However, with a couple of relays, thermocouplers, and a microcontroller, I am sure the temperature could be controlled to remain fairly stable, as would be necessary for the etching process.
If you look up the TDA1023 info (device no longer made), it has good examples of Proportional Control using whole cycle switching (ie relay or Zero Cross Triac / SSR).
To do this, they superimposed a slow, low amplitude triangle wave, onto the temperature error signal.
This avoids the over-shoot of bang-bang control, and may allow more choice on where the sensor is placed.
Ideally, you want to avoid a submersible sensor, but instead use an externally attached one, baffled to avoid direct heat-lamp pickup. Smarter control may let you do that.
However, with a couple of relays, thermocouplers, and a microcontroller, I am sure the temperature could be controlled to remain fairly stable, as would be necessary for the etching process.
As for this previous comment of mine, it is something that will probably be a little further down the road, but thanks for the input. I will probably wait until I have a full grasp on this system and know a little more about what I really want to do, and then I will create some nice control boards for the system.
Although I will probably have to buy an additional table in the future, since my projects are always evolving, my immediate goal is to prepare the table as stated above, so that I can start making PCBs more easily and reliably. By recessing the main components of my system into one table, I believe I will be creating a much more productive work environment for myself and any others that may decide to follow my path.
I would imagine that it will take quite some time before I get it all figured out, but I truly believe that I am well on my way now. I look forward to making the control boards for whole system, but that will take some serious thought. Until then, I guess I will be switching the heat lamps on and off manually.
Once again, thanks for the input. I have downloaded the datasheet for the TDA1023, for future reference.
With the bulb approximately 3" from the bottom of the tray, it took 8 minutes to heat the water up from 95 degrees fahrenheit to 104 degrees fahrenheit. When I turned the bulb off, the temperature did not continue to go up. And it took approximately 3-1/2 minutes for the water temperature to drop below 100 degrees fahrenheit, which is definitely enough time to develop the board.
Well I just got finished with a small experiment.
One way or another, there is no way for me to accurately measure the starting temperature, but I can tell you this:
To shroud escaping light, I wrapped the heat lamp in aluminum foil. After turning the lamp on, It took approximately 5 minutes for temperature to change on a thermometer beginning at 92 degrees fahrenheit. It took another 5 minutes for the temperature to reach 102 degrees fahrenheit, at which point the lamp was shut off. By wrapping the heat lamp in aluminum foil, the heat dissipation of the lamp was reduced and the temperature of the water continued to climb after the lamp was shut off. And basically settled at 105-1/2 degrees fahrenheit.
So imagine if I shut the lamps down at around 101-1/2 degrees fahrenheit, I should probably hit my mark of 104 degrees fahrenheit. I should mention that the bulb was encased in heavy aluminum foil.
I am getting ready to try another experiment. For this experiment, I will be coating one of the heat lamps with high temperature engine enamel, which is rated to withstand 500 degrees fahrenheit. I highly doubt that this experiment will be successful, but I will checking two different items, one of which is the transluceny of the paint, and the other is it's ability to withstand the heat generated. However, if the paint is highly translucent, it's ability to withstand the heat is a worthless benefit. On the other hand, if the paint coating is opaque and can withstand the heat, painting the bulbs with high temperature engine enamel will be a quick remedy to prevent escaping light rays.
That was a very interesting experiment that definitely requires further research. I experimented for approximately 3 minutes with power applied to the bulb.
LOL The bulb did not burst into flames, but it made me worried because it started to letting off some serious smoke. However, I must say that the light blocked approximately 90% of the light, and I am sure that with a couple more coats that I could make it opaque. Additionally, there was to peeling or flaking of the paint from the bulb. The paint on top of the bulb was discolored, but otherwise intact.
I believe I will have to continue this experiment outdoors, due to the smoke and fumes, just until the paint burns in or off
I have heard it mentioned before that some people don't like to babysit there boards during the etching process. At this current point in time, I personally like to be part of the etching process. When it is time for etching a board, I put on a nitrile glove, and while holding the board, I place it in the etchant, constantly moving it around, back and forth, flipping it over, etc.... That way, I have a good eye on the progress taking place and it is also a learning process for me. Perhaps in the future, maybe I will make a nice holder, agitator, and bubbler, but for now, a rubber glove and active participation works well for me.
While using my new PCB Prototyping Table last night to create a sample, I left the heat lamp on under the etchant to drive up the temperature. The heat lamp did not have any type of covering and light was shining right through the translucent Rubbermaid tray. Considering that the board had already been exposed and developed, exposing the board to this new light was not detrimental. In fact it was quite interesting and helpful. As it turns out, ferric chloride (etchant) is quite translucent, and when a sufficient amount of unwanted copper has been removed from the board, light will shine through the ferric chloride and the board substrate thus allowing you to see both top and bottom layers of wire traces, as well as some of the remnants of unwanted copper. It was really a quite interesting effect.
With this newly acquired information, I have now altered my PCB production process. As a result of exposing a board in the Exposure Box/Cylinder, the board becomes quite warm, well above the temperature prescribed for the developer. If the board were immediately removed from the Exposure Box/Cylinder and place into developer, it would be pratically equivalent to placing a cool board in hot developer. It is needless to say that the board needs to cool down before developing, during which time the developer and etchant could be heated.
Now take into consideration a previous comment that I made, which was:
With the bulb approximately 3" from the bottom of the tray, it took 8 minutes to heat the water up from 95 degrees fahrenheit to 104 degrees fahrenheit. When I turned the bulb off, the temperature did not continue to go up. And it took approximately 3-1/2 minutes for the water temperature to drop below 100 degrees fahrenheit, which is definitely enough time to develop the board.
Providing that I prevent any unprotected board material from accidentally being exposed to light, I can now safely process a PCB without worrying about covering the bulbs in any fashion (paint, aluminum foil, shroud, etc...), by following the simple procedure below.
While working under a safe light, place the target unprotected PCB material into the Exposure Box/Cylinder.
Power up the Exposure Box/Cylinder lamps, the developer heat lamp, and the etchant heat lamp.
At the proper exposure time (approximately 1 minute and 45 seconds), power down the Exposure Box/Cylinder lamps, but continue to heat the developer and etchant.
When the developer temperature has reached 104 degrees fahrenheit (approximately 6 minutes beyond exposure time), power down both the developer heat lamp and the etchant heat lamp. At this point, the board has cooled enough for proper developing.
Place the PCB into the developer solution and develop the PCB (approximately 1 minute).
Remove the PCB from the developer solution and rinse the PCB in cold water to deactivate the developer (approximately 1 minute). Upon deactivation of the developer, the PCB will no longer be sensitive to light.
Once again, power up the etchant heat lamp and place the PCB in the etchant solution to begin the etching process. If the etchant solution becomes to hot, simply power down the etchant heat lamp until the etchant solution reaches a suitable temperature. The etchant heat lamp can be turned on and off as needed to maintain the desired temperature. Continue to etch the PCB, until all unwanted copper has been removed (approximately 8 minutes).
Remove the PCB from the etchant solution and rinse the PCB in cold water to deactivate the etchant (approximately 1 minute).
Total Approximate Process Time For A Double-Sided Board: 19 minutes
In summary, the heat lamps are a perfect solution to heating up the chemicals, and nice boards can be processed without blocking any of the light rays emitted by the heat lamps, by following the outline above.
Comments
If you look up the TDA1023 info (device no longer made), it has good examples of Proportional Control using whole cycle switching (ie relay or Zero Cross Triac / SSR).
To do this, they superimposed a slow, low amplitude triangle wave, onto the temperature error signal.
This avoids the over-shoot of bang-bang control, and may allow more choice on where the sensor is placed.
Ideally, you want to avoid a submersible sensor, but instead use an externally attached one, baffled to avoid direct heat-lamp pickup. Smarter control may let you do that.
As for this previous comment of mine, it is something that will probably be a little further down the road, but thanks for the input. I will probably wait until I have a full grasp on this system and know a little more about what I really want to do, and then I will create some nice control boards for the system.
Although I will probably have to buy an additional table in the future, since my projects are always evolving, my immediate goal is to prepare the table as stated above, so that I can start making PCBs more easily and reliably. By recessing the main components of my system into one table, I believe I will be creating a much more productive work environment for myself and any others that may decide to follow my path.
I would imagine that it will take quite some time before I get it all figured out, but I truly believe that I am well on my way now. I look forward to making the control boards for whole system, but that will take some serious thought. Until then, I guess I will be switching the heat lamps on and off manually.
Once again, thanks for the input. I have downloaded the datasheet for the TDA1023, for future reference.
Bruce
Well I just got finished with a small experiment.
One way or another, there is no way for me to accurately measure the starting temperature, but I can tell you this:
I am getting ready to try another experiment. For this experiment, I will be coating one of the heat lamps with high temperature engine enamel, which is rated to withstand 500 degrees fahrenheit. I highly doubt that this experiment will be successful, but I will checking two different items, one of which is the transluceny of the paint, and the other is it's ability to withstand the heat generated. However, if the paint is highly translucent, it's ability to withstand the heat is a worthless benefit. On the other hand, if the paint coating is opaque and can withstand the heat, painting the bulbs with high temperature engine enamel will be a quick remedy to prevent escaping light rays.
Bruce
That was a very interesting experiment that definitely requires further research. I experimented for approximately 3 minutes with power applied to the bulb.
LOL The bulb did not burst into flames, but it made me worried because it started to letting off some serious smoke. However, I must say that the light blocked approximately 90% of the light, and I am sure that with a couple more coats that I could make it opaque. Additionally, there was to peeling or flaking of the paint from the bulb. The paint on top of the bulb was discolored, but otherwise intact.
I believe I will have to continue this experiment outdoors, due to the smoke and fumes, just until the paint burns in or off
Bruce
I have heard it mentioned before that some people don't like to babysit there boards during the etching process. At this current point in time, I personally like to be part of the etching process. When it is time for etching a board, I put on a nitrile glove, and while holding the board, I place it in the etchant, constantly moving it around, back and forth, flipping it over, etc.... That way, I have a good eye on the progress taking place and it is also a learning process for me. Perhaps in the future, maybe I will make a nice holder, agitator, and bubbler, but for now, a rubber glove and active participation works well for me.
While using my new PCB Prototyping Table last night to create a sample, I left the heat lamp on under the etchant to drive up the temperature. The heat lamp did not have any type of covering and light was shining right through the translucent Rubbermaid tray. Considering that the board had already been exposed and developed, exposing the board to this new light was not detrimental. In fact it was quite interesting and helpful. As it turns out, ferric chloride (etchant) is quite translucent, and when a sufficient amount of unwanted copper has been removed from the board, light will shine through the ferric chloride and the board substrate thus allowing you to see both top and bottom layers of wire traces, as well as some of the remnants of unwanted copper. It was really a quite interesting effect.
With this newly acquired information, I have now altered my PCB production process. As a result of exposing a board in the Exposure Box/Cylinder, the board becomes quite warm, well above the temperature prescribed for the developer. If the board were immediately removed from the Exposure Box/Cylinder and place into developer, it would be pratically equivalent to placing a cool board in hot developer. It is needless to say that the board needs to cool down before developing, during which time the developer and etchant could be heated.
Now take into consideration a previous comment that I made, which was:
Providing that I prevent any unprotected board material from accidentally being exposed to light, I can now safely process a PCB without worrying about covering the bulbs in any fashion (paint, aluminum foil, shroud, etc...), by following the simple procedure below.
Bruce