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Tutor profile: Kent J.

Inactive
Kent J.
Co-Founder & VP Avionics for Advanced Rockets Corp.
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Questions

Subject: Electrical Engineering

TutorMe
Question:

Can you help simplify Kirchhoff's current law for me?

Inactive
Kent J.
Answer:

I like to use the analogy of water flowing through a pipe. For KCL think of current as water flowing through a pipe. When it reaches a junction in the pipe some of the water may go one way and some of the water may go the other but you always end up with the same amount of water. It is just now dispersed across multiple pipes. So likewise, the current going into a given junction is always the same as the current going out of that junction!

Subject: Entrepreneurship

TutorMe
Question:

How do I start a business when I don't have any money?

Inactive
Kent J.
Answer:

Starting a business requires some capital PERIOD and unfortunately, there are no shortcuts. A common misconception is to believe an 'idea' or 'business concept' has inherent value on its own. The truth is, your reliance on a napkin pitch for fundraising is a pipe-dream. Don't let anyone tell you that a startup requires anything less than blood, sweat, and tears! Pay-your-own-way Often the most cost-effective solution is going to be to "bootstrap" or self-fund your venture (at least for the initial stages). But keep in mind that 90% of startups fail so before you mortgage your house make sure you have an exit plan should things go south! Angel If bootstrapping is not an option then you will need to find a benefactor. Most often this is friends and family who have a vested interest in seeing you succeed on a personal level. It is also possible that an angel would invest simply because of passion for the concept but those kinds of angels are few and far between in my experience. Crowdfunding There is a strong temptation to jump straight into crowdfunding your business. There may have been a few cases where that has worked but for the vast majority of crowdfunding campaigns, this is not the case. The amount of preparation that takes place behind the scenes of your average successful campaign is comparable to the prep that goes into pitching institutional investors. If you do happen to get funded this way just be aware that having this capital doesn't make you any less likely to fail if you haven't laid the groundwork before and your "investors/customers" are going to have far greater expectations and put much more pressure on you than an angel investor or even a VC. VC's Raising venture capital will require you to show traction. Don't approach a VC without having made significant strides in your business already. This can be a great option to raise larger amounts of money but will require demonstrable progress The long and short of it is there is no easy way to get your business off the ground. It is always an insane amount of work with a low probability of success and in the end, it all boils down to how driven you are and how much you are willing to sacrifice to make your dream a reality!

Subject: Arduino Programming

TutorMe
Question:

I want to precisely control the speed of a small motor with just an Arduino! Would you please walk me through that process?

Inactive
Kent J.
Answer:

First of all, as with any project, you should start by defining your design parameters. For example, what type of motor are you using? How much torque do you require for your application? At what speeds will you be running the motor? What degree of accuracy do you require? What is your budget? etc... Once you have outlined the constants, you will be faced with some crucial design decisions. You won't be able to directly power a motor from your Arduino so I assume you will be using the Arduino Motor Shield for this example and a brushed DC motor. Open Loop vs Closed Loop: Feedback control systems (closed-loop systems) keep track of the speed or rotation of the motor so that the system can self-correct if it gets out of spec. Open-loop systems, on the other hand, don't keep track of this information and therefore cannot self-correct. In the case of the motor shield from Arduino, the system is open-loop which means you can never be sure that the speed value you input for the motor will reflect the actual speed of the motor. The actual speed will be dependent on the load applied to the motor. Open-Loop If the load being driven by the motor is fairly constant you could measure the output speed for corresponding input values and build a chart for your Arduino program to reference. If you want more accuracy you would have to interpolate to determine intermediate values. This is a fairly simple way to get a fair degree of accuracy but it only works if you know the load on the motor is constant. Closed-Loop Often the load on the motor is NOT constant. If you have a variable load or you just need that extra degree of accuracy you could use a motor with a built-in encoder or some other kind of feedback sensor. An encoder would send back pulses to the Arduino every time the shaft of the motor rotates a fixed amount which you can use to calculate the speed or position of the motor. With this feedback, you could implement many different types of control systems. One of the most common types is a PID. PID (proportional-integral-derivative) is a method of interpreting the feedback and quickly adjusting the motor's input values to maintain the desired output. PID's adapt to your real-world hardware and therefore need to be 'tuned' for your application. Arduino has a PID library to which helps you create and tune your PID motor controller.

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