Halloween Hacks!!!

I haven't had much time this month to work on my fun pending side projects: repairing and calibrating my Analogic AN3100 Voltage Standard, Repairing my Tektronix Type 491 Spectrum Analyzer, and cleaning up my Arduino based Function Generator code. My day job is getting in the way..... but my day job pays the bills so that is ok!

Below are some really cool Halloween Hacks I found on YouTube.

Happy Halloween!

Cool Design Idea of the Week - Power Selection Switch!

I was flipping through the latest issue of Electronic Design while flying back from Austin, TX and I came across a not obvious neat idea. On one of Parallax's Basic Stamp boards they intentionally placed the DC Power Jack in a location that would be blocked if a 9V Battery was installed.... thus preventing the 9V battery from getting reverse current if the DC Power Jack was plugged in as well. Brilliant!

It must be the EE in me but I would always think of adding a diode "OR", some FET, or a terribly complex circuit that disconnects power to the 9V battery when the DC Jack is plugged in. This approach, though not practical in all cases, is elegant and wins my Cool Design Idea of the Week award!!!

7400 Series Logic PLL Based Switch-Mode PSU

While building up a simple Seven-Segment LED Up-Counter Circuit a few weeks ago as a brain storming exercise, I thought a cool 7400 Series project would be to build up a "Buck" Switch-Mode Controller out of Logic Gates.

I had built up a few Analog & Digital PLL's before and I thought that might make a neat starting point for a switch-mode controller. Essentially a Digital PLL requires a Reference Frequency (Square Wave), a Digital Voltage-Controlled Oscillator, a Phase Detector (XOR Gate) and a Low Pass Filter. The Reference Frequency and the VCO outputs are the inputs to the XOR Gate (Phase Detector). The output of the XOR Gate is then feed into the Low Pass Filter which creates a DC error voltage. This error voltage is then feed into the VCO input; creating a feedback connection. As this circuit runs the error voltage will settle and the output of the VCO will become the same frequency as the Reference Frequency. What if the Low Pass filter was a typical Buck - Transistor, Diode, Inducator, and Output Cap. and the error voltage was the Output of the Buck Regulator? ..... that was my starting point anyway.

Below is what I came up with:

I built up a 90KHz reference Ring Oscillator using two 74HC04's. Then I built up a XOR Gate using 5 NAND 74HC00 gates. The VCO is based off the same 90KHz reference Ring Oscillator, but I added a capacitivly coupled MV2109 Varactor to vary the frequency when a DC voltage was applied through the 100K pot adjustment. The 5.1V zener diode was a vain attempt to prevent the Vout overshoot from affecting the VCO's output.... I'll explain this more later.

I used a TIP106 PNP transistor, a B321 Shottkey Diode, a 38uH 3A Inductor, and 3x47uF electrolytic caps as the "Buck" (filter) circuit. Since my XOR gate output was referenced to ground and the PNP transistor needed a Vinput based reference I used a 2N3904 NPN to couple the XOR output to the PNP.

Results:
I was able to get the basic converting circuit working. I used 16VDC as my input voltage and then adjusted the 100K pot to bring the VCO frequency closer to the Reference Frequency of 90KHz and I got 5VDC on the output.

 Below are the waveforms:

Issues:
With the feedback disconnected  (Vout to the input of the VCO) I was able to get the circuit to convert a 16VDC input voltage down to 5V reliably. With the feedback disconnected though any change on the input voltage will be seen on the output voltage and any load fluctuations will effect the output voltage as well. I wasn't able to get the VCO's output to stay stable enough when connected to Vout for regulation to work. The XOR Gate is a phase detector not a frequency compare; this means the output of the XOR gate when the VCO is 88KHz is pretty much the same as 92KHz. This is the overshoot problem I was hoping my Zener diode would take care of, but my VCO wasn't stable enough to not have the frequency overshoot and dialing in 5V was nearly impossible with the feedback hooked up.

Someone wise told me that "Experience is what you get when you didn't get what you wanted"... I got a lot of experience on this project. The XOR Phase Detector is probably not the right component to be used in this circuit since the phase polarity can not be distinguished and thus overshoot and run away is a problem when the feedback is hooked up. I ran out of time before the 7400 Series Logic Contest deadline, but I am still entering the "non-regulating converter" since I was able to get the 16VDC to convert down to 5VDC reliably (as long as the input voltage and load are constant).

Maybe I'll have an epiphany or  kind reader will give me some hints as to how to prevent the XOR Gate Output from switching when the frequency of the VCO is greater than 90KHz in the coming weeks.

EEweb Pulse Magazine Cover... Who is that guy!

Very Cool, I just had the neat opportunity to be on this month's EEweb's Pulse Magazine Cover. In the article I got the opportunity to discuss some generality's of my day job as a Design Engineer for a Weigh Scale company.... sorry no specifics about my latest and greatest project, our competitors probably read this magazine too. I also got to talk about some of my side projects and my Touchstone Semi. opamp design contest entry. Check it out!

Thanks EEweb for the opportunity!

The Benefits of Ancient Logic

I was catching up on reading my trade rag magazines from when I was in China the past week and a half and I came across this article on the benefits of 4000 Series CMOS Logic in today's designs. I thought it was ironic timing considering Dangerous Prototypes 7400 Series Logic Design Contest deadline is coming up..... I need to work on my entry. (I got all the pieces now I just have to build it and get it to work... the easy part!)

Enjoy!
The Benefits of Ancient Logic (Analog Devices: James Bryant)

A Year in the Making!

Today is the one year anniversary of the start of my little experiment.... the "Rants from the Embedded Hardware Guy" blog.

It has been so much fun building up projects and taking pictures to meet my "imaginary" personal deadlines, so I can share them on this blog. I would encourage anyone who likes too, or wants too, tinker at home to start a Blog and post your projects. Creating an account on BlogSpot and posting videos on YouTube is free, it just takes a little bit of time.

This Blog has reignited my "Hacker/Maker" drive and has connected me with Engineers all over the world. I have appreciated all the feedback I have received about my posts and love being a part of the Open Hardware sharing community.


Like most Bloggers I am obsessed with my blogs stats (page views, traffic sources, and audience), but one of the neat side benefits is getting to see what web browsers and operating systems are being used to view the blog:

 (Microsoft is in control, but I thought it was interesting that Linux and Mac are both about the same usage in the Engineering community.)


Thank you for a great year and I hope for many more to come!

Free Beer..... Today at Arrowfest!

I just got back from my yearly trek up to Minneapolis, MN USA to attend Arrowfest. For those of you not familiar with Arrowfest, Arrow is one of the top 3 Electronic Component Distributors in the world and once a year they put on a large event called Arrowfest. The event consists of 24 different technical seminars during the day (you pick 4 you are interested in) and a tent exhibition with vendor booths, free swag giveaways, drawings for prizes, free food, and yes free beer (And a handy Arrowfest Glass Mug to put it in.)

My wife gives me a bit a grief for continuing to fill our kitchen cabinets with Arrowfest mugs (I think I am up to 10 or 11 now). They make great beer & coffee mugs though!

I am a pretty firm believer in you get what you pay for when it comes to technical training seminars. If you attend a 2-day seminar and it costs you $1,500 to attend it is probably going to be a lot more in depth and worth wild than a free 1.5 hour seminar.... that being said, I do enjoy the Arrowfest technical seminars, and appreciate that they hand out the slides (on a CD) so I can check out the other 20 classes that I had to miss.

The Exhibition Tent is worth wild as well; there were booths from more than 85 different electronic component manufacturers and sales representatives all showing off there latest and greatest products. The big guys Texas Instruments, National Semiconductor (aka Texas Instruments), Linear Tech, Analog Devices, Altera, Freescale, Atmel were there along with many other manufactures. They were also handing out a ton of SWAG!

My Daughters love it when I go to these things, because it is like Christmas when I get home. My favorite swag had to be the Analog Devices Tape Measure, the Atmel pocket knife, and the Kemet Vertical Phone holder (that blue and white thing on the right). I also collected 3 or 4 aluminum tins of mints.... more project hacks coming up I guess :)

I don't make it up to too many training seminars  nowadays, but I always try and make it up to Arrowfest. It is great getting all the reps and manufacturers under one roof and I always run into old coworkers or friends in the industry. Plus a few years ago I got to meet Bob Pease at my local Arrowfest (Very Cool!) ...... I met Dave Van Ess at Texas Instruments Tech Days a few years ago too (a very close second, Very Cool!)


And just in case my Boss is reading this blog post... Yes I did find some cool stuff we could use on future products and I got a few pending questions answered... Thanks for paying for my gas :) 

Just Fooling Around with Logic..... don't tell my Wife!

It's Friday night and my wife and girls (a 4year old and 20month old) are off visiting relatives and I am trying to work out some concepts for my entry into the Open 7400 Series Logic design competition.....

I thought I'd just start with the basics and work my way up. Every Logic based design needs a clock, so I started out building up a 1Hz Ring Oscillator with a 74HC04. (The LTSPICE Yahoo Groups had this great Ring Osc. circuit which I used as a starting point).

Then I thought using a 74HC90 BCD Counter to drive a 74LS47 BCD to seven segment driver would be a fun way to use a 1Hz clock.... pretty Digital Logic 101, but hey I need to start some where.

So here is the first "Brain Storming" part of my entry:

Much more circuitry and trickery to come before the deadline!

Low Cost Misc Parts Kits

Back when I started messing with electronics as a teenager I started a misc parts bin of resistors, capacitors, LEDs, 555 timers, 7400 logic parts, etc. for my projects. Within a few years that bin grew to a box, to many boxes and now I have a parts closet at home; with each shelf sectioned off for Caps, Inductors, Resistors, Connectors, ICs, etc.

While searching on ebay for used Test Equipment (another addiction of mine) I came across these neat parts kits.
SMT Voltage Regulator Engineering Kit w/ SMT PCBs
Analog IC DIP-Only Design Kit #1 (#1120)
Master Op Amp IC Design Kit #1 with PCB (#1565)
Linear IC DIP-Only Design Kit #2 with PCB (#1310)

There are many more kits at Night Fire's ebay store: http://stores.ebay.com/nightfireelectronickits

Even though I have a closet full of parts at home sometimes getting a small bag of parts stirs my imagination enough to think of my next hack. I just received the Master Op Amp kit and I am ready to build something up!

Simpson Multimeter Clock

Lauro posted a link to this awesome project on the blog and it is so cool I needed to share it. It is a Simpson Multimeter Based Clock.

Overview:

The Multimeter Clock consists of three multimeters, the first meter displays hours, the second displays minutes and the last displays seconds. A 16F628A PIC microcontroller keeps track of time and outputs a calculated current to each meter to display the current time.

Here is a link to the Project Page.

 This is a very cool project and a neat twist on making a clock!