May 2005
Beginner to intermediate
398 pages
12h 12m
English
Content preview from Designing Embedded Hardware, 2nd Edition
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.
Switching Big Loads
We've already seen how to use an H-bridge chip to switch relatively large voltages (and the corresponding big currents) needed to drive electric motors. There are many other cases where you want to turn large voltages on or off, and, in this section, you'll learn an easy way of doing just that.
The Freescale MC33298 is a chip that is controlled by a microprocessor using SPI that can switch eight power sources on or off. This chip can handle voltages between 5 V and 26.5 V, with currents as large as 6 Amps. If you need to turn electrical systems on or off, this chip is for you. Its primary use is for industrial and automotive applications, controlling power to subsystems such as heaters, small air-conditioning units, moderate-voltage light bulbs, small pumps, and so on. Obviously, it won't handle the high AC voltages that come out of your wall socket, so don't use it for switching power to your home appliances!
The basic schematic for the circuit is shown in Figure 13-36.
Figure 13-36. MC33298 circuit
The MC33298 has two power-supply pins. VDD is a 5 V supply and powers the chip's internal digital logic. It's decoupled to ground using a 100 nF capacitor. V PWR is the supply voltage for the external subsystems (represented in the figure by each "LOAD" rectangle) and can range from 5 V to 26.5 V. There are eight switch outputs, labeled OUT0 through OUT7. When a given ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.