Thursday, August 28, 2014

High Voltage Designers Begin As Students

This week’s lab introduced students to digital multi-meters.  We measured parallel and series voltages of several different batteries – AA, C, D, and 9V batteries.

There were lots of challenges and a lot of laughs.  Many had never before laid eyes on a multi-meter before.  Some struggled with the concepts of series and parallel connections applied to the real world, while others made the connection between white board schematics and real-world terminal connections.   

Lab Tools
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It was awesome!   

Still others took it to the max and experimented with different parallel/series combinations beyond what was asked of them.  They stacked AA and C batteries, and recorded the results.

 As an instructor, it was gratifying to see the delight on many of their faces.  Lecture material on series and parallel circuits finally started to make sense.  There was another element present too – that of RELIEF!  A few students expressed their relief that it was all starting to make sense.  A hands-on lab helped the puzzle pieces to fall into place

The path to high voltage designs starts with low voltages and currents.  Not much thought is given to ‘safety’ requirements – at least not to the extent that working with high voltage (1kV and higher) necessitates - yet.  However (and that’s a BIG however), learning basic safety and housekeeping practices with low voltage make working with high voltages later on.  If safety is second nature, it doesn’t matter what the voltage and current levels are.  Many students’ eyes glaze over upon hearing the word “safety”.  The trick is to present the material in such a way that doesn’t trigger that automatic response.  Teaching through example can be very effective, especially for those who tend to dismiss verbal instructions.

The hope is that some of these students will continue on and go into math, science, or engineering.  For the ones who go into engineering, perhaps they will gravitate towards electrical design, and flourish in high voltage.  One can only hope.    

I don’t recall now where I heard the phrase, and maybe I’ll google it, but my new mantra is,
“Once a teacher always a student”.  That pretty much sums up my teaching experience so far.  Moreover, I’m loving it!

Tuesday, August 19, 2014

Your Best Resource for Custom, High Voltage Power Supply Designs

The class I teach is learning about cells and batteries.  I am too.  Oh sure, I’ve used the dry cells -  AA, AAA, C, D, batteries, and rechargeable NiCad, and maybe even Lithium ion ones.  Until now though, not much attention was paid to the application or other characteristics of batteries such as the Watt-hour rating.

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Batteries and Hand-held Power Supplies

VMI makes power supplies that run off generated DC voltages and some that are battery powered, both of which can be hand-held applications.  While it differs from manufacturer to manufacturer, some hand-held applications use batteries, others don’t.  The ones that do are generally more portable.      

Light-weight Requirement in Portable Apps

Hand-held applications have other requirements too.  For one, they must be as lightweight as possible.  Who wants to point and trigger a portable x-ray machine that weighs 15 pounds (33kg)?  It’s not easy holding that much weight at arm’s length.  Most hand-held XRF analyzers are under 5 lbs. (11kg).  The light weight requirement flows downhill to the high voltage power supplies as well. 
So, what does that have to do with batteries?  Well….batteries are pretty dense for their weight.  Think of how much a C cell weighs.  It varies from 98 grams to 200 grams depending on whether it’s an alkaline or copper or some other type of dry cell.  Some flashlights use four C cells, or two D cells.  They work great, but, well, they’re not something I would want to take on an extended backpacking trip.  They weigh too much, and they take up too much room.    


Lithium Ion Batteries

Lithium ion batteries are the power source of choice for many portable applications, including portable instrumentation.  12V, 18V, 24V, and 36V are common voltages used in the medical field.  They pack a punch when it comes to delivering power at a rating of 100-250 Watt-hrs/kg.  That could be important when you think the batteries are what is charging a capacitor in a defibrillator. 
Smaller versions of Lithium ion batteries are in smart phones, tablets, and other electronic devices.   


One up from medical applications are Lithium ion batteries used in cordless drills, sanders, hedge trimmers, radio controlled toys, and more.  Still larger versions are used in electrical vehicles, electric wheelchairs, and were even used in NASA’s Mars Curiosity rover.

Electrical power is an important aspect in all our lives.  If you are reading this blog post on the Internet, you know what I mean. 

High Voltage Power Supply Design

VMI specializes in custom, high voltage power supply design, including portable, hand-held ones used in instrumentation.   Contact us to get the design process kick started.  We’re your best resource for custom, high voltage power supply design.

Friday, August 15, 2014

Why the Differences Between SP, SPJ, SPB Are A Blankety-Blank

Recently work was done on several of the high voltage rectifier and single-phase bridge website pages.  One thing that quickly became clear was that it was easy to mix up the part numbers when discussing them amongst ourselves – especially if we were in a hurry, or were not all that familiar with VMI product lines.

At one point, one of the team asked, “What does SPB stand for?”  Perhaps Sublime Pie Burble, or maybe Superstamp Psammophage Beastie?  (These are actual words, folks, courtesy of a random word generator).

Although Sublime Pie Burble sounds exotic and mysterious, it isn't correct.  (Good guess though!).  Once the part numbers were decoded, they were not all that mysterious either.   

SPB stands for “Single Phase Bridge”. 

  • SPB50UF - SPB means it is a single phase bridge.  "50" indicates 5kV, and UF specifies 70ns reverse recovery.  So SPB50UF is a 5kV, 70ns, single phase-bridge.

SP stands for “Slim Pack” – a slim, high voltage rectifier.  The “slim” part refers to a body height of 0.5” compared to the .69” height of the FP – Fat Pack – rectifiers. 

  • SP200UF - SP stands for Slim Pack.  "200" specifies 20kV, and UF means it's a 70ns device.  So the SP200UF is a 20kV, 70ns, high voltage slim pack rectifier.

Lastly, SPJ stands for “Slim Pack Junior”.  The SPJs are miniature versions of the Slim Packs, featuring lower current, but higher reverse voltages.

  • SPJ100F - It is a "slim pack junior".  "100" specifies 10kV, and "F" means "Fast".  So SPJ100F is a 10kV, 70ns, slim pack rectifier. 

Between the FP, SP, and SPJ, there’s a rectifier for your every need.  
Download the data sheets.  Easy peasy.

But try and say, "FP, SP, SPJ" three times really fast.  It's quite the tongue-twister. 

Thursday, August 14, 2014

An Unconventional Comparison Between High Voltage Diode Selection and Teaching

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 I have been a student on and off over the years, and am quite comfortable in that role.  Things like registering for classes, logging on to college servers, checking school email, posting to discussion boards, submitting homework on- line, taking timed finals dressed in p.j.s and fully armed with a fresh pot of coffee…Yes, I know the drill. 
Recently I started teaching a class at the local college. Now, for the first time, I am on the other side of Blackboard.  It has definitely been a learning experience – much like specifying diodes in a high voltage application – and one I’ve enjoyed immensely.  

For instance, navigating the ins and outs of submitting final rosters, requesting faculty office hours, dropping students who don't show up, and submitting paperwork to Human Resources, can be daunting for the first timer trying to learn my way around.   

Nevertheless, like any new challenge, perseverance furthers.  Just like the first time you have to specify a diode.  There are many diodes to choose from.  So, where to start?  A good place is the reverse voltage requirement.  Designers usually have a good idea of what is needed.  They may not know if it should be 3kV, 4kV, or 5kV, but even knowing that narrows down the field when you can choose from devices between 2.5kV and 45kV.    

Once the reverse voltage has been selected, work on the next important rating – usually either Forward Current, Io, or Reverse Recovery Time, Trr.  Not all current ratings and reverse recovery times are available in all reverse voltages.  If you select a particular reverse voltage that doesn't come in a specific current rating, you might have to start fresh by re-examining the voltage and current requirements.  A decision may be needed to determine which is more important - current or voltage. 
Sometimes a faster recovery time is more important than the current rating, or vice versa.  Sometimes the most important factor has less to do with electrical ratings and everything to do with the package or termination style.  Through-hole printed circuit boards may want to stick to axial-leaded devices, which can limit choices in voltage and current combinations.  The same is true for surface mount applications.  Not all SM diodes come in is every current and voltage rating.  

Even so, once you’ve been through the selection process, it’s a lot easier the second time.  Help is never further away than a phone call or email.  Contact VMI is you need help selecting the best diode for your application.

I hope you enjoy selecting a diode as much as I’ve enjoyed my first week as a college prof.  

Thursday, August 7, 2014

Find Out the Secret Ingredient to Stellar Customer Service

Products, services, and pricing can be easily replicated; extraordinary customer experiences cannot." -  Darryl Speach, Chief Customer Officer at Greystone, writing at Fast Company online

Last week VMI held quarterly “State of the Company” meetings where Dennis Kemp, VMI President, talked about where the company came from (for new employees), where we’re headed (goals), and how we’re going to get there (strategies). 

Even though the news is not always pleasant – 2009 was a very tough year for VMI and the world in general – VMI has consistently taken the long view and knows a “bad” quarter or two is not necessarily reason to panic.  The news this quarter was positive.  Business and profitability are trending in the right direction.  This blogger doesn’t want to jinx it, but so far, 2014 has been a very good year for VMI in many ways.        

Competitive Advantage

There are only three high voltage diode manufacturing companies left in the world.  Two of them are in China, the other one is in Visalia, California, USA.  Voltage Multipliers Inc., is that company. 
One of VMI’s competitive advantages lies in the fact that they value their employees and treat them accordingly.  Turn-over rate is very low.  The first employee ever hired still works here.  Lest  you think VMI is just a bunch of dinosaurs sitting around resting on their laurels, banish the thought!  The average age of the engineering group is 39.42 years old.  The range is 62 to 24 years old.  Similar demographics are reflected throughout the company.  VMI is a thriving enterprise, and all that collective knowledge is being passed on to next group of leaders.             

 Secret Ingredient
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Treating your employees well translates to continuity in customer service that cannot be duplicated in companies focused on quarterly profits.  Treating employees well results is low turn-over, which means lower training costs.  It's easier to invest in employees who are going to stick around longer, and not jump ship at the next better offer.  The entire company benefits from a well-educated, well-trained work force.  People who feel good about their jobs will feel good about their customers.  It brings out the best in people. 

The secret ingredient is loyalty.  VMI is loyal to its employees, and to its customers.

We’re leading by example because in the end, it’s people that matter.