Distance between lcd and uC

hayee · Joined: 05 Sep 2007 Posts: 252

Hi,
I am using PIC16f877A and LCD. I am showing some data on LCD.
I want to know that how far I can place the LCD from microcontroller (my required distance is 250ft). I am using the 6 pins of LCD (4 for data and 2 for signals). Can I use this scheme for longer distance or do I have to use any protocol like rs485?

I also want to connect temperature and humidity sensors.
I am willing to use LM35 for temperature.
Which humidity sensor I will use. Can anyone tell me?
Thanks.

Ttelmah · Guest

You need to be using a signalling standard like RS485.
RS485, is a _signalling standard_, _not_ a 'protocol'. You can choose your protocol to suit.
The maximum for TTL varies with frequency, and environment, but is somewhere around 10'. Realistically, it'd be much simpler, and more reliable, to add a small PIC at the LCD, and use normal asynch serial over RS485, to send what you want to display. It'd also be worth considering opto coupling, if you want this to have any chance of surviving very long....
You don't say what type of humidity measurement you actually want to make?. I'd guess relative humidity (the commonest)?. Simplest, probably the HC610. Just read the voltage with an ADC. Things like the HS1101, get more complex to drive, requiring 10v AC, or you have to purchase an entire module....

Best Wishes

Guest · Posted: Mon Feb 15, 2010 4:42 am

Thanks Ttlemah.
ya have to use relative humidity.

bkamen · Posted: Mon Feb 15, 2010 10:51 am

arunb · Joined: 08 Sep 2003 Posts: 492 Location: India

Or even wireless ? Like the MRF24J40MA module from Microchip ??

Thanks
arunb

hayee · Joined: 05 Sep 2007 Posts: 252

The option of wireless data transfer is good but i also have to consider the cost of the system.
What would be the min price of any wireless module,which will be reliable?