Computer electrical question



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Danny Colyer

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For the past week, my Cateye Astrale has had no speed reading. The cadence reading is fine. The
problem probably occurred as a result of removing the wheel. I had no computer problems in the
morning on the way into work. Near the office I picked up a puncture, which I repaired just before
leaving at the end of the day. After fixing the puncture, I had no speed reading.

The obvious first thought was an alignment problem between the magnet and the sensor. But the
alignment really couldn't be better. I've tried waving other magnets passed the sensor, and nothing.

The next thought was a broken cable. The cable has been broken in the past, so I wondered whether
one of my soldered repairs might have broken. I don't know whether they had or not - by the time I'd
removed the insulating tape from around the wires to check, they were certainly broken. So I
resoldered them, but no joy.

The next thing was to clean the terminals. Seemed a long shot, and sure enough it's made no
difference at all.

I think the most likely problem is a broken wire. There's no visible damage, but a wire may have
broken inside the plastic outer. But I don't know how to test for that, or how to work out just
where it's broken. Any ideas?

--
Danny Colyer (remove safety to reply) ( http://www.juggler.net/danny ) Recumbent cycle page:
http://www.speedy5.freeserve.co.uk/recumbents/ "He who dares not offend cannot be honest." -
Thomas Paine
 
A

Anonymous

Guest
"Danny Colyer" <[email protected]> wrote in message news:[email protected]...
> I think the most likely problem is a broken wire. There's no visible damage, but a wire may have
> broken inside the plastic outer. But I don't know how to test for that, or how to work out just
> where it's broken. Any ideas?

Volts box/circuit tester, and do standard 'search for the break in the wire' stuff. Tape a magnet to
the sensor, such that the reed switch is permanently shut and the circuit should then be complete
bar your break. Finding breaks in wires can be tedious - probably easier to replace most of it.

It may be worth just checking the computer first - it's almost certainly fine, but repeatedly
shorting the two contacts should simulate normal use and a speed should appear.

cheers, clive
 
T

Tim Dunne

Guest
news:[email protected]...

> such that the reed switch

Sorry to be difficult, but the sensor is more likely to be a hall-effect device than a reed switch:
these have no moving parts and generate a voltage when exposed to a moving magnetic field.

Tim
--
Sent from Brum, UK... ...scheduled completion Sept 2003 'What's keeping the White House white? Is it
chalk, is it fog, is it fear?' Steve Skaith, 'America For Beginners' Look, mum, an anorak on a bike!
Check out www.nervouscyclist.org
 
A

Anonymous

Guest
"Tim Dunne" <[email protected]> wrote in message
news:[email protected]...

> news:[email protected]...
>
> > such that the reed switch
>
> Sorry to be difficult, but the sensor is more likely to be a hall-effect device than a reed
> switch: these have no moving parts and generate a
voltage
> when exposed to a moving magnetic field.

Try it:

Take a cycle computer made by Cateye (OP was using the astrale). Take a magnet and move it to and
from the sensor. You can hear the reed switch ticking.

You can test the other end by repeatedly shorting out the (relevant pair of) contacts on the
computer (I normally use a pair of keys on a key ring to demonstrate this). It displays a speed. You
don't need to apply a voltage, just close the circuit.

I think the avocet computers may work in a different way, but they're the only ones I've heard of
that are different.

cheers, clive
 
T

Tim Dunne

Guest
news:[email protected]...

> I think the avocet computers may work in a different way, but they're the only ones I've heard of
> that are different.

The Sigma I have is hall effect. I'm surprised a reed is fast enough... fair enough, I'll get me
coat... :)

Tim

--
Sent from Brum, UK... ...scheduled completion Sept 2003 'What's keeping the White House white? Is it
chalk, is it fog, is it fear?' Steve Skaith, 'America For Beginners' Look, mum, an anorak on a bike!
Check out www.nervouscyclist.org
 
D

Danny Colyer

Guest
Clive George wrote:
> It may be worth just checking the computer first - it's almost certainly fine, but repeatedly
> shorting the two contacts should simulate normal use and a speed should appear.

You're absolutely right, I just got it up to 14 mph. Thanks for that tip.

Oh well, I thought I'd probably end up replacing it anyway. Searching for the break doesn't seem
worth the effort, since I'll have to remove all the insulation first.

--
Danny Colyer (remove safety to reply) ( http://www.juggler.net/danny ) Recumbent cycle page:
http://www.speedy5.freeserve.co.uk/recumbents/ "He who dares not offend cannot be honest." -
Thomas Paine
 
D

Dr

Guest
"Tim Dunne" <[email protected]> wrote

>
> > I think the avocet computers may work in a different way, but they're the only ones I've heard
> > of that are different.
>
> The Sigma I have is hall effect.

Sure it isn't an inductive loop? Would a battery give sufficient life with an HE sensor? Doesn't an
HE sensor need 3 terminals?

David Roberts.
 
T

Tim Dunne

Guest
"DR" <[email protected]> wrote in message news:[email protected]...

> Sure it isn't an inductive loop?

Could be. It's certainly not a contact.

> Would a battery give sufficient life with an HE sensor? Doesn't an HE
sensor
> need 3 terminals?

I'm sure I've seen two-wire hall devices. I kind of assumed it was hall because it was non-contact
and magnetic.

As I said, I'll get me coat :)

Tim

--
Sent from Brum, UK... ...scheduled completion Sept 2003 'What's keeping the White House white? Is it
chalk, is it fog, is it fear?' Steve Skaith, 'America For Beginners' Look, mum, an anorak on a bike!
Check out www.nervouscyclist.org
 
P

Pete Biggs

Guest
Tim Dunne wrote: I'll get me coat... :)

That's alright :) ...I just would like to point out that /most/ cycle computers use reed switches
(they're cheap, simple and reliable), including the Cateye Mity 3. I don't know about the Astrale
but I suspect it has the same sensor (or at least a very similar one).

~PB
 
P

Pete Biggs

Guest
Danny Colyer wrote:
> For the past week, my Cateye Astrale has had no speed reading. The cadence reading is fine. The
> problem probably occurred as a result of removing the wheel. I had no computer problems in the
> morning on the way into work. Near the office I picked up a puncture, which I repaired just before
> leaving at the end of the day. After fixing the puncture, I had no speed reading.
>
> The obvious first thought was an alignment problem between the magnet and the sensor. But the
> alignment really couldn't be better.

Difficult to tell by sight (the alignment can be a bit weird and you might have forgotten what it
was like if something's moved).

> I've tried waving other magnets passed the sensor, and nothing.

...Quickly alternating from very near to far for at least a few seconds? Assuming so...........

> The next thought was a broken cable. The cable has been broken in the past, so I wondered whether
> one of my soldered repairs might have broken. I don't know whether they had or not - by the time
> I'd removed the insulating tape from around the wires to check, they were certainly broken. So I
> resoldered them, but no joy.
>
> The next thing was to clean the terminals. Seemed a long shot, and sure enough it's made no
> difference at all.

Cateye's are generally good, but the terminals on some computer brackets can become misaligned or
squashed down - so may fail to contact the computer. This has been the case with a cheap Atech model
I got recently. Bending the contacts with a screwdriver fixed it.

> I think the most likely problem is a broken wire. There's no visible damage, but a wire may have
> broken inside the plastic outer. But I don't know how to test for that, or how to work out just
> where it's broken. Any ideas?

Meter or some other low voltage circuit accross the contacts, then test with magnet.

The sensor (probably a reed switch) is unlikely to be faulty, but I suppose it's possible.

Cateye do replacement fitting kits, so that'll be your last resort instead of having to buy a whole
new computer.

~PB
 
T

Tim Dunne

Guest
"Pete Biggs" <pLime{remove_fruit}@biggs.tc> wrote in message
news:[email protected]...
> Tim Dunne wrote: I'll get me coat... :)
>
> That's alright :) ...I just would like to point out that /most/ cycle computers use reed switches
> (they're cheap, simple and reliable), including the Cateye Mity 3. I don't know about the Astrale
> but I suspect it has the same sensor (or at least a very similar one).

I'm surprised. I wouldn't have thought they'd be fast enough and have the reliability. Just goes
to show...

Tim
--
Sent from Brum, UK... ...scheduled completion Sept 2003 'What's keeping the White House white? Is it
chalk, is it fog, is it fear?' Steve Skaith, 'America For Beginners' Look, mum, an anorak on a bike!
Check out www.nervouscyclist.org
 
D

Danny Colyer

Guest
Pete Biggs wrote:
> Difficult to tell by sight (the alignment can be a bit weird and you might have forgotten what it
> was like if something's moved).

Embarassingly, I think that's it. I've fitted quite a few computers in my time (at least 7), and
they've all needed occasional adjustment, so I thought I had a pretty good idea how to line them up.
The magnet was passing somewhere between 1-2mm from what I thought was the correct part of the
sensor, but I got no reading even if I held it so that the magnet touched the sensor on each pass.

This afternoon I borrowed a much more powerful magnet than any I've got at home and managed to get a
reading, which made me think perhaps the reed switch was bent and couldn't be closed by the flux
from a normal bike computer magnet.

I tried another computer magnet this evening and couldn't get any reading. Then I took the sensor
off and started waving it around next to the magnet, and got a reading.

Finally I fished the manual out, and found that the part of the sensor that the magnet was supposed
to be passing was a few mm lower than I'd thought (I was confusing the positioning with the Trek
computer on my ATB, whose sensors are very similar in appearance but have to be aligned
differently).

So I now have a reading. I'll know after measuring the trip distance to work tomorrow whether it's
reliable, otherwise I'll probably still be looking at a replacement.

> Cateye do replacement fitting kits, so that'll be your last resort instead of having to buy a
> whole new computer.

But of course I'd already started looking at new computers :)

I don't think I'll find anything better than the Astrale. I quite fancied a wireless computer, but
the cadence function is important to
me. I've found a couple of wireless computers with a wired cadence option - the Sigma BC1400 looks
promising, but is a lot more expensive than the Astrale.

--
Danny Colyer (remove safety to reply) ( http://www.juggler.net/danny ) Recumbent cycle page:
http://www.speedy5.freeserve.co.uk/recumbents/ "He who dares not offend cannot be honest." -
Thomas Paine
 
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