EEVblog #1351 - Mailbag

[EEVblog]

Mailbag time!



SPOILERS:
00:00 - GPS Tracker Battery Leak
06:47 - Guest RF Lab - Chuck Kummer W7CLK
09:46 - Marklin HO scale railway turnout point
19:29 -  GVDA GD118B Pocket Multimeter review
https://s.click.aliexpress.com/e/_Ab3RNe
39:10 - GVDA GD116A AC Voltage Detection Stick review
https://s.click.aliexpress.com/e/_AD7szi
43:41 - E-design Tweezer LCR Meter
https://www.seeedstudio.com/Mini-Digital-Tweezers-DT71-p-4696.html
45:11 - Low Temperature Bismuth Solder (a.k.a ChipQuik)
http://jfsolder.com/product-1-4-sn-bi-based-solder-wire-en/146145/

[Barny]

My dad had an model railway.
He used rails and points from "Kleinbahn".
This Points had an drive which had relais-contakts in them to switch contacts depending on position for feedback.
That was like 30 years ago.
I thought all points work this way.

Perhaps its possible to fit feedback inside the the drive.
Or do it like some hardcore model train guys and girls which buy the cheaper points without drive and fit small model servos to switch the position from below in a slow more realistic way.
(Dont forget to turn of power after position change to extend the life of the servo)

[Kleinstein]

The drive for the model-railway switch is a little similar to bistable relay coils. I would expect some solution for the detection. Reading the inductance sounds doable. One just has to find a clever way to combine it with the driver(s) and not to use to much effort in this.

One can use something like a diode matrix to switch relays. It works reasonably and save on the drivers if you have a larger number (e.g. more than 10 or so) However it can get a little tricky with bistable relays, as the coils are couples, but it can work.

[Microcheap]

Those GVDA meters can be found selling with various different brands: Aneng 619A, Habotest HT122B, Kaiweets, Mustool...

There is another similar model with touch screen (Aneng 618C) that seems to be very popular, I don't know if it is any good but, at least, the screen looks nice.

[floobydust]

Sometime, can you use the LCR tweezer on the railway switchup and confirm if the inductance shift is enough to sense position. I kept thinking of metal detectors using a bridge circuit. Nobody wants their train to crash, right?
If you do an LCR tweezer shootout, there are issues when measuring large MLCC's, depending on the voltage and ramp, measured capacitance value can be way off.

[switchabl]

Shrouded 2mm connectors are a thing:
https://www.sks-kontakt.de/en/test-measurement/products/2-mm-safety-system
https://www.staubli.com/en/connectors/test-and-measurement/test-and-measurement/products-for-test-accessories/test-leads-2-mm-and-4-mm/test-lead-slk205-k/

Haven't seen them on a multimeter before though.