DIY arduino circuit boards optimized for electronic indexing head

[chucketn]

TB, you just keep on keepin' on. I am learning/re-learning much from your posts.
I, too, am waiting on that slow boat. I've ordered drivers, another LCD, a serial module for the LCD, and a motor/servo/stepper shield that are still outstanding.
I have received the stepper Chuck F recommended, but no way to make it move. I have received the flex couplers to connect the stepper to the RT worm and formulated a plan for an adaptor.
I had already started to make a NEMA23 mount for my RT, but still have some features to add and probably some mods to that. I have Chuck F's program working on my Arduino, but am dead in the water until the other parts arrive.
It's still too cold to be comfortable working in my unheated garage/shop, so I try to use my time to learn...
You are helping the learning part. Thanks for that!

Chuck

 

[TorontoBuilder]

Hey Chuck... cold? Huh, we've had a spell of really cold weather, around -10C, its even prevented me from going about 1 block to the library to renew my library card so I can borrow ebooks again... I live in the wrong climate for my tastes.

Im glad you're learning something... writing these posts is helping me to refresh my memory of electronics and to learn new things. There have been a million developments since I learned simple electronic circuits decades ago.

My hope is that by having a firm understanding of the exact electronic processes it will help when I go to program arduino sketches, or rather more accurately when I go to modify existing sketches for my needs.

Its not like I really intend to create a shunt/op-amp circuit for my arduino to measure current.... but it helped me understand how the 185mV output of ACS714 based current sensor relates to the arduino analog-to-digital converter.

For those not familiar with it, the ACS714 is a hall sensor based current sensor, its based on a copper plate placed perpendicular to the current flow. the magnetic flux created by that current flowing thru our sensed circuit creates a proportional voltage across the sensor plate. They two circuits are electrically isolated which is nice... and just like our set-up they have a voltage amplifier circuit, with proprietary filtering to clean up the sensed voltage signal.

The one difference between the hall sensor and a circuit we could build with a an op-amp is that we could alter or mV output multiplier by our choice of resistor in our amplifier circuit....

Still, the hall sensor will give me a resolution of 26mA which is very close to the 25mA I could get by using a 20x multiplier in my amplifier circuit... but... I'm getting ahead of myself and my next post.

 

[xpylonracer]

Hi TorontoBuilder
I am following your posts with interest but yes I do find all the electronics a bit heavy, but interesting.
I guess like a lot of forum members I will be more interested in the working item when completed and tested,
and all components listed and available.
Emgee

 

[TorontoBuilder]

Hi TorontoBuilder
I am following your posts with interest but yes I do find all the electronics a bit heavy, but interesting.
I guess like a lot of forum members I will be more interested in the working item when completed and tested,
and all components listed and available.
Emgee

I'm glad that you're following along with interest. I'm sure looking forward to the completed indexing head too! I'm trying to expedite this project now since I dying to begin using it.

I'm close to having a good finalized bill of materials with links to suppliers, and alternatives if people wish to use a purchased arduino compatible rather than building one from bare PCBs and components.

 

[Swifty]

I'm also keen to see that finished product, my knowledge of electronics is virtually zero, but I want to make an electronic divider. The mechanics are no problem, just the electronics. Still, I will have a go at making one once everything is sorted.

Paul.

 

[Scott_M]

Hi TB
I am also following along. I have no need for this particular project as I have a 4th axis for my cnc mill. However I do have a need for a small microcontroller for an upcoming project, and recently purchased an Uno and I'm trying to wrap my head around "Arduino C". I am reading "Beginning C for Arduino" listed earlier in this thread or maybe it was Chucks ? But I am reading anything I can find regarding these little marvels.
So many thanks for taking the time to share !

Scott

 

[TorontoBuilder]

Hi TB
I am also following along. I have no need for this particular project as I have a 4th axis for my cnc mill. However I do have a need for a small microcontroller for an upcoming project, and recently purchased an Uno and I'm trying to wrap my head around "Arduino C". I am reading "Beginning C for Arduino" listed earlier in this thread or maybe it was Chucks ? But I am reading anything I can find regarding these little marvels.
So many thanks for taking the time to share !

Scott

I'll try to post links to specific projects if you tell me what you wish to do with your controller. It's amazing ho many fantastic tutorials there are out there. Especially youtube videos. I've been soaking up the knowledge from them.

 

[Scott_M]

Hi TB
Thanks for your help on this, however I feel that I may be on my own with a lot of this. I know there are a bunch of sketches out there but trying to meld them all together may prove to be more work than just starting fresh. Anyway here is what I would like to do, and at the risk of hijacking or going off topic feel free to respond via PM or just ignore my sorry butt

I would like to automate a job I do a lot. It involves cutting a piece round plastic to a specific length and burning one end.
I would like to use 3 motors, I think I need 1 stepper but could use simple DC gear motors for the others.
Process
Step motor turns rubber feed wheel an exact amount feeding stock a specific distance.
first DC motor brings down a hot wire past the end of the plastic rod and retracts, this polishes the end
2nd DC motor brings down a razor blade and cuts the plastic rod to length and retracts.
repeat a specified number of times.

The acrylic plastic rod is 1.5mm diameter so none of the motors need to be very big. I was looking at Nema 11 size for the stepper.
The hot wire motor will have no resistance so a small motor will work there too and distance is not critical so time or a micro switch could control its retract trigger.
The razor blade will require some force, maybe 4-5 pounds based on me pushing a razor blade through the material on a scale. So I was thinking gear motor driving a rack and pinion.

I would really appreciate any insight or links you could provide.

And I really don't mean to wander off-topic too much or hijack

Thanks again

Scott

 

[TorontoBuilder]

Hi TB
Thanks for your help on this, however I feel that I may be on my own with a lot of this. I know there are a bunch of sketches out there but trying to meld them all together may prove to be more work than just starting fresh. Anyway here is what I would like to do, and at the risk of hijacking or going off topic feel free to respond via PM or just ignore my sorry butt

I would like to automate a job I do a lot. It involves cutting a piece round plastic to a specific length and burning one end.
I would like to use 3 motors, I think I need 1 stepper but could use simple DC gear motors for the others.
Process
Step motor turns rubber feed wheel an exact amount feeding stock a specific distance.
first DC motor brings down a hot wire past the end of the plastic rod and retracts, this polishes the end
2nd DC motor brings down a razor blade and cuts the plastic rod to length and retracts.
repeat a specified number of times.

The acrylic plastic rod is 1.5mm diameter so none of the motors need to be very big. I was looking at Nema 11 size for the stepper.
The hot wire motor will have no resistance so a small motor will work there too and distance is not critical so time or a micro switch could control its retract trigger.
The razor blade will require some force, maybe 4-5 pounds based on me pushing a razor blade through the material on a scale. So I was thinking gear motor driving a rack and pinion.

I would really appreciate any insight or links you could provide.

And I really don't mean to wander off-topic too much or hijack

Thanks again

Scott

Hey Scott, I dont mind a little off topic stuff on this thread... if it grew to be a lot of info we could start a new thread.

It sounds like linear actuators may be the way to go for the razor cutter and hot wire motions. How much travel do you need for the cutters?

You could make your own from cheap low torque steppers motors and achieve precise motion control at a low cost. You would build upon the hardware already being discussed.

Have a look at this:

http://www.ebay.ca/itm/NMB-Linear-A...907?pt=LH_DefaultDomain_0&hash=item541921711b

Just curious, couldn't your hot wire act as both your cutter and polisher?

I edited out the question you had already answered in your post... I read read more closely. silly me

 

[Scott_M]

I like that actuator !!!
It will work fine for the hot wire.

The "cutter" has to be a blade or scissor, to give a clean edge. The hot wire will leave a rounded bulbous end. Which is what it is doing on the "polishing" end.
The cut is about an inch behind the polished end.
I am going to order a couple of those actuators and see how much power they have. The actual cut is only 1.5mm plus over travel and clearance so 10mm may be enough to get a little mechanical advantage on a scissor mechanism.
Thanks a lot !! that is a big help

Scott

 

[TorontoBuilder]

I like that actuator !!!
It will work fine for the hot wire.

The "cutter" has to be a blade or scissor, to give a clean edge. The hot wire will leave a rounded bulbous end. Which is what it is doing on the "polishing" end.
The cut is about an inch behind the polished end.
I am going to order a couple of those actuators and see how much power they have. The actual cut is only 1.5mm plus over travel and clearance so 10mm may be enough to get a little mechanical advantage on a scissor mechanism.
Thanks a lot !! that is a big help

Scott

The throw on that actuator may not be long enough to use alone but you may be able to use a linkage. You'll likely find a nice 2" stroke actuator suitable... on ebay they range from $10 bucks from china, or $35 to $50 each from US.

http://www.ebay.ca/itm/Heavy-Duty-5...t-Motor-/201275680079?&_trksid=p2056016.l4276

http://www.ebay.ca/itm/TWO-Heavy-Du...332?pt=LH_DefaultDomain_0&hash=item20e65f0104

 

[canadianhorsepower]

Hi TB
my head around "Arduino C". I am reading "Beginning C for Arduino" listed
Scott

Hi Scott
I did post that link but there is anoither one in the download section called build a robot but it's all interfacing with the arduino board
have a look

cheers
Luc

 

[chucketn]

Searching the downloads area doesn't return anything on build a robot...

Chuck

 

[canadianhorsepower]

Searching the downloads area doesn't return anything on build a robot...

Chuck

here is the link

http://www.homemodelenginemachinist.com/downloads/files/how-to-build-a-robot.pdf

enjoy

Luc

 

[chucketn]

Got it, thanks LUC.

Chuck

 

[Scott_M]

Thanks Luc !

I suggest we get back on topic.

Sorry for the side step.

Scott

 

[TorontoBuilder]

So to follow Scott's advice I'll post something back on topic, and that is rather brief too since it has changed my plans a little....

I wanted to see if I could design a custom arduino clone from scratch and build one especially suited for my project. I've achieved a design and went about sourcing components from digikey canada and elsewhere, and put together my bill of materials.

While this doesn't come as a surprise it is never-the-less surprising... just the cost of my board for an arduino clone will cost me about $30 Canadian, without tax. That's without any volume discounts of course but comparable to what an arduino Uno clone will cost me here in Canada. The two Uno R3s I ordered from sainsmart are costing me under $10 bucks each, plus whatever customs charges me, I doubt it will be much.

Another downside is that some of the nano clones dont have polyfuses to protect computer you will use to program the arduino.

Similarly, and more to my size considerations and needs I can buy a MINI USB Nano V3.0 ATmega328P clone from ebay for less than $5 or $4.25 in quantity. The one downside of the nano is that it uses a surface mount chip that cannot be easily replaced if you fry your control controller, BUT the upside is the entire board costs less than the cost of a new atmega328P-PU chip with bootloader.

So, I think I will design a different variant of the main control board into which I plug the nano as if it were a large chip using a couple of header strips. I'll then have headers to easily plug in the other components. Ease of use and cost effectiveness will be the main considerations

.
For those curious people I'll be uploading the bill of materials spreadsheet to the downloads section later today

 

[Holt]

I haven't posted for quite a while, but recently I got a mill, and have been looking for a dividing head for it, then I came across Chuck Fellows Arduino powered head, and fell in love immediately.
I really appreciate that someone take the time to make a "how to" for this project, but I wondered if some of you genius people could make an improvement that would make the head perfect. In C F's tread there was a link for a mill with synchronized index head for use when hobbing gears.
[ame]https://www.youtube.com/watch?v=ZhICrb0Tbn4&x-yt-cl=85114404&x-yt-ts=1422579428[/ame]
I have a rotary encoder with 1000 pulses per revolution, if I mount that on the mill spindle, I would imagine it would be possible to write a program that would rotate the dividing head in the desired synchronized speed.
The perfect solution would be a switch where I could choose between the two programs.
What do you think? would it be possible?


Holt

PS: I have no idea how to program the Arduino, so I can't do it myself, but I just ordered a education set, so hopefully I will be able to do some simple programming in the future.

 

[TorontoBuilder]

I haven't posted for quite a while, but recently I got a mill, and have been looking for a dividing head for it, then I came across Chuck Fellows Arduino powered head, and fell in love immediately.
I really appreciate that someone take the time to make a "how to" for this project, but I wondered if some of you genius people could make an improvement that would make the head perfect. In C F's tread there was a link for a mill with synchronized index head for use when hobbing gears.
https://www.youtube.com/watch?v=ZhICrb0Tbn4&x-yt-cl=85114404&x-yt-ts=1422579428
I have a rotary encoder with 1000 pulses per revolution, if I mount that on the mill spindle, I would imagine it would be possible to write a program that would rotate the dividing head in the desired synchronized speed.
The perfect solution would be a switch where I could choose between the two programs.
What do you think? would it be possible?


Holt

PS: I have no idea how to program the Arduino, so I can't do it myself, but I just ordered a education set, so hopefully I will be able to do some simple programming in the future.

Hi Holt,

I saw the same video and wanted to perform the exact same task. I don't have a CNC mill or the software in that video, but am pretty sure that it is possible to have the arduino perform the same tasks.

First we need to add a rotary encoder to the mill, and program an arduino interrupt to trigger our program whenever the mill motor rotates... then we'd have the arduino read the speed based on the steps per rotation. Finally we'd have the arduino output the step command to the stepper driver at a rate proportional to rotation of the mill shaft. I think it shouldn't be that difficult to figure out, especially since we only need to encode for rotation in forward if we want to make things dead simple.

One key is working out a suitable number of slots per revolution to assure fast accurate shaft speed rotational measurement. large plotters often had 200 holes per rotation... which actually matches the steps of common stepper motors.

The dividing head will be my first arduino project, but not my last. I also know how optical encorders work to some extent so I can undertake that for my mill. The problem is that each mill owner will have to make modifications to suit their own machine. Otherwise we can develop standard hardware for that project

 

[rodw]

John, there is a much easier way to measure rotation. Just grab one of these https://www.sparkfun.com/products/11102

You'd have to check the maximum RPM of the mill spindle vs the speed at which the Arduino can sample the rotary encoder pulses when selecting the steps per revolution of the encoder you use. The other limiting factor will be the maximum stepper resolution. From Memory, the NEMA 17 and 23 I played with maxed out at about 400 RPM with both the Polou and Gecko microdrive. Its been a while since I looked at these encoders with the same idea in mind. Pretty sure they also sense direction.

Glad you know about interrupts. You'll need them.