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Posts from — November 2011

XY Table Part 6: Determining Stepper Configuration

Since I couldn’t find a datasheet on my Sanyo Denki stepper, I decided to figure out how the motor was wired myself.  There are a variety of sources; PIClist has the best list of methods I found, and RepRap is also worth a look.

If you’re not familiar with stepper motors and their terminology (such as unipolar or bipolar), Wikipedia’s article is a good start.  A 4 wire stepper can be used in bipolar mode only, a 5 wire stepper can be used in unipolar mode only, but 6 and 8 wire steppers can be used in either bipolar or unipolar mode.

The exact procedure to use will vary depending on the motor (and its number of leads) and the equipment you have.  Since I have an 2 channel oscilloscope, I decided to use it and look at the phase differences between the leads of my Step-Syn 103-771-16.

My Step-Syn is a 5-wire stepper motor so it has one common wire connecting the center-taps of both coils, and four wires connected to the ends of the two coils.   The wire colors are black, red, blue, yellow, and orange.

The first step is to find the common wire:  the resistance between the common wire and any other wire will be half of the resistance between any other two wires.  The resistance  between the black wire and the other wires was 130 Ohms; between all the other wires, 260 Ohms.  So the black wire is the common.

The next step is to set up the oscilloscope with the black (common) wire connected to the oscilloscope probes’ ground and the two channels connected to any two wires.  You then spin the motor and adjust the oscilloscope settings (V/Div, timebase, triggering, etc) until you can capture a good set of data.  If the waveforms are 180 degrees out of phase, the wires are from the same coil.  If they are 90 degrees out of phase, the wires are from different coils.

Same Stepper Motor Phases, Normal Oscilloscope Mode
Phase Difference for Wires on Same Coil, Normal Oscilloscope Mode
Different Stepper Motor Phases, Normal Oscilloscope Mode
Phase Difference for Wires on Different Coils, Normal Oscilloscope Mode

If your oscilloscope can be used in XY mode (often used for showing Lissajous patterns), it’s even more obvious: wires from the same phase create a diagonal line while wires from different phases create a circular pattern.  My Fluke 196 doesn’t have a real XY mode, but I used a Tek TDS210 to get the pictures below.

Same Stepper Motor Phases, XY Mode
Wires on Same Stepper Coil, XY Mode
Different Stepper Motor Phases, XY Mode
Wires on Different Coils, XY Mode

If the wires are connected to the same coil, then the other two wires are the other coil.  If the wires are connected to different coils, then swap out one wire until you find two wires on the same coil.

Suppose I connect the Step-Syn’s orange and yellow wires to the scope.  The scope trace would show they are connected to the same coil; therefore, the other two wires (red and blue) are the other coil.  Or, suppose I connect the orange and blue wires to the scope; the trace would show they are connected to different coils, so I would swap out one wire (for example blue for yellow) and try again until I find two wires connected to the same coil.

The procedure would be similar for a 6-wire stepper motor, except you have to find two common wires, but the procedure would be considerably more complex for an 8-wire stepper.

The final part is determining the how to connect the wires to the driver.  Basically, connect the coil wires up using your best guess.  If you swap wires within a coil or swap the coils you will change the direction of rotation.  I’ll give a real world example in a paragraph or two.

When I got ready to connect my Step-Syn motor to my Stepnet I discovered I had a problem: the motor is unipolar only while the Stepnet is bipolar only.  The Stepnet manual doesn’t state that (there is no mention of bipolar or unipolar stepper motors), but it became obvious when I looked at the motor connection diagrams in the manual.

Sometimes you can convert a 5-wire motor to a 6-wire by taking the motor apart, cutting the connection between the two center-taps, and then bringing out the second center tap.  I did take the case off the Step-Syn, but I didn’t see any obvious way to bring out the sixth wire.

Since I still wanted to test this motor, I decided connect it to a Allegro Microsystems UCN5804 unipolar stepper driver.  I connected the black wire, Pin 2, and Pin 7 to +24VDC, orange to Pin 1, yellow to Pin 3, blue to Pin 6,  red to Pin 8, and Pin 14 (Direction) is tied to ground.  The motor rotated the direction I wanted: clockwise when viewed from the front.  Using the UCN5804 datasheet, I determined that in 2-phase drive the wires were energized in the order yellow/red, red/orange, orange/blue, and blue/yellow.  In wave mode (1 phase), the wires were energized in the order red, orange, blue, and yellow.

Swap two wires within a coil, for example, yellow and orange.  yellow is now connected to Pin 1 and orange is connected to Pin 3.  The motor now moves counter-clockwise.

November 30, 2011   4 Comments

XY Table Part 5: Finding Information

I don’t have complete information about any of the motors I selected so this post is about how I search for data.

I normally start by googling around.  In my experience Google returns better results than Bing for technical searches.  I typically start with the manufacturer (Sanyo Denki) or type (“Step-Syn”) and part number, and modify my search approach depending on the results.

If the manufacturer has a good datasheet on their website, googling will typically find it faster than going to their website.  Unfortunately, many manufacturers do not provide datasheets for their older, not in production, products.

I recommend reading up on advanced search techniques.  Here are some I use frequently with Google:

  1. Add filetype:pdf to search only PDFs (since datasheets are often PDFs)
  2. Add site:url to search only within the given URL.  For example, adding site:sanyo-denki.com returns results only from within the sanyo-denki.com domain.
  3. Use quotation marks to search for a complete phrase.  Searching for Sanyo Denki will return results that have both words in the page (but not necessarily together), but searching for “Sanyo Denki” will only return pages that has the phrase Sanyo Denki.
  4. Use a dash to eliminate search results; for example, adding –eBay will skip results with the word eBay in them.  -eBay is very handy if a whole bunch eBay sellers are cluttering up your results.
  5. There are many more, so try searching for posts about how to search…

I also look at the manufacturer’s web site; occasionally the web site’s search box returns results Google can’t find.  Sometimes you can find data based on the product line, not the specific part number (which may not appear because there are so many variations; the datasheet just lists the possible options).  For example, I received the best results for the Oriental Motor Vexta PH265L-04 by searching their catalog for PH265*.

Let’s look at some searches for the Sanyo Denki 103-771-16:

  1. Searching for Sanyo Denki 103-771-16 currently brings up 8 results, none of which look useful (and 3 refer back to here!).
  2. Searching for Sanyo Denki 103-771 brings up a lot more results, but I didn’t find any useful data.
  3. Now let’s get creative and add the wire colors: Sanyo Denki 103-771 blue red black orange yellow returns interesting looking results.  Unfortunately all of the Sanyo Denki PDFs are for newer motors that are wired differently.

So sometimes even Google can’t find what you want; instead, in the next post, I’ll look at how I determined the Sanyo Denki stepper’s connections.

November 29, 2011   No Comments

Review: ActiveMetal Metal Switch

The box

The box

Front View

Front View

Side View

Side View

Back View

Back View

I recently bought an ITW ActiveMetal button because the price was somewhat reasonable, because it uses a unique technology, and because they are no longer readily available after ITW sold the technology to Texzec.

The only distributor with any stock left is Newark; when I ordered mine, they had a total of 5 units available in 3 models.  I bought a T01-042203-006-NO-M2 which breaks down as follows:

  • ActiveMetal button using ultrasonic energy trapped in resonant cavities.
  • Zinc alloy housing.
  • 22mm size
  • 10-24 VDC input, Open collector output.  Since I’m using it with a PLC, I like 24VDC, and the open collector outputs let me use the button with sourcing or sinking inputs.
  • Bright chrome color (I also considered the mirror black color)
  • Normally open switch status
  • Momentary switch action
  • Medium sensitivity level.

The price ($37) is OK for a metal button.  The chrome looks very sharp, but might scratch easily (mine already has a scratch); I would probably pay extra for stainless steel if I were going to use them on a machine.

I won’t make any promises,  but it appears to be ESD-safe; all the exposed metal is grounded together with the black ground wire, although there is noticeable resistance when measuring between various places on the metal surface and the ground wire.

I have the button connected to a Panasonic FP Sigma PLC with PLC inputs configured as sinking (the load provides 24VDC), since I am currently using the PLC with a few PNP-output Pepperl Fuchs inductive sensors.   I have the connected the  button’s red wire to +24VDC, the black wire to ground, and the green wire and a 4.7K Ohm pull-up resistor to the PLC input.

The button does take a little pressure to actuate, so anything that presses hard enough on the button should actuate it (I tried various objects with no problems).  However, because there’s no mechanical feedback, you can’t tell if you’ve successfully pressed it.  I would always use the button with some kind of feedback; currently, I’m using the PLC’s input status LED.

If you need to press a button frequently, the ActiveMetal’s light touch could be an advantage compared to a typical 22mm mechanical pushbutton.  Recently, I was testing out an Allegro UCN5804 stepper driver using my ActiveMetal button to generate the step pulses, and I appreciated its ease of actuation.

In most cases I think I’d rather use a nice illuminated mechanical pushbutton (such as the IDEC LW7L), but if I need the unique advantages of a non-mechanical button (such as better ESD safety, longer life, or greater robustness), I’ll definitely consider ActiveMetal buttons.

November 23, 2011   No Comments

Cool Components VII: Hall Effect Pushbuttons

Maybe, just maybe, I’m finished writing about buttons for a while.   But first I want to mention a last few groovy pushbuttons.

Hall Effect Pushbuttons

Hall effect pushbuttons are cool because they have a stroke, like a mechanical pushbutton, but can last for millions of cycles.

  • ITW Switches has a wide variety of hall effect pushbuttons, including metal and illuminated large panel mount switches, such as the Series 48SS, the 48M-SS, 57M-SS, and 58M-SS.  However, availability is poor; for example at Mouser I only found a few 48SS models (but they were all less than $20).
  • C&K has the HP series.
  • APEM has the IH Hall Effect Switches.  The IHS models are panel mount switches start at ~$40.  The IHL models are unique: they have a linear 0.5->4.5V analog output over the switch’s 4mm travel, and cost ~$60.  However, I think a T-Bar or one axis joystick would be a lot easier to use, although they would typically be larger and more expensive.

Finally, I have to mention Schurter’s MSM CS series: they are mechanical vandal-resistant switches with a ceramic actuator.  The ceramic material makes for a very cool looking button; see the PDF datasheet for pictures.  Prices start ~$25.

November 14, 2011   No Comments

Cool Components VI: Non-Moving Metal Buttons

While looking into ESD-safe buttons, I discovered quite a few metal buttons with no moving parts.  These buttons do have some potential advantages including:

  1. Easier to use in ESD-safe applications (since there is only one part to ground, and many models are made of conductive metal).
  2. Great durability, up to 50 million cycles or more, since there is no mechanical wear.
  3. Better washdown and cleaning for medical and similar applications, because they have fewer cracks to hide nasty stuff.
  4. Better resistance against vandals (since the exposed part is made from one piece of metal).

Potential disadvantages include:

  1. No tactile feedback; great feedback is one of the best features of a good pushbutton.
  2. Very limited current switching ability; many mechanical switches can easily handle 10A currents.
  3. Potential problems with gloved fingers not actuating the button, or with water or nearby objects actuating the button.  I suspect in most cases you won’t have these problems, but you should verify first, starting with the datasheet.
  4. High prices, typically $20-$100 (although a comparably sized mechanical button is typically $15-$30).

I found buttons from Schurter (Switzerland), APEM (France), Grayhill (USA), Texzec (USA), C&K (USA), EAO (Germany) and Barantec (Israel); there may be others, too.  I think it’s interesting that almost all of these companies are either European or American.

There appears to be a limited market for this switch type; several companies have dropped lines soon after introducing them, and ITW Switches sold its ActiveMetal line to Texzec.  I’ll mention some of the “missing in action” lines below.

So here are some of the more interesting switches I found, sorted by sensing type:

Piezo Electric Buttons

  • Schurter has the PSE line of piezo switches, available in 16 mm, 19 mm, 22 mm, 24 mm, 27 mm and 30 mm sizes.  Cases are made of plastic, anodized aluminum, or stainless steel.  Illumination options are none, spot (1 LED), and ring.  Prices range from ~$20 (CSE 16 plastic), ~$25 (CSE 16 aluminum), ~$45 (CSE 16 stainless) and up.
  • Grayhill has the 37F series of piezo buttons.  Cases are aluminum, and prices start ~$20.
  • APEM has the PBA series, available in 16mm, 19mm, and 22mm bushing sizes, with and without illumination, and with anodized aluminum or stainless steel cases.  Pricing starts >$30.
  • Barantec has a wide range of piezo buttons in 16 mm, 18 mm, 19 mm, 22 mm, and 27 mm sizes encased in aluminum or stainless steel.  Illumination options are none, point, and ring.  Barantec only sells direct in the US.
  • C&K had the KP series of piezo buttons back when they were part of ITT Canon, but they are no longer available.

Capacitive Buttons

  • Capacitive buttons use a sensing technique similar to capacitive touchscreens.  They can have problems with gloved fingers; however, Atmel claims that many gloves (including typical household, medical, and clean room types) should work fine.  The buttons can often work through a thin non-conductive layer such as glass.
  • Schurter had several lines of capacitive switches, including the CSE16, CSE 15 uG and CSE 25 uG.  The CSE 16 models were round metal switches, while the uG models were designed to be used under glass.  Mouser still has a few CSE16 switches left at >$90.
  • EAO had the Series 75 capacitive touch buttons, but they are no longer available.
  • APEM has just introduced the CP line of capacitive buttons; as far as I can tell, they are not yet available.  The CP line will be available in 16 mm, 19 mm, and 22 mm sizes with anodized aluminum cases.

Ultrasonic Buttons

  • Texzec‘s ActiveMetal buttons use ultrasonic energy trapped in resonant cavities.   Available materials are stainless steel, aluminum, plastic, and zinc alloy.  Sizes include 19mm, 22mm, and 30mm.  As far as I can tell, Texzec has no distributors; however, Newark is selling the last of the ITW ActiveMetal buttons for ~$35 (22mm, zinc alloy).

Optical Buttons

I haven’t seen any metal ones, but there are some plastic models, such as these  from Banner Engineering.

 

November 10, 2011   No Comments

Cool Components V: ESD Safe Buttons

This was supposed to be a quick post on one piece metal buttons.  But it’s spiraled totally out of control, zooming past one post before finally settling down, I hope, on three posts.

I first researched metal buttons because I needed an ESD-safe button, and I couldn’t find one.  Plenty of buttons have specs for ESD immunity, but I needed one that wouldn’t cause ESD (Electro-Static Discharge).

ESD can create a high voltage spark which can kill nearby sensitive electronic circuits.  Everything close to the ESD-sensitive part needs to be either conductive and grounded or dissipative (material with resistance of 10^6 to 10^9 ohms/square so current will flow, but not too rapidly) and grounded.

Normal plastic is especially bad, because it is an insulator, and can be tribocharged: friction caused by rubbing the plastic part can create a large static charge.  You can get dissipative plastics, but I don’t know of any buttons that use them.

Anodized aluminum is also an insulator; for an ESD-safe aluminum part you have to use electroless nickel plated aluminum.  For example, Banner’s ESD safety light curtains use electroless nickel plated aluminum for the bodies and static dissipative plastic for the optical covers (BTW, as far as I know, they are the only readily available ESD-safe light curtains).

You can’t reliably ground through a moving part.  So if a button has a moving button, then the moving part has to be grounded with a ground wire as well as the stationery part.

While there aren’t any buttons that are advertised as ESD safe, there are some that might work.  What characteristics would help?

  1. Be able to ground the both the body and the actuator.  A single piece, non-moving body is ideal if it can be grounded and is conductive or dissipative.
  2. Everything that an operator could touch must be made of conductive or dissipative materials such as stainless steel.  If the button is illuminated, the plastic lens would have to be made of dissipative material.

So what are some possible solutions?

  1. One piece conductive metal buttons, such as a Schurter 1241.2611 PSE16 16-mm stainless steel piezoelectric button (~$45) or a Texzec T01-012203 22-mm stainless steel ActiveMetal ultrasonic button.
  2. Two piece conductive metal buttons such as a stainless steel vandal-resistant pushbutton (available from Schurter, ITW, and many others).  As noted above, you’d have to figure out how to ground both pieces.
  3. Use an ESD-safe cover: cover a regular pushbutton with a fixed body that captures a moving part (to depress the button’s actuator); the cover parts have to be conductive or dissipative.  One advantage: if you use a clear, dissipative plastic for the moving part, you can use an illuminated pushbutton underneath.  This ESD-safe cover will probably cost substantially more than the pushbutton.
  4. Spray on anti-static spray.  Although anti-static spray should help short term, I’m skeptical that it will continue to work well for a substantial period of time.

All of these possible solutions would have to be verified: you will need to verify that all external parts of the button are grounded and that the button will conduct or dissipate any static charges.

November 7, 2011   No Comments

XY Table Part 4: Stepper Motors

Sanyo Denki Step-Syn 103-771-16

Sanyo Denki Step-Syn 103-771-16

I had planned to use a Sanyo Denki Step-Syn 103-771-16 stepper motor, but since it will not work with my Stepnet, I will be using another motor.  (The Step-Syn is unipolar only and the Stepnet is bipolar only).  For more information on the Step-Syn please go to its Trac page.

Vexta PH265L-04

Oriental Motor Vexta PH265L-04

So right now I’m planning on using an Oriental Motor Vexta PH265L-04 in bipolar mode.  I’ve created a Trac page for it, too.

The Vexta was easy to connect to the Stepnet.  The Vexta really benefits from a higher supply voltage; using a 24VDC power supply, I could only reach around 600 RPM no load, but using my 48V Logosol power supply I could reach over 1200 RPM no load.  OK, that’s not impressive compared to a servo motor (my Emoteq BH023 has reached 20000 RPM), but it’s still a big improvement.

A personal note: since the Christmas season has started, I probably won’t be able to blog as much.

November 2, 2011   No Comments