[PIC] water temp monitoring & heater control

[KVN1477]

hi all,
i have developed a small project using PIC16F877A to monitor water temp and heater control.
in this project i have made provision to set temperature manually , when temp of water reaches to set temperature value heater will be automatically disconnected by relay. project is working fine if there is no power cut during operation. if there is power cut during heating of water manually set temperature value becomes zero. i need solution to retain manual set temp value to be retained during power failure also.

 

[horace1]

The PIC16F877A has 256 bytes of data EEPROM - could you use that to store non volatile data?

 

[milan.rajik]

Stote Set Temprature value in eeprom. If your set temperature value doesn't exceed 255 degrees then you can store it at any one eeprom address (1 byte wide). If temperature is more than 255 then you have to store it at 2 eeprom locations as low byte and high byte.

Mention Compiler used, Temperature sensor used. Provide Circuit and also Zip and post Complete project files.

 

[wp100]

Hi,

As said you can use EEProm to store and retain your data when power is off.

You can also pre load your EEProm with data during programming time so it can have a default Temperature vaalue in there.

Your program loop would be to start up and first load/read the EEprom Temperature value and work with that.
You can copy the value into RAM to make things work quicker rather than reading from slow EEProm all the time.
If you manually change the temperature then once that subroutine has ended the value should be written into the EEprom.

 

[KVN1477]

Re: water temp monitoring & heater control

thanks a lot for suggestion.......

- - - Updated - - -

thanks a lot for suggestion...

- - - Updated - - -

got it ....thanks a lot for suggestion

 

[KVN1477]

sir,
can eeprom value is changed every time as per requirement?
or it will be stored permanently in that location once it is programmed

 

[wp100]

sir,
can eeprom value is changed every time as per requirement?
or it will be stored permanently in that location once it is programmed

Hi,

The Eeprom is Re -writeable so you can change the values in the same or different locations.

The only restriction is that you can only rewrite to the same area about one million times before it wears out :wink:

 

[horace1]

sir,
can eeprom value is changed every time as per requirement?
or it will be stored permanently in that location once it is programmed

writes to EEPROM are limited (typically 100000 times) - if you intended to write more than this in the system lifetime you can use FRAM none volatile memory (which is also faster), e.g.
https://www.fujitsu.com/global/services/microelectronics/product/memory/fram/app-mb85rs256a.html

 

[wp100]

writes to EEPROM are limited (typically 100000 times) [/url]

Hmmm.. for the chip mentioned they quote 100k as the Minimum, 1meg is Typical.

Did some endurance test on that chip some years ago and it was 500k R/W before a single bit error given; and that routine really 'worked' the chip.

For his project think standard eeprom would be fine, saving the data once a hour , every hour he could get 12 years use based on the minimum target of 100k writes...

 

[horace1]

Hmmm.. for the chip mentioned they quote 100k as the Minimum, 1meg is Typical.

Did some endurance test on that chip some years ago and it was 500k R/W before a single bit error given; and that routine really 'worked' the chip.

For his project think standard eeprom would be fine, saving the data once a hour , every hour he could get 12 years use based on the minimum target of 100k writes...

we had a number of systems installed where the user assured us that the number of writes would mean a system lifetime of 10 years (writes were triggered by event from machines)
in practice systems began to fail after 2 or 3 years - it was a very electrically noisy environment so this may have contributed to the problems
these days we use FRAMs not EEPROMs

 

[wp100]

we had a number of systems installed where the user assured us that the number of writes would mean a system lifetime of 10 years (writes were triggered by event from machines)
in practice systems began to fail after 2 or 3 years - it was a very electrically noisy environment so this may have contributed to the problems
these days we use FRAMs not EEPROMs

Interesting, have used regular saves and restores to eeprom for several years on the same chips without a problem, but only in a domestic environment; expect other areas could well cause such problems, though not a device I have ever looked at, not sure how or why Fram would be any less susceptible ?

Also a bit surprised that only eeprom would be affected and nothing else on the pic. though as you say if using Fram cures the problem, other areas clearly are not being affected ..

 

[horace1]

Re: water temp monitoring & heater control

Interesting, have used regular saves and restores to eeprom for several years on the same chips without a problem, but only in a domestic environment; expect other areas could well cause such problems, though not a device I have ever looked at, not sure how or why Fram would be any less susceptible ?

Also a bit surprised that only eeprom would be affected and nothing else on the pic. though as you say if using Fram cures the problem, other areas clearly are not being affected ..

we did have some other components fail due we think to electrical noise (better filters on the electrical supplies seemed to help) - the application was machine control and monitoring with reports being sent to a server over ethernet using UDP datagrams every few seconds
I think the main problem with EEPROMs was that there were more events from the machines than originally estimated and the FRAMs fixed it