Thursday, June 28, 2012

Anode vs. Cathode in a High Voltage Diode

SMF6533 High Voltage Diode with Cathode Band
SMF Type High Voltage Diode w/ Cathode Band
VMI’s high voltage diodes almost always include a marking of some type to indicate the cathode end of the device. Sometimes the cathode is indicated by a band, or one or more dots.

Distinguishing between the anode and cathode end is important when the diode is under test or part of a circuit.

Formed Lead High Voltage Diode with Cathode Band
Formed Lead High Voltage Diode w/ Cathode Band

There are two main conventions when dealing with current. They are the engineer’s convention, and the physicist’s convention. Neither is incorrect, it just depends on your definition of ‘current flow’. For the following discussion, we assume the engineering convention - that is, current will flow from anode to cathode or from positive to negative. A diode will block current flow when the cathode becomes more positive than the anode.

High Voltage Glass Body Diode with Cathode Band
Axial-leaded High Voltage Diode w/ Cathode Band
If you want a diode to normally conduct in a positive current, but insert the diode so that the current sees the cathode side first, the device will block current and it will look like you have an open circuit.

Likewise, if you want the diode to normally block, but insert the diode so the anode side sees the current first, the diode will conduct, and you might think you have a short.

 Just a few tips to the wise….contact VMI if you have any questions about high voltage diode anode/cathode conventions.  It can be a little confusing sometimes.    
For a quick reference, feel free to refer to the figure below that ties anode/cathode to blocking and conducting states.

Conducting and Blocking High Voltage Diodes

Tuesday, June 26, 2012

Deer-in-the-headlights Freeze

image credit

I know I need to make a blog entry, but I have a confession to make. I have had ‘writer’s block’ for going on two weeks now. 

To make matters worse, not only have I been suffering from writer’s block, I cannot even come up with a suitable topic to write about. Maybe if I could do that, I could create a reasonable blog post! 

(Care to share your ideas on potential voltage multiplier, high voltage component blog posts?  Is there something you'd like VMI to address???). 

Blogging is important in making and keeping business and social connections.  It is a wonderful avenue for providing better information to our customers.  That knowledge, combined with the anxiety of being stuck in time, can really, really, really create a lot of pressure, ya know?

Of course you know what I'm sayin'!  Most all of us experience external pressure from time to time – some of us more often than others. I am lucky in that most of the stress I feel is self-inflicted by way of artificial deadlines, impossible (or nearly so) goals, sleep deprivation, and over-scheduling.  

This entry doesn’t have much to do with engineering, high voltage diodes, or designing new power supplies, except it does have things in common with life in general.

Sometimes we need to take time to sharpen our sword, to take the pressure off, to take a breather…..all in the hopes that we’ll come back sharper, stronger, and healthier than before.

Here’s hoping that the next blog entry will be tied more closely to high voltage diodes, power supplies, and life in general.

How do YOU get over your fear of the blank, white page, or the design deer-in-the-headlights freeze?

Monday, June 4, 2012

Invisible Helmet for Bicyclists

Kind of like an airbag for your head, these bicycle helmets are beyond state-of-the-art!  They are INVISIBLE!  In the photo below, the view on the left shows the model wearing a collar.  On the right, the actual helmet is demonstrated. 

For all practical purposes, the helmet looks like a collar.  It is worn around the neck.  A micro controller monitors angular and linear momentum from sensors positioned in the device. 

This is also a great example of technology meets user feedback.  The project largely came about because people do not like to wear bike helmets despite studies clearly demonstrating they save lives.  A helmet-in-a-collar approach addresses everything from helmet-hair to bulkiness, to hard to carry around. 

The helmets are manufactured by Hövding.  They conform to EU safety regulations (CE-marked) and can be bought in Europe through

They sell for 3998 SEK, or approximately $560, depending on the exchange rate. 

How cool is that?  No more helmet-hair!  Do they make them for motorcycles or scooters? 

Too bad they probably don't use VMI high voltage diodes.  Maybe when they incorporate night vision capabilities, they might use some of our hybrid multipliers.  How 'bout that for a kick?!