driver for LCD display

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Volter
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driver for LCD display

Post by Volter »

I just replaced a AAA battery in one of those devices that displays inside temperature and outside temperature, I could switch that from F to C and also I could set it as clock BUT after the battery change I cannot see anymore the outside temperature. It defaults to LLL.
So, I guess by changing the battery I blew the IC, size of a speckle, and cannot be fixed.
I wondered, would anyone know of a circuit that could do the same stuff or show the Ts at least? I am sure it was programmed in the IC and I do not think there are out there ICs like that. What it would take to build circuit like that?
Thanks.
:mad:
Bigglez
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Re: driver for LCD display

Post by Bigglez »

Volter wrote: BUT after the battery change I cannot see anymore the outside temperature. It defaults to LLL.
I use a similar product, made by Oregon Scientific.
The outside temp is from a remote sensor on a cable.
If the cable is shorted or open-circuit the display will
show HHH or LLL (not sure if LLL is open or shorted...)

Check your cable! Possibly the wire was damaged or
pinched when the battery was replaced.
Bigglez
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Re: driver for LCD display

Post by Bigglez »

Volter wrote: I wondered, would anyone know of a circuit that could do the same stuff or show the Ts at least? I am sure it was programmed in the IC and I do not think there are out there ICs like that. What it would take to build circuit like that?
Correct, the construction is probably COB (chip on board),
and covered with a blob of epoxy.

No chance of hacking it. Better to replace the entire unit.
I use one outdoors for patio (indoor reading) and swimming
pool (outdoor sensor on a cable). As the unit is for indoor
use I have to bring it inside and of the winter rains (when
the pool is closed, anyway).

Water or moisture contamination and the unit fails.

There are single chip temps sensors, or an all-analog circuit
with op amps will work. The sensor in your case is a thermistor
that changes resistance with temps.

The digital chips require a uC to configure the chip and
receive the digital data stream. The uC is also needed
to run the display. LEDs are much easier to use than
raw LCD displays. An LCD module (complete sub-system
to drive the LCD glass is an easy alternative to LEDs,
and better suited to battery power and daylight readable.

A bit more than a weekend project, but not by much!
Robert Reed
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Re: driver for LCD display

Post by Robert Reed »

"Check your cable! Possibly the wire was damaged or
pinched when the battery was replaced."


Good info - I have had the exact same situation with two units in the past. Seems like these asian devices are so cheap, they cannot stand moderate 'manhandling' needed to just replace batterys.
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philba
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Re: driver for LCD display

Post by philba »

one other possibility - it takes a fair amount of time to acquire the wireless signal. I had something very similar on mine (Lacrosse, I think) when I changed the battery. It eventually got sync'd up and displayed the outside temp.

Ditto on them being fragile. Our maid knocked one unit off the shelf for a 1 M drop to carpet. It's never been the same.
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MrAl
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Re: driver for LCD display

Post by MrAl »

Bigglez wrote:
Volter wrote: BUT after the battery change I cannot see anymore the outside temperature. It defaults to LLL.
I use a similar product, made by Oregon Scientific.
The outside temp is from a remote sensor on a cable.
If the cable is shorted or open-circuit the display will
show HHH or LLL (not sure if LLL is open or shorted...)

Check your cable! Possibly the wire was damaged or
pinched when the battery was replaced.
Hi,

I have to agree with Bigglez here in that when the cable is open you get a strange display.
I had one that did this when the cable opened up (constant flexing) and once i soldered
it back together it worked again. I think they use the 10k, 1 percent NTC thermistors
for the sense element in these things but i guess it could vary.

You can build your own 'digital' thermometer in a number of ways...
1. Start with a microcontroller and use a thermistor as sense element and read it with the uC.
2. Start with a microcontroller and use a digital output sensor and read it with the uC.
3. Start with a basic circuit that converts temperature to voltage calibrated for 10mv/degC
and read it with a digital multimeter.
4. Start with a basic sensor that outputs 10mv/degC and use a digital meter to read it.
5. Go to Walmart and buy a new one for 8 US Dollars...probably the easiest and fastest and
maybe cheapest way to do this.

I find that when using a thermistor with the right resistor value i get a decent range of
linearity reading the thermistor voltage directly which simplifies the algorithm, although
there are other ways to read the thermistor too which work even better and helps to
keep the resolution over the temperature range pretty much constant.
LEDs vs Bulbs, LEDs are winning.
DocJC
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Re: driver for LCD display

Post by DocJC »

If the remote is also a wireless remote then change its battery.

This may help. Removing and re-inserting it will reset the remote.

JC
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