Hardware Design on Bald Engineer

5 LDO Regulator Considerations other than voltage and current

Wed, 30 May 2018 13:03:28 +0000

For an AddOhms series, I created a DIY Arduino I am calling the “Pyramiduino.” It is an ATmega328p based board in the shape of a triangle. Other than being cute, the shape does not offer any other benefit. The design features a 3.3 volt LDO Regulator, which is also the subject of this post. I forgot a fundamental aspect of design: read the freaking datasheet. The board’s LDO regulator was not turning on. Adding a passive scope probe to the circuit suddenly fixed the problem. The regulator turned on. When touching the enable pin, it measured about 1.25 volts. While I am sure Rohde & Schwarz would like me to ship scope probe with each board, that was not an option. With the impractical fix in place, I got to thinking about that voltage level. I remembered that the datasheet mentioned about 1.2 volts was needed for the “HIGH” threshold. Which meant, 1.25 volts applied to the pin enabled an active low input. Not only that, I remember the datasheet clearly said it had a pull-down resistor built-in. What was going on?

DIY Arduino PCB Pryamiduino (Video)

Wed, 28 Feb 2018 14:00:03 +0000

Continuing the DIY Arduino tutorial series, this AddOhms episode shows how to create a PCB in KiCad. I make a joke that the original design was a rectangle, which I found boring and pointless. So instead, I designed a triangle to give the board 3 points. Get it? Puns! I am calling it the Pryamiduino. To be honest, I found not having a constraint to be a problem. By forcing a specific board size and shape, many decisions were more manageable.

DIY Arduino Schematic board and Checklist

Wed, 17 Jan 2018 14:00:18 +0000

One of the last significant steps in a project is designing the custom PCB. This stage means creating a DIY Arduino board that is custom to the application. Two examples of my past projects are BinBoo, a Binary Clock, and Open Vapors, my reflow oven controller. While working on a project for a friend, I got to thinking; it would be nice to have a checklist for circuit elements to include on a DIY Arduino board. In the early days, I forgot to add a filter cap to AREF, for example.

Arduino Keyboard Matrix Code and Hardware Tutorial

Fri, 15 Dec 2017 14:00:26 +0000

As a kid, I got the book " Upgrading and Repairing PCs." (Now in its 22nd edition.) It was the first book to explain to me the PC architecture. I considered, how were there so few pins on an AT-style keyboard connector when there were 101 keys on the keyboard? That is when I first learned about the keyboard matrix. Intel_P8049_AH_controller The keyboard matrix itself did not amaze me, but instead the idea there was an entirely separate 8-bit microcontroller inside of the keyboard. Early keyboards may have used the P8049AH, which, there is still some stock available to purchase. I was fascinated with the idea an entire computer was necessary to run the keyboard, to use my “real” computer. Why did it take something as complicated as a microcontroller?

Current Flow Direction

Wed, 22 Jun 2016 13:00:15 +0000

A couple of weeks ago I wrote about four current flow direction myths. As a follow up to that popular post, I decided to dedicate this month’s AddOhms electronics tutorial video to Current Flow. In episode #19, I tackle the question of which way does current flow. You might have heard about “conventional flow” and “electron flow.” In conventional flow, we assume that current flows from the positive voltage towards the negative voltage. In digital, the “negative voltage” is usually called ground. However, that’s not how the electrons move nor is it how they carry the charge around a circuit path.

Watch this video on YouTube

P-Channel MOSFET Tutorial with only Positive Voltages

Thu, 09 Jul 2015 01:20:55 +0000

On every page of my blog, you might notice a chat window. If I’m not busy, we can chat in real-time. If not, the messages come to me by email. Here’s one I got from Matt the other day: Let’s talk a bit about how (and why) you would use a P-Channel MOSFET. Matt, and he’s not the only one, is probably asking this question based on the “myth” that P-Channel MOSFETs require “negative voltage” supplies.

How to find parts for your electronics projects and designs

Wed, 24 Jun 2015 13:00:58 +0000

What part is the most important part in building a project? All of them! Okay, bad joke. Selecting the right parts or components for a design is an area where both new hobbyist and veteran engineers struggle. The wide variety of devices make it almost impossible to know if you are selecting the right one. Looking at a curated List, using component search engines and browsing DIY shops are how I tend to find parts for my projects.

What's the difference between Series and Parallel Circuits?

Wed, 27 May 2015 14:00:28 +0000

Tutorial on schematics basics The funny thing about schematics is that they are much easier to draw than they are to read. There are many common circuits. When an experienced engineer looks at them, it’s like a second language. When someone less experienced looks at them, it looks like random lines and symbols thrown together at the last-minute. (Or maybe that’s just the schematics *I* draw.) Other than reading Schematic Symbols themselves, one of the basic skill necessary to read a schematic is recognizing series and parallel circuits.

Awesome 3D Board (BRD) Viewer for EAGLE

Thu, 12 Mar 2015 15:05:44 +0000

2018-JULY-18 UPDATE: It appears Peter has shut down his rendering tool. It is no longer available. 3D Render of MSO Demo Board Earlier I posted a PCB Checklist of items to double-check when sending your board out to a fab. The Dangerous Prototypes blog pointed to a 3D EAGLE PCB tool from a Bulgarian-based developer called Cytec that takes an EAGLE BRD file and renders it in 3D for you.

Autorouters Suck: Autorouter: 0. Baldengineer: 1

Tue, 03 Mar 2015 15:06:54 +0000

I am not a fan of relying on the Autorouter in EAGLE – or any PCB CAD software for that matter. When laying out a board, I’ll use the autorouter to get an idea if the part placement is going to work or not. In this case, I was reminded how much autorouters suck! Even after running for while, the autorouter could only route up 50% of the nets (signals).

iCircuit's circuit simulator goes from iOS to Desktop

Wed, 28 Jan 2015 17:53:48 +0000

When it comes to schematic capture and circuit simulation on a mobile device, iCircuit for iOS got it right from the start. iCloud integration, intuitive touch controls, and fast application performance. Now (or Finally?), my favorite mobile circuit simulator, iCircuit, is available for OS X. iCircuit is based on the Falstad Circuit Simulator, which sadly, is a Java-based web app. For years I’ve installed the App on my iPhone and iPad almost immediately after turning on iCloud [for Android users, that’s basically the first step of activating an iOS device].

Clean Ground Planes on DIY Boards

Thu, 15 Jan 2015 15:14:41 +0000

If you’re making your own PCB with the toner transfer method, you might find that getting nice clean ground planes is difficult. John on twitter (@ johngineer) realized a simple, but effective method. Use a hatch pattern for your planes and then fill in the squares with a Sharpie. Simple, but effective. The paper detaches easier and the etch comes out cleaner. For help on creating ground planes in EAGLE, check out this video tutorial I put together.

Signal and Power Integrity - Simplified (2nd Edition)

Mon, 29 Dec 2014 16:25:32 +0000

Let me start by saying, this book is not for new comers, or (ugh) “newbies”, to electronics. This book is intended for those who have a solid understanding of electrical engineering fundamentals, but want to expand to the next level. Bogatin’s amount of detail is on-par with a textbook but writing style is more casual. Understanding signal integrity use to be “Black Magic.” It is taught in a language which resembles engineering speak, but sounds like randomly assembled terms purposefully meant to confuse people. Personally, I remember hearing “signal integrity engineers talk” and wondered if they were speaking in code.