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  • Author Author: Robert Peter Oakes
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The Modular Bench Power Supply ++, testing it all on the bench with the BreadBoard

Robert Peter Oakes

Back to the Main post The Modular Bench Power Supply ++, The Essential DIY Build for Every EE Student and Old Timer alike...

 

Ok, so based on the last two or three videos an posts it is time to test everything out on the bench with a breadboard and read power to see how it performs

 

so this is the final schematic I have, I still am pondering changing it up a bit more but I will play with it a little first, ideas I have are around using 10V control signals instead of 5V and of course adding a pre-regulator switching in order to reduce heat dissipation in the regulator significantly, but thats for a future epesode image

image

RPO: The Schematic was updated to reflect the correct volts on the op amps of +12 and -12

 

and of course the video to explain it all

  • in reply to Robert Peter Oakes

    Hello,

     

    I've been trying to recreate this power supply, so if you could, would you be able to point me towards a complete schematic? Throughout your videos you've been changing little bits here and there, and I got really lost now.

     

    Thanks!

  • in reply to Robert Peter Oakes

    But just to be clear, the op-amp 0V, is floated onto the positive rail of the main raw power supply (as a reference), just before the sense resistor?

  • in reply to nikolajbrinch

    yes, the op amps are running on their own 12V +- supply, 9 volts would also work ok. there are many techniques you can use to derive the supply for the op amps but it does need to be isolated from raw PSU supply as it is "Floated" onto the output rail of the power output. so the 0V of the op amps is NOT the same as the zero for the main power supply.

     

    The opamp in the schematic with the actual +- connections is representative as you correctly identified.

     

    As the supply for the control (Op Amps and later the uController) will not draw much current so it can be built from small power adapters, PCB Power bricks etc or as you say, another small transformer. then again, you can get transformers with separate low current windings available for this purpose. Just need to shop around.

  • Hi Peter,

     

    I love your series on the power supply. Of course ideas about soft start, short circuit protection, bleeder resistors and output on/off comes to mind, as other modules that I would like to see integrated in the design. I must say that the simplicity and the use of that beefy MOSFET, and the theory and use of the op-amps are all extremely nice, and well laid out.

     

    One thing I need to have confirmed is, that the control-circuit that needs +/- 12V is a different power source all together? So i.e. 4x9V cells in series with a center tab could provide the power (in theory - in practice a dual source with a separate transformer, rectifier, caps and regulators - 7812/7912 probably)?

     

    Furthermore, there is an op-amp in the schematic on the +/- 12V input, is that to be disregarded as a symbol of how to connect the other 4 op-amps?

  • Hi Peter,

     

    I also left this msg on your blog.

    There is a small error on the diagram.

    The +12V is labeled +2V.

    You may want to clean-up the connections to the feedback resistor of the voltage comparator.

    Your schematic capturing probably messed that up.

     

    Looking forward to the next episode, I'm glued to the Tube.

     

    Paul