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PIC controlled output of variable power supply based on input

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jinrs

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Hi. I need help for my final project in school. Please forgive my ignorance on electronics because I am a physics major.

My professor has asked me to make a system for electroplating using PIC as the main controller of the circuit. Its function goes like this:

I have three electrodes A, B, C. All are immersed into a chemical solution. A and B will be connected to a power supply (output). A and C are connected to a voltmeter (input). Then I will specify the duration of plating and reference voltage (for example, 3 minutes on constant 5V DC). But during the process, the resistance of my solution will vary and the voltage between A and C will not always be 5V. Manual adjustment of the power supply is not advisable because the changes are very small and very quick. PIC will provide the automation by measuring the voltage between electrodes A and C compare it with the reference voltage (5V), and will compensate for the changes in resistance by providing a higher or lower output on electrodes A and B. After the specified duration (3 minutes), the power supply will either shut off or the output will be 0V.

I only need a voltage range from 0 to 12V DC. I think the whole system is just like a variable DC power supply similar to the one posted on this thread:

https://www.electro-tech-online.com...-supply.7110/?highlight=variable+power+supply

But instead of the potentiometers, the output is controlled by the PIC. Also, I think it is possible to use the comparator of PIC. Compare the voltage on electrodes A and C and the reference voltage. If higher, decrease the output. If lower, increase the output.

If there are questions regarding my project, I would gladly explain it. Please help. Thanks in advance.
 
Last edited:
as per the description i understand the setup as follows
Code:
----------A------
dc              |
----------B     V
                |
          C------
ok.. as u describe in any config the electrode C is not connected to any potential source . then how could a voltmeter could read something ?

any way from ur description i think u need a 16f88 , which has a built in adc for u to read voltage and a pwn generator , by which u can adjust the plating voltage using a series pass transistor or mosfet , and also has timers for monitoring.
 
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I think that there are two issues here:

PIC programming
and
Variable power supplies.

For the PIC programming, may I suggest that you look here to start you off: https://www.electro-tech-online.com/threads/pic-newcomers-please-read-upd-0xd1.15035/

For the power supply, I dont think that the one you referred to in your original post is well adapted to your current problem. At the moment I am struggling to think where I have seen an appropriate circuit. What I have in mind is a PSU where the reference input to the error amplifier is easy to "get at" and can be replaced by a voltage from an analogue output from the PIC.

JimB
 
akg said:
as per the description i understand the setup as follows
Code:
----------A------
dc              |
----------B     V
                |
          C------
ok.. as u describe in any config the electrode C is not connected to any potential source . then how could a voltmeter could read something ?

The three electrodes are immersed in a chemical solution and by definition, the solution must conduct electricity else no electroplating can work.

There would be a certain resistance(formed by liquid) between electrode B and C so a voltmeter at C will read nearly the potential of electrode B.
 
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