Author Topic: EEVblog #1069 - Mailbag  (Read 2373 times)

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Online EEVblog

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EEVblog #1069 - Mailbag
« on: March 29, 2018, 12:10:01 pm »


SPOILERS:
SPOILERS:
ServoShock PS2 Playstation wireless controller for servo motors.
http://www.servoshock.com/
Papyrus gift
PSM400 Arduino Mains Line Monitor
https://amzn.to/2E3PBLA
http://austinsproject.com/psm400/

Fran Blanche
http://www.youtube.com/user/ContourCorsets

MakerBuino DIY handheld game console
https://www.makerbuino.com/

4 Wire Short
https://github.com/EleDes/4-wire-short

Blinkenrocket
http://blinkenrocket.de/
https://hackerspaceshop.com/
 
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Online Brumby

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Re: EEVblog #1069 - Mailbag
« Reply #1 on: March 29, 2018, 01:47:15 pm »
It's pronounced:  PAP - PIE - RUSS
 
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Offline MiDi

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4-wire short
« Reply #2 on: March 29, 2018, 08:41:03 pm »
Thanks for reviewing the 4-wire short, you always get the shortcomings and that's what I appreciate!

Did them for my purpose on old Keithley, but thought it would be nice to share for others.

The plugs are soldered at the bottom, the screws are only to get the force out of the soldering joints. I take this as a kudos that the soldering looks that good, that they are not recognizeable  ;)

I am not shure if you pushed it into the Keithley completly, if not, that could cause bad contact. The changing resistance is normal, as there are thermal emfs that cannot be avoided. It takes around a minute to settle all junctions to same temperature, after that it should stay quite stable.

The Keysight really has recessed terminals, not shure if common bananas would make good contact  :-// But nevertheless, the plugs used are a bit shorter than normal bananas and do not fit into this type of terminals.
« Last Edit: March 29, 2018, 08:43:27 pm by MiDi »
 
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Offline jonovid

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Re: EEVblog #1069 - Mailbag
« Reply #3 on: March 29, 2018, 11:56:50 pm »
Servo Control with PS4 Controller not PS2.   
now you can have your own eevblog animatronic puppet.  cyborg Dave  :-DD
from the lab's unused components.

the 4 Wire Short,  why a pcb? use a 2mm thick square of sheet of copper.  :-//

the Fran T-shirt  :-+
Hobby of evil genius      basic knowledge of electronics
 

Offline Fungus

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Re: EEVblog #1069 - Mailbag
« Reply #4 on: March 30, 2018, 12:06:08 am »
the 4 Wire Short,  why a pcb? use a 2mm thick square of sheet of copper.  :-//

It would bend after two insertions.

But yeah, I don't get why you wouldn't just flood-fill both sides of the board. The resistance can never be too low.
 

Offline Kleinstein

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Re: EEVblog #1069 - Mailbag
« Reply #5 on: March 30, 2018, 12:33:19 am »
There a 2 type of 4 wires short. The simple one have sense Hi and sense Lo connected, current Hi and Current lo connected and than a single "thin" wire going sometwhere from the sense to the current side, usually in the middle to make a look a littel like an H.

The meters should read really 0 in 4 wire ohms more - any residue would be from the meter unless you have one that can resolve pOhms or better. 2 wire resistance can be higher. So this 4 wire short looks like a fail  :-X.

The more complicated zero would be a symmetric 4 contact zero, so that one could interchange the 4 contacts at will. This is more tricky and usually not that perfect, with often a residual resistance (4 wire) in the nOhms - µOhms range. A possible shape (on a board) might be a symmetric triangle with contacts at the corners and a center via.


The mains detector looks a bit scary - It looks like there is not really much clearance / creep distance at around the opto-coupler. So it might be an unsafe product  :blah:.
 

Offline MiDi

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4-wire short
« Reply #6 on: March 30, 2018, 02:02:41 am »
In contrast to a 2-wire short, a 4-wire short does not need to be the lowest resistance.
And remember: there is always twice a contact resistance from the connectors, that could be the highest resistance in the chain.

All sort of shorts should have a low thermal mass to settle the temperature quite fast.
Temperature differences induce thermal emfs (Seebeck effect), that cannot be avoided when there are different materials involved.
Recommend reading of Metrology 101 from Fluke

There are a couple of forum users who have this short and I got no negative feedback, only that the force to push in is quite high.
This 4-wire short is not for metrology purpose, but TiN did a quick test on his Keithley 2002 and had nothing to complain about  :-//
 

Offline Kleinstein

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Re: EEVblog #1069 - Mailbag
« Reply #7 on: March 30, 2018, 04:47:01 am »
Looking at the Github pictures, the 4 wire zero looks Ok - at least if there is no connection on the backside.
So it is odd to see so much sensitivity to contact pressure / wiggling.
 

Offline jonovid

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Re: EEVblog #1069 - Mailbag
« Reply #8 on: March 30, 2018, 02:56:58 pm »
thermal mass is a bit on the high side. but this is a short  :-DD
Hobby of evil genius      basic knowledge of electronics
 

Offline Dr. Frank

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4-wire short
« Reply #9 on: March 30, 2018, 06:17:56 pm »
Hi Dave,

this 4W short is just fine, and designed as it should be.
Every volt-nuts has designed his own version in a similar manner, featuring the original connection path by HP, FLUKE or KEITHLEY.

And there have been several discussion threads about that.. http://www.eevblog.com/forum/testgear/diy-34401a-calibration/

Instead, you should get accustomed to the Offset Compensation feature of your KEI 7510, or the KS 34470A, though.
That would've get rid of these odd negative resistance readings, and also any apparent contact resistance readings would've vanished also to exact zero.. as these do not appear at all in a proper 4W measurement with OCOMP, and with that exact design of a 4W short.

Maybe you should also set the 34470A to 7 1/2 digits, or use statistics display for an additional digit.

Frank
« Last Edit: March 30, 2018, 07:02:33 pm by Dr. Frank »
 
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Online Mr. Scram

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Re: EEVblog #1069 - Mailbag
« Reply #10 on: March 30, 2018, 06:25:20 pm »
How often did Dave start that Protel sentence? Six times? ;D
 

Offline SeanB

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Re: EEVblog #1069 - Mailbag
« Reply #11 on: March 30, 2018, 07:47:08 pm »
Stamps because the Post office had no computer to print out a label, plus they also did not have any labels as well to go with the printer. Done on an old fashioned analogue mass meter for the mass and then a lookup in the rates sheet, and then a hand written receipt for the stamps, and then placed in the post box with the rest.
 

Offline ebastler

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Re: EEVblog #1069 - Mailbag
« Reply #12 on: March 30, 2018, 11:13:40 pm »
If you have an excess of servos lying around, here's what to do:



(Not mine. Wish it was. ;))
 

Online Mr. Scram

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Re: EEVblog #1069 - Mailbag
« Reply #13 on: March 31, 2018, 08:39:36 am »
Though I susupect I won't change anyone's mind, I just wanted to note that the classic view on video games being a waste of time or harmful to developing minds turns out to be wrong. Just like real world playing, playing games turns out to be a wonderful way of developing skills in a benign setting. Research indicates that different genres develop different skills, from hand-eye coordination through planning to working in a team.

There's a reason normal training and education is being gamified. It simply works.
 


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