General Cycling Discussion Have a cycling related question or comment that doesn't fit in one of the other specialty forums? Drop on in and post in here! When possible, please select the forum above that most fits your post!

Custom Cycle Computer Features

Old 07-13-18, 07:47 PM
  #1  
UniChris
Senior Member
Thread Starter
 
UniChris's Avatar
 
Join Date: May 2017
Location: NYC
Posts: 661

Bikes: 36" Unicycle

Mentioned: 13 Post(s)
Tagged: 0 Thread(s)
Quoted: 281 Post(s)
Liked 30 Times in 25 Posts
Custom Cycle Computer Features

Think I'm going to sit down and build myself a custom (spoke magnet based) cycle computer.

If you were going to do this or have someone do it for you, what (perhaps non-standard) features would you want to include?

One of my primary goals is to track resting vs. riding time, so thinking of having it beep annoyingly when I've been stationary too long, on top of displaying the length of the current break and an overall riding/resting percentage and the correspondingly falling net speed average...

I'm also thinking of being able to set a target speed range and indicate over/under achievement (riding an implicitly fixed gear unicycle on gently graded rail trails, hills make only about a +/-10% difference to appropriate speed anyway). As a longer term form of that, also want to do some sort of progress against goal thing that considers miles accomplished and remaining hours to sunset against the plan of an all-day ride.

I think I have enough memory to log an all-day ride on a rotation by rotation basis, at least approximately.

Will probably have it transmit some sort of periodic status packet via Bluetooth LE to be captured by a cooperating phone app and saved alongside GPS data.

Not sure if I'm going to be able to afford battery to keep the display on all the time, if not will definitely make the timeout adjustable during a ride.

Leaning more towards a rotary knob with push function than buttons for menu navigation, but not committed to that yet...

I do have one ride with a geared hub where cadence and wheel rotation do not alway match; may support that eventually with another magnet and sensor on the crank but not really worrying about that right now, other than obviously leaving an input path for a 2nd sensor in the circuitry.

Last edited by UniChris; 07-13-18 at 07:51 PM.
UniChris is offline  
Old 07-13-18, 08:58 PM
  #2  
TiHabanero
Senior Member
 
Join Date: Nov 2012
Posts: 2,240
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 630 Post(s)
Likes: 0
Liked 17 Times in 16 Posts
Don't bother with the "pace" arrow or other such "motivator" gimmick. Have one on a computer I use and it is about as stupid as stupid gets. Never pay attention to it and makes no difference to the quality of the ride. Elevation gain and temperature (temp not really needed) are nice plus having some way of figuring the degree of angle of the road you are on would be sweet.
TiHabanero is offline  
Old 07-13-18, 10:02 PM
  #3  
UniChris
Senior Member
Thread Starter
 
UniChris's Avatar
 
Join Date: May 2017
Location: NYC
Posts: 661

Bikes: 36" Unicycle

Mentioned: 13 Post(s)
Tagged: 0 Thread(s)
Quoted: 281 Post(s)
Liked 30 Times in 25 Posts
Originally Posted by TiHabanero View Post
Don't bother with the "pace" arrow or other such "motivator" gimmick. Have one on a computer I use and it is about as stupid as stupid gets. Never pay attention to it and makes no difference to the quality of the ride.
Hmm, won't say you aren't right, but a pacing indicator is actually pretty key to my motivation for tackling the project as a route to accomplishing my current riding goals - granted, it would be one tailored to my specific goal, but a large part of the motivation is that I've historically not been covering enough ground per hour of useable daylight. For me that's a combination of a speed I've determined I want to be rolling at (which I basically want to maintain without change - not going to fast is as much a concern as going to slowly) and an amount of time I can allow for breaks (which I need to improve on).

Elevation gain and temperature (temp not really needed) are nice plus having some way of figuring the degree of angle of the road you are on would be sweet.
On a bicycle, doing incline is readily possible with an accelerometer (just have to calibrate it with the bike facing both ways on the same surface) and recording that against speed (or even better, power) could indeed be useful. Unfortunately on my own unicycle there's no consistent reference against which to judge the incline of the path - in fact there are sections of my usual rail trail that I'd swear are (gently) uphill both ways as I can only get a true perspective if I dismount. But a phone app can get the altitude change from GPS data.
UniChris is offline  
Old 07-14-18, 03:36 AM
  #4  
TiHabanero
Senior Member
 
Join Date: Nov 2012
Posts: 2,240
Mentioned: 7 Post(s)
Tagged: 0 Thread(s)
Quoted: 630 Post(s)
Likes: 0
Liked 17 Times in 16 Posts
My dad was an electrical engineer and in the 80's had an intern he introduced me to that was building a bike computer as a final project for school. It was interesting how he approached it as he showed me the array of chips available in a catalog for the project. The thing was not as miniaturized as they are today, it was slightly larger in size than the old Cateye ring computer and ran on 4 AA batteries. Very limited function selection. It had a temp function because it was easily incorporated.
I did not understand the thing is to be used on a unicycle! Since the mag feeds the CPU, the CPU will Bluetooth to a phone app for readout, correct?
TiHabanero is offline  
Old 07-14-18, 09:11 AM
  #5  
UniChris
Senior Member
Thread Starter
 
UniChris's Avatar
 
Join Date: May 2017
Location: NYC
Posts: 661

Bikes: 36" Unicycle

Mentioned: 13 Post(s)
Tagged: 0 Thread(s)
Quoted: 281 Post(s)
Liked 30 Times in 25 Posts
Originally Posted by TiHabanero View Post
Since the mag feeds the CPU, the CPU will Bluetooth to a phone app for readout, correct?
It's going to have a roughly traditional sized display mounted between what are basically bar ends on a hand rest, though likely a more power hungry but easier to work with OLED one. I have a basic conventional cycle computer on there right now and can see it until it gets dark. Actually more of the annoyance is that I'm constantly taking the handlebar off for transport - if I didn't make a custom computer, I should probably just cut the cable on the existing one and put a connector in the middle of it.

I've thought of radio remoting the display, but more likely to a watch type device (I'd originally even been thinking something helmet mounted, but watch is probably better). I wouldn't have a phone that was worth anything out while riding, rather I keep it in my backpack and pull it out at rest stops to take pictures and consider overall progress. So the BLE transmit idea is a combination of something that could drive a secondary wrist display and to keep records on the phone that can be cross referenced with GPS location, as otherwise I'd have to go back and match progress logs saved inside the device to distance along the the trail guided by an assumption that breaks happened mostly at road crossings and hill crests.

Unlike what some of the really low end wireless computers do, I would not transmit the actual sensor pulses, but instead a checksumed packet containing their total count and a recent average of their spacing - so missed packets only mean the display is slow to update, the actual ridden distance doesn't get corrupted.

Last edited by UniChris; 07-14-18 at 11:32 AM.
UniChris is offline  
Old 07-14-18, 11:01 PM
  #6  
rgconner
Senior Member
 
rgconner's Avatar
 
Join Date: Mar 2017
Location: Sacramento, CA
Posts: 1,154

Bikes: Curtis Inglis Road, 80's Sekai touring fixie

Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 471 Post(s)
Liked 2 Times in 2 Posts
Shock collar if you go under pace or stop too long...

Raspberry Pi with a touch color screen and built in BT?

Then you could get BT sensors for HR/SPD/CAD
rgconner is offline  
Old 07-14-18, 11:59 PM
  #7  
UniChris
Senior Member
Thread Starter
 
UniChris's Avatar
 
Join Date: May 2017
Location: NYC
Posts: 661

Bikes: 36" Unicycle

Mentioned: 13 Post(s)
Tagged: 0 Thread(s)
Quoted: 281 Post(s)
Liked 30 Times in 25 Posts
Originally Posted by rgconner View Post
Shock collar if you go under pace or stop too long...
Probably more of a piezo beeper, but I did consider a phone vibrator motor if doing an auxiliary watch display.

Raspberry Pi with a touch color screen and built in BT?
No, a raspberry pi is completely unsuited to this. People forget, but that line of chips was made for TV boxes that are plugged into the wall. It's missing all of the engineering to support efficient operation on battery that a phone has. And this application doesn't need anything nearly so powerful, just a small Flash-based ARM Cortex MCU - probably one integrated with the Bluetooth LE radio itself though it's looking like I won't even try to get the BLE up in the first version.

It was not a focused or productive day, but I did spend some time putting dummy info on the tiny OLED with an off-the-shelf Ardruino library and planning what I want where. Power consumption of the OLED and a whole Arduino in the first test looks to be around 22 milliamps, which is high (absurdly high compared to a traditional one that can run on a coin cell), but a 400 mAH cell should be enough for an all day ride. Reminds me I need to repeat the test and see if consumption varies with the number of pixels turned on; I would expect so. Would also expect I can drastically drop the MCU's part of the power consumption by properly leveraging sleep modes.

Last edited by UniChris; 07-15-18 at 12:02 AM.
UniChris is offline  

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

Copyright 2018 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.