Interesting observation. Many of us who are not hardware people by trade
could probably use a good primer on soldering.
Would it help to use an aluminum heat sink between the switch body and the
end of the pin? (There's not very much room, but one might be able to fit
a small heat sink in there.)
I like these switches too, so I'd like to understand the cause of the
failures people have experienced.
John
On Thu, Jan 19, 2017 at 9:56 AM, Vern Knowles <knowles.vern@xxxxxxxxx>
wrote:
I have used many Schurter switches over the years and not had any issues.
I am wondering if maybe the problems some people have had with them is
related to soldering. I just did a quick test and discovered that the
surface finish on the internal switch contacts does change visibly if a
terminal is heated to soldering temperature for more than a few seconds.
With the soldering iron I used, a couple seconds is okay but at about 4-5
seconds there was enough heat conducted into the switch to change the
contact surface finish. I have no proof the change in surface finish is
detrimental to the operation of the switch but frankly, under the
microscope, it does look somewhat “degraded”. The finish is not as nice
and smooth. It would not surprise me if the number of reliable switching
cycles is significantly reduced by this but I have not tested it. (By the
way, the switch is very easy to take apart for inspection. Just squeeze
together the two plastic posts sticking out the bottom. It is also very
easy to re-assemble. Just push it back together.)
It would be easy for someone to do some testing to see if this is a
problem. (hint, hint!).
Vern Knowles
www.multitronix.com
*From:* roc-chat-bounce@xxxxxxxxxxxxx [mailto:roc-chat-bounce@
freelists.org] *On Behalf Of *R Dierking
*Sent:* Wednesday, January 18, 2017 7:35 PM
*To:* kurtgug@xxxxxxxxx; roc-chat@xxxxxxxxxxxxx
*Subject:* [roc-chat] Re: Switch Warning - Schurter 110-220
I think the 3D printed switch arrangement that Mike brought to the meeting
is better. So are the screw-type Aerocon switches, and the one that holds
the PCB switch that someone posted. I’m doing this mostly for people that
have the 110-220 switches already in their rockets. Also, of course, I’m
looking for a reassurance for the switches I’m using in my L3 project.
I’ll definitely take the test switch apart after the testing concludes.
I’m not sure what number of cycles to stop, but I’m thinking about dropping
the test box on the garage floor every 100 cycles after 500. Really give
the switch a shock to see what happens.
I’ll be taking one of the new switches apart too. I want to see if I can
pot one of the Aerocon PCB switches inside the 110-220 switch case. So,
retrofit with no re-wiring.
*From: *kurtgug@xxxxxxxxx
*Sent: *Wednesday, January 18, 2017 5:27 PM
*To: *roc-chat@xxxxxxxxxxxxx
*Subject: *[roc-chat] Re: Switch Warning - Schurter 110-220
Hey Richard. Great work you are doing there. You should also dissect the
switch at the end of the testing to see if you can see any wear and tear on
the housing or the contacts.
I'm also interested in making a switch like what Kramer came up with, a
micro switch and screw. That could also be a viable solution.
Kurt
Sent from my iPad
On Jan 18, 2017, at 2:37 PM, R Dierking <applerocketry@xxxxxxxxxxx> wrote:
After the group of posts on this switch and other types used to arm
electronics, I wanted to run a simple test. Maybe to provide some
reassurance to people that already have this switch installed for their
project. On the other hand, there’s no way I can guarantee a favorable
result.
There were a couple of concerns voiced during the last thread for the
110-220 selector switch. One was the lifetime specified in the
manufacturer’s documentation: 300 operating cycles (without load). The
other was reports of failures including high resistance, unreliable
connection, and switches actually cracking during use.
I believe that at least some failures could be attributed to installing
what is intended to be a flat panel mounted switch on curved airframe
tube. I’m thinking that some switches are being over-tightened creating
stress on the rotatory selector.
Please see the attached photos.
*Installation:*
The hole for these switches is not ½”, but it is close. The
manufacturer’s dimensions for installation are metric. If you just drill a
½” hole, the hole will probably be too large to use the small protrusion
that should be used to prevent the switch from rotating. Please see the
arrow on the first photo. The switch doesn’t have to be tightened much at
all on the mounting panel. Unfortunately, I’ve never seen any
documentation on installation when you buy them. Anyway, you should drill
a smaller hole, and gradually increase the size until the treads just
clear. Also, the notch needs to be filed for the small projection to
prevent rotation.
*Durability:*
To test the lifetime, I installed a *new* switch that powers a small
light bulb (9 volt battery for power) and also has posts to check the
voltage. I’m keeping track of how many times I cycle this switch on-off.
I’m occasionally operating the switch 10 times when I go out into the
garage. I observe the light for intermittent connection, occasionally tap
the test box, and jog the selector. So far, I’m at 80 cycles. Again,
looking for any problems. I’m keeping the box on my clothes dryer because
it vibrates when operating, and even the temperature varies. This morning
it was 45 F in my garage, and after operating the dryer for a couple loads
of laundry, the test box was 80 F.
So, we’ll see how many cycles I get from this switch. Please keep in mind
that this simple test is not designed to check mean time between failure
(MTBF) because those tests are a lot more involved.
Questions and comments are appreciated.
Richard Dierking
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