Release Updates

We've been loosely planning on using a TI Stellaris ARM M3 cortex for the processor, <$10 per chip and more than powerful enough with USB and SD card lines, with lots of GPIO and PWM and timers, etc...

Basically the CCD needs a few control lines with a master clock at 1mhz and analog data coming in at 1/4 the master clock speed. 16-bit ADC is desirable, and we figure at 3648 pixels per CCD read (its a linear array, right) that would be about 7kb of data, in good light I think we can get between 60-120 lines per second transferred to a micro SD card onboard, or maybe with your help over USB to an Android or iPhone.

My buddy here has already been working on user interface ideas for the device, and he thinks it would be best in a web-kit package (google chromium browser engine), which is really easy for any platform.

The chip we have now is the Toshiba TCD1304AP, google it datasheets are on the first page, its less than $20 and can be had from eBay or other suppliers.

We've got some TI dev kits now with a coupon a while ago: http://www.ti.com/tool/eks-lm4f232

and some code for one of these baby's (I had this at OSS): https://estore.ti.com/TMDX28069USB-F28069-Piccolo-controlSTICK-P2257.aspx

This is the code for the Piccolo controlStick with a almost-working state machine to pulse the CCD control lines: https://github.com/aks4896/OpenSpec-F28069

we need to find the right amplifier and ADC still, preferably with noise at least or lower than audio quality.

We're waiting on some more optics to arrive to really play around with that stuff, as there are many design choices to make which all range in cost, difficulty to build, and SNR.

---

Update - from an email sent to a collaborator:

Optics is a steep learning curve, but I'm climbing up. I've discovered that light is very complex, and a really smart/talented optician can do things in a variety of simple or clever ways.

Copy pasting from Kickstarter comment " The 3 spectrometer mounts (the way optical components are arranged in a system) we've identified for being useful for this project are: 1) Transmission grating, cheapest, easy to build, lens optional (increases signal), worst SNR 2) Modified Czerny-Turner, hardest to build (emphasis on this), median price, good SNR 3) Concave holographic aberration-corrected, easiest to build, most expensive, best SNR, best dynamic range Because of the complexity of #2 (modified Czerny-Turner), we aren't focusing on that right now, so the low-res version that we're pitching now is poised to use a transmission grating which would likely not work for UV, due to the plastic material absorbing it. It could work, but that's untested, and as I mentioned the SNR is more appropriate for teaching/education. P.S. I'm looking into getting gratings from Chinese vendors now, so prices for option #3 could decrease. "

So on the last line, I am looking for a grating to be used like this (flat-field spectrograph): http://gratings.newport.com/information/handbook/chapter7.asp#7.5.3

From these guys (who own the manufacturing company that is here in Rochester where I am now) they cost ~ $550 USD: http://gratings.newport.com/products/T6.asp

I heard back from the first one of these companies (searched "concave grating" or maybe "concave grating holographic"), they said they would send me a free sample of the CHGF-001 (~$150 USD, see attached documents which I received from them) http://orienvac.en.alibaba.com/product/361037953-0/productdetail.html http://zhongyuxinda.en.alibaba.com/product/311588137-209630123/productdetail.html http://www.alibaba.com/product/us103456329-215551399-0/productdetail.html

I sent the following message: " Hello, do you have concave aberration-corrected holographic flat-field gratings? Do you have efficiency curves for those gratings? What pricing would you offer? "

I also want to get pricing from these guys, can you do the talking and see about samples? These chips would support NIR spectroscopy, which someone asked me about today for use in snow pack science. (I searched 'InGaAs array') http://www.alibaba.com/product-free/244326677/Focal_Plane_Arrays.html

There are other things we'll need too, like connectors and maybe some fiber optics (we're looking into the possibility of using commodity audio fiber optic cables.