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DIY Bike Computer: case, mounts [hypothetical discussion]

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DIY Bike Computer: case, mounts [hypothetical discussion]

Old 05-05-19, 09:52 AM
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DIY Bike Computer: case, mounts [hypothetical discussion]

Hey guys,
2 disclaimers ahead of time:
1. I'm an electrical engineer and this post relates a bit to that. The electronics/programming parts are fine with me.
2. I'm on vacation. On vacation, my mind generates new ideas eventually (a good sign of resting!), but usually, vacation has ended before I can realize those ideas. During work weeks, I usually don't want to do more electronics stuff in my spare time. Cycling is better. In that light, I do expect that this post is more about musing on how to do it, rather than actually implementing it. Please be aware.

Here we go:
I am a fan of standard bike computers, i.e. wheel magnet, long battery life, mount&forget. I'm not interested in strava, power meter, or HR functionality. However, something that has always bugged me is that some more functionality (mostly software-based) is sold at gigantic extra cost. The difference between a VDO M2.1 and and M6 in hardware and software isn't THAT big. I have an M3 (plus mounts on 5 bikes with 3 different wheel sizes). I like this one, but would like to have more functions, such as:
- support more than 2 different bikes. Auto-detect them.
- altimeter functions
- maybe some basic compass & navigation stuff?
- computer connectivity and basic information storage?

That's all fairly easy to do with an arduino, custom circuit board design and aliexpress OLED display. The part that is not obvious to me is the mechanical part:
How do I get a nice, compact, waterproof computer case with buttons and handlebar mount together? I could try to salvage a defective bike computer with large screen. But I see issues with that regarding space and design.
Anyone has any direct and practical ideas on how/where a good case and mount system could come from? Something that is even usable by an EE without a lot of extra study?
I see a lot of bike computer DIY projects online, but they either lack a good mechanical solution or just use phone/tablets (both dislike. I want that VDO M6-style look).
In the most ideal situation, I would just reuse my VDO handlebar mounts...
Is 3D printing something easy to get into and a good thing here?

Thanks for dreaming with me!
alias5000
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Old 05-05-19, 11:09 AM
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Originally Posted by alias5000
How do I get a nice, compact, waterproof computer case with buttons and handlebar mount together? I could try to salvage a defective bike computer with large screen.
.
.
.
Is 3D printing something easy to get into and a good thing here?

Thanks for dreaming with me!
alias5000
I second 3D printing. Are you close to University of Waterloo?


Last edited by ChrisWagner; 05-05-19 at 11:14 AM.
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Old 05-05-19, 12:46 PM
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Neat Any good free software to get going?

Another thing will be to find a good combination of display and battery. CR2032 batteries don't give a lot of energy. Looks like those Nokia 5110 displays can still be obtained for cheap, drawing 6mA (3.3V) when operated (back light off) - apparently (https://components101.com/nokia-5110-lcd).
A CR2032 gives about 0.63Wh. That would give about 31hrs of display use, minus microcontroller energy. That's not quite 1 year of use that you often get out of commercial bike computers.
DOG displays seem to be better, here's one with 128x64 pixels and 0.32mA (3.3V) power consumption (https://shop.lcd-module.de/grafik-di...splay-493.html). That would make for 600hrs of use minus microcontroller energy, about a month. When turning off the display in standby, that might work pretty well. Need to see about arduino power consumption and which one to use.
In this case, I'd also have to see how to cover the display and make sure it's waterproof and how to add some buttons to this construction.
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Old 05-05-19, 01:51 PM
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Cool

shimano had one with buttons in the rubber brake lever hood..

I didn't care for more than the Odometer and resettable mile function, on my touring bike,

so I hid it down on a fork blade.. off the bars.. OK with stopping to read the numbers.
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Old 05-05-19, 05:41 PM
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Originally Posted by alias5000
However, something that has always bugged me is that some more functionality (mostly software-based) is sold at gigantic extra cost. The difference between a VDO M2.1 and and M6 in hardware and software isn't THAT big.
The M6 is $150.

If you earn $40k/year ($20/hr), that's about 8 hours worth of work.

Cobbling your own cycle computer will likely take many more hours than that.
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Old 05-05-19, 08:23 PM
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I know you said no phones but if you use an old Android phone and put Lineage on it you can then re-program to your heart's content. I use an old Motorola E with Lineage and then removed all the superfluous Android apps related to a phone and just have bike related apps. Someone even hacked it so it picks up ANT+ speed/heart sensors which the original cannot. Some phones have altitude meters too (Sony xperia compact for example). If you think a 4" screen too large there are tiny Android phones out there like Uniherzt Jelly and some tiny 2.5" phones from China and you can glue a garmin style mount on the phone's back and get a cheap plastic garmin bar mount on Ebay.
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Old 05-06-19, 12:03 PM
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when I was much younger I would start projects like this to save money. I'm not sure it's a good thing, but I don't do that any more. I have so many projects that I wouldn't want to waste time on one just to save money. I would have to be really frustrated with the current commercial offerings to try to make something like a bike computer. Mind you, I have some really goofy projects that I have wasted a lot of time on. but there was always some payoff other than money

Fusion 360 is free for hobby use. So is Solidworks.
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Old 05-06-19, 02:37 PM
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Originally Posted by unterhausen

Fusion 360 is free for hobby use. So is Solidworks.
Thanks, I'll have a look into fusion 360. Fumbled around with solidworks years ago and don't remember it very dearly.

This is all about fun, not about saving money or efficiency. My existence as EE comes from hands-on work which I don't get to practice a lot these days (phd students have too much theory/computations to do...). A sign of holidays doing their work well is me getting this drive to create back - here are first signs :-)
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Old 05-06-19, 03:24 PM
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the undergrad engineers all love fusion 360 because you can usually grab and pull on edges to get things to change the way you want. You need a decent graphics card to make it work well. My computer has plenty of cpu, but it suffers on the gpu side, and fusion doesn't run that well.
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Old 05-06-19, 04:21 PM
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Typically hobby 3d prints are too porous to be waterproof, but I'm not sure I'd worry about it that much for a DIY project.

If you built it, you can probably clean the board if it gets minor water deposited gunk or induced corrosion, and you can re-print the housing if it doesn't dry out.

Or you can try painting the prints with something - my cousin's kid does that for high school underwater robotics competitions, I was a little surprised it works but reportedly does, not sure what the sealant is but it's probably known in the publications of that community.
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Old 12-20-22, 02:31 AM
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For the "box", you can make a mold and use fiberglass, too. Thin weaves will work with small enclosures.

For the LCD: the ones in bike computers of old are specific made for the job, and obviously, they use less energy. The most energy efficient LCD is, e-ink. Newer ones have very high refresh rates compared to older generations. They are quite cheap, too. Instead of Arduino, I'd use something simpler like PIC12, maybe. ATMEL's sleep or low power modes are not that efficient, or cannot be controlled perfectly as in PIC's. PIC's are more efficient.

As a battery alternative, you can use rechargeable LıPo batteries - they' re cheap and comes in sizes that can fit inside a watch. If you hook up a TP4056 module, you can charge them under an hour!
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Old 12-20-22, 10:20 AM
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#zombiethreadreboot
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Old 12-23-22, 12:50 AM
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alias5000, did you ever play around with this idea any further?
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Old 12-23-22, 09:28 AM
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Originally Posted by retswerb
alias5000, did you ever play around with this idea any further?
No, I didn't. Still in my head, but between getting a Garmin for my birthday and having a busy engineering job (this craving non-electronic hobbies to balance), it hasn't advanced
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