2002]

Dave,

Have you fixed the delorean time board yet? Very interested to find out what broke and would love to see it in working condition!!!

[Napalm2002]

Dave have u fixed th Delorean time board yet?