What is with the maximum speed on cheapo computers?

[dgk]

I've only had two bike computers. The first was a wired cheapo from
Kmart which worked fine but the maxiumum speed indicator was always
some weird negative number. Seemed odd but otherwise the thing worked
fine.

So now I bought a nicer one, wireless, model dB4LW - no brand
mentioned on it and I don't recall. Still pretty cheap. The really odd
thing is that this one registers my maxiumum speed, which should be
around 28, as -77.4. Yes, minus 77.4. So, two computers, two negative
numbers. Am I riding backwards? The odometer on this one is 574.65
which seems right. Very weird.

 

[Ken]

"dgk" <[email protected]> wrote in message
news:[email protected]...
> I've only had two bike computers. The first was a wired cheapo from
> Kmart which worked fine but the maxiumum speed indicator was always
> some weird negative number. Seemed odd but otherwise the thing worked
> fine.
>
> So now I bought a nicer one, wireless, model dB4LW - no brand
> mentioned on it and I don't recall. Still pretty cheap. The really odd
> thing is that this one registers my maxiumum speed, which should be
> around 28, as -77.4. Yes, minus 77.4. So, two computers, two negative
> numbers. Am I riding backwards? The odometer on this one is 574.65
> which seems right. Very weird.

Funny, but I bought a "Schwinn" computer from the local Wally-World mart a
couple of months ago, and for $10.00 it has been one of the best investments
I have made. No funny happenings. Never misses a beat.

Ken

 

[Dan]

Ken wrote:
> "dgk" <[email protected]> wrote in message
> news:[email protected]...
>
>>I've only had two bike computers. The first was a wired cheapo from
>>Kmart which worked fine but the maxiumum speed indicator was always
>>some weird negative number. Seemed odd but otherwise the thing worked
>>fine.
>>
>>So now I bought a nicer one, wireless, model dB4LW - no brand
>>mentioned on it and I don't recall. Still pretty cheap. The really odd
>>thing is that this one registers my maxiumum speed, which should be
>>around 28, as -77.4. Yes, minus 77.4. So, two computers, two negative
>>numbers. Am I riding backwards? The odometer on this one is 574.65
>>which seems right. Very weird.
>
>
> Funny, but I bought a "Schwinn" computer from the local Wally-World mart a
> couple of months ago, and for $10.00 it has been one of the best investments
> I have made. No funny happenings. Never misses a beat.
>
> Ken
>
>


I've got one of those too, paid like 11.95 at another department store.
Mine works great as well. Main features are speed, total distance,
trip distance, avg speed, max speed, trip time & time. It's a wired
type. Odd that the you keeps getting negative max speed. I'm assuming
you have the right wheel size inputed, but even so that shouldn't give a
negative number. I'd be a little concerned about a cheap wireless.

Dan

 

[dgk]

On Mon, 20 Jun 2005 11:15:25 -0400, Dan <[email protected]>
wrote:

>Ken wrote:
>> "dgk" <[email protected]> wrote in message
>> news:[email protected]...
>>
>>>I've only had two bike computers. The first was a wired cheapo from
>>>Kmart which worked fine but the maxiumum speed indicator was always
>>>some weird negative number. Seemed odd but otherwise the thing worked
>>>fine.
>>>
>>>So now I bought a nicer one, wireless, model dB4LW - no brand
>>>mentioned on it and I don't recall. Still pretty cheap. The really odd
>>>thing is that this one registers my maxiumum speed, which should be
>>>around 28, as -77.4. Yes, minus 77.4. So, two computers, two negative
>>>numbers. Am I riding backwards? The odometer on this one is 574.65
>>>which seems right. Very weird.
>>
>>
>> Funny, but I bought a "Schwinn" computer from the local Wally-World mart a
>> couple of months ago, and for $10.00 it has been one of the best investments
>> I have made. No funny happenings. Never misses a beat.
>>
>> Ken
>>
>>
>
>
>I've got one of those too, paid like 11.95 at another department store.
> Mine works great as well. Main features are speed, total distance,
>trip distance, avg speed, max speed, trip time & time. It's a wired
>type. Odd that the you keeps getting negative max speed. I'm assuming
>you have the right wheel size inputed, but even so that shouldn't give a
>negative number. I'd be a little concerned about a cheap wireless.
>
>Dan

I've had no trouble with the wireless part. Everything seems accurate
but that max.

 

[trg]

"Ken" <[email protected]> a écrit dans le message de news:
[email protected]...
|
| "dgk" <[email protected]> wrote in message
| news:[email protected]...
| > I've only had two bike computers. The first was a wired cheapo from
| > Kmart which worked fine but the maxiumum speed indicator was always
| > some weird negative number. Seemed odd but otherwise the thing worked
| > fine.
| >
| > So now I bought a nicer one, wireless, model dB4LW - no brand
| > mentioned on it and I don't recall. Still pretty cheap. The really odd
| > thing is that this one registers my maxiumum speed, which should be
| > around 28, as -77.4. Yes, minus 77.4. So, two computers, two negative
| > numbers. Am I riding backwards? The odometer on this one is 574.65
| > which seems right. Very weird.
|
| Funny, but I bought a "Schwinn" computer from the local Wally-World mart a
| couple of months ago, and for $10.00 it has been one of the best
investments
| I have made. No funny happenings. Never misses a beat.
|
| Ken
|
Quite a few motorcyclist hook up cycle computers since they are able to be
calibrated and have max speed and other functions. The Sigma BC 800, far
from the top of the Sigma line, is quite popular for this. I believe it goes
to 180 mph or so. No reports of negative speeds, AFAIK.

 

[Leo Lichtman]

Turn the magnet around. <G>

 

[John Everett]

On Mon, 20 Jun 2005 09:01:28 -0400, dgk
<[email protected]> wrote:

>I've only had two bike computers. The first was a wired cheapo from
>Kmart which worked fine but the maxiumum speed indicator was always
>some weird negative number. Seemed odd but otherwise the thing worked
>fine.
>
>So now I bought a nicer one, wireless, model dB4LW - no brand
>mentioned on it and I don't recall.

It's a Filzer.


jeverett3<AT>earthlink<DOT>net http://home.earthlink.net/~jeverett3

 

[Rich]

dgk wrote:
> I've only had two bike computers. The first was a wired cheapo from
> Kmart which worked fine but the maxiumum speed indicator was always
> some weird negative number. Seemed odd but otherwise the thing worked
> fine.

It's not unusual for computer to display a negative number when the the
highest number the programmer thought would be needed is exceeded by the
user.

Typically, if a computer has allocated enough space to store 256
different numbers for a particular use (such as speed), it'll use the
first 128 to store positive numbers, and the last 128 to store negative
numbers. So after getting to 127 (0-127 are 128 numbers), the next
number displayed would be negative.


> The really odd
> thing is that this one registers my maxiumum speed, which should be
> around 28, as -77.4. Yes, minus 77.4.

I can't figure out why -77.4 would show up.... computers is complex.

Rich

P.S. A cateye Mity 8 (?) will go up to at least 55mph (we have big
hills in Colorado).

 

[dgk]

On Mon, 20 Jun 2005 10:30:55 -0600, Rich <[email protected]>
wrote:

>dgk wrote:
>> I've only had two bike computers. The first was a wired cheapo from
>> Kmart which worked fine but the maxiumum speed indicator was always
>> some weird negative number. Seemed odd but otherwise the thing worked
>> fine.
>
>It's not unusual for computer to display a negative number when the the
>highest number the programmer thought would be needed is exceeded by the
>user.
>
>Typically, if a computer has allocated enough space to store 256
>different numbers for a particular use (such as speed), it'll use the
>first 128 to store positive numbers, and the last 128 to store negative
>numbers. So after getting to 127 (0-127 are 128 numbers), the next
>number displayed would be negative.
>
>
>> The really odd
>> thing is that this one registers my maxiumum speed, which should be
>> around 28, as -77.4. Yes, minus 77.4.
>
>I can't figure out why -77.4 would show up.... computers is complex.
>
>Rich
>
>P.S. A cateye Mity 8 (?) will go up to at least 55mph (we have big
>hills in Colorado).

!!!! I don't feel safe going 30. Downhill at 55 would scare the ****
out of me.

I'm a programmer, yes I love overflows. My favorite was the first
tetris, which went negative at scores over 32767 (two byte integer). I
figured that meant that I had won.

 

[Rich]

dgk wrote:

> !!!! I don't feel safe going 30. Downhill at 55 would scare the ****
> out of me.

It was on an old MTB to boot. I kept trying to increase my top speed on
each ride, of which this hill was a part, until a biker friend of mind
told me that last year a rider had died going down that hill (it's not
straight, and one edge has a gaurd rail and then a pretty steep dropoff.
After being clued in to the obvious danger, I've stopped going so
fast. I now just don't tuck in as far.

> I'm a programmer, yes I love overflows. My favorite was the first
> tetris, which went negative at scores over 32767 (two byte integer). I
> figured that meant that I had won.

Tetris on old palm pilots (actually a visor) overflow at the same point.

Rich

 

[C.J.Patten]

"dgk" <[email protected]> wrote in message
news:[email protected]...
> I've only had two bike computers. The first was a wired cheapo from
> Kmart which worked fine but the maxiumum speed indicator was always
> some weird negative number. Seemed odd but otherwise the thing worked
> fine.
>
> So now I bought a nicer one, wireless, model dB4LW - no brand
> mentioned on it and I don't recall. Still pretty cheap. The really odd
> thing is that this one registers my maxiumum speed, which should be
> around 28, as -77.4. Yes, minus 77.4. So, two computers, two negative
> numbers. Am I riding backwards? The odometer on this one is 574.65
> which seems right. Very weird.

I'm copying this from another thread - I have the same computer and solved
the problem.

Heheheheh. It's a setup issue.

That "negative" symbol isn't describing your speed. It's telling you your
CURRENT speed is less than your maximum or average, depending on what mode
you're in.

If you ever see a "wonky" speed, (eg: -96mph) in max or average, perform a
"trip-reset" (my words) - not the reset that kills all your settings but the
one that resets the trip time and distance.

If the signal from the sensor is weak, you'll get erroneous readings. One
cause of this is computer position. I had to adjust mine so the computer
wasn't obscured by the handlebars. They now sit about half over and half in
front of the bars with a clear line of sight to the sensor. I haven't had a
bad reading since I did this.

Aside from getting used to the interface and modes, the dB4LW has been by
best computer to date. (as I said, I've had a few ranging from cheap-imports
to expensive Cat-Eye's with cadence)

Manual online: http://www.filzer.com/images/dB/4LW-instructions.pdf
All model info here: http://www.filzer.com/catalog.html

C.