Category Archives: Hardware

QEMU/KVM Attaching a Virtual NIC Directly to a Physical Interface

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Man, it took me a while to figure out how to do this! Over on Attaching a Virtual NIC Directly to a Physical Interface I figured out I could use this XML in Virtual Machine Manager (virt-manager) for my NIC device:

<interface type='direct'>
  <source dev='enp9s0' mode='bridge'/>
</interface>

That then gets expanded automatically to something like this:

<interface type="direct">
  <mac address="52:54:00:ce:5b:09"/>
  <source dev="enp9s0" mode="bridge"/>
  <target dev="macvtap4"/>
  <model type="rtl8139"/>
  <alias name="net0"/>
  <address type="pci" domain="0x0000" bus="0x10" slot="0x01" function="0x0"/>
</interface>

Update: ah, balls. This doesn’t completely work, because the guest can’t connect to the host, and vice versa, even though both the host and the guest can connect to the internet. This is a problem for another day. Maybe this or this will help?

Watch Loupe

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This morning my new eyeglasses arrived, they are these ones from AliExpress: Watch Loupe Glasses Magnifying Repair Tool Loop Magnifiers Watchmaker Jewelry Jewelers Magnifier Foreye Convenient Professional.

Rather than do an unboxing video I thought I’d just write it up in this blog post.

There’s a headband type thing that comes with them that looks rather cheap and flimsy (it is), but it’s actually quite functional and practical.

The 20X magnification is my fav, and I might even see if I can get something with higher magnification one day.

John's new eyeglasses

The headband that goes with the eyeglasses

AliExpress diodes

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I ordered a bunch of SMD diodes from AliExpress (nine different types), and nine packages arrived, but they weren’t labeled. I tested everything to infer what I got, and they didn’t ship me what I ordered. My notes are here and the video of me doing all this is here.

I kept a note of the seller and will try to not order from them again. In the mean time I think I have filed the components that did arrive in the correct drawer.

Below are two happy snaps from this project. I guess on the bright side I got some practice doing SMD soldering and using my signal generator and my scope.

Oh, and I added a new item to my debugging notes, viz “is it plugged into the right socket?” (I had my output cable on the signal generator plugged into the wrong BNC connector on the device, that took some figuring out…)

John's test rig

John's test rig, labeled

Switching diodes and rectifying diodes

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I had an envelope full of SMD diodes arrive today. Three different types in three different sizes, so nine bundles. Unlabeled!

I’m not sure what they were thinking at the shop. I got them from here.

I managed to figure out that the ones marked ‘S4’ were the Schottky diodes (1N5819WS). I think the ones labeled ‘T4’ are the switching diodes (1N4148WS) and the ones labeled ‘T7’ and ‘A7’ are the rectifying diodes (1N4007), but I’m not sure of that yet.

I asked ChatGPT for help and it explained how I can devise a test circuit, so that’s on my TODO list for tomorrow.

In The Lab With Jay Jay – September 7, 2023 – Unboxing AliExpress TE-801 Third Hand With Magnifier

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This post is part of my video blog: In The Lab With Jay Jay.

In this video I unbox two “different” helping hands (AKA “third hand”) only to discover they are the same TE-801 model.

I purchased these separately on AliExpress:

They are exactly the same product so if you’re planning to purchase might as well get the cheapest option. Note that the first link above also has a separate more expensive option which is actually a different product, I didn’t get one of those.

In addition to unboxing these third hands I also add some 4mm heat shrink to the alligator clips to take the bite out of the teeth.

Note: in this video I have the annoying habit of calling “heat shrink”, “shrink wrap”. The correct term is heat shrink, shrink wrap is a different type of thing.

In the video I use 4mm yellow heat shrink:

The hot air gun I use is a part of my Horusdy Soldering Station.

The batteries I use are Duracell AAA batteries.

My gloves are:

UV light

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Got myself a USB powered UV light. It came with a few tubes of solder mask:

I’m gonna keep this in my booth where it will be used. Don’t want to use it anywhere near where I keep my UV solder mask because I don’t want to accidentally cure it!
John's UV light, switched off
John's UV light, switched on