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Andrew_G
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Joined: 18/10/2016
Location: Australia
Posts: 871

Posted: 01:11am 28 Feb 2018

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Hi all,
What do you do to protect your PC's USB from wiring errors/shorts in MM and other circuits?
Do you just plug your console straight to the USB port, for 5V and comms, or do you have any protective device?
(I use MMEdit - thanks Jim).

I had a close call when I connected my latest creation (via a USB to Serial adapter) to my PC's USB - a rude message about excessive current etc and it was clearly not happy. No smoke but the USB stopped working until I rebooted. It seems OK now . . .

Cheers, Andrew

(I HAD carefully checked the veroboard circuit but there was a very small bridge between two strips).

TassyJim

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Joined: 07/08/2011
Location: Australia
Posts: 6283

Posted: 02:01am 28 Feb 2018

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Your PC 'should' have over current protection but I wouldn't like to test it too often.

I use a USB hub to give physical protection to the ports. It's easy to replace the hub if a port gets damaged.
It's a powered hub but usually runs without the external power. Most of my devices are powered separately.

A hub also means that I can easily reach the ports.

Jim

VK7JH
MMedit

Grogster

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Joined: 31/12/2012
Location: New Zealand
Posts: 9610

Posted: 02:48am 28 Feb 2018

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I use a Hub too for the reasons Jim mentions.

Smoke makes things work. When the smoke gets out, it stops!

OA47

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Joined: 11/04/2012
Location: Australia
Posts: 986

Posted: 06:16am 28 Feb 2018

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I USE A HUB TOO NOW

The notebook didn't take too kindly getting 12V fed back into the USB.....Edited by OA47 2018-03-01

G8JCF

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Joined: 15/05/2014
Location: United Kingdom
Posts: 676

Posted: 02:29am 01 Mar 2018

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USB ports are usually protected by a 500mA self-resetting fuse, or polyfuse, see https://elinux.org/Polyfuses_explained so a short circuit "shouldn't" cause damage.Edited by G8JCF 2018-03-02

The only Konstant is Change

SteveA
Regular Member

Joined: 10/03/2017
Location: United Kingdom
Posts: 48

Posted: 08:48am 01 Mar 2018

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My Flukescope has a optically isolated serial i/o, for which Fluke sell a very expensive USB lead.

I made my own with a FTDI module, and an ir led and sensor, ripped from an old remote control. It works in both directions, I can send commands to the scope and receive plots/readings from the it.

At 9600bps it works very reliably.

Andrew_G
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Joined: 18/10/2016
Location: Australia
Posts: 871

Posted: 09:14am 01 Mar 2018

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Thanks to you all - much appreciated.
I'm off to get a hub sometime soon!

Thanks,

Andrew

WhiteWizzard
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Joined: 05/04/2013
Location: United Kingdom
Posts: 2944

Posted: 10:08am 01 Mar 2018

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SteveA said At 9600bps it works very reliably.

@SteveA

At what maximum speed do you think an IR approach could work reliably (over a very short distance)? Curious to know if you tried it

SteveA
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Joined: 10/03/2017
Location: United Kingdom
Posts: 48

Posted: 11:52am 01 Mar 2018

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WhiteWizzard said At what maximum speed do you think an IR approach could work reliably (over a very short distance)? Curious to know if you tried it

I built mine into an old 9 pin d plug housing which plugs into the scope, so the optical distance is probably only 2 to 3mm.

9600 is as fast as my scope will go, so I don't know how much the faster the adaptor could be pushed. In the URL below users have tried 19200, but have experienced problems.

Circuit diagram here: Circuit and discussion

WhiteWizzard
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Joined: 05/04/2013
Location: United Kingdom
Posts: 2944

Posted: 04:31pm 01 Mar 2018

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Thanks for the useful link Steve

Frank N. Furter
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Joined: 28/05/2012
Location: Germany
Posts: 949

Posted: 08:45am 02 Mar 2018

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This circuit worked with up to 115200 bps for me....

WhiteWizzard
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Joined: 05/04/2013
Location: United Kingdom
Posts: 2944

Posted: 08:59am 02 Mar 2018

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Thanks Frank for that circuit; however, the circuit I need has to have 'physically' separate IR Tx's and Rx's.

My two concerns are 'crosstalk' and speed limit.

Currently unable to try much due to lack of fast IR parts in my spares bin; so more of a theoretical build at the moment!

Azure

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Joined: 09/11/2017
Location: Australia
Posts: 446

Posted: 06:15am 03 Mar 2018

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@WW

Can you explain a little more about your requirements needs like speed, distance, environment, power sources, etc might be able to offer suggestions if we know more.

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