Pommie

Yes, a pic can do all of that and more. Do you have a link to a description of what the circuit does?

Mike.

karenhornby

If you refer to my first post it has a gif of a circuit that i did.
The basics of the circuit was taken from this page http://www.escol.com.my/Projects/Pro...)/Proj-03.html
which is basically a thermostat, that once the temp probe (lm35) has reached the preset temp it trips a relay.

My circuit follows on from that one, and using on using a single LM324 comparator instead of the original LM358, 2 complete temperature sensor circuits and a timer circuit based on a 555 chip that once activated latches a relay for a set period of time (ideally 65 seconds)

To do the design using a PIC, IF its possible i'd like as much done in the PIC itself and as few external components as possible.

I've decided on a 2 line display OR if its possible to make it work "this" http://cgi.ebay.co.uk/128x64-LCD-Scr...QQcmdZViewItem


What I'm hoping for in the end, is to have a device that will measure 2 temperatures (water and diesel) in my car, and once the water temp is 75ºC AND the diesel temp is 50ºC 2 relays will operate 2 relays in various configurations, and a timer/buzzer circuit depending on the values of the LM35DZ's

Pommie

Most of what you need is on the site of a member here Gramo's site. Especially, this page. The spare pins on the pic in the diagram can be connected to switches, relays or more LM35s.

As for the LCD, some time ago I did a demo using such a display - clicky. The advert doesn't state which controller chip it uses but going by the price I'd guess it is the KS0108.

Have you done any programming?

Mike.

blueroomelectronics

Don't think I'd use the diode pairs, typically 1N914 diodes are sensitive to temperature and are unnecessary for the LM34 / LM35.

__________________
Bill
Smart Kits build Smart People
http://www.blueroomelectronics.com

karenhornby

Thanks for all the help so far, its quite interesting reading and I'm very keep to try this out.

BILL what would you use instead of the 1n914's? which would you recommend the LZ35DZ or the DS18S20 temp sensors?

No I've not done any programming at all "yet" however hopefully I will soon.
would a development board be worth buying to "experiment" with?

I've been looking for a good one at a decent price and stumbled on this

http://www.mikroe.com/en/tools/easypic5/

anyone have any experience with this or anything similar?

I've still got to decide what programmer to get yet. IF I got that EasyPIC5 board would I need to buy a seperate programmer or would it program the PIC from the computer?



ANY thoughts on using 3 or 4 DS18S20 temperature sensors instead of the LM35DZ's?


Anyone any ideas how (IF) i can get an output to trigger at a set temperature and stay even if the temperature goes higher than the temp I want it to trigger at?

Temp sensors either LM35dz OR DS18S20 depending on which is easier to incorporate and get working

This may sound a stupid question to most of you, but is there a comparator in the pic's that can be used to compare 2 (temp inputs) and trigger different output pins and logic circuitry (AND OR gates etc) for example
(this is what I've got in my mind so far)

INPUT A0 (temp sensor) (set for 75ºC)
INPUT A1 (temp sensor) (set for 50ºC)
INPUT A2 (temp sensor) the LCD Display shows this actual temperature AND shows the word OUTSIDE TEMP (actual temp) ºC (LINE 3 of display)
INPUT A3 (temp sensor) the LCD Display shows this actual temperature AND shows the word INSIDE TEMP (actual temp) ºC (LINE 3 of display)
INPUT B1 +V (from ignition switch)
INPUT B2 +V (from battery)
INPUT B3 push to make non latching switch

OUTPUT A0 (normally LOW) to relay driver circuitry
OUTPUT A1 (normally LOW) to relay driver circuitry
OUTPUT B3 (normally LOW) Siren/buzzer circuitry
OUTPUT 4
OUTPUT 5
OUTPUT 6
OUTPUT 7




IF input A0 ≥ 75ºC AND input A1 ≤ 50ºC AND input B1 is HIGH OR input A0 ≤ 75ºC AND input A1 ≥ 50ºC AND input B1 is HIGH THEN outputs A0 and A1 and B3 stay LOW

AND the LCD display shows the word DIESEL


IF input A0 ≥ 75ºC AND input A1 ≥ 50ºC AND input B1 is HIGH THEN outputs A0 AND A1 go HIGH driving the circuitry needed afterwards needed to activate a relay on each line output)

AND the LCD display shows the word the word VEG-OIL

( IF I remember my maths equations for MANY years ago then ≥ means equals or greater than and ≥ means equals or less than)

IF input B3 goes high AND INPUTS A0, A1 and B1 are HIGH, THEN output A0 stays HIGH AND output A1 goes LOW AND a timer starts that counts for 65 seconds

AND the LCD display shows the word PURGING

IF TIMER = 0 (65 seconds reached) AND INPUT B1 is LOW THEN outputs A0 and A1 go LOW AND power to LCD module goes LOW
IF TIMER = 0 AND INPUTS A0, A1 and B1 are HIGH, THEN OUTPUTS A0 and A1 GO LOW, and the LCD display shows the words POWER OFF! DIESEL ONLY (on 1 or 2 lines)

IF input B1 goes low BUT INPUT B3 has NOT gone high THEN
outputs 1 and 2 go low (inactive turning OFF both relays) BUT output B3 goes HIGH (sounding a siren/buzzer)

AND a timer starts that counts to 65 seconds

AND the LCD display FLASHES the word WARNING (line 1) and shows the word NOT PURGED (line 2)

WHEN TIMER = 0 (65 seconds reached) THEN outputs A0 and A1 and B3 go LOW THEN power to LCD display module goes LOW



IS it possible to program a PIC controller to do all that? and IF so any ideas what kind of external circuitry I'd need as well?
Can you drive an LCD circuit direct from the same PIC chip, or would it need a seperate controller to do this, and if so how would you interface the two?
sorry lots of questions and I'm showing my ignorance of PIC's and programming, but you cant learn if you don't ask questions.





the 3rd and 4th lines of the LCD display and the extra 2 temp circuits are not needed, it would just be handy if I had a 4 line display instead of a 2 line one, or something like 240x 128 LCD Screen



HOPE I've made that clear enough to understand but the last programming I did was in college and they had only JUST got a computer with 4K of ram (yes 4K not MEG) and a printer attached, they hadn't even got a display of any kind, this was in 1977! how things have changed



Future "mods" (IF I ever get this working) and have the LCD SCREEN instead of the 4 line display would incorporate a fuel level sensor that either shows a bar graph of fuel level with the word FUEL next to it, (or above it if this was a vertical bar graph) and the sensor would be a fuel level sensor which I think the values are 240 - 33Ω

blueroomelectronics

Depends on what temperature range you want to read as far as the diodes are concerned. As for the DS18S20 they're great little ICs, you can network them on a single 3 conductor cable. There is a DS18S20-PAR which works with a 2 wire cable too.
Yes many PICs have a pair of comparators which would work fine with an analog sensor like the LM34/35
The EasyPIC5 is popular and IMO kind of overkill, take a peek at the Junebug threads here; it has a 1-wire sensor socket on the front. It's also got an MPLAB compatible programmer / debugger and 18F tutor onboard.
And I'd recommend looking at Swordfish BASIC the free SE version can do all the things you're looking for.
PS I'll throw in a free ROBIN PCB (small LCD device that might just be what you're looking for) if you buy a Junebug

PS you probably don't want a GLCD display (like you described) but a 20x4 character display can do block graphics.

__________________
Bill
Smart Kits build Smart People
http://www.blueroomelectronics.com

Salgat

I personally have found the AVR line of micros to be the easiest to program. The flexibility it offers (32 registers allowing for many programs to never touch RAM) and the universal instruction set are very nice. (I learned how to program an AVR with most of the features in roughly a week).

Super_voip

If you were to use digital temp sensors, DS18S20, LM74 or LM75 for example, the signal conditioning circuitry needed for the analog sensors can be eliminated and as you are using this in an auto this can be a big advantage.

karenhornby

Thanks for that info, Its one of the things I was wondering, but how exactly would you connect the sensors to the PIC?

Sorry I've no experience at all with digital temp sensors like the DS18S20 and the LM74/75 and no idea at all about how I2C Bus interface works, I'm only just starting to get interested in Digital stuff.

Would each sensor go to a different input? and how could you monitor the temp, and trigger an output once a specific temp was reached or went higher than the temp needed?

Super_voip

All the digital sensors would use 1 or 2 pins, they are connected in parallel and each has its own address. There are plenty of examples on the web, most with code, on how to connect. The micro reads the temp of each sensor and once it has exceeded the trigger point then messages or alarms can be sent.

karenhornby

Thank you, that has cleared a lot up for me
now "ALL" i have to do, is learn how to program a pic, and figure out how to drive external relays from the outputs, and also drive a display module

Lots of reading/studying

Super_voip

Most of the code is floating around and there are BASIC packages around with all these drivers built in, the PIC programmer is simple, in fact so simple I didn't realise I had one and bought a second (much nicer, flashing lights) one.

karenhornby

Would I be right in assuming that you mean there is code "floating around" that will do the same or similar to what I've said I need it to do in the 7th post above this? All i'd need is to find this code and modify it for my purpose? All i'd have to do is how to interface the external circuits to the PIC?
any idea what to look for if I tried to search for code?
Sorry for all the question, but like I said I know NOTHING at all about digital electronics so far, but I HAVE used a programmer back in the late 90's when I used to watch satellite from abroad and had to program "smart cards" to decode the various channels, however all I did was use readily available (then) bin or hex files but i dont even have that programmer these days (yet)