[TriEmbed] Transistor as switch

Van Watts vanwatts at gmail.com
Mon Jun 15 21:59:35 CDT 2015


Guys, interesting discussion to me because I have been recently
learning about motors and motor drivers for projects at work.

Maybe i'm wrong but im not sure I heard it answered whether Brian's
proposed transistor is likely to be "good enough" for his class for
kids--or is it more likely to blow up his RaspberryPi?  As it is, his
class is coming up very soon.  And I know how "perfection is the enemy
of good enough" when you're running up on a deadline!

Also, a distinction I just recently learned (and someone can correct
me if this is wrong):  Back-emf (bemf) is the positive voltage
generated by a spinning motor (think "generator"), while fly-back
voltage is the negative voltage spike generated by the motor
(remembering that a motor is a big inductor) when the power to it is
suddenly cut and the magnetic field collapses.  Both need to be
considered but take different forms and take different means for
handling them.

I learn a lot reading y'all's posts. :)

Thanks!
Van


Sent from my iPhone

> On Jun 15, 2015, at 9:00 PM, Jon Wolfe via TriEmbed <triembed at triembed.org> wrote:
>
> When I decided to get into electronics, and learn the pragmatic "get it done" approach as opposed to the electrical engineering electives I was forced to take in college, I found the "robot building" series of books by David Cook really well done. I know he covered making your own h bridge motor drivers from basic discrete transitors,  and how they work. I know I did the exact same thing in labs in colllege, but the presentation was so different it was enjoyable to learn.
>
> -------- Original message --------
> From: Grawburg via TriEmbed
> Date:06/15/2015 8:02 PM (GMT-05:00)
> To: triembed at triembed.org
> Subject: Re: [TriEmbed] Transistor as switch
>
> The basic electronics book the student get (Make: Electronics (Learning by Discovery)) doesn't cover MOSFETs so I can't use them for this segment. However, later on this summer I have another class and will introduce them then. I do need to think of a good low-cost project that basically is a "proof-of-concept" project and not an actually a big project.
>
> The opto-isolated relays I used for my conveyor/train humpyard are what we'll use this time. Safe and easy to set-up.
>
> Don't know what I'd have done with the Raspberry Pi had I not found TriEmbed!
>
>
> Brian
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