Bicycle Mechanics - Cyclometers and Sun.........

Evidently, cyclometers and sun do not mix well. Went for a ride yesterday, and left the bikes, with cyclometers on them, in the back of my truck, while we took all the gear in, took the dogs down the street for a walk, grabbed some ice water, etc. Was probably around 20 minutes they sat there. Upon unloading the bikes, noticed one of them (an inexpensive wireless house brand) had all the display showing, every function, zero's for all of the numbers, whatever could appear on the screen did appear on the screen. Was hoping it would work after it cooled down, and luckily, it does. So, don't leave your cyclometers out in the sun for long periods of time. The only thing I can figure is that LCD's must work by heat generated by electrical impulses?? Just wondering, figured that the LCD's being heated up brought them up on the display.

LCD's must work by heat generated by electrical impulses??
Nope. For the types of displays used by cyclometers, the presence of a small electrical field changes how the material polarizes the light passing through it, making the area look different.

Integrated circuits have an upper temperature limit above which they cease to function. Military-grade logic is closely spec'd and tested for this, but consumer stuff is sort of hit-or-miss, with a much lower designed temperature range. Also, battery voltage increases as the cell gets hotter, and may have caused the power circuit to cut it off, or the higher voltage may have cause a reset.

Data saved in non-volatile memory may or may not be affected by any of this.

Data saved in non-volatile memory may or may not be affected by any of this.

Well yes, that are the two choices

There are three states of information: positive, negative, and unknown.

When diagnosing a problem, knowing that a symptom has no diagnostic value is as real and valuable information as knowing that the symptom state is determinate of X.

Smarm, otoh, has no value.

Standard LCDs don't work in high (~>120F) heat. The sun on the unit can easily get it to to that range.

The computer still will work, but the display wont.

In the summer for my ride home the display always stops working. Once home and cooled down all the correct data from the ride is available.

Al

an inexpensive wireless house brand

That's all the troubleshooting you need, right there.

I've never had a problem with a bike computer in the sun while riding. I have had a computer reset itself while being stored in a hot car. It wasn't a cheap brand, either.

The instruction booklet of the cheapo Nashbar C-comp specificly warns against leaving the unit in direct sunlight.
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Didn't it all show up correctly after it cooled off? LCDs do tend to show every line when too hot, but mine always returned to normal. It isn't sun, it's heat. Usually just riding it enough to cool 'em off.

If your cyclocomputer craps out after been in the sun for 20mins this time of the year, it's time to look for a new one. Standard LCDs are typically good for up to 50degC. High temp version go up to 100+degC. Cyclocomputer makers should know that these things are inherently outdoor duty devices and will be under the sun for extended periods.

If your cyclocomputer craps out after been in the sun for 20mins this time of the year, it's time to look for a new one. Standard LCDs are typically good for up to 50degC. High temp version go up to 100+degC. Cyclocomputer makers should know that these things are inherently outdoor duty devices and will be under the sun for extended periods.
Cyclocomputers exposed to the sun can easily reach 50C. (After all I've cycled in 49C air temps before)

Do you know what voltage/power requirements the non-standard versions require? I don't but I wonder if there are downsides (beyond cost) for using them in small, low power portable units?

http://www.altadox.com/lcd/knowledge/lcd_temperature_ranges.htm
http://www.pacificdisplay.com/lcd_temp_range.htm

Anyway the 3 different Cateye cyclocomputers I've ever used have all had displays crap out in the summer afternoon.

Al

Smarm, otoh, has no value.

I would bear your children were I capable.

But yeah, you wanna have some fun, gather up a bunch of electronics from around your house and put them in the back of your truck on a sunny day, come back in 20 minutes and see what's not broken or damaged. My guess is not much. Also don't put them in the microwave, underwater (esp. while plugged in), or in fire.

Oops, that's kinda smarmy.

But being in the back of a steel vehicle with a lens over it is not a good thing for the temperature of the LCD. While the ambient might only be 30-40 deg C, add in reflection from the steel truck bed (try touching one on a hot day!) and focused sunlight from the lens over the screen, and it'd be pretty easy to see temps close to 90 deg C. Way beyond the failure point for most consumer-grade electronics components.

Cyclocomputers exposed to the sun can easily reach 50C. (After all I've cycled in 49C air temps before)
Do you know what voltage/power requirements the non-standard versions require? I don't but I wonder if there are downsides (beyond cost) for using them in small, low power portable units?
http://www.altadox.com/lcd/knowledge/lcd_temperature_ranges.htm
http://www.pacificdisplay.com/lcd_temp_range.htm
Anyway the 3 different Cateye cyclocomputers I've ever used have all had displays crap out in the summer afternoon.
Al
The LCDs we routinely spec out at work go -30 to +85C. Our stuff have to work in the middle east desert as well as Canadian winters. The LCD bias voltage is higher on the extended temp version, but it's to add excitation to the LC for the low temp side, which shouldn't be a concern for cycling. I doubt too many would brave much below freezing. I think high temp tolerance has to do more with the construction of the LCD than the electrical requirements.

Evidently, cyclometers and sun do not mix well. Went for a ride yesterday, and left the bikes, with cyclometers on them, in the back of my truck, while we took all the gear in, took the dogs down the street for a walk, grabbed some ice water, etc. Was probably around 20 minutes they sat there. Upon unloading the bikes, noticed one of them (an inexpensive wireless house brand) had all the display showing, every function, zero's for all of the numbers, whatever could appear on the screen did appear on the screen. Was hoping it would work after it cooled down, and luckily, it does. So, don't leave your cyclometers out in the sun for long periods of time. The only thing I can figure is that LCD's must work by heat generated by electrical impulses?? Just wondering, figured that the LCD's being heated up brought them up on the display.

Actually, the display just activated all the segments due to the heat. Functionally, it would have worked fine. any miles logged with the display overheated would have likely been logged, etc. If the display gets way too hot, the whole LCD will go black. Even hotter, it might have permanent black "blobs" under the display. Hotter still, the display will crack and/or stay black.

This is the opposite of a cyclocomputer display acting really sluggish or failing to "come online" in really cold weather.

The electronics themselves would probably work up past 250 degrees fahrenheit. The watch battery and/or LCD display would fail at a much lower temperature.

In short, your computer wasn't malfunctioning. You weren't paying attention to the "operating conditions" section of the manual, though, either.