Readit News logoReadit News
simonrobb commented on A Bluetooth Low Energy soil moisture sensor   github.com/rbaron/b-paras... · Posted by u/Whitespace
_spduchamp · 3 years ago
It is my understanding that capacitive moister sensors don't have this problem.

Can anyone confirm?

simonrobb · 3 years ago
That's correct in my experience. Galvanic corrosion was never a problem for the capacitive sensors I developed a few years back (unlike the resistive sensors linked by the parent). However you typically want them more rugged than a bare PCB for industrial settings and since the capacitive field can pass through plastic I had them in a plastic housing filled with resin. Perfectly isolated from the outside environment and hard as a rock.

Here's a prototype: https://imgur.com/9yO28CY

simonrobb commented on Kenyan recycles plastic waste into bricks stronger than concrete   reuters.com/article/us-ke... · Posted by u/elorant
bluGill · 5 years ago
Bricks are not nearly as strong as you intuitively think. They do great in compression, but terrible in tension. Bricks are also terrible insulation. Real structural engineers take this into account, and thus often use wood or steel (or other materials) depending on what really matters. And of course the entire structure needs to be designed as a whole.
simonrobb · 5 years ago
Unreinforced masonry is weak in tension because of the weak binding interface between the masonry unit and the mortar. The reason masonry is used in wall construction and not in, say, a suspended floor, is precisely because walls don't typically experience tensile forces. Any tensile force resulting from e.g.: wind loading on the entire structure is typically overcome by the self-weight of the masonry.

If there is a special case where tensile forces are expected, for example a retaining wall, or a mid-rise structure, or earthquake load, the engineer will specify the the masonry is reinforced with steel and then it can resist tension through the unit/mortar interface just fine.

It is a poor structural engineer who tells the architect masonry isn't an option because tension.

simonrobb commented on Sydney now runs on 100% renewable energy   electrek.co/2020/07/06/eg... · Posted by u/aritraghosh007
simonrobb · 5 years ago
Link text should match the article headline; City of Sydney is a much smaller municipality than Greater Sydney, as this title suggests.
simonrobb commented on Woodworking for Engineers   woodgears.ca/... · Posted by u/jakear
robotmay · 6 years ago
Has anyone found any good non-American-continent woodworking YouTube channels?

Nothing against the Americans/Canadians etc, but this is one area where regional differences make a pretty huge difference in terms of wood and products available. If, like me, you're in the UK and looking for vaguely specific details regarding woodwork online, you're going to find an awful lot of American content and very little local stuff (a blog opportunity there perhaps).

A good recent example of this effect for me was when I was looking up pine stains. You will find constant references to something called "pre-stain conditioner" online; this basically doesn't exist in the UK. Everyone online is insistent that you need it, and you can just about buy it here (it's expensive), but it turns out it's pretty irrelevant. In the UK our pine is typically a different variety, and so therefore has a different composition, and our terminology is different here too; wood stain in the UK is, I think, "wood dye" in the USA? Please correct me if you know better :)

For reference I use this stain: https://www.wood-finishes-direct.com/product/manns-pine-wood..., which makes no mention of pre-stain conditioner, and I've had very good results with it so far.

simonrobb · 6 years ago
Matt Estlea is only young but he has a real talent for teaching. Fun to watch, goes pretty deep into the basics: https://www.youtube.com/channel/UCxWzA3ZlYEOLr1JkKH0ZMyg
simonrobb commented on Launch HN: Art in Res (YC W20) – Buy art directly from artists    · Posted by u/JohnFriel
simonrobb · 6 years ago
Spectacular! Well done on shipping a product/service which I've wanted for a long time. In particular the financing option will enable me to take the leap into the world of fine art for the first time.
simonrobb commented on Launch HN: Art in Res (YC W20) – Buy art directly from artists    · Posted by u/JohnFriel
sushisource · 6 years ago
Not to mention the fact that I suspect most people interested in purchasing fine art aren't exactly the type who care to finance the purchase.
simonrobb · 6 years ago
I mean, anecdotal data ra ra ra, but this is super appealing to me, and I'll probably be making my first art purchase >$500 as a result.
simonrobb commented on CNCF's Cortex v1.0: scalable, fast Prometheus implementation   grafana.com/blog/2020/04/... · Posted by u/netingle
gouthamve · 6 years ago
The only one I know with "non-experimental" local-storage is VictoriaMetrics. But the big thing there is that data in VM is not replicated, so when you lose a disk/node, you lose that data.

Having said that, both Thanos and Cortex have experimental local-storage modes that are pretty good. You could also try them for now while they get production ready.

simonrobb · 6 years ago
M3 provides local storage but is not experimental, on top of that with cluster replication which VictoriaMetrics does not provide, and has a kubernetes operator to help scale out a cluster.

Disclosure: I work on the TSDB underlying M3 (M3DB) at Uber. Still worth checking out though!

Deleted Comment

simonrobb commented on The U.S. economy is growing and using less and less stuff to do so   hbr.org/ideacast/2019/09/... · Posted by u/Anon84
logfromblammo · 6 years ago
Though it seems like it might be easier to ship sand for pre-stressed concrete crossties, given that all the materials must necessarily be connected to the rail network.

Also, I wonder why concrete crossties don't use neoprene bearing pads under the rails to reduce the abrasion problem.

simonrobb · 6 years ago
Are concrete crossties pre-stressed? It makes sense now I think about it, but I'm just surprised more effort than "pour concrete into a mold" goes into such an unassuming structural member.
simonrobb commented on Uber lays off 435 people   techcrunch.com/2019/09/10... · Posted by u/coloneltcb
debug-desperado · 6 years ago
Can you tell me if the M3 (time series db) team is still healthy? I was planning to evaluate it soon.
simonrobb · 6 years ago
Chronosphere (https://chronosphere.io/) was recently started by ex-Uber engineers to build a commercial ecosystem around M3. M3 is Uber's metrics platform and isn't going anywhere. M3DB (the TSDB built to support M3) is becoming fairly integral to Uber in its own right. I'd say the trajectory is positive.

Disclaimer: I work on the M3DB team.

u/simonrobb

KarmaCake day260May 20, 2012
About
Engineer and founder (ex-Uber). Structural engineer in a previous life.

sajrobb [at] gmail dot com

View Original