Advice wanted on a UV/Light Meter project

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Hello everyone. Having not had access to the space in months has made me want to actually make better use of it than I have the past year. As it’s been sunny and at the best of times I’m slightly obsessed with photography I have been making cyanotypes. The problem there is with the sun as a light source it’s pretty uneven and calculating exposures is mostly squinting and sticking your tongue out at the right angle. Hopefully understandably that isn’t exactly great when you’re trying to make reproducible prints.

I have however found this UV exposure meter project and figured I’d have a go making it and modifying it to suit my needs.

One thing I would really like to change on this is have it run off either a standard little lithium battery pack or 18650 cells, rather than 9 volts. I don’t know if it’s better to run everything here at 3.3 or 5 volts, shifting between the two seems like an exercise in annoyance.

Being rather new to electronic projects any more complicated than making an LED flash I thought I’d turn to the experts for some advice in how to do this and where to look for parts. I will doubtless even with a guide mess something up and need some advice I’m sure.

My next step is to try and copy his design on a simulator of some kind to just get a better understanding of how it all works together. Currently looking at what there is out there for that.

Materials list:

  • Arduino board - probably a micro or a nano? Can’t really tell what the difference is between them
  • UV Sensor module - Seemingly all three I have found are listed as discontinued on various sites but are available in small quantities in a few places like ebay. Options are ML8511, Adafruit VEML6070 and Adafruit VEML6075 which seem to be able to run on 5v or 3.3v.
  • OLED display - low power use and ideally either monochrome or red (so I could use it in a darkroom). This is 3.3v rather than 5v though, so maybe I need something different here?
  • Some kind of battery. I do also have some spare 18650 cells that Howard kindly gave me, with a battery holder alongside the remains of a mini power bank that conveniently has a charger/discharge board. Not sure if that’s any use though
  • Switches - hoping I can fish some spares out of the parts bins.
  • Beeper
  • Enclosure - Not sure how big this will be, but possibly something like this box as inelegant as it is, with suitable holes for everything drilled into it. Maybe a reason to learn how to 3D print too?
  • perfboard
  • some kind of voltage regulator for the battery to the power for everything?
  • input panel - He uses a keypad which I’m not sure I like as an input device but I also can’t really think of a better way to do it

additional modifications:

*A visible light sensor - ideally I’d like to be able to use this for UV and standard light measurements

Well I’m in the space and looking at buttons. I feel like I have to use this:


Okay so I’ve got an order going for I think everything I need for the project, aside from the case. Hoping the space has some beepers somewhere and I remembered I have an arduino uno I can at least use for prototyping.

I have this mini-power bank, minus case. I’m wondering if I can desolder the USB output and just use the 5v out from this to power things, then run the micro usb-in for charging?

Okay so I’ve had some more time to work at it again. While I don’t have any inputs hooked up yet (that’s the next step) I’ve managed to get the software and basic wiring happy. Never used i2c or really done anything in C before so it’s a bit hard going but I’ve managed to get it calculating UV & visible light levels. As well as those I did a bit of maths and worked out how to calculate rough exposure values too.

Starting to regret not checking how small this screen was but it’s really crisp so that’s nice.

Not sure the best way to mount everything inside a case, maybe that stuff with holes in it like a breadboard? Do we have any of that in the space? I don’t want pushing a button to make everything crack.

Came in to do more and managed to forget my laptop, so hardware design it is.

Searching through the drawers I found this box which looks like a reasonable size, if on the large size.


But on taking it apart it’s just too beautiful inside, wire wrapped parts!


I probably will use it but I just have to admire that style of manufacture.

Having some trouble with working out the switches and how to mount them to a case, do we have any of that pre-drilled board for soldering things to, sort of like permanent breadboard? I couldn’t find any header pins either. Then maybe bolt it on somehow?

I did find a little Arduino board in a drawer and it got me thinking about using one with a built in battery connection, that would make powering this thing so much easier. I’ve realised my 18650 idea, while beefy, currently needs me to solder onto some tiny pads to not use it with a huge usb cable.

This is my current basic plan for a layout. Might want to add another switch for a few easy to get to settings but not sure how many / how to connect that to an Arduino.


Lastly, there seems to be a lot of these rotary switches (is that the term?) but they all just rotate around and I’d like to find a way to limit them, is that possible or do I need to search harder / buy some specifically.


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