4 Channel Thermostat using PID loops

[Mike, K8LH]

Hi Malcom,

Thank you for the brief description of the user interface. It sounds very easy and very intuitive.

A couple more questions, please? (1) Do you "lock out" the pots' to prevent someone from accidentally bumping them and changing the settings? (2) Could you use a single pot' to adjust the four zones, one zone at a time?

Cheerful regards, Mike

[malc-c]

Hi Mike,

In the current format I use 4 pots, one for each channel, and having selected the manual temp setting option from the menu can set all 4 channels to whatever temps I need which are picked up when exiting out of the menu and back to the live screen. You could re-write the code to use one pot and cycle through each channel if you wished, however I preferred to use 4 pots.

No the pots are not locked as such, but you do need to select the menu option to adjust them. Once they have been set and the menu returns to the live screen you can twiddle the knobs as much as you like and it won't change the values - this does prevent accidental changing of the set temperatures.

I'm still working on taking the project from the development board to a working prototype, and once I've done that and had it running for a while I'll update the project with the final release of the code and some project notes.

[malc-c]

Well I've just completed the two boards in the MKII prototype, and was pleased to find that when I plugged the mains lead in there was no bang, no smoke but the thing actually powered up and displayed temperatures on all 4 inputs with the LEDs flashing away indicating the outputs were also running.

All that's needed now is to make up the sensor leads properly, fit the correct 3 core cable for the supply and hook up the output board to the controller via 7 way cable - then install it and monitor how it performs...

I'll post up a few more photo's as the installation progresses.

[malc-c]

Well, seven months after the initial post, and with the welcome assistance from DT to develop the code, the hardware has finally been completed and tested. All that remains is to remove the old commercial ON/OFF stats and hook the heaters and light up to this new unit.

I might look at having some PCB's made up as I've been asked if I could build a unit by other reptile keepers... and who knows, there may even be a market for such a device....

[Ioannis]

Nice! Wish you good luck with the new bussiness field!

Ioannis

[Mark J]

Hi Malc long time no speaky hehehe....

Love the project! very nice bit of kit you guys have developed there!
Been updating my bits and bobs so that I can start developing some bits for my small reef tank etc and cant wait as along with the usual temp reader, im also looking at adding water level detectors (going to try sonic sensors as got a few laying about) and when funds allow, will be having a go at using the larger powered LED's to make a new light unit where i can control dawn to dusk etc (thing with LED's are the large amounts of them you need for penetration/cover on a reef tank)

If I can get anything that remotely resembles the quality bit of kit you created i'll be a very happy chappy

Mark.

[malc-c]

Hi mate,

I'm sure if you could encapsulate the DS18B20's in some form of heat shrink boot you could use this project to control heaters in up to 4 tanks, and with the DS1307 and a bit of adaptation program seasons with shortening / lengthening days to switch in those lights.

The version of the code I'm now working on is so far advanced than that listed here, but what is listed can be used as a base if you wish.