Soemarko Ridwan

iOS & Web Developer ⟡ Coffee Addict ⟡ Scuba Diver

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DIY O₂ Analyzer: Part 1 — Understanding Oxygen Sensor
DIY O₂ Analyzer: Part 1 — Understanding Oxygen Sensor

DIY-ing O₂ analyzer is one of the simplest project you can do, for those of you who’s electronically literate will understand this after taking a look at a sensor’s data sheet. While when we mentioned this to other divers, they’ll say, “you’re making your own analyzer? You’ll die.”

So, I’ll split this into 2 parts. First is this post, I’ll basically just explaining data sheet and how the sensor operates. And I’ll go into the actual build, BOM, source code, etc. in part two. I’ll use my own sensor as an example, it is the cheapest one that checks all the boxes for it to be scuba oxygen analyzer. Let me know if you found anything cheaper 😜

O₂ sensor tech specs

Pictured above is the technical specs from the sensor data sheet. From the data sheet we know that if you expose the sensor to gas, it’ll spit out mV out of the other end. With the only caveat it being in the most ideal conditions, hence the calibration button. As mentioned in there, the numbers will drift over time, and humidity will affect the numbers too.

DMM output

Let’s use the pic above as example, We know “air” is 20.9% oxygen, so 9mV = 20.9% we use this as the baseline, the calibration value if you will. From that, if we were to expose the sensor to EAN32, it’ll spit out 13.8 mV. 13.8 / 9 * 20.9 = 32.05

That’s it! All you really need is a millivoltmeter really, and you can math it out. But ideally, you’d want a screen that display the actual oxygen percentage to simplify a lot of things. As mentioned, I’ll get into the how to in part 2.

On writing in 2018
On writing in 2018

… or lack there of 😝 As promised let’s get into the reasons why there were significant lack of writing this year. I probably has mentioned this before, but for me, writing organizes my thoughts into something more coherent so that I can progress and plan further into a topic or a certain subject.

Read more…

The Six Stages of Debugging

  1. That can’t happen.
  2. That doesn’t happen on my machine.
  3. That shouldn’t happen.
  4. Why does that happen?
  5. Oh, I see.
  6. How did that ever work?


I won...
I won...

I think. Typo in the name, but I may change away from this theme soon :D

Update: I did win!! yeah...

Flat file CMSs quick comparison
Flat file CMSs quick comparison

Something clicked with me when I came across htmly. It made perfect sense for the future of my writing. So I wanted to make the move ASAP, and here we are. I only did a cursory look into these flat files CMSs, and installed and tests a few of them, so take these thoughts with a grain of salt;

htmly: abandonware, it’s no longer actively developed. Doesn’t look good out of the box (and none of the available themes are particularly good).

Grav: very powerful, too powerful. The only one (that I’ve looked into) that can be setup without dashboard / admin site. But, it’s a bit tricky to setup as a blog because file structures is needed for these flat file CMSs, blog posts are a bit cumbersome to manage as flat files.

I’m not a fan of the admin side, reminded me a lot of the complexity of Wordpress. There are these “skeletons”, it’s kinda like this premade sites to get you up and running faster, but that just screams finicky to me.

Kirby: read good things about it. Not free, so a pass for now.

Bludit: perfect for my case, see that bolded text on my previous post about tumblr? This is exactly that. Dead simple blogging system (it’s not a platform), add new page, write in markdown, save, bam a new blog post. Looks good out of the box, but I’m using the micro theme (modified it so it's slightly larger, and I'm calling it Mini -- which I may or may not release it, no promises).

Pico: haven’t installed this one, since my heart is set on Bludit. It seems more capable than Bludit, but not as complex as Grav.

I’m really liking these flat file CMSs. Like, mechanically simple, yet robust. They can't do any of the tricks with database like left join etc. Do we really need those features for blogs? The contents are files so the search function will be on the terrible side, but we have google for that. Even with database you'll likely to roll another indexing engine to have a better search anyway.

Seriously, look into these flat file CMS, it may be perfect for your next web project.

Proof that I've planned the blog migration for awhile
Proof that I've planned the blog migration for awhile

Even though I wasn't really a fan, Wordpress was really the only viable option. I can get it up and running in no time. Has pretty good themes / templates for free. And being able to migrate away from tumblr was a requirement then, I mean like moving all of the contents, use the same permalink, and just point the subdomain to this server instead of tumblr's. It has to do all of those, or none of it and keep the tumblr as the archive. After seeing Bludit, I opted for the latter. No regret so far. Much restrictions, such fun.

Also, I've set the RSS to tweet on IFTTT so you can "subscribe" to this blog by following me on twitter.