Sawmill and Timber

Sawmills and Sawing => Sawmill Building/construction => Topic started by: tamarackmiller on July 16, 2022, 10:03:03 AM

Title: Limit Switches and Relays
Post by: tamarackmiller on July 16, 2022, 10:03:03 AM

I'm currently building an edger. And instead of having to race the board to the other side, I'd like to build a table that flips the finished board to a conveyor that returns to board to me. I'd like to keep it all on 12v as I have already have a bunch of things around the mill running on 12v by way of a 12v generator and I have access to some 12v electric motors. Essentially, the logic would be:

• hit a momentary switch that energized a relay
• send power to a 12v motor connected to the table by way of a chain that raises one side of the table
• table hits a limit switch
• timed relay gives the board a few seconds to drop the board on a conveyor
• relay reverse the polarity to the motor to bring the table back down
• table hits second limit switch cutting power to the motor

I know just enough about electronics to know that the above is possible but not enough to know what parts are required to do it. Anybody out there more knowledgeable that could point me in the right direction?

thanks

Title: Re: Limit Switches and Relays
Post by: Kirk Allen on July 17, 2022, 07:10:50 AM

Is there a need to "flip" the board for the return or am I misunderstanding the use of the word flip?  I have seen several return runs that simply have the board slide off one run down to another taking it back. When the board hits the switch it gets kicked off the one belt to an angled run that drops it onto the return belt.

Title: Re: Limit Switches and Relays
Post by: tamarackmiller on July 17, 2022, 07:49:39 AM

You hare absolutely correct. I meant to write lifting one side of the table and let the board slide sideways on a conveyor that brings the board back.

thanks

Title: Re: Limit Switches and Relays
Post by: Ox on July 18, 2022, 08:32:15 AM

Your plan and knowledge of the systems you're talking about is all you need by the sounds of it!  I have nothing to add.  We'd like to see pics when you're done with it!

Title: Re: Limit Switches and Relays
Post by: Crusarius on July 18, 2022, 07:11:38 PM

you just need to have a table drop. As long as the outfeed table is long enough (does not need to be powered) you can have an optical limit switch that opens when the board clears and then drops the end of the outfeed table that is closest to the edger. gravity should feed the board down under the edger to a waiting operator to reload the board.

the table lowering device just needs to be an offset circle (cam) or a rotary arm. the motor will not need to reverse it can run the same direction and the cam will just roll around again lifting the table back to flat.

probably need some time delay relays in there to get enough time to have the board return before.... hmmm wait. that same limit switch may be able to be used to lift the table back up.

Title: Re: Limit Switches and Relays
Post by: tamarackmiller on July 19, 2022, 11:26:45 AM

I'm researching timed relays right now.

Almost finished the edger itself. I was having a heck of time getting the boards to feed straight. I just installed a thin piece of metal behind the fixed blade to act as a fence and it now appears to be working. I just have to guide the board for the first foot or so until it starts pushing against the fence. I may revisit this later on and add in-feed and out-feed conveyor belting instead.

Had a bit of a scare. The spring that keeps tension on the idler for the belt decided to break. The belt proceeded to ride up onto the edge of the sheave. In the few revolutions the engine made before I managed to shut it of, it bent the saw blade shaft making one of the blades impact the protective top cover. Made a nice gouge in it! Back to the parts store for a new shaft and blade.

Title: Re: Limit Switches and Relays
Post by: Crusarius on July 22, 2022, 12:53:27 PM

can you run a riving knife on the edger?

Title: Re: Limit Switches and Relays
Post by: tamarackmiller on July 24, 2022, 06:44:37 AM

That’s what I ended up with:

(https://sawmillandtimberforum.com/gallery/1/1275-240722063838.jpeg)

Title: Re: Limit Switches and Relays
Post by: Crusarius on July 26, 2022, 06:54:05 PM

hows it work?

Title: Re: Limit Switches and Relays
Post by: tamarackmiller on July 27, 2022, 06:18:29 AM

I only managed one pass through the edger before the belt came off bending the saw-blade shaft in the process. However that one pass was much more controlled. I will modify the out-feed press-down tire to angle it towards the riving knife a bit. Kinda like the Thomas edger.

I just received my new mill (Norwood HD36) so I've been busy putting that together. The edger will return to the garage for final assembly and tweaking next week. 

Title: Re: Limit Switches and Relays
Post by: joasis on August 07, 2022, 06:09:07 AM

I am currently building a home for an electrical engineer....just a thought, but I could direct him to this post to maybe offer a little help. Or maybe give you his email and you could converse with him.

Title: Re: Limit Switches and Relays
Post by: tamarackmiller on August 14, 2022, 12:21:21 PM

Thank you. That's very kind of you but I think I have it figured out. I simplified my design to have a 12v motor connected to what is essentially a cam that pushes an arm across the out feed table. This greatly simplifies the amount of relays and limit switches as the motor simply does a full rotation and stops.

I will post pictures once I have it all complete.