Archive for category how-to
Photos of mechanical, front panel design
Posted by Michael Beach in how-to, parts, tools, vendors on October 28th, 2009
Portable electronic instruments. These photos show knobs, nuts, knurled, and know-how (Pete’s). These are working photos of our differential amplifier project. They show how we can get the electrical boards to line up with the mechanical connectors, and controls. And how an extra layer of plexi can be used to add a nice finish, and provide a solution to the incompatible height of the controls (note the nut is recessed by the plexi).
overall view of assembly, showing how it slides into the case
close up of the BNC connectors
BNC aignment of pcb, fron panel, and mounting BNC panel
cardboard pcb mock-up, with the real board and assembly behind it - we like to make quick mock ups as we design, just to check everything is going well
Detail of the plexi layer used to 'bury' the nut needed to hold the front panel control. The plexi is an additional part, but the incompatible heights of the controls meant there had to be some way to accomodate all these part variations.
SPIE Photonics West 2010
Posted by Michael Beach in SPIE, how-to, tech notes on October 13th, 2009
We’ll be teaching a ’short course’ at the Photonics West 2010 show this January.
Titled ‘Fluorescent Detection: System Design and Tradeoffs’, it’s based on work we did to help develop a hand-held chemical detection instrument for Cogniscent Inc., (homepage for Cogniscent Inc.) who have granted us permission to show off some of the things that went into that product’s design.
We also discuss various design options that were not selected for the Cogniscent system, and what motivated those decisions.
Here’s where you can find more information, at the SPIE website:
Light uniformity testing
Posted by Michael Beach in how-to, metrology, optics, photo, prototype, tech notes, tools on July 15th, 2009
For both a clinical test microscope, and a home theater HDTV projection display, the light from the source must be quite uniform.
To test some non-imaging illumination optics, we set up our digital camera, and wrestled with the RAW data files from the camera. Most cameras have some ability to ’see’ infra-red, so we can also test the pattern from the remote control output, or for other purposes.
Here we test the light uniformity of an LED source using a digital camera and some Thor Labs mounts.
These graphs were generated by ImageJ from the RAW data files of the Nikon D1x camera.
Custom front panels
Posted by Michael Beach in how-to, parts, prototype, tech notes, tools, vendors on July 14th, 2009
Here’s a vendor we recommend, and a photo of some parts they made for us.
When you make one or 10 of something it can be difficult to make it look ‘real’, that is, to make it look finished. Sometimes the Dymo-Marker labels are OK, say in a sci-fi movie, for your Custom Flux-Capacitor. But other times, you want the prototype to look clean.
We have enjoyed using the services of FrontPanelExpress to make some custom front panels for our projects. They provide free software, that’s simple and easy to use, and you upload the files to their on line ordering … and you get great parts back. A variety of anodized aluminum options and thicknesses.
http://www.frontpanelexpress.com/
They will engrave text, add paint colors into the text -makes a very nice professional looking prototype or short run of parts.
Just imagine – they can easily make a D-shaped hole for the BNC – so it won’t UNSCREW and FALL OUT !!! That alone is worth the price of admission. I can’t find my D-shaped drill bit …
They can do a lot of things that are a pain to do by hand – countersink holes, nice RS-232 type D-cutouts, square holes, etc. Check out their site for some examples.
We also made a Plexiglass panel – this allows us to compensate for the very annoying differences in height of the switches and knobs – and it allows simple paper graphics to be protected. We also considered making a glowing logo, but have not yet done that.
Radiometric Measurements
Posted by Michael Beach in application notes, books we like, how-to, metrology, optics, tech notes on July 6th, 2009
It’s easy to confuse the units of LED light output. Steradians, luminous intensity, etc.
Here’s a link to an application note that explains these well, written by C. Richard Duda of UDT (now part of OSI Inc.). Apertures, intentional and otherwise, are discussed, along with typical test configurations.
Link to pdf of application note titled Radiometripdf of Radiometric and
Please tell us if the link gets broken!
CCD Cameras, eyes, and physics
Posted by Michael Beach in application notes, how-to, math, metrology, optics, tech notes, technical articles on March 14th, 2009
This tech note was motivated by the question – how does the response of our eyes
differ from the response of a CCD camera sensor.
Using the data of a particular Hammamatsu CCD camera as an example,
we compared how silicon ’sees’ to the photopic eye response
and compared both to a Planck black-body curve of a light at a particular
color temperature.
We don’t know what those lumps are in that CCD response curve – maybe some
strange reflection interference??
If you know – tell us!
Vision response vs. Planck’s Black Body Curve
Posted by Michael Beach in application notes, how-to, math, metrology, optics, tech notes, technical articles on March 14th, 2009
Color temperature is based upon the idea of a Planck black-body radiator.
Here’s a Tech Note that shows how our eyes respond to the Planck Black-Body radiator.
For a lamp filament at a certain ‘color temperature’ there’s a curve of how our eyes
respond to the lamp. Pete put this into a MathCAD model, and there’s a pdf here
that shows off a few nice graphs.
attenuators, connectors, etc.
Posted by Michael Beach in how-to, parts, prototype, tech notes, tools, vendors on March 13th, 2009
Here’s where to get quality attenuators and connectors
Testing any high gain low noise amplifier requires a nice clean attenuator.
You need to drop the level of your function generator,
or that x1000 gain amp would need to supply 100 V output.
Pasternack Enterprisese sells a nice 30dB atten for about $42.
Their part number is PE7000-30.
If you put 2 of these in series, you have about x1000 attenuation.
(These assume a 50 Ohm load, so buy one of those too).
Here’s a link to their website:
http://www.pasternack.com/
Actinica Book List
Posted by Michael Beach in application notes, books we like, how-to, math, metrology, optics, research papers, tech notes on May 31st, 2008
Ok, we have a book problem.
Both of us waay like good engineering books. A good explanation, or a great
graph that sums up why that camera ’sees’ differently than my eyes, etc.
Since we’re always stumbling on more good books, this list will grow.
Drop by later see what’s new.
Here’s some of the books we like, as a pdf file here,
and here’s some more books we like:
- the Feynman Lectures on Physics, a 3 volume set. Here’s a guy who can explain anything well. Like how sine, cosine and the magic number e all relate to the imaginary number i (square root of -1). He also has a great description of how a ‘50 Ohm’ transmission line acts like ‘50 Ohms’ no matter how long it is. For a really great puzzle – read his description of how charging a capacitor really involves magnetic fields outside the cap’s plates.