This project was done under Dr Jason Hogan in Professor Mark Kasevich's lab at Stanford in Summer 2014. Using KICAD, I developed and designed an intelligent customizable PCB in order to shield the lab's devices and equipment from anomalies, disruptions and surges in the power supply.

1. Summer
Internship Project
Nikhil Ghosh (Gunn High School)
May - August, 2014
Kasevich Lab, Stanford University

2. Internship Goals
To acquire fluency in KiCAD, circuit design, and
electrical engineering concepts
To build a board which can be used to protect
the lab’s “slow analog out” board, therefore
protecting the apparatus and setups from
damage

3. Premise and Background
All channels of slow board are set to different
voltages, as they all serve different purposes
Voltages of each channel are manipulated and
preset by the computer

4. Main Problem and Desired Outcome
The 10V Crisis:
When the board is turned off and on again (e.g. in a power
outage), all of its channels are reset to 10V. This overrides
the computer’s preset voltages for each channel, and is
dangerous for the connected instruments
When the voltage is reset, all channels should be broken to
avoid potential damage to instruments

5. Initial Focus
To design a board and install a switch, which can
make or break the channels’ connections
depending on its comparative analysis of the
current voltage, using:
1. Analog switches
2. Comparators
3. Timer/Delay systems

6. Stage 1: Brainstorming and Planning
After pondering the problem and researching methods
available to avert “The 10V Crisis”, I designed a basic
layout for what the solution board would look like...

7. Solution: Black Box Diagram of Board

8. Stage 2: Component Selection
By studying the specs of the Analog Board and
a multitude of parts found online, I narrowed
the field of types of usable components

9. Solution: Detailed Black-Box Diagram

10. Stage 3 Stage 4
DigiKey and several other
online catalogues were
used to select specific
components which met our
requirements. These
included analog switches,
NOR gates, and window
comparators
KiCAD was used in order to
create a schematic for this
project. The project is now
going through the final
development stages of
KiCAD’s process (i.e. PCB
layout, etc)

11. General Step by Step Solution
1. Comparator and switch break the channels (at 10V)
2. Computer resets channels 39-2 to ideal voltages
3. Then, computer sets Channel 1’s voltage to one within the frame of
the window comparator, which gives out 5V (Logic 1)
4. This sets forth the action to close the switch, but it is delayed by the
RC delay circuit
5. While the switch is closing, the computer sets Channel 1’s voltage to
that needed by the device connected to Channel 1
6. The switch closes, and all channels are running at their ideal
voltages

12. Details of the Solution (Parts, etc)

13. Significant Components
Window Comparator: Compares a given voltage to a preset
and adjustable frame of reference. Based on this
comparison, it outputs Logic zero or one (0V/5V)
The LM-393

14. Significant Components Cont’d
NOR Gate: This is a type of logic gate, and it only allows
the first set voltage (to Channel 0) to influence the switch
RC Circuit: Delays the current so that the computer has
time to reset Channel 0’s voltage (again) before the switch
fully closes

15. Additional Parts
Diode clamps, voltage regulators, and filter capacitors to
protect the components and to pare down signal noise
SMA connector plugged into logic output so that coaxial
cables can also be connected (not just ribbon wires)
Trimpots (adjustable resistors) make it possible to
customize the window of voltage reference

16. Additional Parts Cont’d
LED connected to logic output as well, using minimum
current (on/off = logic 1/0)
+ Monitor status visually
+ Assist in debugging (voltage flow)

17. Challenges and Interesting Bits
Understanding error messages in KiCAD and knowing
when to disregard them
Importing and creating footprints/components and
understanding how to manage KiCAD’s libraries
Controlling the board through one of the channels,
eliminating the need for any additional external wiring

18. Lessons Learned
- KiCAD proficiency, and basic circuit design
- Basic understanding of electrical rules and concepts
- Troubleshooting in KiCAD
- Footprint design and implementation
- Strategic circuit-oriented problem solving
- Familiarity with spec sheets, properties of components

19. Acknowledgements
Jason Hogan
Christine Donnelly
Alex Sugarbaker
Susannah Dickerson
Tim Kovachy
Chris Overstreet
Raj Krishnakumar
Mark Kasevich
Thanks to all of these people for
their support and for giving me
this amazing opportunity to
learn so much.
This exposure has opened my
eyes to a huge number of fields
and I am extremely grateful.