Re: [Emc-users] Halcompile Quirk

[Phill Carter]

> On 2 Feb 2021, at 12:33 pm, andy pugh  wrote:
> 
> On Tue, 2 Feb 2021 at 01:17, Phill Carter  wrote:
> 
>> It seems to build ok here.
> 
> Good to know. Which OS / kernel / realtime?

It is in a VM:

(master) buster:~/git/linuxcnc-dev/src $ uname -a
Linux buster 4.19.0-13-rt-amd64 #1 SMP PREEMPT RT Debian 4.19.160-2 
(2020-11-28) x86_64 GNU/Linux

> 
> -- 
> atp
> "A motorcycle is a bicycle with a pandemonium attachment and is
> designed for the especial use of mechanical geniuses, daredevils and
> lunatics."
> — George Fitch, Atlanta Constitution Newspaper, 1912
> 
> 
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Re: [Emc-users] Halcompile Quirk

[andy pugh]

On Tue, 2 Feb 2021 at 01:17, Phill Carter  wrote:

> It seems to build ok here.

Good to know. Which OS / kernel / realtime?

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1912


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Re: [Emc-users] Halcompile Quirk

[Phill Carter]

> On 2 Feb 2021, at 11:51 am, andy pugh  wrote:
> 
> I am not currently able to compile userspace comps in-tree on my dev machine.
> 
> This includes the sample comp on the halcompile manpage (rand.comp)
> 
> I can compile it OK with plain halcompile, but if I put it in the
> hal/components directory and then try to build LinuxCNC with "make" I
> get:
> 
> /hal/components/rand.c:27:10: fatal error: stdlib.h: No such file or directory
> 
> Is anyone else in  a position to see if they have the same problem, or
> if it is just me.

It seems to build ok here.

> 
> -- 
> atp
> "A motorcycle is a bicycle with a pandemonium attachment and is
> designed for the especial use of mechanical geniuses, daredevils and
> lunatics."
> — George Fitch, Atlanta Constitution Newspaper, 1912
> 
> 
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[Emc-users] Halcompile Quirk

[andy pugh]

I am not currently able to compile userspace comps in-tree on my dev machine.

This includes the sample comp on the halcompile manpage (rand.comp)

I can compile it OK with plain halcompile, but if I put it in the
hal/components directory and then try to build LinuxCNC with "make" I
get:

/hal/components/rand.c:27:10: fatal error: stdlib.h: No such file or directory

Is anyone else in  a position to see if they have the same problem, or
if it is just me.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1912


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Re: [Emc-users] EDM from scratch

[dave engvall]

EDM of one sort or another comes up every few years. Pete 
Grundemann(sp?) put one together. His demo was to edm threads in a file.
tomp ... now in Thailand has a lot of experience in edm. 
tjtr33...atgmailcom
Someone brought a non-working commercial wire edm to Galesburg and 
almost had it working at the end of the week. This was a stepper driven 
unit made by Bridgeport but had a different label. My memory seems to be 
fading
I worked a little bit at getting something going but other pressures out 
voted the project. Still have a bunch of graphite and electrolyte around 
here someplace.


Dave

On 2/1/21 8:41 AM, Jon Elson wrote:

On 01/31/2021 07:22 PM, John Dammeyer wrote:
I found some of the earlier articles in Home Shop Machinist Issue's 
May/June 1995 and September/October 1995.   I do not have part 2 
published in July/August 1995.


However, in the 3rd part Robert Langlois describes the stepper motor 
operation in conjunction with the capacitor voltage.  His front panel 
has switches allowing combinations of 50uFd, 100uFd, 200uFd and 
400uFd in parallel.
Note that Robert Langlois is the home shop expert on WIRE EDM, which 
is a bit different from
sinker EDM, as the wire is moved fairly rapidly past the cut.  So, the 
spark generator setup is

quite different.

I met him at a couple NAMES shows in the late 1990's.

Jon


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[Emc-users] Sheet metal operations.

[John Dammeyer]

I've posted this under a new subject because Andy's EDM project had me looking 
through 25 year old copies of MEW and Home Shop Machinist etc.  Brought back 
memories of building the Gingery Hacksaw and Slip Roll so I could fabricate the 
propane fired foundry in order to be able to make the Gingery lathe.  Which I 
did and that spawned the Electronic Lead Screw project back in 2006.
 
The plan was to also make the shaper and mill but as luck would have it I ended 
up with a used metal bandsaw,  a 1942 vintage South Bend Heavy 10L with taper 
attachment and finally a House of Tools Mill (similar to the now discontinued 
G3616 from Grizzly).  I also purchased a 3 Ton Arbor press and a 30" 3:1 sheet 
metal tool along with a corner notcher.  My shop isn't large enough to fit a 
box pan brake or larger separate shear.
 
Anyway the plan was to at some time create an ELS controlled movable back fence 
for the 3:1 tool and an XY movement system for the Arbor press to give me 
limited punching capabilities like the attached picture.  
 
Now 14 years later I'm running out of ELS kits and still haven't built the back 
fence control and China dominates the cheap market with Encoders, Arduinos and 
stepper drivers.  Not to mention far less expensive linear rails and carriages. 
 
 
Given that I had a Pi4 with the MESA 7i92H running my mill for a while it seems 
like LinuxCNC may be a better choice for both the 3:1 back fence and XY 
positioning simply because it's an easy way to bring in the sequences.  One 
really only needs a few different size punches in square, triangle and round to 
be able to nibble out most holes in sheet metal thin enough for working with a 
3:1 tool.
 
But there's also a company nearby me that has a laser cutting system that can 
now operate lights out.  The sheets are picked, placed, punched and removed all 
automatically.  So for production it's not logical to do that sort of thing in 
house.  They also bend metal.
 
But, for that prototype or hobby, just like having a CNC Mill and Lathe, being 
able to bend and punch metal does come in handy.  Especially since I do more 
electronics than machining; at the moment.  The 3D printer now also finds a 
place that was there 25 years ago but done with other technologies.   Where 
before I'd bend up a box to hold an ESTOP switch now I 3D print switch holders 
and boxes for electronics.
 
What I'm wondering is if it's worth the trouble to add XY to a 3 ton arbour 
press.  The back fence for the 3:1 tool is almost done so it's just a matter of 
finishing it.  But I can't see how any of the CAD/CAM software out there 
addresses using a small punch to nibble out a larger hole.  And truthfully my 
JGRO based CNC router with a small end mill can just as easily cut out metal 
plate.  Or for that matter the mill.
 
The shearing, bending and rolling are still valid operations.  The press is 
still handing for pressing broaches through holes or bearings etc.  But is an 
XY punch even worth the effort?  So many of the projects from 1995 to about 
2005 in the magazines were pretty cool but from a time when some things just 
weren't available at low cost.  Now I think one would have to be nuts to try 
and build your own CNC mill from bar stock and rails.  
 
John Dammeyer
 
 
"ELS! Nothing else works as well for your Lathe"
Automation Artisans Inc.
www dot autoartisans dot com 
 
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Re: [Emc-users] EDM from scratch

[Jon Elson]

On 01/31/2021 07:22 PM, John Dammeyer wrote:

I found some of the earlier articles in Home Shop Machinist Issue's May/June 
1995 and September/October 1995.   I do not have part 2 published in 
July/August 1995.

However, in the 3rd part Robert Langlois describes the stepper motor operation 
in conjunction with the capacitor voltage.  His front panel has switches 
allowing combinations of 50uFd, 100uFd, 200uFd and 400uFd in parallel.
Note that Robert Langlois is the home shop expert on WIRE 
EDM, which is a bit different from
sinker EDM, as the wire is moved fairly rapidly past the 
cut.  So, the spark generator setup is

quite different.

I met him at a couple NAMES shows in the late 1990's.

Jon


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Re: [Emc-users] To Sam Sokolik re opencv on linux

[Dr. Nikolaus Klepp]

Anno domini 2021 Mon, 1 Feb 08:55:43 -0500
 Gene Heskett scripsit:
> On Sunday 31 January 2021 17:48:47 Sam Sokolik wrote:
> 
> > http://electronicsam.com/images/emco/terco/
> >
> Got it, thanks Sam.
> 
> > Now - iirc the capture python script is copied to usr/bin/ and made
> > executable..
> >
> > It looks like I used opencv-2.4.9  (again - it was over 6 years ago)
> 
> [...]
> 
> Cheers, Gene Heskett

Thank you from me, too.

OpenCV 2 is still working, but I've got some performance problems when the 
image has more than 10 circular objects.

Nik



-- 
Please do not email me anything that you are not comfortable also sharing with 
the NSA, CIA ...


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Re: [Emc-users] To Sam Sokolik re opencv on linux

[Gene Heskett]

On Sunday 31 January 2021 17:48:47 Sam Sokolik wrote:

> http://electronicsam.com/images/emco/terco/
>
Got it, thanks Sam.

> Now - iirc the capture python script is copied to usr/bin/ and made
> executable..
>
> It looks like I used opencv-2.4.9  (again - it was over 6 years ago)

[...]

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page 


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Re: [Emc-users] EDM from scratch

[Gerrit Visser]

Thank you Thomas, filed your excellent info for my project.

Just finishing up a shop built cnc gantry machine (uses Pathpilot), then
onto the next project which I think will be a WEDM machine.

Gerrit

-Original Message-
From: Thomas J Powderly [mailto:tjt...@gmail.com] 
Sent: February 1, 2021 12:57 AM
To: emc-users@lists.sourceforge.net
Subject: Re: [Emc-users] EDM from scratch

Hi Gerrit

the difference between senkung and draht erodien generator

is the pulse width

in wedm 1-10uS is the entire spectrum

in sink edm 1-3000uS is the spectrum

in any edm that uses the very sort pulse,

it is important that the current shut-off be complete and very fast ( all
inductanc ein system must be watched)

if you can turn the power OFF very very quickly, you will increase the metal
removal a LOT.

the reason is

the metal removel is the expulsion of a tiny crate pool of molten material

if the thermal change ( from current supplied an heating the pool)

to the time hwne current is removed and the thermal mass of the surrounding
environment ( oil water gas )

that makes for a more IMplosive force on the hot plasma bubble channel over
the pool.

The quickness of the bubble collapse cause more of the puddle to be ejected

a slower deflating lets most of the melted material to cool back on the
surface

look for Dr. Schumakers description from AGie

i cant find it now but it was an excellent presentation of how a spark
removes material

the 9 or so pictures are a whole edm education

but try this instead

https://core.ac.uk/download/pdf/34635871.pdf

best of luck with the wedm

(btw it will be a good hole drill spark generaor if it works for wed, just
needs up to 100uS max on time )

tomp

On 2/1/21 12:53 AM, Gerrit Visser wrote:
> Another source of information about pulse generator design: 
> https://langfordw.pages.cba.mit.edu/desktopWEDM/electronics/
>
> https://www.cnc.info.pl/drazenie-metoda-domowa-moje-proby-t11692-20.ht
> ml (Google translate helps here:-))
>
> Again, my focus is on wire EDM but there must be similarities
>
> Gerrit
>
>
>
>
>
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Re: [Emc-users] EDM from scratch

[andy pugh]

On Mon, 1 Feb 2021 at 09:42, Thomas J Powderly  wrote:

(Snip the other stuff, all noted)

> a use of adaptive feed wull never apprach the needed jittery advance of
> edm, adaptive feed never reacts negatively,

That is no longer the case. LinuxCNC now supports negative adaptive
feed, introduced specifically for EDM use.

-- 
atp
"A motorcycle is a bicycle with a pandemonium attachment and is
designed for the especial use of mechanical geniuses, daredevils and
lunatics."
— George Fitch, Atlanta Constitution Newspaper, 1912


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Re: [Emc-users] To Sam Sokolik re opencv on linux

[Sam Sokolik]

http://electronicsam.com/images/emco/terco/

Now - iirc the capture python script is copied to usr/bin/ and made
executable..

It looks like I used opencv-2.4.9  (again - it was over 6 years ago)

On Sun, Jan 31, 2021 at 3:03 PM Sam Sokolik  wrote:

> Ok.  I found the config/python script I was working on...  Late 2014..
> Boy.  I will put them up somewhere tonight..
>
> On Thu, Jan 28, 2021, 9:36 PM Gene Heskett  wrote:
>
>> On Thursday 28 January 2021 21:12:31 Bari wrote:
>>
>> > On 1/28/21 4:55 PM, Gene Heskett wrote:
>> > > That's not the video I saw, and can't find again. I think it was one
>> > > of yours where you were auto finding a red target dot by calculating
>> > > the offset and a button click then drove the machine at a high rate
>> > > of speed to put the red dot precisely in the cameras target circle.
>> > > Wasn't that one of yours video's?
>> >
>> > This one maybe?
>> >
>> > https://www.youtube.com/watch?v=Pe2RACwiEbg
>> >
>> Yes, that's it exactly Bari. Thanks.
>>
>> But I did not realize until checking the youtube submission date, that it
>> was so old. 2014. Now, I'd like to see if I can make it work with
>> opencv. camview was glaringly slow back then with the video running 3 or
>> 4 seconds behind the machine, and crashing so often and hard that it
>> took a reboot to run it again, and had more bugs than a 10 day old road
>> kill carcass in august, making it very impractical to try to use so I
>> gave up.
>>
>> Now I've found another promising camera that I'd like to try. But this
>> time I'll start with our 2.8 install iso so I'm not also battling with a
>> 7 yo OS called wheezy.
>>
>> Buster is running TLM, and ran one of my mills right well a few days ago,
>> for a few hours, but after the install, the video went away on that
>> D525MW in an ARK shoebox.
>>
>> So now I've bought 4 used optiplexes with i5 cpu's. So the hd with that
>> install goes in the optiplex when it gets here.
>>
>> Which is what I did when this box caught fire last year, at one of the
>> mobo's usb 2 headers, so I replaced that Asus mobo with its phenom with
>> another Asus carrying an i5, still booting from the same hd with stretch
>> on it.  The phenom had horrible latency on a stock kernel, but this new
>> 6 core i5 is good enough to run machinery without a preempt-rt kernel.
>> Time marches on as its doing it on 20% of the phenoms power draw.
>>
>> Thanks Bari.
>>
>> Cheers, Gene Heskett
>> --
>> "There are four boxes to be used in defense of liberty:
>>  soap, ballot, jury, and ammo. Please use in that order."
>> -Ed Howdershelt (Author)
>> If we desire respect for the law, we must first make the law respectable.
>>  - Louis D. Brandeis
>> Genes Web page 
>>
>>
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>> https://lists.sourceforge.net/lists/listinfo/emc-users
>>
>

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Re: [Emc-users] EDM from scratch

[John Dammeyer]

I found some of the earlier articles in Home Shop Machinist Issue's May/June 
1995 and September/October 1995.   I do not have part 2 published in 
July/August 1995.

However, in the 3rd part Robert Langlois describes the stepper motor operation 
in conjunction with the capacitor voltage.  His front panel has switches 
allowing combinations of 50uFd, 100uFd, 200uFd and 400uFd in parallel.

Essentially he moves the stepper motor down (electrode) if the voltage rises 
above a pot set reference voltage and moves it up if below a second pot set 
reference voltage.  It doesn't move the motor if the voltage is between these 
two set points.

The voltage on the capacitors ranges between 0V and 100V which is divided by 20 
for a 0V to 5V value compared to the Pot values.

John Dammeyer

He also references 
Model Engineer 1976 July, August, November and 1981 October.
Strictly I.C.  1993 Aug/sept, Oct/Nov, 93-94/Dec/Jan., 94 Feb/Mar, 95 Feb/Mar 
(letters)
Home Shop Machinist 91 Jan/Feb, 91 Jul/Aug, 92 May/Jun, 94 May/Jun



> -Original Message-
> From: ken.stra...@gmail.com [mailto:ken.stra...@gmail.com]
> Sent: January-31-21 11:51 AM
> To: 'Enhanced Machine Controller (EMC)'
> Subject: Re: [Emc-users] EDM from scratch
> 
> Problem solved.
> 
> -Original Message-
> From: John Dammeyer 
> Sent: January 31, 2021 2:35 PM
> To: 'Enhanced Machine Controller (EMC)' 
> Subject: Re: [Emc-users] EDM from scratch
> 
> Rats.  I'm missing #169 for some reason.
> 
> The series I was thinking about was in issues #57..#60 and with addendums in
> #64 and #68.  The #68 issue discussed dielectrics safe for the home workshop
> and the liquid mentioned may still be available in the UK.
> 
> John Dammeyer
> 
> 
> > -Original Message-
> > From: Gerrit Visser [mailto:gerr...@psgv.ca]
> > Sent: January-31-21 11:06 AM
> > To: 'Enhanced Machine Controller (EMC)'
> > Subject: Re: [Emc-users] EDM from scratch
> >
> > Issue 168, Oct 2010 is the first installment
> >
> > Gerrit
> >
> > -Original Message-
> > From: John Dammeyer [mailto:jo...@autoartisans.com]
> > Sent: January 31, 2021 1:31 PM
> > To: 'Enhanced Machine Controller (EMC)'
> > 
> > Subject: Re: [Emc-users] EDM from scratch
> >
> > Andy,
> > Check out this page:
> > http://mikesworkshop.weebly.com/a-spark-erosion-apparatus.html
> >
> > Also Model Engineer's workshop had a 4 part series on building one.
> > I'll go through my archives and see if I can find them.  I'm pretty sure I
> had all 4.  An online search doesn't pinpoint which issues.
> >
> > John Dammeyer
> >
> >
> >
> >
> >
> > ___
> > Emc-users mailing list
> > Emc-users@lists.sourceforge.net
> > https://lists.sourceforge.net/lists/listinfo/emc-users
> 
> 
> 
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> 
> 
> 
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Re: [Emc-users] EDM from scratch

[Thomas J Powderly]

Hi Gerrit

the difference between senkung and draht erodien generator

is the pulse width

in wedm 1-10uS is the entire spectrum

in sink edm 1-3000uS is the spectrum

in any edm that uses the very sort pulse,

it is important that the current shut-off be complete and very fast ( 
all inductanc ein system must be watched)


if you can turn the power OFF very very quickly, you will increase the 
metal removal a LOT.


the reason is

the metal removel is the expulsion of a tiny crate pool of molten material

if the thermal change ( from current supplied an heating the pool)

to the time hwne current is removed and the thermal mass of the 
surrounding environment ( oil water gas )


that makes for a more IMplosive force on the hot plasma bubble channel 
over the pool.


The quickness of the bubble collapse cause more of the puddle to be ejected

a slower deflating lets most of the melted material to cool back on the 
surface


look for Dr. Schumakers description from AGie

i cant find it now but it was an excellent presentation of how a spark 
removes material


the 9 or so pictures are a whole edm education

but try this instead

https://core.ac.uk/download/pdf/34635871.pdf

best of luck with the wedm

(btw it will be a good hole drill spark generaor if it works for wed, 
just needs up to 100uS max on time )


tomp

On 2/1/21 12:53 AM, Gerrit Visser wrote:

Another source of information about pulse generator design: 
https://langfordw.pages.cba.mit.edu/desktopWEDM/electronics/

https://www.cnc.info.pl/drazenie-metoda-domowa-moje-proby-t11692-20.html 
(Google translate helps here:-))

Again, my focus is on wire EDM but there must be similarities

Gerrit





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Re: [Emc-users] To Sam Sokolik re opencv on linux

[Gene Heskett]

On Sunday 31 January 2021 16:03:55 Sam Sokolik wrote:

> Ok.  I found the config/python script I was working on...  Late 2014..
> Boy.  I will put them up somewhere tonight..
>
Great, Sam. But in 2014, weren't you using camview?

My experience has been that its slow, and buggier than a ten day old road 
kill carcass in August. Or, I've had a whole row of bad cameras. If the 
axis display is expanded on a 1920 by screen, to the  point where the 
autosize has to start expanding the image to fill the tab, by even 1 
pixel, every camera I have tried has gone away to a black screen. 
Stopping linuxcnc and running cheese can't find a camera and requires a 
machine reboot to restore the camera to functional.  Now I've found a 
higher resolution camera that is spindle mounted and much sharper that 
just works, and I've installed eclipse and opencv and hope to get that 
working. Its a hundred bucks, has a cheesy mount that is very fiddly to 
adjust for parallax and certainly won't survive running into a fixture 
bolt, but the image is several times sharper too. I've got at least 2 
versions of camview, but the machine I was going to use it on lost its 
video about 18 hours after updating it to buster.  Onboard video on one 
of the now elderly D525MW boards.

So, I've a couple boxes of Dell's with i5 cpu's headed this way.  They 
should have the cajone's to run LCNC for a good long time.  And it will 
put me with 3 machines all alike plus one to program mesa cards with 
plus the pi4b running the biggest lathe.  And a trailer load of old 
stuff to clear out come warmer weather.

Anyway send me a url when you can.  And thanks a bunch.

[...]

Cheers, Gene Heskett
-- 
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
 - Louis D. Brandeis
Genes Web page 


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Re: [Emc-users] EDM from scratch

[Thomas J Powderly]

Hi Andy

if your path is a straight line
dont use linuxcnc , just hal

use steppers to advance
use an opamp window comparator
with a too high and a too low threshold

when your measured voltage is too high advance 1 step
else dont move, just wait
if too low, turn off the power , maybe retract
no linuxcnc needed
it cuts as fast as it can automatically


in most edm (any electrode material to steel workpiece ) the optimal gap 
voltage is near 30V=

its almost 2 volts lower when roughing
and 2 volts higher when finishing


The discharge voltage Ua) varies with 'paarung' the pairing of material, 
so for carbon wheel to wolfram, its will be even less,

i have seen stable cutting al low as 18V ( do not try to go lower )
a transistorized or FET generator is way better for MMR and wear.

to cut carbidem use a carbon of copper-graphite or copper tungsten wheel

edming carbide is mostly removing the binder.

using parrafinics is better than water but requres filtering and pumps
the nature of edm grinding is the 'best' flushing in all edm realms ( 
sink, orbiting, wire, hole drill )
because the tool to workpiece junction is continuosly new (like wedm, 
but free on each side, unlike wedm )

so a bath of 'white spirits' may be enough

on AGie edm-grinders ( used mostly by sewing machine companies ) they 
used thin ( low -visc) edm oil


there is no such thing as edm oil, its merely a layer in the cracker 
tower that is removed and labeled (kerosene or edm fluid or axle grease)

get a copy of the OEL-HELD book on edm fluids

a higher supply voltge ( 80-100V=) makes it easier (and more accurate) 
for a comparator to decide wether to adance , hold still, or retract.


a use of adaptive feed wull never apprach the needed jittery advance of 
edm, adaptive feed never reacts negatively, it can only reacts 'less-ly'

the motion techniques for mills is not the motion for edm.

I did a lot of work for Union Special on such machines 
http://www.unionspecial.com/


are you using a lathe spindle as the edm spindle?

the plans that Garret Visser link to at MIT are a good idea
previous 'the garden of edm' was good but remains unfinished
https://cscott.net/Projects/FabClass/final/edesign1.html

oh, splash/spray guards are neccesary, high rpm is not


hth
I'm kneedeep in rpi-gpio driver here . is **cp same as [] ??

hahaha i have to write a lot of test code to see how the original code 
worked.

best o luck

tomp


On 1/31/21 8:28 PM, andy pugh wrote:
I have started to play around with EDM. The intention is to make an 
EDM "grinder" to profile tool steel and possibly carbide cutting tools 
using CNC-turned profiles. At the moment I am using a cobbled-together 
XY table with a couple of STMBL drives. One of the STMBL analogue 
inputs is used to measure the current through the gap. (ie using the 
voltage across the resistor that a capacitor is charged through). Then 
a PID controller tries to achieve a target current by adjusting the 
adaptive feed pin. I think that it shows promise, but only partly 
works. I am using a 50R resistor and a 1000uF capacitor. I suspect 
that this is too high on both counts. I am working at 40V and it seems 
that the tool welds to the work too readily. I suspect that I would 
get different results if I controlled to the gap voltage, rather than 
charging resistor voltage. And probably better still with some sort of 
signal processing on that voltage. What combination of R, C and V 
would be typical for a servo-controlled eroder? I imagine it might be 
different to a "doorbell" style one. Current set up: 
https://youtu.be/nxpmEFnmK-A



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