PCB Etcher

After UV-80 vas built there was a thought about automatic PCB Etcher with autonomous Heater and bubble machine. This project is hanging in prefinished phase but it does a job. It was used to etch several PCB’s. As this etcher supposed to be used for making PCB’s using photoresitive technology, the controller supposed to control both = the heater of etching tank and heater of developer. As Sensors there are used AD7416 digital temperature sensors. I decided to publish this small project as this is not clear when it will be finished. When it will be, I will update this article.

There is a little dirty drawing with dimensions:

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The dimensions are as follows 215x275x30 exterior. Inner volume is smaller as glass is 4mm thick. So overall volume is less than 1,2 liter. It is ideal volume to use one bag of ammonium persulphate or 250 grams of FeCl3. The glass plates are glued with aqua silicone. Sides are strengthened with aluminum profiles (not necessary if you have skills of gluing aquariums).

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As you can see it is only manual control 🙂 Thermometer, heater and tank with etchant.
Thermometer has scale with more than 50°C as solution shouldn’t exceed this value. Heater is used from fish tank 90W:

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This heater heats solution up to 50 degrees in about half an hour. This is enough time to expose and develop your PCB. If you need to heat water faster – you should use more powerful heater.
This is nothing to add more to this part. This is working well, but you have to stare and not to overheat the solution.
In order to make heater work automatically we decided to create controller with temperature sensor. Due to problems in assembly, this part is not finished. And there is no bubble machine purchased. Bubble machine is good to speed up etching and process is going smoother. As bubble machine we probably will use aquarium bubble pomp.
So what do we have now?
We have simple circuit on atmega8 with ability to read two temperature sensors and ability to control two relays to control two heaters.

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There also is two temperature sensors soldered to be ready to glue to tank glass. I thin it should read temperature quite well – maybe little calibration will be needed.
The sensor view:

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All control board will be placed in PC power block – we just have one spare to use. As it has already 5V to power controller and 12V for relays and developer heater. FYI, developer heater will be heating wire from some medical equipment. It is powered from 12V and takes about 2 – 3 A (36W). It is enough, as developer shouldn’t exceed 30 degrees.

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And here is the total view of controller. It still looks messy and not assembled. I hope one day it will be finished

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To be continued…

Source code: Source Code

8 Comments:

  1. André Dias Mesquita

    Hi, Im Building UV BOX for PCB exposure really a great project congratulations. Im try to build a PCB etcher and find your project at the same page. About thesource code? Im very interested in your project, could you send me the source code to program microcontroller?

  2. I attached source code to the bottom of article. This is not finished. Here is the link:
    http://www.scienceprog.com/wp-content/uploads/2006/04/Termostatas%2020051216.zip

    It would be great the you would send me your project success. I could put few lines about it in my page. Anyway good luck on making your PCB making station 😉

  3. André Dias Mesquita

    Is this circuit functional?
    How do you setup the reference temperature? In the source code or setup manually ???

  4. What do you mean reference temperature? The temperature when relay is turned on and off. Then is is done in code. The temperature is read and compared to reference. If is equal, then relay is turned on/off. There is hysteresis made in source code as well.

  5. André Dias Mesquita

    Okay!I understand now.
    Sorry for the fool questions, Im a physician and electronic is my hobby. Reading the source code the temperature reference is in this interval between 17 and 20 Celsius. May I change to higher levels in the source code? What do you need to finish this project? It is functional if I try to build it now?

  6. The code and circuit is functional. I had bad luck, because I short-circuit the wires, and it burned. But it worked properly, before :). And yes you can change temperature values to any you want.
    I hope my one will be finished in near time. Don’t hesitate to as anything you want – there is no fool question you could ask 😉

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