DIY Controller (Atmel based)

[kwirky]

I've ordered some ATMEL128 boards from futurlec.com along with some opto-relays and a serial interface. Each board is aprox $29 and each opto-relay board is $14. the optorelay boards have 4 relays per board. (relays let you turn 110AC high voltage wall-socket power on and off using low-voltage electronics)

I'm learning atmel programming and electronics interfacing for both my fine arts practice and my aquarium hobby. I'm pretty excited about the potential of these guys . I've been going through tutorials using the emulator built into AVR Studio. kinda neat.

I could use it to control water pumps for elaborate wavemaking, auto top off, all sorts of stuff. An ambitious idea would be to emulate the Tunze controllers and control the AC frequency the same way the controllers do (like what the profilux does). you get 48 inputs and outputs along with analog inputs and outputs (for probes and temp sensors n such).

i'm sourcing out a pH probe interface or schematics to make one. pH probes don't work with normal 5V resistance. You need to work the pH probe with an interface. kinda hard to find these things but I'm getting close.

I also ordered a 16x4 character LCD screen with backlight and a 128x64 pixel screen (b&w, no greyscale).

I'll be getting the stuff probably about 3 weeks from now. it's 3-6 days shipping USPS express but it'll probably be held up at the border.

I'll let u all know how it goes . Any work I do will be open source and I'll post code examples of working stuff as I go.

information on the ATMEL chip:
ATMEL assembly programming for beginners: http://www.avr-asm-download.de/beginner_en.pdf

ATMEL boards and other tidbits of electronics: http://www.futurlec.com

the ATMEGA board i'm using: http://www.futurlec.com/ATMEGA_Controller.shtml

ATMEL forums and projects: http://www.avrfreaks.net

AVR studio IDE for programming ATMEL chips: http://www.atmel.com/dyn/products/to...p?tool_id=2725

[Robw]

This sounds like an interesting project. I remember seeing a schematic for a ph probe interface somewhere on the web. I will try and find it and post a link to it. Being an electronics tech I should be able to help with making pc boards for the ph probe interface etc. Any web or pc interface for these boards? Would be nice to log temps and ph etc to a pc for review. My biggest problem is finding time to do all the research.

Rob

[kwirky]

Originally Posted by Robw

This sounds like an interesting project. I remember seeing a schematic for a ph probe interface somewhere on the web. I will try and find it and post a link to it. Being an electronics tech I should be able to help with making pc boards for the ph probe interface etc. Any web or pc interface for these boards? Would be nice to log temps and ph etc to a pc for review. My biggest problem is finding time to do all the research.

Rob

there are PC and Web interfaces. the ATmega control module interfaces with serial out of the box. You can get a USB interface for about $25. Would have to write a driver for it and then write assembly code in the Atmel chip to support it.

A web interface is difficult. There are network interfaces but then you'd have to code a web server entirely in assembly. It might be easier to instead set up a client-server relationship where software's run on the PC and the controller sends data to the software.

I thought about ordering a USB and network interface but I'll be so busy just learning the Atmel assembly that I wouldn't use them right away.

[Robw]

I did find one schematic so far for a ph probe. The output from the circuit is 0-140mv which corresponds to the ph value. No link to the probe used though.
http://damien.douxchamps.net/elec/ph_meter/

Assembly language! I haven't used that in more than 20 years. I do remember it was fun once I figured out the codes etc. That was for the 8085 microprocessor. Time to start reading!

[mark]

Kwirky, once you get them running, sounds like a cheap little controller you could market to fellow reefers.

Robw, I was looking for the output for figuring the slope/intercept for a pH probe awhile back (was hooking to a datalogger) and got this e-mail from American Marine (AMI):
"After proper calibration the probe will generate 59 mV per each unit of positive pH and the opposite will be negative mV. Example pH 7.0= 0 mV; a ph of 8.0=59mV a pH of 6.5= -30mV Good Luck...Lou Dell/AMI"

[midgetwaiter]

Originally Posted by mark

"After proper calibration the probe will generate 59 mV per each unit of positive pH and the opposite will be negative mV. Example pH 7.0= 0 mV; a ph of 8.0=59mV a pH of 6.5= -30mV Good Luck...Lou Dell/AMI"

Did he by any chance explain how to correct for temperature with this? The closest I've ever found to a bona fide reference is the table on the back of pinpoint's calibration packets and I bet that doesn't necessarily correspond with SW.

[kwirky]

Originally Posted by midgetwaiter

Did he by any chance explain how to correct for temperature with this? The closest I've ever found to a bona fide reference is the table on the back of pinpoint's calibration packets and I bet that doesn't necessarily correspond with SW.

with the temperature we run our aquariums at temperature callibration is almost negligable. I saw a chart somewhere once and it's like a 2% difference. (ph 8.302 instead of 8.297)

[KrazyKuch]

Here is a schematic I just did up for an Orp interface

[kwirky]

does the orp interface work the same with a pH probe too? only the calibration points would be separate?

[KrazyKuch]

Yeah thats basically how all probes work.....All you have to do is amplifi the signal to a stat that is easily readable from your controller then it's a matter of figuring out how the signal gets converted into the proper reading.....for PH after it's amplified 1 millivolt will stand for a ph of 1 a 10 millivolt signal stands for a ph of 10....If you want I can get the calculations for the orp!