LCDX & Thermistor Query

Started by query_again May 15, 2006
Hi,

Appreciate if anyone could kindly advise the followings:
1) I am using a 4X20 parallel LCD, pls advise what is the command
required to goto row3 and row4 (that is line#3 and #4)

2) Anyone has experience in wiring up a 50ohm PTC thermistor to BX-24,
for displaying the temperature on LCD?

Thanks alot;)

Address line 3 as though it was line 1 except that the column is offset
by &h50. To position the cursor at column 1, line 3, send a command to
move the cursor to column &h51, row 1. Similarly, for row 4, send a
command to move the cursor to column &h51, row 2. The 4 row LCDs
actually only have 2 rows that wrap at offset &H50. This info is in the
data sheet for the LCD and LCD datasheets are readily available on the web.

Paul

query_again wrote:
> Hi,
>
> Appreciate if anyone could kindly advise the followings:
> 1) I am using a 4X20 parallel LCD, pls advise what is the command
> required to goto row3 and row4 (that is line#3 and #4)
>
> 2) Anyone has experience in wiring up a 50ohm PTC thermistor to BX-24,
> for displaying the temperature on LCD?
>
> Thanks alot;)
>
>
> ... wiring up a 50ohm PTC thermistor to BX-24...

A 50-ohm thermistor is too low a nominal value to usefully directly
connect to an analog input, I think.

I believe you'll need to, minimally, use an additional fixed series
resistance to form a voltage divider; for the resultant voltage change
to offer any reasonable resolution, that resistor will need to be
similar in value to the thermistor. Consequently, I suspect you will
see a significant current - and self heating - through the sensor. You
can reduce or eliminate that with an opamp, but I suspect that's a few
steps ahead of where you are.

Many folks have used thermistors with BX-24s but I think usually with
much larger values. Lots of information is available, like
http://groups.yahoo.com/group/basicx/messagesearch?query=thermistor&submit=Search&charset=ISO-8859-1
Tom
--- In b..., "query_again" wrote:
>
> Hi,
>
> Appreciate if anyone could kindly advise the followings:
> 1) I am using a 4X20 parallel LCD, pls advise what is the command
> required to goto row3 and row4 (that is line#3 and #4)
>
> 2) Anyone has experience in wiring up a 50ohm PTC thermistor to BX-
24,
> for displaying the temperature on LCD?
>
> Thanks alot;)
>

Hi,

Are you constrained by something for using PTC thermistor? As far as
I know, they are primarily used for other purposes, like current-
limiting devices to protect from over current conditions.

For temperature measurements they usually use NTC thermistors.
Following are the code examples and wiring diagram from Dr. Peter H.
Anderson site:

http://www.phanderson.com/bx24/therm_1.html
http://www.phanderson.com/bx24/adc0831.html
http://www.phanderson.com/picaxe/picaxe_thermistor.html