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Jason Sachs's Embedded Systems Blog

Jason Sachs
Jason has 17 years of experience in signal conditioning (both analog + digital) in motion control + medical applications. He likes making things spin.

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My Love-Hate Relationship with Stack Overflow: Arthur S., Arthur T., and the Soup Nazi

Warning: In the interest of maintaining a coherent stream of consciousness, I’m lowering the setting on my profanity filter for this post. Just wanted to let you know ahead of time. I’ve ...

posted by Jason Sachs on Feb 15 2015 under Miscellaneous 
Comments (41) |

Two Capacitors Are Better Than One

I was looking for a good reference for some ADC-driving circuits, and ran across this diagram in Walt Jung’s Op-Amp Applications Handbook: And I smiled to myself, because I immediately rememb...

posted by Jason Sachs on Feb 15 2015 under Circuit Design | Analog Circuits | Signal Processing 
Comments (2) |

How to Estimate Encoder Velocity Without Making Stupid Mistakes: Part I

Here's a common problem: you have a quadrature encoder to measure the angular position of a motor, and you want to know both the position and the velocity. How do you do it? Some people do it poorly -...

posted by Jason Sachs on Dec 27 2012
Comments (21) |

Adventures in Signal Processing with Python (MATLAB? We don’t need no stinkin' MATLAB!)

OK, now back to some down-to-earth topics after that last philosophical diversion. This post will be a short tour of PyLab, and a springboard for a number of other topics — including that long-a...

posted by Jason Sachs on Jun 23 2013
Comments (6) |

Thermistor signal conditioning: Dos and Don'ts, Tips and Tricks

In an earlier blog entry,  I mentioned this circuit for thermistor signal conditioning: It is worth a little more explanation on thermistor signal conditioning; it's something that's often don...

posted by Jason Sachs on Jun 15 2011
Comments (5) |

Analog-to-Digital Confusion: Pitfalls of Driving an ADC

  Imagine the following scenario:You're a successful engineer (sounds nice, doesn't it!) working on a project with three or four circuit boards. More than even you can handle, so you give one of...

posted by Jason Sachs on Nov 19 2011
Comments (2) |

Important Programming Concepts (Even on Embedded Systems) Part V: State Machines

Earlier articles in this series: Part I: Idempotence Part II: Immutability Part III: Volatility Part IV: Singletons Oh, hell, this article just had to be about state machines, didn’t it...

posted by Jason Sachs on Jan 5 2015 under Software Development | System Design 
Comments (5) |

Byte and Switch (Part 1)

Imagine for a minute you have an electromagnet, and a microcontroller, and you want to use the microcontroller to turn the electromagnet on and off. Sounds pretty typical, right?We ask this question o...

posted by Jason Sachs on Apr 26 2011
Comments (8) |

How to Build a Fixed-Point PI Controller That Just Works: Part I

This two-part article explains five tips to make a fixed-point PI controller work well. I am not going to talk about loop tuning -- there are hundreds of articles and books about that; any control-sys...

posted by Jason Sachs on Feb 26 2012
Comments (4) |

Help, My Serial Data Has Been Framed: How To Handle Packets When All You Have Are Streams

Today we're going to talk about data framing and something called COBS, which will make your life easier the next time you use serial communications on an embedded system -- but first, here's a quiz: ...

posted by Jason Sachs on Dec 11 2011
Comments (8) |

How to Build a Fixed-Point PI Controller That Just Works: Part II

In Part I we talked about some of the issues around discrete-time proportional-integral (PI) controllers: various forms and whether to use the canonical form for z-transforms (don't do it!) order ...

posted by Jason Sachs on Mar 24 2012
Comments (2) |

Voltage Drops Are Falling on My Head: Operating Points, Linearization, Temperature Coefficients, and Thermal Runaway

Today’s topic was originally going to be called “Small Changes Caused by Various Things”, because I couldn’t think of a better title. Then I changed the title. This one’s...

posted by Jason Sachs on Jan 19 2015 under Circuit Design | Analog Circuits 
Comments (0) |

Lost Secrets of the H-Bridge, Part IV: DC Link Decoupling and Why Electrolytic Capacitors Are Not Enough

Those of you who read my earlier articles about H-bridges, and followed them closely, have noticed there's some unfinished business. Well, here it is. Just so you know, I've been nervous about writing...

posted by Jason Sachs on Apr 29 2014 under Tutorials | Circuit Design | Power Electronics 
Comments (7) |

10 Circuit Components You Should Know

Chefs have their miscellaneous ingredients, like condensed milk, cream of tartar, and xanthan gum. As engineers, we too have quite our pick of circuits, and a good circuit designer should know what's ...

posted by Jason Sachs on Nov 27 2011
Comments (0) |

Lost Secrets of the H-Bridge, Part III: Practical Issues of Inductor and Capacitor Ripple Current

We've been analyzing the ripple current in an H-bridge, both in an inductive load and the DC link capacitor. Here's a really quick recap; if you want to get into more details, go back and read part I ...

posted by Jason Sachs on Aug 24 2013 under Power Electronics | Signal Processing 
Comments (4) |

How to Estimate Encoder Velocity Without Making Stupid Mistakes: Part II (Tracking Loops and PLLs)

Yeeehah! Finally we're ready to tackle some more clever ways to figure out the velocity of a position encoder. In part I, we looked at the basics of velocity estimation. Then in my last article, I tal...

posted by Jason Sachs on Nov 17 2013 under Applied Math | Signal Processing 
Comments (4) |

Another 10 Circuit Components You Should Know

It's that time again to review all the oddball goodies available in electronic components. These are things you should have in your bag of tricks when you need to design a circuit board. If you read m...

posted by Jason Sachs on Oct 30 2013 under Circuit Design 
Comments (1) |

Understanding and Preventing Overflow (I Had Too Much to Add Last Night)

Happy Thanksgiving! Maybe the memory of eating too much turkey is fresh in your mind. If so, this would be a good time to talk about overflow. In the world of floating-point arithmetic, overflow is p...

posted by Jason Sachs on Dec 4 2013 under Software Development | Tutorials 
Comments (0) |

Which MOSFET topology?

A recent electronics.StackExchange question brings up a good topic for discussion. Let's say you have a power supply and a 2-wire load you want to be able to switch on and off from the power supply us...

posted by Jason Sachs on Sep 1 2011
Comments (4) |

How to Include MathJax Equations in SVG With Less Than 100 Lines of JavaScript!

Today’s short and tangential note is an account of how I dug myself out of Documentation Despair. I’ve been working on some block diagrams. You know, this sort of thing, to describe feedba...

posted by Jason Sachs on May 23 2014 under Tools | Miscellaneous 
Comments (3) |
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