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Messages - Davetech

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1
Heliostat Projects / Re: Heliostat Array Project
« on: September 10, 2009, 05:54:27 AM »
Wow Gabriel, that's good outside the box thinking!  The place a micro shines is its versatility and the nice thing about heliostats is that the timing of the adjustments is not critical. Doesn't matter if the mirrors are adjusted in a sequence and a few relays (or electronic equivalent) could be used by the micro to address each each mirror in the array individually. That would cut out the problems of linking the mirrors mechanically and let software do the work.

I think that idea deserves much consideration. Meanwhile, I'm still stuck just getting one mirror working correctly. Although my cnc will plot the control pc board perfectly with a pencil, when I try to mill a pcb, even with a brand new bit, there is enough sideways pull on the z-stage to slightly move it and skew the cut. And it does it even at 2 inches per minute travel. I guess I'm going to have to rebuild the stage stronger and it is ticking me off.

2
CNC Machine Builds / Re: My desktop CNC Build (many pictures)
« on: September 07, 2009, 05:27:24 PM »
Good lookin' machine there Travis.  I see you made use of electrical conduit for your Z rails. Interesting gadget you have holding that sealed bearing with rubber hose? How's that work?

I've been quiet too, although I've been answering a few of the questions on Tom's Instructable. I haven't seen him respond since last spring, so I've tried to field a few of the questions myself.

I've also been reworking my machine, including the Z-stage. I had finally gotten everything working well enough that I tried to make my heliostat control board and it just barely fit the working area my machine had. I still don't know how I did it but I managed to botch the alignment and some of the traces ended up off the board. Wasting a 6"x8" piece of double-sided ticked me off enough that I said "That's it! I need more room!" And I proceeded to tear the machine down and replace the 10" iron pipe legs with 18" ones. That allowed me to space the X rails 15" apart instead of 9".  Made lots of other changes too but I'll detail them later on the easy mill thread.

3
Heliostat Projects / Re: Heliostat Array Project
« on: August 28, 2009, 09:29:30 PM »
Great job, Gabriel!

I was thinking... about testing your unit out... if you mounted a sight tube on each heliostat, you could rapidly step the mirrors through a day's movement and check the alignment through the tubes?

Have you tested a piece of vinyl siding with it yet?

Getting rain down here lately too.

I put my ramp idea on hold. I'll tinker with it later. Right now I just want to get the thing working, so I'm going to go ahead and add a tilt motor and the electronics for it. Ran into a snag though. Turns out that the two wireless doorbells I got DO work on the same frequency and will interfere with each other. Thought I had checked that out. So I've wasted two days playing with other ways to get the signal wirelessly delivered. Fooled around with a couple of old wireless computer mice but I couldn't get more than about 10 feet of range out of them. Now I'm bidding on a toy helicopter that is controlled by a two channel IR system supposed to be good up to 50 feet. Also got a cheap Bluetooth dongle and a headset, but I've got no experience with Bluetooth and don't know if I can get them to communicate without software/computer.

4
 "Do the local hardware stores know you by first name?"

Well, they used to.  When I moved here back in 1968, this was a small rural town, ~35 miles south of Atlanta. Mostly farming, raising hay and a few cows. Cars on the road were few enough that you usually gave them a wave whether you knew them or not.  My parents had a ranch where we raised Appaloosa show horses. The local hardware store was also the feed store so they saw a lot of me. I had an open account and I could just tell them "charge it to my account", no ID needed.

Since then, mainly due to "white flight" the little friendly town has grown up and is indistinguishable from any other Atlanta suburb, complete with crime and "damn yankees". The wave has turned into a one-finger salute in the daily traffic jam around the Town Square. Used to be 5 police cars to cover the entire county and it was no secret that the Sheriff was a moonshiner... now you can't turn around without tripping over one, and these new cops look at this old long haired fart with a suspicious eye every time they see me.

The old feed/hardware store has gotten run out of business by the now-local Home Depot, Lowes, and Walmart. Nobody farms or raises cows... too busy building subdivisions... or they were until the road apples hit the fan last year. Looks like the local tractor dealer is about to throw in the towel too. 

So it just ain't what it used to be and I'd love to sell my property and move somewhere out west... maybe Colorado... to a small town where people are still civil and not over-stressed city dwellers.  So there's my Rant for the day... lol


5
CNC Machine Builds / Re: Building Tom's "Easy Mill"
« on: August 25, 2009, 09:06:45 AM »
Well, actually I don't recommend using a dimmer to control anything that has its own speed control built in, like a Dremel or a RotoZip. My Dremel didn't like it at all. But my RotoZip had already developed a problem. I had not used it but a little when its speed control seemed to short out. It would only run at high speed and sliding the switch to the medium speed position didn't make any difference. So I went ahead and tried it with the dimmer, not caring if it burned out the speed control since it was shot anyway, and the motor worked okay.  The only problem was that at low speed the Rotozip had little torque. When you put a load on it, like grinding into something, it slowed the motor down easily. But at medium up to high speed it had enough torque to do work. I guess it might have its uses, but it is not a priority with me now.

Shortly after that, the RotoZip developed another problem. While I was milling some thin plywood, a scraping noise started up inside the motor and I started getting hit by tiny pieces of black plastic flying out of the cooling vents. When I took the motor apart, I found that the cooling fan had slipped down the armature shaft and was scraping on the case. A little Googling provided some answers.

I found that this was not an unusual problem with the early RotoZip models. As a matter of fact, I think it caused the RotoZip company a bit of pain and probably had something to do with the sale of the company to the Bosch Corporation, who now makes it known that they have redesigned the fan in all the newer models to prevent that problem.  I wrote to Bosch and asked them if they could recommend a fix and they basically said it was unfixable but they could offer me a replacement new model at a discount. I did; however, find a post that recommended using Loctite Bearing Cement to hold the fan in place on the shaft, but I have not gotten by an auto parts store to get some (I don't get out much).

In the meantime, my engraving bits have arrived from China. Yeaaa..!  And they are everything I had hoped they would be. I could go ahead and make the heliostat control board now... what this whole CNC journey has been about in the first place... but actually, now that I have built the controls on the picaxe prototype board, I'm more interested in concentrating on getting the heliostat working.  I'm finding that my ramp idea is not as easy to implement as it sounded. But I haven't given up on it.

@ Gabriel - BTW... I plugged your YouTube heliostat vid in the comments section of Dan Rojas' latest vid about parabolic reflector mounting with a magnet. Someone had asked if he was going to present how to make heliostat control for his mirrors or dishes and I couldn't resist. Dan wrote back "Good Video!"
 ;D

If you get any of these "V" shaped engraving bits... be careful!  They are damn sharp!  I was picking up a piece of work under the Dremel and my index finger touched the bit and it pricked me. Instinctively I jerked my hand back and that drove the bit deep into my finger! Bled like a stuck pig! So I'm nursing my finger today.


6
CNC Machine Builds / Re: My ATX power supply
« on: August 25, 2009, 05:50:33 AM »
Nice power supply... nice presentation.  Thanks!

7
CNC Machine Builds / Re: It works! (many pictures)
« on: August 24, 2009, 02:45:10 AM »
Wow Travis! Thanks for the tour! 

That's a great looking machine you have built. My complements on your building skills too. (I'm jealous of your workshop, I can't turn around in my little space without tripping over something).

I think those motors will serve you well. My motors are only 1 amp and I was surprised at how strong they are. I may upgrade them someday if I get lucky on eBay. Really nice output interface on the computer supply. How did you apply the lettering around the terminals? It looks very nice. I wonder though if you won't be wanting more than 12v when you start speeding the motors up. Did you combine all the yellow lead wires in the psu as suggested at http://www.reprap.org/bin/view/Main/PCPowerSupply ?  My attempts at using an ATX supply were unsuccessful. It kept shutting down as soon as the motors demanded current, but I didn't combine the wires.

Thanks for the tip on the sprinkler wire. I'm running my motors in bi-polar mode so only 4 wires are needed. I used 4-wire telephone cable but I'll pick up some of that sprinkler wire because I'm sure it will come in handy somewhere down the line.

Keep us updated on improvements  :)


8
CNC Questions and Answers / Re: Setting up limit switches
« on: August 18, 2009, 04:59:41 PM »
Hi GGB,

Thanks for that.  When I first posted the question, I didn't have the hardware finished and was not yet familiar with the software. Once I had something to work with, I saw that my question was pretty much a non-issue since K-Cam and the other packages are very configurable.

So far as the home position, I'm with Gabe, in that it is easy to pick a point you want to be home, manually jog to that position and zero the axis'.

I've learned a lot, but I'm still a noob.  ;D

9
Heliostat Projects / Re: Heliostat Project
« on: August 15, 2009, 09:58:12 PM »
My first attempt using led's as sensors used an LM339 dual comparitor and I bumped into the same problems with "grey areas".  Perhaps if the comparitor were followed by a flip-flop...   but, yes, a micro does make the whole system a lot more versatile and easier to configure.



I've gotten a little more done on my project.

Back when I saw it was going to take weeks to get the engraving bits to make my control board, I ordered a picaxe project board. I hate perf- boarding but it is better than nothing. Well, it arrived the other day and I built the controller on it and wired up the door bell receiver to it. I've installed the mechanism and the electronics in an enclosure along with a motorcycle battery and have taken it outside and attached it to my mirror assembly.

The wireless door bell receiver output goes high for about 2 seconds when it is triggered and I thought that was going to be a problem because the mirror would move too far in 2 seconds, but I found that the picaxe could easily handle the problem by just telling the motor to run for 250 milliseconds and then pause for 2000 milliseconds, then check to see if the sensor pin was still high. It works great, with the motor just bumping the mirror about a degree at a time.

Today I tried to learn something about my ramp idea. I took hourly notes on the position my mirror assembly was in to reflect on the collector box and then I cut a piece of wood in a semicircle that I thought was close to what the ramp needed to be like. I needed about six arms to hold everything in place and was having a difficult time with it. Part of the problem was the heat. I can only work a for a while in this heat and then I start feeling my pulse in my temple and my vision whites out in the center. My peripheral vision stays okay, but what I'm looking at is just a big white spot. Then I have to go inside and cool off. So I didn't get near as much done today as I had hoped.

In retrospect, building the electronics on the picaxe project board is probably a good thing because it is something "Everyman" has access to since they are available on eBay. And my goal is to present something that anyone handy with tools and who knows at least how to assemble an electronic kit would be able to build this system for themselves.

10
Heliostat Projects / Re: Heliostat Array Project
« on: August 15, 2009, 09:43:47 PM »
Wow. you've been busy!  And it is looking really good too, Gabe.   Can't wait to see your video of this working!



11
CNC Machine Builds / Re: Building Tom's "Easy Mill"
« on: August 08, 2009, 10:47:34 AM »
-

Still awaiting arrival of the engraving bits. ETA - Aug 23.  Dang! 

---------------------------------------------------------------------------------------

Got the mill power supply mostly built... and changed course again!

I decided I really wanted a variable voltage supply. I remembered an old power supply I had picked up at some hamfest back in the 70's that has been sitting around gathering dust since.  It was a bench supply meant to be used while servicing tube-type equipment. It had outputs for a 6.3 volt ac filament voltage, and a plate voltage output that was variable from 0 to 300 volts dc at 100 milliamps max. 

Well, that was of no use to me... my tube days are long gone and 100 ma was not enough to run my stepper motors. But it would make a good basis upon which to build the supply I wanted.  I had never even opened the box up and was delighted to find inside a vintage, original General Radio Company Variac model 200 B in beautiful shape.




General perfected the Variac back in the 30's, got a patent on it in 1935 and copyrighted the Variac name. This was one of their early production models. It is hardly rare, but is a nice conversation piece among us electronics nerds and is very useful.

Anyway, I decided to gut the box and build in a modern, regulated, variable supply for the cnc mill, but I wanted to keep the external appearance vintage. So out came the old paper capacitors, the big selenium rectifiers, etc. I hated chopping all that up as it really was a handsomely built unit inside, very professionally done.  There was a single spdt switch on the front panel which would cause the D'Arsonval meter to read either output voltage or amperage.  I installed a stepdown power transformer after the Variac to provide isolation and to lower the voltage for the rectifier/regulator board I made with the mill. It has large traces and I was able to mill it with the bit I have.  With the Variac all the way up, the rectifier delivers 27 volts dc to the driver board.




The board just has a full-wave bridge rectifier, a smoothing capacitor, an LM7805 5 volt regulator for the driver board, and a glass 4 amp fuse. I kept the old wiring harness I chopped out and reused the wire. They made really nice wire back then.  The frosted, bayonet-mount power indicator bulb was replaced by a white led and current limiting resistor. To do this I took a bayonet-mount bulb and cracked and removed the glass with pliers, then soldered the led to the filament leads and gobbed a bit of gorilla glue to hold it in place. It shines out through the original, red plastic dome lens. I found a couple of terminal blocks in the junk box and put them to work on the board too.

I had to open up the meter and remove the internal shunt. It was only made to handle 100 ma and was as thin as thread. I gave the meter a good cleaning while it was apart and re-glued the glass to the meter face because it had turned loose over the years. I made an external shunt that calibrated the meter to use the top 0 to 500 volts scale to indicate amps; thus, 100 volts on the scale means 1 amp. Similarly, I calibrated the lower scale that used to be 0 to 100 ma to be 0 to 100 volts, so that the 25 mark means 25 volts.

On the left side of the picture, there used to be some wierd connector going through the case side. I removed it and was left with a 3/4" square hole. So I cut a piece of ABS plastic, mounted it on the inside and drilled it out to hold an bayonet ac fuse assembly that fuses the power cord as soon as it enters the box. The power cord was old and frayed. It was an electrocution / fire waiting to happen. It got replaced by the power cord from my microwave that died last fall.

The supply is now connected to the mill and is working flawlessly. But there was not room to install the light dimmer for the spindle speed control and it would have ruined the appearance anyway, so it will be in its own enclosure.

With that done, I'm building an enclosure for the linear actuator for the heliostat and while waiting for glue to dry I'm boring people by posting this stuff on the forum.

Don't miss the next exciting episode!



12
Think Tank / Re: Soda Bottle Lighting
« on: August 04, 2009, 12:06:44 PM »
Okay, it was nice and sunny most of today so I made the light tube I was talking about (took about 5 minutes) and I hauled it out to the shed and held it up over one of the soda bottle lights. I'd say it was a success!



The other bottle is stealing the tube's thunder a bit, but you can see there's a lot of light coming out the end of that tube!

I went to no great pains installing the mylar in the tube. I just spot hot-glued it a few places around the top rim and just let the rest of it hang down in the tube. From experience, I know that if I had tried to glue the whole mylar sheet, it would have had lots of wrinkles and lots of light would have been reflected back towards the opening. The mylar is happy to hang, nice and straight.

Next I guess I'll make some kind of white plastic diffuser to go on the bottom.

"Look Daddy! There's soda bottles sticking out of that man's roof!"   

"Yes, Son... that guy's a nut case. Stay away from him!"


13
Heliostat Projects / Re: Heliostat Array Project
« on: August 02, 2009, 01:11:18 PM »
Lookin' great there, Gabe. 

If I were working for a power utility, they'd demand super precision and it would make a difference in their bottom line. But for me, if I'm able to just keep most of the reflection on target most of the time, I'll be quite happy.

You can usually find just the lazy susan bearings on eBay. Costs less and less shipping if Susan doesn't come along. There's a listing up there right now: LAZY SUSAN BEARINGS -3 INCH-200 lb MADE IN USA  $3.49 with free shipping.

I think it is the same seller I bought mine from.


14
CNC Machine Builds / Re: Building Tom's "Easy Mill"
« on: August 02, 2009, 12:47:41 PM »


I occurred to me that I have not posted a picture of what I replaced the marbles/rails with.  Here's a picture of the present whole setup.




I haven't finished the power supply I'm building so the old AT psu is still supplying the 5 volts for the driver board but the motors are supplied by my bench supply via the red and black wire pair coming from the other side of the room.

You can see I relocated the Y axis motor. Did that a long time ago. The rails are a lot longer than my first ones. Gives me a lot more work area. I didn't have enough steel conduit to make the Y rails but I had some 1/2" rigid copper pipe. It is working just as well. The channel steel slides easily over either of them. The steel strap the Y motor was mounted on was flexing so I gorilla glued three straps together. It still bends a tiny amount but I was able to tune that backlash out with the software.

With the Y motor hanging way out there, it has a lot of leverage and if the y stage was run out close to the motor, the whole mess would try to tip forward. There's nothing holding the stages down on their rails but gravity. The X stage would tip sideways. I went out to my ammo reloading shack, got my lead furnace and made a 6 pound anchor that sits on the x stage platform. You can't see it in the picture because it is under the y stage.

I need to install some dust control because eveything in the computer room is getting coated.




Close up of the steel and copper rails. The spacers are to make up some of the height lost when the marbles were removed. Otherwise my Y lead screw would have been at an angle unless I completely redesigned the motor mount.


The power supply I'm building will have an ac supply for the RotoZip too. I'm building in a 600 watt light dimmer that will control the spindle speed.



15
Heliostat Projects / Re: Heliostat Project
« on: August 01, 2009, 04:21:27 AM »

"Another option to go wireless is with a laser pointer."

I tried that.  A couple of months ago I ordered a laser pointer for that very purpose. It puts out red light and is quite powerful. I could clearly see its spot on the trees across the highway in front of my house at night. That's over 150 feet away I'd guess. But I couldn't get any led's to produce electricity from the light. Wrong wavelength I guess. Besides, the laser spot was so small that I couldn't illuminate more than one led at a time unless the group of three was a long way off.    I also tried an infrared receiver from the front panel of a junked vcr, but no joy.  A regular tv remote control might be useful but I had the feeling it might be susceptible to stray infrared.

---

I mounted the sensor components in a tube today and took the whole bread-boarded sensor/transmitter assembly outside and set it atop my solar collector box. I adjusted a mirror to shine on and off the tube and it worked great... for a little while.   Then it quit working. To make a long story short, I finally discovered that the supplied A23 12volt battery was pretty much dead.  Now I think I know why the units were being sold so cheaply. They probably sat in a warehouse for too long (years) and the alkaline batteries bundled with them ran out of shelf life. It was easier and cheaper to just get rid of them on eBay. 

I didn't have any good A23 batteries so I just dug a 12vdc wall wart out of the junk box and will power the the thing with that for testing until I get new batteries. I think a good battery will power the thing for years and I won't have a lossy wall wart wasting electricity in the form of heat 24/7.

---

"I guess for any "feedback" aiming system, the light sensors will also have to sense when the Sun changes direction after the afternoon....that is, when it starts to go down or lower in the sky.   A motor will be required to change the direction of the heliostat; probably reverse the direction of the vertical adjust stepper motor.  It might take some kind of "logic gate/electronics" such as a logic chip (maby AND perhaps) or transistors to collect and then signal this condition."

The little actuator I've built uses a regular pm motor instead of steppers. I've got a whole box of them from scrapped vcr's. And the circuit I've designed is capable of reversing the motor direction. It probably would not be too difficult to do the basic control with some TTL logic but a picaxe micro with its software can be so versatile. In addition, it is dirt cheap. So the plan, at present, is to let a picaxe do the controlling and it can know when and where to go back to the morning position, and maybe through software I can teach it to do an occasional search if the sun is playing hide and seek. But that's further into the future than the end of my nose, so I haven't given it any deep thought.  I tend to learn by doing and I can't do that part yet.




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