Randy's Bench

A repository for projects past and present

Leave a comment

A Compact Solar Spectrograph

Back in 2003 I designed and built a grating based spectrograph primarily used for casual solar spectral studies as well as gaining an appreciation of the beauty and elegance of it’s spectral lines.

This served reasonably well for many years of on and off again operation, but always had a few niggles I never quite worked out. The grating turret was a bit wonky and would sometimes get hung up. Additionally it would slightly wobble during rotation causing a shift in spectrum placement on the camera sensor or viewing eyepiece

Another source of occasional frustration was the adjusting mechanism on the entrance slit which did work…just not very well. The final aspect was it’s rather cumbersome size for it’s purpose…With those things in mind I’m endeavoring to reduce it’s overall dimensions, simplify the problem areas and create a friendlier instrument in practice.

To begin I’ve looked at a rather simple arrangement which offers somewhat less flexibility (in my own implementation) but in return gains solidity, portability and simplification of operation (at least, that’s my wish).

Here’s my proposed layout diagram based on a German spectroscopy forum’s Minispec design by author Danial Sablowski:

And here’s a few pieces and parts I’ve got at this point… First a pair of cheap Walmart Pencil sharpeners I purchased for a whopping 47 cents each:

And the parts we need from the sharpeners (blades for our entrance slit)

And the completed (for the most part) spectrograph slit assembly:

Next in order, to properly determine optimal part configuration, I found a suitable cardboard box of roughly similar dimensions to act as a flexible test bed to this end. As shown, I placed the entrance slit assembly and 35mm collimator lens to better gage focal length adjustments. The slit assembly tube(s) allow two points of adjustability, which were set at midway.The collimator lens was set roughly at its correct focal length. A small hole was cut out in line with the slit/collimator positioning to permit a finder scope, set at infinity focus, in order to make the necessary adjustments to bring the slit into sharp focus. Those readings were jotted down in my project notebook.

The final enclosure will also have a 20mm hole bored to ensure the collimator lens has good focus on the slit jaws.

That’s the story so far…back when I’ve further progress to report…..Thanks for looking

“To invent, you need a good imagination and a pile of junk.”
-Thomas A. Edison

Leave a comment

Documenting a Stellar Journey – Notebook one

Presented is the initial journal offering of my time spent exploring Amateur Spectroscopy. This first notebook covers the time period of October 1995 to November 1996. There’s several additional journals I’ll upload over time…

Thanks for watching!



Leave a comment

Documenting a Stellar Journey Part one

Since I appear to be engaged a bit less (read, alot less) in bench projects currently I thought it would be an opportune time to gather my experiences, both unfruitful detours and modest successes, with an amateurs endeavors into Spectroscopy.

With that in mind I present the first in a line of videos primarily to document my story with which I spent a great deal of time in the past. Along with my observations and ensuing results (Parts 1 & 2), I plan to additionally document my Journals kept during what was an exciting time for me…

So I present to you part 1 of this series.

And here’s a link to my YouTube channel…

Subscribe if you like…Thanks and  best regards


Leave a comment

A strange thing happened on the way back to the Bench…

Well here I was finally crawling back to the bench after an extended leave and was distracted yet again…..dam those PC’s! Gaming coupled with my enjoyment with all things Star Trek again caught my attention. So I present to you a few videos I uploaded to my YouTube channel recently…please enjoy!



Oh and here’s my YouTube channel link..


Subscribe if you like…Thanks and  regards (I’ll be back)





Long Overdue Bench Update

I seem to be slowly crawling my way back to the bench after a needed and necessary break from the world of components and wires. During my break I pretty much ended up putting everything on hiatus, including the Arduino-based chess computer (Lily) that I had began when we last spoke. In times past when my enthusiasm begins to wane I’ts rather gradual over a few weeks time and that’s the time, since this happens every so often, I’ve learned to recognize it and begin the process of documenting my progress before the inevitable complete and utter collapse occurs. So I do have a few pics and a schematic of where I am (was) at with Lily later on in this post…

During my time, along with other matters, I ended up making a needed bench improvement that I’d been putting off for far too long. That being a new and shiny Win7 PC. The old XP machine suffered a bit with video editing tasks and a slew of other problematic performance area’s…low RAM and a Celeron are like that..Now that’s been supplanted with App loads, configurations and endless operating system updates. But I’ve moved on and I’m pleased I finally did.



Now on to Lily, our delayed chess computer wiz, and here’s a look at her…




And the current state of Lil’s schematic:


Initially I ran into an issue with the published schematic that concerns the 7-segment display(s) called out. It indicates using a jumper arrangement to accommodate either a CC or CA display(s) that may be used. However looking at the diagram the common anode displays (quite generic) I’ve got in my bins simply wouldn’t work as noted. So I ended up drawing an updated schematic which made a bit more electrical sense (to me anyway) and also incorporates the Arduino UNO platform connects. The original design overclocks the ATMEGA328 to 25MHz (20MHz chip) but given my desire to keep it simple I’ll go with the onboard 16MHz crystal and live with it (again, this is more of an Arduino learning exercise than full on chess and dedicated chess computers path).

But before tackling the ongoing Lily chess project and firmware and all thing’s chess I’ll revisit the Hobby Spectrum Analyzer (HSA) briefly and do a little further documentation for it. The HSA is still in the flat as I’ve yet to get around to place it in it’s proper enclosure…well it happens. Below is a short video of the Hobby spectrum Analyzer and what one might expect from this inexpensive DIY instrument…

Well I guess that’s my story at this point. Take care and thanks for looking…Randy

Leave a comment

Caution…detour ahead

Now that the latest receiver seems to be functioning pretty well to date (ignoring the noise issue I’ve got at my QTH), I thought I’d take a minor break from receiver building (I definitely need a break). But before my needed respite from the shortwaves I put together a few items as shown below..
1st is a small whip antenna module plugable on the receiver input BNC:


And secondly an alternative Amplitude detector circuit I showed in an earlier post:


So, at least for the moment that’s the state of my shortwave Meanderings…

Initially I considered putting back on the bench the Z80 SBC I’ve worked abit over the last 3-4 years. I ‘d never finished wiring up the I/O ports nor a front panel display arrangement for this guy. However the thought of all the wiring that would need to be done is a bit daunting for me at the moment and as it was in the past, couldn’t face it with any level of the necessary enthusiasm this would require.


So I thought this might be a nice opportunity to explore the Arduino family of microcontroller’s that seemed to have avoided my radar in the last few years. I’ve still got that new, better, smarter RF Spectrum Analyzer build running around my mind…oh boy.

I noticed during my last trip to our local Microcenter store they have a DIY section that I never noticed before. Loads of microcontroller bits and pieces that are for reasonably priced. I actually didn’t know that Microcenter was founded way back in 1979 by two former Radio Shack employees. Since I myself worked at the Berkeley Ca. Radio Shack store in 1972 (doesn’t really seem that long ago). So I guess I feel a minor kinship with this retailer. Indeed this section of their store is very much like what Radio Shack used to be, of course without the back of the store Tube tester that was my experience!

A few weeks later, after a little research I headed back to the store and picked up an UNO development kit and small 1.8″ TFT display show below.



I’ve since put together a small breadboard setup including the UNO and TFT display. I added a ‘386 audio amp as well. Initially I considered resurrecting a speech synth project I played with a bit many years back. This is the familiar ’80s era SP0256-AL2 allophone based speech chip. The UNO seems idea for this and indeed, I’ve found a variety of links with folks doing just that.



But I decided to start looking at the Arduino development platform first with a little fun and games. I’ve put together a small breadboard with a few switches and some RCA jacks. Then using the TVout library I downloaded a few old school games from Hackvision’s site, loaded them up and did have a little fun. This was a good learning experience as it worked out. Becoming familiar with the IDE, adding libraries and the overall process was good…just what I had in mind.


It made me think about a TRS-80 Model 1 I bought used back in 1986 or so and the enjoyment I got from that, well minus the hardware quirkiness anyway. I put together a video of a few of the games I tried out:

Beyond that learning experience, next I thought it would be interesting to revisit computer-based chess programs. I’ve got a Fidelity Chess Challenger 7 4MHz Z80 based SBC (1979) I salvaged from a beat up unit and am considering pitting it against an Arduino opponent. The little investigation I’ve done shows up several candidates using a Mega in one case and a 329P-based board design which looks like a good choice. The Arduino chess computer I found here and is called “Lily”.


And a few photos of the Fidelity Chess Challenger 7 SBC..



That’s all I have at the moment till I begin Lily’s construction and programming.