Comparing 4 types of tact switch: ALPS unsealed, ALPS sealed, Omron sealed and TE sealed
Established in September to October 2010, for the ALPS and Omron switches (Part 1)
This considers Omron and ALPS sealed
tact switches as replacements for the TB-303 and TR-606, with some
consideration of the TR-808 and JP-8 (and a few other Roland devices)
which need a stem-less tact switch.
I decided that the Omron sealed tact switches were a better choice than the ALPS ones.
Part 2 -Extended to cover the TE sealed tact switches in May 2015 (Part 2)
Josh Forgione in California kindly alerted me to some TE sealed tact
switches, and sent me some samples. I considered these as
replacements for TB-303s and TR-606s and find them a possible
alternative to the Omron switches.
I am also interested in replacements for the Cyclone Analogic Bass Bot
(TT-303), which uses surface mount unsealed tact switches. The TE
ones have stems which are too small for the Bass Bot buttons. There is a workaround for this, but the
best option I know of at present is to adapt the Omron sealed switches
for surface-mount (Omron doesn't make SMT sealed 12mm tact switches).
Part 1: Comparing 3 types of tact switches (ALPS and Omron)
This section was written in September to October 2010 and has not been updated since.
Tactile (tact) switches are momentary action on/off
switches. This page is a comparison of three types of tact switch
which could be used in the TB-303. This discussion applies
directly to the switches used in the TR-606, and more generally to
stem-less versions of the same kinds of switches, as used in the
TR-808 and JP-8. For more discussion of those
switches, and for details of how to modify the Omron sealed tact
switches discussed here, so they fit the TB-303 / TR-606 buttons nicely, please see:
That page also contains a datasheet for the Omron switches.
Since August 2010, we are installing the modified Omron switches
in Devil Fishes. As a service to people who want to replace their
own switches, we are also selling packs of modified Omron
switches. Please see these sections of the main Devil Fish page:
Since our choice of Omron switches implies a criticism of the use
of the original unsealed ALPS switches, or the other alternative –
sealed ALPS switches – and since the reliability of these switches is
so important, I have created this page to give people some insight into
the characteristics of these switches, and why we chose the Omron
To the main Devil Fish page.
An update history is at the end: #updates
Dust appears to cause tact switch failure
Before mid-2010, starting with the first Devil Fishes in 1993, I
installed the original kind of unsealed ALPS tact switch, with a "dust
guard" – a thin mylar sheet with holes punched in it for the switch
stems and LEDs. (The plastic was from a 3M overhead transparency
protector.) This greatly prolonged the life of the switches – I
guess by a factor of 5 or 10.
The failure mode of these switches
is that they become erratic and "bounce" – more than one open-close
transition when pressing or releasing the switch, as detected by
whatever de-bounce algorithm which is implemented in the TB-303's CPU's
firmware. As far as I can tell, the reason is that dust, I guess mainly
100% protein flakes of skin, get inside the switch and are compacted
into thin layers on both the stationary contact and the moving metal
contact which clicks down against it. With a badly bouncing
switch, the coating is thin and appears to be
transparent. It is visible under a stereo microscope, and easily
removed once the switch is dismantled. I have seen no sign of
corrosion or actual wearing of the metal contacts. The
switches, once dismantled, can't be re-assembled, so this is not a
method for fixing erratic switches. They must be replaced.
The dust guard reduces the amount of dust around the switch which
can enter via the circular gap between the moving shaft and the metal
the body of the switch. This lends support to my theory that dust
is the cause of failure, since the dust guard can't affect any
corrosive elements in the atmosphere, or the actual mechanical movement
of the switch. The electrical current in the TB-303 switch
scanning circuit is very low – about 0.3mA, with an open-circuit
voltage of about 5V. I think this is probably too low to "self-clean" the
contacts, by way of a little spark or similar.
Perhaps increasing the drive current, by altering the 15k resistors R223, R219,
R218 and R48, say to 1k or 2.2k, would introduce some kind of
self-cleaning current. I have never tried this. It is
difficult to anticipate the long-term impact of this, since perhaps
that process would also erode the metal surface, leading to corrosion
or other problems.
I was pretty happy with this dust-guard approach, since I think that an
intensively used machine without such protection might need its
switches replaced after a year or so, and it was clear that the dust
guard greatly extended this time.
However, there were some instances of these replaced switches
becoming erratic after 7 to 10 years, at least with the machines which
were intensively used. Ideally, we would replace the switches and
no-one would have to worry about replacing them for decades, even if
the machine is intensively used.
Searching for alternatives
In mid-2010 I evaluated two kinds of alternative tact switches. I
hadn't been aware that a sealed ALPS tact switch had been available for
some years. I purchased some Omron sealed tact switches and
started using them. These Omron switches had stems a little too wide
for the TB-303 buttons, so I developed an elaborate jig with a small
grinding wheel on a high-speed drill press to grind down the four sides
of the top of the stem, evenly, about a thickness of human hair. This
was difficult and error-prone. Later I devised a simpler technique of
cutting the stem twice, to make it springy. This is described in ../303-mods/
During this time, I became aware of the sealed ALPS tact switches and
purchased 100 of them. I found they had a very poor feel compared
the original unsealed ALPS switches and the Omron switches. There
little travel in the "click" operation, and little difference between
the force required to activate the click and that required to hold the
switch closed once it was in the down state. (This was not a bad
batch of switches. I was later sent some of these switches by someone
who sells them, and they feel identical to the ones I tested.)
I kept two of these switches and returned the remainder.
I can't be absolutely sure these Omron switches will last a long
time. However, their datasheet specifies their life as 3 million
operations. There's no specification for what this means, but
this is a high number for a switch.
I think that as long as dust is excluded, and the switches are not
exposed to a corrosive atmosphere, then they will last a very long
time. The Omron switches are completely sealed against dust and
Summary of results
The short version is that the Omron
sealed tact switches have a very good click feel, at least as good as
the original unsealed ALPS switches. They involve a somewhat
higher activation force, but I think that is fine.
The sealed ALPS switches which we purchased had, in our opinion, a much
poorer click action. The travel was much smaller and there was
less difference between the activation force and the holding force:
that required to hold the switch closed in the downwards position
before it snaps up.
According to the spec sheets,
both the original and the sealed ALPS switches have the same travel:
0.3mm. However, our experience is that the sealed ALPS switches
have a much shorter travel between the point where they snap downwards, and the downwards position.
I intend to obtain some sealed ALPS switches from someone who is happy
with them. When I do, I will update this page to confirm or
reject the possibility that the sealed ALPS switches we tested behaved
differently from the switches that this supplier, and his customers,
are apparently happy with.
If you accept our choice –
if you lack a profound
curiosity about the inner workings and behaviour of tact switches –
then there's probably no reason to read further.
In early September 2010, I did some simple tests on the switches and
put them up on the 303-mods page. These tests, of activation and
holding forces, were in accordance with our judgment about the
clicking actions of these switches.
A few days later, I figured out a way of doing better tests. The
results of those tests are detailed below. I removed the earlier
test results from the 303-mods page.
The most important results can be summarised, but first a few terms I invented for these tests:
- Activation force. The force required to almost bring the
switch to the point where it clicks to the downwards state. This
is measured in Newtons, where 1 Newton is the force exerted by the
Earth's gravity, at sea-level, on an object whose mass is about 102
- By the time this activation force is applied, the stem will have
moved somewhat from its zero force position. This movement is
what I call the "Initial Displacement".
- Holding force. Once the switch is in the downwards state,
the force which is required to keep it down. This is less than
the activation force, due to the snap-action hysteresis of the
switch. Once a force less than this is applied, the switch snaps
back to the up position. That new "up" position is not necessarily fully
up, as with no force, and it may be marginally higher than when the
activation force is applied in the Up state.
- Delta force = Activation force - Holding
force. This is how much force must be removed after pressing the
switch down with the Activation force, before it will snap up.
ratio, as a percentage = 100 * Delta force / Activation force.
This is the ratio of the Delta force as a fraction of Activation force.
- Click displacement. The distance between the position just mentioned – with the Activation force, or just a little less, applied –
and the Down position after the switch has clicked, and a force similar
to the Activation force is still being applied. The stem may go
with greater pressure (probably only the Omron sealed switch would do
this, since it involves a thin synthetic rubber sheet transmitting the
force), but this "Click displacement" is the distance we feel the
stem fall when the switch clicks.
Here is a summary of the most important measurements. "mN" means milli-Newton.
|Original unsealed ALPS
Please note that these tests were not done in a fancy laboratory
did not attempt to sample multiple batches of switches. The
force measurements for the sealed ALPS switches were based on two
switches and the displacement measurements were based on one of these
The figures in red show how different the sealed ALPS switches (at
least the ones I tested) were from the other two types:
The Activation force of the sealed ALPS switch was higher than that of the other two switches.
The Holding force was much higher – nearly twice that of the other two switches.
The Delta force was less than half that of the other two switches.
The ratio of the Delta force to the Activation force was much lower:
about 38% of that of the Omron switch and about 35% of that of the
unsealed ALPS switch.
The Click displacement was much less – only about 55% of that of the others.
I tested 10 unsealed ALPS switches for forces, and chose two of them
with close to average forces for the displacement tests. I used
10 sealed Omron switches in the same way. I only have two sealed ALPS tact switches, and one of them I had partially
dismantled. So I used those two for the force tests, and the
non-dismantled one for the displacement tests.
Even allowing for variation between batches, the differences between
the ALPS sealed switches and the other two types are highly significant, and
explain why we felt their click action was so poor.
Maybe some people like a lower Click displacement and lower Delta force, but we don't.
Details of the switches
The photo above shows the three types of switch. The ALPS site http://www.alps.com
and Omron sites http://www.components.omron.com
have rather long and perhaps not stable URLs. These are all 12mm snap-in tact switches.
- ALPS unsealed tact switch SKHCBEA010, previously known as SKHCAA. These are the same as were used in the TB-303, and are still in mass production nearly 30 years later. URL
Force: 1.27 Newton (~130 grams)
Operating life (5V, 5mA): 1,000,000 cycles
- ALPS sealed tact switch SKQEAAA010. URL
Force: 1.57 Newton (~160 grams)
Operating life (5V, 5mA): 10,000,000 cycles
- Omron sealed tact switch B3W-4050. URL Datasheet archives here: ../303-mods/Omron-Tact-Switches-2010-B3W_1109.pdf .
Operating force (max): 160 grams (~1.57 Newtons)
Release force (min): 30 grams (~0.29 Newtons)
Pretravel 0.29 to 0.32mm
Service life (min): 3,000,000 operations
Width of top of stem: 3.8mm +/- 0.1mm. (But I measure 3.84 to 3.33mm in one dimension and 3.83 to 3.82mm in the other.)
The Omron datasheet contains this graph which relates force (vertical scale) to displacement (horizontal):
The lower curve applies to the B3W-4050. I am pretty sure that
these curves are an artist's impression. The real displacement is
less on the way to 150 grams: 0.164mm. Then (according to our
tests), the switch snaps and goes towards the bottom of its travel,
which takes it another 0.234mm, for a total travel of about 0.4mm.
Here are some pictures of the insides of the switches.
They all operate by the centre of the spring disc (phosphor bronze or
beryllium copper, I assume) popping inwards, inverting its normal
concave shape. Here is a 15 second video of popping some isolated
discs. (Sorry about the erratic brightness.)
Each of the 4 videos on this page is available in two
formats: 3GP and Real Video. Both of them play OK with the
free version of Real Player for Windows XP: http://www.real.com
. Please let me know if you have any difficulty viewing the videos.
Here are some more photos of the switches.
The unsealed ALPS switch has its stem with a cylindrical flat-bottom
plunger, which presses directly against the top of the disc. The
disc is shown in its normal orientation (curve up) on the left, and
upside-down, to show the contact surface on the right. While the
centre of the disc pops in, the disc doesn't pop inside out. So
it is still being pressed against the two contacts at the top and
bottom of the circular cavity, while, in its down state, the centre of
the disc (which is plated with something more silvery) is also pressing
against the centre contact.
The sealed ALPS switch on the right has its disc entirely enclosed by a
thin adhesive plastic cover. The plunger at the bottom of the
stem has a hemi-spherical shape, and presses against the plastic sheet,
which is stuck to the disc. So the sealed switch has a more
acutely focused force on its metal disc than the unsealed one.
The plastic seal looks like it would do a good job of keeping out dust
and any liquid which didn't dissolve the adhesive. I imagine the
hemi-spherical plunger would soon wear a hole in the plastic, but that
wouldn't affect the operation of the switch, or the sealing against
dust and liquids, since the entire bottom surface of the plastic is
adhesive, and so it is stuck to most of the top of the disc.
(BTW, the groovilicious triangular graph paper is "L110X Isometric
grid", by Gormack Graph Papers, Christchurch New Zealand. I think
it is from the late 70s or early 80s.)
This is the Omron sealed switch, with the one on the right modified so it fits TB-303 buttons.
The black circle is a disc of 0.4mm synthetic rubber, or similar.
The bottom of the stem has a circular plunger, which presses against
this rubber, and the rubber presses against the centre of the disc.
This circular plunger would spread out the load more than the
hemi-spherical plunger of the ALPS sealed switch. I assume that
this design will not involve erosion of the rubber sheet. If
enough force was placed on the stem, often enough, I am sure this would
occur. However, there's no need for people to press the buttons
with much more than the activation force.
At first I thought the rubber disc doesn't seem to be pressed
especially hard onto the circular edge of the main body of the switch,
by the black plastic ring and the metal retaining clip. However .
. . . this picture shows the underside of the rubber disc indented from
being pressed into the circular cavity in the switch body. It is
pressed down by the black plastic ring above it, which is in turn held
down by the metal frame.
From left to right: flat cylindrical plunger of the unsealed ALPS
switch, hemi-spherical plunger of the ALPS sealed switch and the
circular plunger of the Omron switch.
The centre contact of the Omron switch is circular, with a depression in the middle –
very different from the broadly round centre contacts of the ALPS switches.
Here is a close-up of the sealed ALPS switch, with its stem
removed. I have previously pulled this adhesive plastic off, so
this is not exactly what it would look like. There are three
pieces of plastic to hold the disc in the right position.
This shows the underside of the disc of the sealed ALPS switch.
Activation and holding forces
In order to test the switches, I needed
to ensure the force was placed directly in line with the switch and
that the stem was not able to move side to side, tilt etc.
I made a little test jig which mounted the switch upside-down, on a
piece of old TR-606 front panel board, such that when I applied force
to the back of the board, the switch stem would be moved without any
rocking or eccentric forces.
The Haldex (Halda) LMV 1097 force gauge is presumably pretty accurate. This one goes to 1.5 Newtons.
I used a digital scale to decide at what point of the arm the force
should be taken from, and found it was about at the end of the
tip. (It should be about 102 grams per Newton.) I attached
a metal connector and drilled a hole in it, for the vertical bent
paper-clip force transductor rod you see above. It is important
to keep the arm, which moves according to the force, at right-angles to
the transductor rod, and to keep this rod aligned with the axis of the
The switch is inverted, sitting in the PCB, at the lower left.
Here are three videos of how I measured the forces. Its best to
watch them in order, since the first one explains the concepts.
Testing forces for the unsealed ALPS switch
Testing forces for the sealed ALPS switch
Testing forces for the sealed Omron switch
The raw results are in results.txt
The averages appear in the table in the Summary section above, and here. The units are milli-Newtons:
Holding Delta Delta
force force ratio
It can be seen from these figures that the ALPS sealed switches (at
least the ones we tested) have a much lower delta force and ratio –
meaning there is not such a positive action of the switch staying down
until quite a lot of the activation force is removed.
Measuring the displacements
I used a series of digital camera (Sony
DSC F707) images to measure the displacement of the stem under various
conditions. In the raw camera image, after rotation and unsharp
mask (unfortunately the camera was not quite focused correctly) there
are images such as displacement-ALPS-sealed-activation.jpg
. A zoomed to 0.25 version of that image is below.
In the original camera image, after rotation, 10mm is represented by 640 pixels. So each pixel corresponds to 0.0156mm.
By pasting cropped versions of such images in a row, side to side, all
in alignment vertically so their ruler part is exactly level with the
left-most image, it is possible with Photoshop to measure the downward
displacement of the PCB with the switch, in terms of pixels. If
you want to look, PNG versions of the raw-camera-scale image, and
a zoomed x 2 PNG version are named after each image. They are
not hyperlinks - add them to the URL of this page if you want to see the file.
My original plan was to use a thin piece of wire-wrap wire as the
pointer to track between the images. However, it became bent and
was no longer horizontal. So I chose features of the edge of the
PCB instead as reference points. I coloured the edge silver and
then black, so it has some bright points.
To measure displacement, for instance for the second of the two Omron
switches I tested, measuring the difference between the "Active force"
position and the "Down" position, I used Photoshop to draw a rectangle
between the same reference points on the two sub-images. The Info
window then tells me the height of this in pixels, in this case
30. This is with the zoom-x2 file, where each pixel represents
0.0078125mm. So 30mm is 0.234mm.
Here is a description of the displacements we might like to
measure with a tact switch. All these are with reference to the
Up state, in which no force is applied:
- "Active force" position. How far the stem moves when the
"Activation force" is applied. This is the force which is almost enough to
make the switch click downwards. This would be a combination of
metal disc deformation before it pops inwards, plus any elasticity in
the stem and whatever lies between the stem and the metal disc.
The unsealed ALPS switch has direct contact from the stem's plunger to
the metal disc. The sealed ALPS switch is similar. The
Omron switch has a 0.4mm thick piece of synthetic rubber, which I guess
would contribute significant elastic movement when something like the
Activation force is applied.
- Down position. After the switch clicks, and we are still applying the Activation force.
- Hold position, which may be somewhat above the Down position: how
far down the stem is when we relax the force, almost to the Holding
force, at which point the switch would click up again.
- Once it clicks upwards, if we still apply something like the
holding force, then the position may be somewhat higher then the
"Active force" position, due to elasticity.
The photographs enable the measurement of 1, 2 and 3 above. In
fact, I didn't quantify the Hold position, since it is clearly close to
the Down position for all the switches. The most important
tactile characteristic of the switch, together with the Active and Hold
forces, is the displacement between the Active position and the Down
position. I call this the "Click Displacement".
The initial movement from being fully Up to the Active force position,
is less important, since it is a smooth function of the increasing
force as the force rises towards the Active force level. I call
this the "Initial Displacement".
The individual results are in results.txt
. The final results are:
type Initial Displacement Click Displacement
ALPS unsealed 0.148mm 0.230mm
ALPS sealed 0.123mm 0.125mm
With a lot more work, and switches from several batches, it would be
possible to get more accurate figures. However, these figures are
consistent with my perception that the ALPS sealed tact switches (not
just the one I tested here, but all the ones I tried of the 100 I
initially purchased) have a very small "Click Displacement" compared to the other two switches.
Part 2: Comparing 4 types of tact switches (ALPS, Omron and TE)
This section was written in May 2015.
The TE sealed tact switches
The TE switches of interest are:
1571219-1 without locating posts
1571219-2 with locating posts
The TB-303 and TR-606 have holes for locating posts, but either type of
switch would do, since the actual location is fixed by the four pins,
with or without locating posts. Here I will refer to the
1571219-2 as simply "the TE switch", however, at Digi-Key, the -1 is
significantly less expensive and so might be a better choice.
TE Connectivity is a big company with a vast range of products.
Here is how I found information about these switches in May
2015. From this page:
there is "Tactile Switch" section with a link to another section with 176 switches:
instructed to save to disk:
Searching for sealed tact switches (long URL
) I found the page for the 1571219-2 (really long URL
) both of which illustrate a different switch, without a stem. (The 1571219-1 page is here
These switches have stems. The -1 and -2 pages link to the same
PDF drawing, ENG_CD_1571219_F1.pdf , with a PDF date of 2008, from Tyco
Electronics Harrisburg PA. These pages are not very helpful,
since it is difficult or impossible to discern which have locating
posts. The Tyco Electronics catalog just mentioned, also from
2008, is a little more helpful. Page C40 has a chart of the
various options with product keys and part numbers. Here is the
Digi-Key carry these 12 x 12 mm tact switches. The prices are USD$ for quantity 100, 2015-05-06.
1571219-1 Through Hole without locating pins $0.5902
Through Hole with locating pins $1.2078
1571217-3 SMT with locating pins $1.4438:
Here are my photos:
The Bass Bot's unsealed tact switch
For reference, here is a photo of the insides of the unsealed tact switch from a Bass Bot.
ALPS unsealed SKHCBEA010 ~140 gm
65 gm 7
Mechanical characteristics of the stem
Before considering the feel of these switches, here is a discussion of the size of their stems.
I measured the dimensions of the approximately square stems
of several switches:
ALPS unsealed SKHCBEA010 (SKHCAA) 3.765 to 3.770 mm
ALPS sealed SKQEAAA010 3.760 to 3.780 mm
Omron sealed B3W-4050 3.870 to 3.880 mm
1571219-1/2 3.785 to 3.810 mm
3.880 to 3.890 mm
The brand name of the switches originally installed in the Bass Bot is unknown.
In addition to replacing switches in TB-303s and TR-606s, I am looking
for SMT (ideally) sealed tact switches to install in the Bass
Bot. In the future we plan to do Devil Fish mods on these, and
the sealed switches which come with the machine will not do, since they
will inevitably be contaminated by dust in the years to come, and so
become erratic. Below I discuss the suitability of the TE sealed
The first question is how the sealed switches fit the TB-303 / TR-606 buttons
ALPS sealed: http://www.firstpr.com.au/rwi/dfish/303-mods/#1
These fit well.
The stem is too big. I cut them
with a special circular saw jig (as shown above), but you can do it
with a fine hacksaw. Then they fit nicely since the four sections
spring inwards a little.
The stems may be made of nylon, and they are difficult to file to a
smaller size. A more serious objection to filing is that it is
impossible to file all four sides in perfect alignment, so the button
position would typically be rotated somewhat by filing. Cutting
is the only way I know to make these switches work in the TB-303 or
They are a very tight fit. You could probably file them a little to get them to fit better, and since there is not much to be done to achieve this, you might be able to do so without risk of altering the angle of the buttons. In
principle I could use the cutting jig, but there is more plastic to cut
through than with the Omron switches, due to a much smaller hole in the
stem. Also, I suspect that the stem of the TC switches is a
harder, less flexible, plastic than that of the Omron switches.
This may not matter, since the stem is only marginally too big and so
would not need to bend as much as the four sections of the cut Omron
The second question is how well these stems fit the Bass Bot buttons
These are far too loose. However,
by laying 3 or perhaps 4 layers or plumbers' Teflon tape over the stem
and then pressing the button down, the button seemed to fit reasonably
I have no plans to use these switches, since I don't like their
feel. I was surprised to find no matching long-life (sealed) 12mm
tact switch in ALPS' surface mount tact switch list: http://www.alps.com/prod/info/E/HTML/Tact/SurfaceMount/SurfaceMount_list1.html
These fit the Bass Bot buttons perfectly.
These are too loose. However, by
placing two layers of plumbers' Teflon tape over the stem, the button
can be made to fit quite well.
TE do make an SMT version, so this might be a suitable choice over
using Omron through-hole switches with their pins bent and
trimmed. However, I would need to test this extensively to ensure
the Teflon tape did not introduce any errors in button location, and to
be confident that after years of use, the tape would not compact or
soften and so cause the button to come loose.
The switches have somewhat different heights for the bottom of the button with respect to the PCB
I think this is not critical for the TB-303 and TR-606 which both have
a thin aluminium panel through which the buttons protrude, enabling the
button to work freely over a wide range of mounting heights.
However, the Bass Bot has a polycarbonate front panel around the
switches on top of the molded ABS case. The combination of the
two is 3.5mm thick. Since the distance from the rim of the button
(which is inside the case) and the top is about 4.7mm, this leads to
the top of the button being only 1.2mm above the panel, if
it was possible to exactly align the entire front panel PCB at exactly
the right distance that the rim of the button just gently touched the
inside of the case. This is difficult or impossible to
achieve. It may be possible to mill or rout (or maybe abrade with
belt sander) the inside of the case, at least around the button holes,
to reduce the thickness and so to allow the PCB to be close to the
case, with the top of the buttons higher above the front panel.
The height above the panel needs be considered in light of the travel
of the stem as the switch is activated, and in the next sub-section I
describe how the TE switches have a greater travel than the others.
ALPS unsealed SKHCBEA010 (SKHCAA) 4.4 mm
ALPS sealed SKQEAAA010 4.2 mm
Omron sealed B3W-4050 4.4 mm
1571219-1/2 4.6 mm
Fortunately these heights are pretty close to each other.
I no longer have the test jig from 2010 - nor the patience . . .
The TE switches have a higher activation force (that required to cause
the stem to depress and the switch to close) than the Omron or any of
the other switches. They have a very positive click action, with
a long travel distance when this happens. They have a higher
delta force (how much the force must be reduced to cause the switch to
spring up and turn off) than the others, the delta force percentage
(100 minus the release force as a percentage of the activation force)
is higher too. I think they feel good - and I think the
activation force is not excessive.
Here are fresh measurements of the switches, using a micrometer for
travel distance and digital scales (with the switch sitting on the
scales, pressed via a plastic ruler, to enable the elasticity required
for the switch to click) to estimate the force of activation and
release - with the delta being the difference. For simplicity,
the forces are in grams as force, not in the proper unit of
measurement: the Newton, which is the force exerted by gravity at the
Earth's surface on a mass of about 102 grams.
Activation Release Release
ALPS unsealed SKHCBEA010 ~140 gm ~65 gm 46% ~75 gm 0.40 mm
ALPS sealed SKQEAAA010 ~175 gm ~135 gm 77% ~40 gm 0.26 mm
Omron sealed B3W-4050
~132 gm ~86 gm
65% ~46 gm 0.35 mm
~200 gm ~76 gm
38% ~124 gm 0.88 mm
169 gm 93 gm 55%
73 gm 0.29 mm
I only tested one Bass Bot switch. There was a spread of values
for the TE switch forces over the four I tested: 200/68, 200/86, 195/73
and 207/78. The forces for the original ALPS switches varied
I do not like the feel of
the ALPS sealed switch. The others feel OK to me. I am
happy with the force, feel, travel etc. of the Omron switch, but the TE
would probably be fine too. It has a significantly greater travel,
higher force and much higher delta force, so its click is very clear and pronounced.
We will keep using the Omron B3W-4050
for the TB-303 and TR-606. They have worked fine for the last
five years and I have a cutting jig. The TE switches could be
used, but I would probably need to file them down on two or four sides,
which I think would be more difficult and error-prone than the cutting
We will keep using the B3W-4000 for the TR-808.
For the Bass Bot I will try using B3W-4050s with their leads cut and
bent to suit the SMT arrangement. An alternative would be to use
the TE sealed SMT version, but this would require Teflon tape to keep
the buttons in place, and I would need to check that the 0.43mm extra
travel was not a problem, considering how little the buttons project
above the Bass Bot's front panel.
- 2010 September 5: Initial version.
- 2010 October 26: Confirmed that there was nothing unusual
about the ALPS sealed tact switches I tested. I had previously
written that perhaps the switches I tested were from a "bad batch".
- 2015 May 5: Added Part 2 for the TE switches.
© Robin Whittle 2010 – First Principles and Real World Interfaces
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