For every student of Electrical / Electronic Engineering and also the more mature Hobbyist, there is one thing you MUST build for your self at one time or another in your career, preferably earlier on
That's a Bench Power Supply and if you don't know how to start or are interested in having a second go at it then welcome to the show, it is going to be a fun and educational ride for all of us.
Blog #3 - OP Amps and the Power Stage : http://www.element14.com/community/groups/test-and-measurement/blog/2014/10/04/op-amps-1--intro--the-modular-bench-power-supply
Blog #4 - Displays - Digital and Simple http://www.element14.com/community/groups/test-and-measurement/blog/2014/11/13/the-modular-bench-power-supply--simple-display-setup
BLOG #5 - Power Output Stage (BJT/MOSFET) http://www.element14.com/community/groups/test-and-measurement/blog/2014/11/16/the-modular-bench-power-supply--power-output-stages
BLOG #6 - Basic Unit The Modular Bench Power Supply ++, Putting it all together, the bare bones
So firstly why should every EE build one of these, well for starters it is a very useful tool for any EE to use for prototyping, testing and many other things from Battery Charging to help test the power limits of a new control system
the second and an equally important reason is it provides numerous opportunities to learn some great skills regarding controlling power, feedback loops used for current limits and voltage stability, you can learn the difference between Accuracy and Stability (Which do you think is more important for a voltage reference in a power supply, well you will find out).
So who am I to show you how. Well I'm a certified electronics engineer who went through an apprenticeship in the north of England with a great company called Welwyn Electric (Now I believe part of the Vishay group). Anyway I learned my trade there and also had the awesome opportunity to work in a second level Calibration LAB where I got to play with all sorts of electronics equipment to numerous to list, learning how to calibrate them way beyond the manufacturers standard cal procedures but I also learned the value of having certain good equipment to help with project design, testing and maintenance. A good Meter, Scope and Power Supply, the first two are out of reach as a tutorial but the supply is not. I built my first one when I was 17, there were no micro-controllers, no LCD Displays, it was all analogue and Moving Coil Meters... Ah those where the days.
Anyway, the whole process from designing it, figuring out why things worked the way they did and also how to improve on the design over time to make it more accurate, more stable and provide more power was always a great learning opportunity
Now I wish to share this with everyone on a new and improved Modular Bench Power System, and when I say modular I mean modular. I have seen so many designs claiming to be modular but in reality it is one design and one fixed result. Some good and some bad.
Element 14 has been kind enough to sponsor me for this project and I will be providing links to all the components used in he project so you can also use the same if you so desire.
What I am planning is a power system that can be as upgradeable as most desktop computers (Need a new video card, great, swap out the old for new, need a better CPU, Same thing). In our case each significant module of this power supply will go through two or more versions as we ride the project to its destination. My Target destination anyway, you will be welcome to ride all the way with me or get off part way through depending on your budget and time. Oh and of course you can also stay on the train and take it beyond my design and make it yours. and you don't have to do everything, there is plenty of opportunity to mix and match as we go.
by now yo may be wondering, why do I keep calling it the Bench power System and not Supply, well this is why:-
My ideal target specifications
There will be three significant parts that can be built as separate projects or included into the Power System
Dual Channel Power Supply each outputting 30V @ 4A or 15V @ 8A, user selectable, independently adjustable
DC Load 60V /10A (But not 600W ) controlling Volts and Current
Power Meter showing Watts, Watt Hour, Volts, Current
Battery Charging Profiles
Logging on all modules above
Network and USB support for LXI and VISA protocols (SCPI)
All modules controlled by micro-controller/s with a master control unit based on embedded Linux
4" touch screen display / control
Not all of the above features are needed or essential, and there is no need to build yours to the same specification, I will tell you where the opportunities are to put in parts to meet your budget and requirements
The main power supply is broken down in to several sub modules as follows
Voltage Reference circuit, providing feeding the other modules
DC Power, this module converts the mains supply to a safe and smooth voltage for the rest of the supply
Output Driver. This module will be power transistors providing the actual limiting of the output to supply channels
Output and Sense, this is the actual output and also the voltage sense circuit needed for control
Voltage Control module set and vary the desired output voltage of the supply
Current control module will allow the user to pre-set the current limits of the power supply outputs
Displays and Controls, how else will you see and adjust things
We will start with the basics, a backgrounder on the modules purpose and basic functionality, the simpler analogue design and accurate enough for basic projects, this will help you understand Voltage references, OP-AMPS, feedback loops, Curent shunts both high side and low side and the benefits of each
Later, once we have the basic PSU working, we will upgrade modules to improve the regulation, accuracy and then some form of digital control in the form of a micro-controller, at this point we will discuss ADC, DAC resolution, over sampling etc.
This is a block diagram of the first modules we will tackle:
Oh and don worry if your unsure of handling mains voltages , there will be an option to cover that off too, I don't want to put anyone in harms way or take them out of their comfort zone (If your new to electronics and don't have experienced help, take the simpler approach I will present)
Oh, just so were clear. not all the designs are complete, only the concepts and target specifications are known at this point, I have many parts selected based on experience but what we end up with is unknown at this time and like I said at the beginning, its going to be a fun ride. So buckle up and get the soldering irons tuned
So what do you think, I'm open to ideas and nothing too crazy will be rejected from the considerations pile, if there is something you would specifically like covered, let me know
I look forward to your input and support
First lesson coming soon all about Voltage References.