Homegrown Setworks

[shaworth]

Shannon
That was an interesting read, and makes me want to scratch an itch when reminded of the 70's and being involved in the new digital (and analog) control design and build (then testing to locate the problems in the design layout or the failure of a chip to do its job). Then out with the solder wick and put in a new chip, etc., etc. Things were big those days compared to the mini-chips now.
 

Digital computing in the '70s, talk about a golden era.  I was a teenager with next to no money, it would be another 6 years before I would start to hack hardware.  The chips have gotten so much smaller, are largely self sufficient, and of course more powerful.  Ah, the bad old days...

If you really feel like scratching that itch less than $100 bucks will get you back in the game.  Heck, the avr butterfly (google it) costs $20 and contains a CPU, plenty of IO, a LCD, buttons - and being an avr based device can be reprogrammed in 'C' using the free winavr software.  Together with a $15 programmer and you are on your way.  Check it out here:  http://www.atmel.com/dyn/resources/prod_documents/doc4249.pdf

Shannon

[rs1626]

HEY SHAWORTH WOULD YOU BE INTERESTED IN BUILDING ANOTHER ONE ?  IF SO HOW MUCH?

[sgschwend]

60 amp at 12V sounds correct.

There are also table saw digital gages that can measure position up to multiple feet.  The gage is mounted on a aluminum bar and the detector can slide up and down the bar.

They use a positional coded tape so the reader know distant and position.  There is a problem with vibration that makes reading position difficult.

[shaworth]

HEY SHAWORTH WOULD YOU BE INTERESTED IN BUILDING ANOTHER ONE ?  IF SO HOW MUCH?

Hmmm.... The thing is actually a collection of parts. 

There are several custom parts:
  1) a relay circuit board
  2) the circuit board that holds the positional sensor
  3) the encoder wheel that holds the magnets and attaches to the drive pully
  4) the software that runs the entire thing
  5) the "control board" enclosure that holds the circuit boards, buttons, joystick and LCD display

There are also a bunch of "off the shelf" ingredients, most of these live inside of the control board enclosure.
  A) An arcade machine joystick (about $20.00)
  B) Arcade machine buttons     (about $8.00 total)
  C) The circuit board holding the CPU and power supply (about $30.00)
  D) 60A automotive relays  (about $20.00 total)
  E) The LCD display module (about $100.00)  - I'm searching for a cheaper alternative that will perform well in direct sunlight.

Anyone who plunks down hard earned money should expect a reliable system.  That means #1 - #5 need to be professionally built.  The circuit boards are easy, this outfit (http://www.batchpcb.com/) will take my schematics and turn them into finished circuit boards.  I expect the final cost per set of boards will be about $30-$40 bucks.  Of course the chips need to be soldered onto the boards by someone...

The encoder wheel needs to be perfectly constructed, it can't wobble or move around. My current plan is to have it laser cut out of a sheet of 1/4" thick plastic (nylon or ABS).  I will actually need to build a sandwich with the magnets completely enclosed.  This means three layers of plastic.  These guys seem reasonable: http://www.customlasercutting.com/ for custom laser cutting.  However I may have to go with an aluminum disc for durability.  I don't know what this will cost yet.

The software is tough - part of me wants to give this away.  But the reality is that I've got a lot of time invested in this and I could have billed that time to my clients (I'm a professional software developer).  I've got a 3yo son and wife to support - figure $300 for the software loaded onto the CPU. 

The control board is currently a plywood box.  It needs to be replaced with a heavy-gauge metal enclosure.  Plastic or wood isn't going to survive the rigors of day to day use.  I'm looking for an off-the-shelf control box that I can put a custom face-plate on.  I would like to keep the enclosure cost below a hundred bucks.  That isn't as easy as it seems since the entire affair needs to be weatherproof.

Obviously I won't allow anyone (other than my brother)  to invest that kind of money into something before it is fully tested.  As we test it we are going to run into things that alter the design, and could impact the cost.  Adding the above up should provide a realistic ballpark estimate. 

When my brother and I decide the design is finalized and ready for prime-time we will see if there is any interest in having a batch of custom parts built, rather than just one set.

Shannon

[shaworth]

60 amp at 12V sounds correct.

There are also table saw digital gages that can measure position up to multiple feet.  The gage is mounted on a aluminum bar and the detector can slide up and down the bar.

They use a positional coded tape so the reader know distant and position.  There is a problem with vibration that makes reading position difficult.

Agreed, I've been looking at alternatives to the encoder wheel.  One thing that shows a lot of promise is the drive pulley and timing belt used in desktop CNC machines (http://buildyourcnc.com/stuffforsale.aspx).  They are very precise and when properly tensioned.  However, even though they are made of kevlar I'm concerned about cold weather performance.  It gets cold in Nebraska! 

A chain seems like a reasonable solution.  However I am concerned that a chain will have too much play to be accurate.  I need to test it.

Do you have a link to one of these?  My google skills are weak today.

[ronwood]

Shannon,

On my previous post I mentioned about the chain on the head. What I found was that if the chain is not tension properly the setworks would not be as repeatable. This was based on observing the pointer each time I stopped in increments of say 1 inch. Even thought it was not a lot it the accumulated effect could be a issue.  The chain may be a problem.

Ron

[rs1626]

Sounds interesting my mill is homebuilt has .2 pitch leadscrews to move up and down instead of a chain do you think this would be a problem?   let me know when you get a price ironed out   and i think i can help you with alum. wheels

[Chico]

Does your set up have a linear positioner so the head knows where it's at at any time or do you just use as a setworks using preset heights

[shaworth]

60 amp at 12V sounds correct.

There are also table saw digital gages that can measure position up to multiple feet.  The gage is mounted on a aluminum bar and the detector can slide up and down the bar.

They use a positional coded tape so the reader know distant and position.  There is a problem with vibration that makes reading position difficult.

This is why I asked!  My gut instinct was way off on this one.

[shaworth]

Shannon,

On my previous post I mentioned about the chain on the head. What I found was that if the chain is not tension properly the setworks would not be as repeatable. This was based on observing the pointer each time I stopped in increments of say 1 inch. Even thought it was not a lot it the accumulated effect could be a issue.  The chain may be a problem.

Ron

When I'm at my brother's place (where the sawmill is) I'll take a good long look at the chain tension arrangement.  I hate to admit it but this something that I've pretty much ignored up to this time.  Thanks for the tip!

[sgschwend]

I like these guys, on this page there are multiple encoder options:

http://www.sparkfun.com/commerce/advanced_search_result.php?keywords=encoder&x=0&y=0&search_section=products

[shaworth]

Does your set up have a linear positioner so the head knows where it's at at any time or do you just use as a setworks using preset heights

Currently I am tracking the position relative to the last cut, with an accuracy of 1/32".  Nothing is pre-determined as far as the set points are concerned.  You use the joystick and buttons to specify the distance you want to move the sawhead, and then move it.  The distance can anything between 1/4" to the available amount of travel.

Now, I would REALLY like to know the absolute position off of the deck.  And I'm looking at techniques to always have that as a precise measurement.  Obviously that would be the best.

However for now the position is relative to the current blade position. 

[shaworth]

Sounds interesting my mill is homebuilt has .2 pitch leadscrews to move up and down instead of a chain do you think this would be a problem?   let me know when you get a price ironed out   and i think i can help you with alum. wheels

The chains vs the leadscrews is not going to matter.  However I need to see how the drive-chain for the saw-head works to determine how and if I can measure the position of the sawhead. 

Another reason why I'm keeping my eye out for a linear sensor that can be adapted.  A direct measurement of distance will always be better than an inferred measure of distance.

[shaworth]

I like these guys, on this page there are multiple encoder options:

http://www.sparkfun.com/commerce/advanced_search_result.php?keywords=encoder&x=0&y=0&search_section=products

SparkFun rocks, I actually have an order of stuff arriving from them the day after tomorrow.  Their enclosed encoding wheel is interesting, however I'm concerned about long-term durability.  If the hall effect sensor doesn't pan out I will be giving that little package a lot more attention.

[sgschwend]

For a linear digital length reader I used these guys (digi-fence).  Be sure and go with the digital encoded version, you will need to call them to get access to that model.  The table saw version measures just fine but it does not have a position value.  That means if the sawmill's vibration causes a miss read the encoded version will still provide the correct answer, the table saw version will have an error.

http://www.digi-kit.com/digiscale.htm


I used mine for about a year, and decided that my manual sight scale was certainly accurate, so this digital scale was redundant, and it was another thing to take care off.  It was very handy for the jobs that you wanted to drop the saw an exactly amount.

 

[sgschwend]

Actually I was thinking about the wheel encoder.  The kit would provide the wheel and the board.  Attach the wheel to the sprocket and a sheet metal bracket to hold the board side.  Or let the wheel rub on the beam and assume there is no slip.

[Magicman]

However you do it, remember sawdust.  It can/will get into any open space and has a way of covering everything.  Be sure that a layer of sawdust will not affect any measuring device.

[shaworth]

However you do it, remember sawdust.  It can/will get into any open space and has a way of covering everything.  Be sure that a layer of sawdust will not affect any measuring device.

Very good point, sawdust is exactly why I decided to start with the magnetic encoding wheel.

[pineywoods]

BTW Shannon a belated big welcome to the forestry forum. I completely agree with your take on the advantages of using a dedicated micro processor instead of adapting a laptop. You see, I have this old lunchbucket that has a monochrome plasma display, and my mill already has all the relays and drivers in the form of the remote control. A hall effect pickup on the head drive pulley to trigger the data in pin on the serial port..Now lets see, 8 output pins on the parallel port, 1 for head up, and another for head down. Two more for head forward and backward, another to activate the clutch to start the band moving......Might be simpler to program it in machine code, but I've done bit of that. You can probably see where all this is headed, and NAW I'll probably never do it.    Seriously, thanks for posting the links, I already checked them out. It's been decades since I did any of this sort of tinkering and I'm impressed. I think I may be purchasing a butterfly....

[shaworth]

BTW Shannon a belated big welcome to the forestry forum. I completely agree with your take on the advantages of using a dedicated micro processor instead of adapting a laptop. You see, I have this old lunchbucket that has a monochrome plasma display, and my mill already has all the relays and drivers in the form of the remote control. A hall effect pickup on the head drive pulley to trigger the data in pin on the serial port..Now lets see, 8 output pins on the parallel port, 1 for head up, and another for head down. Two more for head forward and backward, another to activate the clutch to start the band moving......Might be simpler to program it in machine code, but I've done bit of that. You can probably see where all this is headed, and NAW I'll probably never do it.    Seriously, thanks for posting the links, I already checked them out. It's been decades since I did any of this sort of tinkering and I'm impressed. I think I may be purchasing a butterfly....

Thanks for the welcome.  Before you make up your mind about the butterfly, you might seriously consider this:  http://www.sparkfun.com/commerce/product_info.php?products_id=766, it obviously has the low-power relays in hand, sadly only 4.  Since it has a RS232 port you can use your laptop as a display / input.  To program it you will need a programmer, I'm using this one: http://www.sparkfun.com/commerce/product_info.php?products_id=13  I've got one and it is a blast to interface with (the screw terminals means no soldering) and is a seriously powerful platform.  It uses the same family of CPU as the butterfly, so everything I've said earlier about the tool chain applies to this board as well.

Happy hacking,

Shannon