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[Reply #15 on:]

http://www.futurlec.com/LEDDisp.shtml

If you use shift registers to drive the leds then you only have to feed them a bit string to change the display. Search on shift register at the same site, 1 shipping charge for 1 order.

If you will lots of these then use the Arduino for development but use stand-alone chips for the end product.

What I don't get is why not include a cheap thermometer? Then they could use the same unit in the experiment itself.

See 78F, hit a button to see 26C -- you might as well use 2-sided flash cards, they will teach just as much just as well for far less unless the real lesson is to waste money and electric on trivial flash. Oh well, that seems to be the way things have headed for decades now anyway.
Waste, waste, waste, it must create jobs somewhere to waste!

[Reply #16 on:]

I wondered the same thing (without the rant, of course) but I assume that the OP has his reasons. He mentioned temperatures of animals. So, the actual temperatures displayed must correspond to something simulated, not real.

OP, mind going into a bit more detail about your project? Perhaps there is more that we can help with.

[Reply #17 on:]

Thanks for the replies guys.  I work for an Aquarium.  We are building an exhibit that teaches the public what is involved in animal care.  The specific piece of the exhibit where I will use my altered temperature controller will be a realistic life sized model of a fish surgery set-up, aimed at kids.  As you can imagine, any type of surgery requires close temperature control, 78degF for the specific species being modeled.  Wasteful would be tempering the water in the exhibit, since it isn't "real".  I could just put a sticker on the controler that shows 78, but wheres the fun in that?  So, I'm putting a little effort into making it as real as possible.  With all that being said, hopefully you understand a little more of what I am trying to do.  If I go Arduino, then i have to write the code which i know nothing about.  If all I have to do is some soldering on the unit I have, then seems easier with no out of pocket other than a button for switching between displayed values.

Retroplayer, I have attached another photo, is this what you are suggesting? 

[Reply #18 on:]

Yep. That is pin 4 on the CPU. You will need to connect it to jumper it to VCC once you lift it to keep the processor in reset. Pin 8 of the eeprom is the bottom right pin in that picture (note the dot which indicates pin 1 - and when no dot is present, you can use the slope on the one side of this type of package to find pin 1.) I was mentioning pin 8 only to help you loacte VCC. Since there is a serial port on those 4 through-holes (on the right side by the eeprom) I bet one of those will be VCC. There should be VCC, GND, RX, and TX. So for whatever circuit you throw in there, you can tap off 5V supply from that point. To find it, just check for continuity between pin 8 and one of those through holes. That blue cap will also have VCC on one side and GND on the other. Another good place.

Again, you could just completely remove the processor if that's easier and nothing else will interfere with the display.

You will have to decide whether to use an arduino or not. The advantage to using the Arduino is that you get to learn to code as well as allowing you to add more features if you get in there and start having fun (it gets addictive!) Because of the way this display is wired up, you will not have an easy time doing what you want to do without the Arduino. This type of display is expecting the characters to be drawn sequentially which means your circuit would have to be designed to to step through several states. That will end up being pretty complex and quite a few parts. I suggest just installing an arduino in there. The seven-segment library linked in this post is designed for the way this display is wired up. The only thing it is missing is the degree symbol, which can be added.

Don't be intimidated by starting an Arduino project. Before you even start, think about what you want to do just like if you were making a recipe. You have steps that have to be taken in a certain order, and there may be tests (like taste for salt at step 2) performed that determine output (add more salt). And there may be interrupts (like the oven timer going off) and delays (waiting for one step to finish cooking.) That's really all programming is. You do it every single day.

[Reply #19 on:]

Wait... those two LEDs on there next to the display. Are those the indicators for Cels and Fer? Could you provide a picture of one of these units in action? I was going to post how to modify the library and such, but maybe you don't need to even do that.

[Reply #20 on:]

The two LED's are output indicators.  I have attached the manual for the controller, it's an 04 type.

So if I go with Arduino, It will be larger than the housing I have (itron 04).  What I was initially hoping was to be able to force a value on the LED's by way of set voltage (emulating a probe voltage at 78 and 26).  The problem with the controller is the on board buttons do not work, but I can change settings with a jumper wire across the button circuits on the board.  So, theoretically, what if I just told it to keep 78degF and then send that corresponding voltage to the input terminal?  How would I figure out what voltage that would be, then how to a make it?  The only problem with doing that would be no symbols (F or C).  I could have a button wired to the input terminal with the two voltages for switching.

[Reply #21 on:]

Found the table here, http://www.omega.com/temperature/z/pdf/z218-220.pdf

if I use a Nickel-Chromium Type K, can I just take the low voltage from the board and resist it town to 1.249Mv (78) and send it right to the input?  Is this even feasible?

[Reply #22 on:]

If your controller is working enough to do that, then that would be the easiest way. I was assuming that the controller just flat-out didn't work. It is normally connected to a thermocouple to sense the temprature. A thermocouple generates a voltage, so you only need to simulate that voltage, as you say. The easiest way to find out what that voltage is is to look up a datasheet for the thermocouple. It will have a formula in there that you use to determine the temperature based on the voltage. Just reverse the math. Or, you could just go and measure the voltage on one that is in use at the temperature you want.

It sounds like the switches are probably just broken. Why not just replace them with your own?

[Reply #23 on:]

A voltage divider would work, yes. Two resistors. You tap off the center and input that into your thermocouple input. BTW, your datasheet for the iTron was corrupted so I can't open it. Does it have the pinout?

[Reply #24 on:]

I'll try and post it again.  I'm probably the first person here to ever take one of these controllers apart.  In the past when they stopped working (meaning un able to adjust parameters) we just replaced them.  Now that I see the buttons are just worn out, I could fix with aftermarket buttons, but would be hard to make it fit back together in its nice enclosure.  I really wish I could make it read F or C after the temp.  Maybe deep in the manual I can find that.  Otherwise, may have to go with the arduino and build an enclosure.  But I'm not giving up on modifying the itron!

edit:  it shows corrupt when i click the link, yet it opens fine on my computer?????  Here's a link to the manufacturer site, under documentation is the datasheet and manual.


http://www.jumousa.com/products/level/controller/1-channel/702040/jumo-itron---compact-controller-702040.html