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Topics - Paul L

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Heliostat Projects / Worm thoughts
« on: March 09, 2016, 09:42:35 AM »
Hi Everyone,

   It's been a while since I've posted, so I thought I'd dust off the keyboard and share a few thoughts here.

   I've been hoping for the last few years that someone here would come up with an accurate, easy to do diy worm gear for all these stepper driven heliostat designs.  It's becoming increasingly clear that it's not going to happen, and that it's not a trivial task do accomplish, so I am begrudgingly abandoning hopes of that happening.

   I've been thinking again lately of the tensegrity design I had posted on the forums a few years ago ( and am thinking about building a small test version.  What originally put me off ever pursing it years ago was the problem with the "bail" not working as the original designer had intended.  What I plan to do now is mount small steppers directly on the tensegrity structure where the bail would have gone.  Most likely 28byj-48 motors since they are readily available and inexpensive.  Since they run with very little power, I plan on chaining a handful of them together for azimuth control and running several mylar mirrors simultaneously, while another stepper controls all or their altitudes,.

  The problem with this idea, I imagine, then would be the holding power of the 28byj-48's.  A large mylar mirror with a small gust of wind would throw alignment of these small motors out.  My solution is to use another fairly common piece of equipment - guitar tuning pegs or gearheads.  They're cheap, small, readily available, are self locking and have great holding power. The gearing ratio on them would also bump up the accuracy of the heliostat considerably - I believe the most common gear reduction is 12:1.  The are remarkably accurate when under tension, but there is some slop when changing direction (at solar noon say, or while pulling off the limit switches)but I assume one could account for those few extra steps in the coding.  Graphtech, a company out of Vancouver supplies tuning pegs with even higher gear ratios - I've contacted them - gave then a brief overview of this site -  and they've graciously sent me a few 39:1 tuning pegs to experiment with.  They seem to be of better quality than the standard pegs I've purchased off ebay, though I assume they'd be quite expensive to buy. 

While I haven't had time to play with this idea yet, I hope to "fairly" soon.  That being said, I'm expecting my first child in...a few days ago, so I'm guessing my free time will be in short supply in the near future.  Just thought I'd throw the idea out there and see where all of you will take it, since it could be applied to any stepper heliostat design, not just 28byj-48s.  Hopefully someone on the forums here will give it a go and post about it!



Think Tank / Oh, deployable things.
« on: January 12, 2015, 05:34:35 PM »
Hi All,

   I've had this idea bouncing in my head for awhile and I feel like it needs to be let out so others can have their say about it.  Let's collaborate!!!  Bring on the ideas!!  I could describe it much more eloquently, but I just want it out for now so sorry for the uglyness that is about to follow.  So here we go: Wouldn't it be cool if it was possible to have heliostats non stationary - mobile in other words?  Imagine, going anywhere you want, pushing a button and then having a heliostat roll on out, find a sunny spot for itself and then self-orient to your set target?  If it gets shaded, it would self move to a new and sunny location.  That's what I've been thinking, but on a grander scale, in a backyard.  Imagine a swarm of micro-helostats, all with sensors for self leveling, orienting and sun seeking.  It really wouldn't be too hard to do I think.  Deployable mirrors could be added, using mylar epoxied to snap band trusses so it could be rolled away in bad weather.  Each heliostat would communicate with each other via cheap nRF24L01 boards.  All use cheap, but incredibly strong 28byj-48 steppers and cheap 3 DOF sensors.  Have them all solar powered.  Waaaaaaaaaaaaaaaaattt?  Am I crazy here?  Now, that'd be cool!


I think it'd be great anyway, to have a dozen of these things running around my yard.         

General Solar Projects / Solar Blinds
« on: September 28, 2013, 09:32:05 PM »
I've been toying with the idea of setting up a set of blinds in my place to be activated when the sun comes up, have the arduino and driverboards shut down during the day, and then have the blinds shut in the evening when the sun sets.  I was thinking about using a photoresistor, and I'm having limited success.  Then I realized that the Heliostat program that Gabriel wrote must somehow figure out the sunrise and sunset depending on the lat. and long inputs.  Is there a way to simply change the program to allow for a setup like this? - or maybe even use it as a "heliostat-blind" to refect the suns rays to an interior ceiling for even distribution of light?   I just happen to have a RTC, easy driver board and an arduino lying around so I though I'd ask.



Energy Storage Projects / Thermoelectric Power
« on: July 11, 2013, 04:25:06 PM »
Though PV is currently more efficient than thermoelectric, I like the idea, especially when combined with a heliostat array - it seems like a robust system with no moving parts and long lifespan.  Came across a PDF that describes using salt water solar ponds, heatpipes (thermosyphons) and thermoelectric modules to produce power (even when the sun isn't shining) in remote villages.  Not tons of power mind you, but still, I think it's cool.  There are instructions on d.i.ying heatpipes on youtube and instructables that seem fairly easy to do.  Anyway, I'll attach the pdf if anyone is interested.  Also, attached you'll find "Recent Advances in Direct Solar Thermal Generation" from 2009, which is pretty technical, but fascinating none the less.  Not really related, but kinda - a local Victoria BC girl made the news recently for making a thermoelectric flashlight powered by the heat of her hand for a google science project :
The Hollow (Thermoelectric) Flashlight - Google Science Fair

Heliostat Projects / Interesting Analog Heliostat
« on: July 08, 2013, 08:35:08 PM »

Came across this instructable and thought it was neat.  Plus, I like the song he's used in the video, since I have some french canadian in me.

Heliostat Projects / Another version of a heliostat...
« on: March 22, 2013, 03:26:10 PM »
Hey All,

   Thought I'd post this since it's been so quiet around here lately.  I've been busy building my army of heliostats, which are slowly taking over the deck in my father-in-laws backyard.  If I have enough scrap wood lying around, I might just build one more...These pictures aren't the completed heliostats - obviously they're missing their mirrors, and am going to enclose the entire machine in a nice pine box, so none of the motors or leadscrews are visible, also making it fairly waterproof.  A 18'' pine shelf will give me two inches to spare without hitting the ground, so the final heliostat will have a nice floating box effect.  I'll post more pics once I get them totally finished!



Update 04/11/13:  Here's the final projects in a short timelapse....   

General Solar Projects / Sterling Engine
« on: November 25, 2012, 07:48:35 PM »
Hi all,

   I've always been interested in solar powered Sterling Engines and noticed a fellow forum member (beez) mentioned he was developing a medium sized system.  Could you elaborate as to how things are going - I'd might like to someday use a similar system!!  Thanks


Energy Storage Projects / Phase Change Materials
« on: January 24, 2012, 10:25:22 AM »
     For those who don't know, phase change materials (pcm) are usually salts or waxes that melt at certain temperatures - the ones I'm interested melt at a little higher than room temperature.  As these salts or waxes go from one state to another (solid to liquid) they absorb enormous amounts of heat.  Once the temperature of the now liquid salts/wax drop (like when the sun goes down) the liquid begins to solidify and release the heat it had stored during the phase change.  Apparently they can store more than five times the energy when compared to conventional thermal mass reservoirs (trombe walls, concrete floors) relative to the volume.
   PCMS were first implemented by the solar energy pioneer Maria Telkes in the late 50's for domestic heating.  She used two tons of Glauber salts (sodium sulfide decahydrate) and heated a Minnesota house for two years using only direct solar.  The Glauber salts however, proved to be an unsuitable PCM, and the search began for other options.  The most commonly used salt for PCMS today is a mix of Calcium Chloride and other salts.  There are also several suitable waxes, but waxes are flammable, which makes me wary of using them when high temps are being used.           
     As someone who builds R2000 houses (the Canadian precursor of the LEED building standard), I know that the best way to make a house energy efficient is to have a small footprint, and insulate the hell out of it.  The problem is that conventional thermal storage and small houses don't mix, since traditional thermal masses take up quite a bit of space - space which is in high demand in a small house.  PCM's solve this problem since they occupy less space, but still pack in the energy.
     There are drawbacks however - compared to conventional thermal mass storage systems (rocks), they are costly.  And they do have a life span - some commercially produced are guarantees for only 10 years after which their efficiency lessens.  They also need to be stored in proper containers, since they are corrosive.  Someone who had spoken to Mr.Lane (see below) suggested using 1L pop bottles would be appropriate.   Apparently in Europe, where their energy costs are more significant, PCMS are more common.
     BASF makes PCM impregnated gypsum board, which I think is a great idea, but I'd like to make my own pcm.  You can see a patent filed by George Lane, who worked for Dow Chemicals at  I'm trying out some of his "recipes", but have no experience in chemistry or the like.  Things are moving along though, and I have several bottles sitting on my windowsill containing several variations of Mr. Lanes work.  They all change phase when I dunk them in hot water, and then revert to solid once I take them out, so I'm doing something right!  Now I just need some sunshine!  The biggest problem I'm running into is getting my hands on a suitable gel like substance to suspend the salt crystals.  If they aren't suspended in the liquid, the eventually filter out, which renders the mixture useless.  If anyone out there has tried something like this out, it'd be great to hear from you.               

Heliostat Projects / Anyone having target problems?
« on: December 09, 2011, 10:16:16 AM »

   I just tired my first target out today and I seem to be having difficulties.  I had planned for a tree to the right of the heliostat and about 3/4 or the way up since it would be easy to see from my livingroom window to monitor tracking.   Anyways, I went out this morn to make sure everything went smoothly and caught the heliostat before it destroyed itself.  The target I imputed was   MachineTargetAlt[0] =30;  MachineTargetAz[0]  =37;.  I think the az was positioned properly, but the altitude was going to the negative direction.  I double checked the numbers, the tried other numbers and found the same thing happening.  The az might have been working screwy too, but I'm not sure.  Anyways, I have it set to Alt=0 and Az=10 right now and it seems like it is in the right place (I don't get sun until around 9:30) but I'll keep my eye on it.  Anyone else encounter similar problems?  Thanks


Heliostat Projects / Caster to attach coupler nut to heliostat
« on: October 29, 2011, 04:50:24 PM »
Hey everyone,

    I've set up my heliostat according to Gabriel's design, but found that there was too much play in the custom made "U" shaped piece that holds the coupler nut to the heliostat frame.  I was finding that there was so much play that once the limit switches where triggered, the 4 degrees of backing off were lost and the switch remained triggered.  Long story short, I've decided to use a caster.  Nice bearings for smooth movement, and it only ran about $3.00 so it didn't break the bank. Plus it looks pretty!  :)  Here's a pic of the caster attachment along with a pic of the heliostat.


Introduce Yourself / Hello World, Paul here
« on: October 26, 2011, 07:28:05 PM »
Hey everyone! 

   My name is Paul Lefebvre, I'm a 31 yr old dude from Victoria BC who wants to try and build a heliostat.  I'm totally floored by this website and the support here!  Looking forward to getting this thing built!

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