Hands-on Guidelines for Good Circuit Implementation

Building electronics can be a fun experience with frequency joy associated with working circuits and hardware. Or it can be a frustrating experience where it seems like circuits only work intermittently depending on the alignment of the stars. While in reality there is always some frustration in getting hardware to work, developing a systematic approach to building, testing, and debugging will serve you well throughout your career, and eliminate numerous hours of frustration. Below are some guidelines to follow.

 

Voltages Current and Power

  • Voltages can easily be measured with a voltmeter or oscilloscope, but currents are harder to measure (you have to take the circuit apart).

  • Therefore you should measure voltages, but calculate current.

  • Do not ignore current since they indicate power (P=VI).

  • Every electronics or electrical component has power input and output specifications

    • There is a minimum amount of power (and current) that every component needs to operate. This power is much higher for components that do significant work such as motors and electromagnets, and much smaller for logic components like a microprocessor.

    • There is a maximum amount of power (and current) that every component can output. This current is generally small for logic chips, and higher for power transistors or some op amps.

 

General Tips for Using Integrated Circuits

  • Do not leave inputs floating (i.e. no specified voltage)

    • use a pull-up or pull-down resistor for inputs that will change

    • tie constant inputs with high (Vcc) or low (ground)

  • Use capacitors to filter noise (often one places the capacitors as close as possible to filter location, since long copper wires in a circuit have a small amount of resistance which can reduce the effectiveness of a capacitor.

 

 

 

Develop Good Wiring Habits

 

  • Follow color guidelines, especially for the power supply (Vcc) and ground

  • Keep the wires neat (don’t create a nest with too much extra length)

  • Use strain reliefs in any wires that attach to moving parts or may be pulled

  • Avoid shorts. Use electrical tape and shrink wrap

 

 

Debugging Skills

 

  • Debugging is an Art and skills can be developed

  • Be systematic and isolate components

    • get each component to work separately before integrating

  • Use a voltmeter (and oscilloscopes for fast changing signals) to measure voltage at all points in circuit

    • If the voltage out of a logic device is less than the high voltage (typically 5V) then one is trying to draw too much current from device.

 

Electronic Do's and Don'ts

 

Have organized wiring.
  -While signal wires (blue, green and yellow) can be somewhat interchangeable make sure that RED=+5V; BLACK=Ground; White=7.2V.
  -If your wiring is messy and you ask for help, we may ask you to rewire it in a more organized fashion.  We're not being mean, often the problem is found as the wiring is cleaned      up. 
  
Have a circuit diagram.
  -Make it clearly labeled.
  -If you update your circuit, update the diagram too.
  -We will also ask for circuit diagrams.

Make good connections.
   -
Have strain relief on moving electronics so you do not get pull out. 
   -Solder things together and use heat shrink tubing to avoid shorts.

Make electronics accessible to swap out components

Test each component in sub-units so that you can be confident it works when thrown together 

Measure a lot (With a multimeter or the oscilloscope)
  
-Voltmeter will be your friend, and if not it should be.
    -Measure the across the system to get the voltage.
    -Make sure you are in DC mode. 
  -Ohmmeter is handy if you don't remember color codes.
    -DISCONNECT the item in question from the circuit.  (If not it won't work and might damage sensitive electronics)
    -Passive components only please. 
  -Ammeter can measure the current going through components.
    -You must measure in series to get a useful reading.

 

References

 

“The Art of Electronics” by Horowitz and Hill. Considered by some to be the “bible” on electronic design.

 

Physics 122 Lecture Notes, by Frank L. H. Wolfs, University of Rochester


 

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