I have to say someday I’d like to make my own metal buttons.
In the past, I’ve covered Microchip’s mTouch metal-over-cap technology (here and here), which uses capacitive technology.Â Microchip has a groovy app note which shows some of the ways you can use it, and has an eval kit available for ~$150 (base mTouch kit plus metal over cap accessory kit).
Now TI has a reference design for creating your own metal buttons using TI’s inductive sensor technology.Â TI’s reference designs provide that: a reference design with layout, calculations, and notes.Â You can’t buy them pre-made, but you can use them as a good starting point.
I’ve glanced through the manual for this reference design, and it is full of good info – and the design is pretty neat, too.Â For example, it includes two different haptic types, ERM/LRM and piezo.Â I have the HapTouch Booster Pack which features the same ERM/LRM haptics technology, and I’m not too impressed – it’s similar to the haptic feedback from a current smartphone.Â (Note that I think the problem is with the basic ERM/LRM technology, not the controller).
Other approaches to non-moving metal buttons include piezo electric and ultrasonic.
March 19, 2015 No Comments
As I’ve mentioned before, I’m planning on getting a keyboard with mechanical Cherry keys.Â I had a challenge: how to figure out color to get?Â For example, the Leopard keyboard is available with Brown, Blue, Black, Red, Clear, or White keys.Â (The Cherry color refers to the stem color, as you can see above, which indicates the feel of the key.)
Since I don’t feel like ordering and returning a whole bunch of keyboards, I added the readily available colors to my most recent connector order; Mouser and Digikey sell the individual switches for $1.00-$1.50.
Even without a key cap, I can tell my order of preference:
- It’s Blue for me.Â I really love the feel of the blue button; it has a great tactile break-over feel, with a satisfying but not too loud click.
- The White is OK; it has some break-over, and is quieter than the blue.
- I’ll pass on the Black for typing; it has a linear response, and just feels “blah” for typing.
So now I’m comfortable with a choice of Cherry Blues, for less than the cost of returning a keyboard.
Update 7/2/2012: when I wrote this, I couldn’t find the geekhack.org Cherry key switch guide.Â Apparently, it’s gone, butÂ Overclock.net has some good info on mechanical keyboards, including the various flavors of Cherry switches.
May 31, 2012 No Comments
At the Design West 2012 / Embedded Systems Conference I had the opportunity to try out a unique technology: Microchip Technology’s mTouch metal over cap buttons.Â This technology provides the capability to fairly easily create affordable custom non-contact metal buttons.
Since this technology uses capacitive sensing, the buttons are non-contact and should have a long life.Â However, they’re still very short stroke and thus provide very little mechanical feedback.Â Microchip’s demo used LED point lights to provide feedback.Â Microchip’s demo kit currently isn’t available for sale, but they said it was coming sometime, probably for less than $100.
You could use this technology to make ESD-safe buttons.Â However, since the metal needs to bend a bit, it won’t be as rugged as the more expensive anti-vandal buttons.
I’ll probably buy the demo kit when it comes out, because it’s a cool gadget…
May 1, 2012 No Comments
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.Â 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.Â 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.Â 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,Â 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.Â Â I have the connected theÂ 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).Â However, because there’s no mechanical feedback, you can’t tell if you’ve successfully pressed it.Â 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.Â 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
Maybe, just maybe, I’m finished writing about buttons for a while.Â Â 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.Â 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.Â The IHS models are panel mount switches start at ~$40.Â The IHL models are unique: they have a linear 0.5->4.5V analog output over the switch’s 4mm travel, and cost ~$60.Â 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.Â The ceramic material makes for a very cool looking button; see the PDF datasheet for pictures.Â Prices start ~$25.
November 14, 2011 No Comments
While looking into ESD-safe buttons, I discovered quite a few metal buttons with no moving parts.Â These buttons do have some potential advantages including:
- Easier to use in ESD-safe applications (since there is only one part to ground, and many models are made of conductive metal).
- Great durability, up to 50 million cycles or more, since there is no mechanical wear.
- Better washdown and cleaning for medical and similar applications, because they have fewer cracks to hide nasty stuff.
- Better resistance against vandals (since the exposed part is made from one piece of metal).
Potential disadvantages include:
- No tactile feedback; great feedback is one of the best features of a good pushbutton.
- Very limited current switching ability; many mechanical switches can easily handle 10A currents.
- Potential problems with gloved fingers not actuating the button, or with water or nearby objects actuating the button.Â I suspect in most cases you won’t have these problems, but you should verify first, starting with the datasheet.
- 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.Â 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.Â 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.Â Cases are made of plastic, anodized aluminum, or stainless steel.Â Illumination options are none, spot (1 LED), and ring.Â 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.Â 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.Â 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.Â Illumination options are none, point, and ring.Â 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 use a sensing technique similar to capacitive touchscreens.Â They can have problems with gloved fingers; however, Atmel claims that many gloves (including typical household, medical, and clean room types) should work fine.Â 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.Â The CSE 16 models were round metal switches, while the uG models were designed to be used under glass.Â 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.Â The CP line will be available in 16 mm, 19 mm, and 22 mm sizes with anodized aluminum cases.
- Texzec‘s ActiveMetal buttons use ultrasonic energy trapped in resonant cavities. Â Available materials are stainless steel, aluminum, plastic, and zinc alloy.Â Sizes include 19mm, 22mm, and 30mm.Â 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).
I haven’t seen any metal ones, but there are some plastic models, such as theseÂ from Banner Engineering.
November 10, 2011 No Comments
This was supposed to be a quick post on one piece metal buttons.Â 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.Â 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.Â 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.Â 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.Â 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.Â 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.Â What characteristics would help?
- Be able to ground the both the body and the actuator.Â A single piece, non-moving body is ideal if it can be grounded and is conductive or dissipative.
- Everything that an operator could touch must be made of conductive or dissipative materials such as stainless steel.Â If the button is illuminated, the plastic lens would have to be made of dissipative material.
So what are some possible solutions?
- 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.
- Two piece conductive metal buttons such as a stainless steel vandal-resistant pushbutton (available from Schurter, ITW, and many others).Â As noted above, you’d have to figure out how to ground both pieces.
- 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.Â One advantage: if you use a clear, dissipative plastic for the moving part, you can use an illuminated pushbutton underneath.Â This ESD-safe cover will probably cost substantially more than the pushbutton.
- Spray on anti-static spray.Â 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
These pushbuttons aren’t well suited for the typical system integrator.Â They’re all designed to mount on a PCB, use a SPI interface (readily available on microcontrollers, but not on PCs or PLCs), and require complex programming.
Most models use a monochrome LCD with a backlights of varying complexity.Â Here’s some product highlights from the three companies I know about:
NKK has the best distribution by far; their distributors include Mouser and Digikey.Â NKK has the widest product range, with prices ranging from about $45 to $80.Â NKK also the most support; for example, I’ve seen SmartSwitch articles in Circuit Cellar Ink.
- Basic buttons include 36×24 and 64×32 monochrome LCDs with single, bicolor, and RGB backlights.
- The OLED models provide 65536 colors with a 64×48 pixel resolution, with prices around $80.
- The OLED rocker switch is unique; it includes a white monochrome 96×64 pixel OLED display, and is also around $80.
ScreenKeys is an Irish company with some normal and one unique product.
- Basic buttons include 32×16 and 36×24 monochrome LCDs with bicolor or RGB backlighting.
- The unique product is the TFT128 button, which has a 128×128 pixel, 65536 color TFT LCD display.Â One minus is that the TFT128 uses a flat, LCD-style cable for communications.Â SparkFun used to carry it at a reasonable price (~$50 IIRC), but does not anymore.
[E3] is a German company that makes pushbuttons with 32×16, 36×24, and 64×32 pixel monochrome LCDs with RGB backlights.Â The RGB backlights provide either 64 or >10,000 calibrated colors.
The SB6432 is available on-line from FunGizmos for $36.
RJS currently offers pushbuttons with 64×32 pixel resolution, a profile similar to that of [E3] pushbuttons, and RGB backlights.Â (Added 5/18/2013)
I’d still like to have an excuse to use one of these buttons in a project; maybe someday…
October 27, 2011 2 Comments
Industrial style does matter.Â Â That’s one reason I like IDEC’s LW7L flush mount pushbuttons.Â Recently I was looking at some of our old equipment with Telemecanique pushbuttons that stick out over 5/8″ — those buttons are functional, but look dated.
The LW family of buttons is extensive (well over 10,000 combinations are available), but the models I like are theÂ LW7L-M1C64MG and similar.Â What is good about them?
- They only need a light touch to operate (lighter than some other IDEC push buttons such as the HW2L series)
- High quality
- Long life LED lights available in amber, green, red, blue, white, and yellow.
- Powered directly by 24V (no resistors to worry about — I’ve destroyed LED lights from other companies).Â 6V, 12V, 120V, and 240V models are available, but I always use 24VDC.
- They are easy to install.
- The price is reasonable (around $30).Â The Telemecanique buttons were much more expensive.Â Â They aren’t the cheapest (e.g. the HW2L buttons are about $20), but I think the difference is well worth it because of the next point.
- They look great, with the square shape and flush mounting.Â The traditional round, stick out 22mm push button makes equipment look like a retro-encabulator from the 1950’s.Â I consider the extra cost over the HW2L buttons a marketing expense.
I also really like IDEC’s XW series of E-STOP switches — especially the models with a LED light.
July 10, 2009 No Comments