This is gonna sound stupid but I just installed my g/f's Cateye Astrale 8 on her 7200 and she doesn't care for how the zipties and everything else looks although she has said she will grow to like it.

Anyone have pics of how they wired their cyclocomputers so I can steal some good ideas from you?

yup...let me go take mine...BRB I have the same computer too

I still need to get a few more zip ties for the area around my BB, but overall I'm quite happy with my wiring job. I didn't want to go down the bottom tube, so I went along the top tube...uses up more wire too, less of it hanging everywhere.

My girlfriend has he Astral 8 setup the same way as my specialized computer on her hybrid. She just got a road bike for christmas so we're moving the astral over in the same way it's set up on my litespeed. It takes a little longer to wrap the wire but the look is very clean.

Mine would have been that way, but not one single wire of mine runs along that bottom tube...nothing to work with

Thanks guys! Is there a similarly priced wireless that has the same functions (except cadence) - she doesn't care about it as much as I do. I've checked out nashbar, performance, pricepoint, supergo but the only cyclocomputers I really read about in here is Cateye's, and Shimano Flight Decks (which I would love for my STI shifters) and specialized. There seems to be a ton of other brands that look similar and are probably the same inside..

Most computers from $20 to about $100 have similar functions.
Here's a good one on sale for $17.99 https://www.performancebike.com/shop/...tegory_ID=4110
It's wireless. No cadance, just the wireless speed sensor, so no wires.
Or wireless speed and cadance $99 https://www.performancebike.com/shop/...egory_ID=4110#
Or wireless speed and cadance in 1 computer, $150 https://www.performancebike.com/shop/...tegory_ID=4110

just so you know HIDs will interfere with wireless computers...just an FYI incase you have a HID. I almost bought a wireless computer when a friend told me of that.

I did not know that HID interferes with the wireless. We don't plan on doing any nite riding - well definately not my gf.. I just put a NiteRider cheepie LED front/rear lights on her 7200 for my peace of mind.

In a way I hope she doesn't like the looks of the Astrale 8's wires so I can put it on my 1000. It's got more stuff than she cares about (like speed, cadence, etc..) she just wants to know how far she went but she won't let me strap my little eTrex vista GPSr on her bars...

Here is my wierd computer setup... see attachment... one rear computer with cadence (trainer) and one flightdeck for on the road...

I'm wondering, what is the effect of changing the placement of your sensors? Obviously putting them closer to the center of the wheel and crank arm will increase the amount of time the sensor parts are aligned, but I'm not sure if that's good or bad. Having them at the end of the wheel and crank arm would increase accuracy a bit, I figure, but might cause some problems from having less contact.

Anyone know the optimal placement for the sensor magnets? I'm suprised my Astrale 8 guide doesn't suggest where on the wheel or crank arm you install the stuff.

I have the Astrale 8, and it's wired along the bottom tube - the other wires look ugly anyway, what does one more hurt?

Seeing as the box of the cateye says they're spec'ed for 186mph, i don't think any cyclists can humanly go fast enough to throw off the accuracy of the sensor.

The computer probably senses when the magnet trips the sensor, not how long its been tripped for. I guess that's why they specify a maximum distance between sensor and magnet in their instructions.

I, too, wonder if there is an optimal place on the wheel you could put the sensor but then again the error difference from 1-30 mph probably isn't as great as 30-185 or whatever its maximum limit is because at speeds up high you're dealing with your tire diameter changing due to centrifugal forces and other variables that would cause the error to be +/- your actual speed. I need to put the GPSr on the bars and see if there is a difference.

Although I have never dissected a Bike computer, I have used similar instruments in laboratories and here is how they work. The sensor has a coil in it called a Hall Effect sensor. When the magnet on the spoke passes the coil, it produces a voltage spike. The faster it passes, the higher the voltage. The slower it passes the wider the voltage spike. A stronger magnetic field (bigger magnet or moving the sensor closer to the magnet) will also increase the voltage. The computer has a frequency counter and an oscillator that produces a stream of pulses. When the voltage from the Hall Effect sensor's pulse gets high enough, it starts the counter. When the next pulse comes, it stops counting. By knowing the frequency of the oscillator and the number of pulses, it calculates how long it has taken to make one revolution. We input how far the bike goes in one wheel revolution so it is a simple matter to convert the data to speed.

Now, to answer your questions. If the magnet is too close to the axle and you are driving real slow, or the sensor is too far away from the magnet, then you may not generate enough voltage to trip the counter. If you move past the magnet real quickly, then the pulse may not be wide enough to start the counter. Modern electronics are very fast and so I would not worry about having enough time to trigger the counter. You are better off making sure you have enough voltage so mount the magnet near the outside of the wheel if you are concerned with the computer's reliability.

Here are some other factors not to consider. By moving the magnet outward, you are increasing the rotation momentum of the wheel ever so slightly which means it takes more power to get up to speed. The mass of the magnet is tiny compared to the mass of the wheel so don't worry about it. It also produced an unbalance force but again it is so small you can ignore it.

Now THAT'S what I call a post.

Thanks GeezerGeek, that was very informative.

I believe bike computers use reed sensors.
You can hear the reeds contacting. Try moving the magnet back and forth over the sensor in a quiet room, you'll hear the sensor clicking.

From reed-sensor.com:

FAQ on Reed Switches and Reed Sensors
What is a reed switch ?
The basic reed switch consists of two identical flattened ferromagnetic reeds, sealed in a dry inert-gas atmosphere within a glass capsule, thereby protecting the contact from contamination. The reeds are sealed in the capsule in cantilever form so that their free ends overlap and are separated by a small air gap.



What is a reed sensor ?
A reed sensor is a device built using a reed switch with additional functionality like ability to withstand higher shock, easier mounting, additional intelligent circuitry, etc.

How does a reed switch work ?
When a magnetic force is generated parallel to the reed switch, the reeds become flux carriers in the magnetic circuit. The overlapping ends of the reeds become opposite magnetic poles, which attract each other. If the magnetic force between the poles is strong enough to overcome the restoring force of the reeds, the reeds will be drawn together.

What magnetic force is required to close a reed switch ?
Minimum force - expressed in ampere-turns, will cause the reeds to close, and is called the just-operate force. Since the force between the poles increases as the gap decreases, a force of approximately half the just-operate force will maintain the operated state. Speed of operation of the reed switch is determined by the excess of operating force over the just-operate force.

What are the advantages in using reed switches ?
They are hermetically sealed in glass environment, free from contamination, and are safe to use in harsh industrial and explosive environments. Reed switches are immune to electrostatic discharge (ESD) and do not require any external ESD protection circuits. The isolation resistance between the contacts is as high as 1015 ohms, and contact resistance is as low as 50 milliohms. Reed switches can directly switch loads as low as a few micro-watts without needing external amplification circuits, to as high as 120W. When used in combination with magnets and coils, they can be used to form many different types of relays.

So basically that's the gist of it.
While it's never been confirmed, if the contact is closed when the magnet passes over it and you park the bike with the spoke that has the magnet directly over the sensor, that might drain the batteries a lot faster in the computer or transmitter (if you have wireless).