Identify and locate a microswitch -

[bernardgreen]

The higher amp rating will not affect the operation of the hedge cutter,

The majority of wear and tear to micro-switches used to control motors happens when the switch opens ( switches OFF) as this creates an arc which wears the contacts. It might be worth buying one or two spare switches just in case.

The rating on the switch is 4(3)A which normally means 3 amps for motor load and 4 anp for lighting or heating loads.

 

[DetlefSchmitz]

Am I correct that the higher rating on most of these switches should not affect operation. This one is rated (i think) at 4 amps. Most supplies seems to be rated at 16 amps.

Yes, that's fine.

 

[333rocky333]

...

 

[ban-all-sheds]

I agree though that getting the correct type is easier & possibly even cheaper.

And avoids being denied a replacement if it fails in the first year.

 

[ban-all-sheds]

The image you posted @ban-all-sheds is an exact match for the item. Is it just a stock image or did you copy it from a purcasable item?

This I found searching for the part number:

This you can buy in Maplins:

I'll have a look at repair. But the button just seems to fall inwards and has no resistance nor a discernable click anymore. So I think the innards are beyond recovery.

Quite possibly, but if you've got any meths leave the switch to soak in some for a bit, just in case it is OK but clagged up.

 

[dishman]

Actually, you can open it up. It was quite easy actually, just a bit of prying with a stanly blade. Although I did snap off a plastic prong (top left).

The inside does not look good. There is a bit of charring.

View media item 99559View media item 99558
The spring mechanism of the switch was stuck (against the casing actually), and could be freed.

However I think somthing else has gone wrong for it to charr up, possibly a lot of arcing due to a bad contact.

The mechanism does not seem to work properly, or is too charred to work smoothly. I cannot press the button an take a photo. But the button side makes contact, while the other side does not seem to do much unless it is held in the correct orientation. I am not sure if it is ment to see-saw or both sides are designed to go up and down togther.

The maplin one looks OK.

This one via farnell is cheaper and probably better too.

http://uk.farnell.com/omron-electro...MCFcFuGwodla8KrQ&CAWELAID=120173390001364401#

 

[ban-all-sheds]

There is a bit of charring.

A bit?

It's trashed.

 

[dishman]

A bit?

It's trashed.

Indeed....maybe I understated it.......

Measurements from the Farnell ones check out, so ordered them. The hedge trimmer has two of these switches, so I will replace both.

Many thanks for all the help.

 

[dishman]

Update:

Replacements arrived, they have been fitted and it all works pretty good.

The quality of the switches seem to be much better. They are Omron branded and the is certainly a better quality "click" and feel to them.

The only slight issue is that somtimes if I am a bit too gentle with the lever when testing, the motor buzzes rather than starting. I do not think this is to do with any blade resistance, everthing is at the right tightness, contacts are all good. So I wonder if it is somthing to do with the switch and the way it operates.

Obviously the solution is not to be too gentle on the lever (and once I am using it properly I will probably be far less gentle)...but...just wondering if there are any other possible causes.....the carbon brushes are in good condition and have a lot left, so it is not that either.

I got a pack of 5 switches so I may open one up to compare the quality and switch action

 

[333rocky333]

Omron im sure are quite a well known brand for that sort of stuff, proberly far better than some of the cheap ebay stuff. i seem to recall the name on a lot of the switches on things like compacters etc, though the same switches, they were encased in an aditional metal housing

 

[dishman]

Omron im sure are quite a well known brand for that sort of stuff, proberly far better than some of the cheap ebay stuff. i seem to recall the name on a lot of the switches on things like compacters etc, though the same switches, they were encased in an aditional metal housing

Indeed, their name seems to come up as a quality manufacturer.

 

[dishman]

For those who are interested....and I was...

The internals and switch mechanism...compared...

http://www.metacafe.com/embed/11498091/microwitchold-mp4/

http://www.metacafe.com/embed/11498084/microwitchnew-mp4/

It would not let me embed it for some reason.

As you can see, the main differance between the old and the new is that the old one has a much bigger throw distance. Maybe three times more. This seemed to make it a lot less reactive in terms of speed, but may have also produce/contributed to a less firm contact.....ultimatly contributing to some arcing and wear.

View media item 99587
I am actually surprised the gap on the new one is so much smaller. How close can two contacts be before they could arc/interact with each other?

Overall you can see that the quality of the new switch is very apparent. Much better quality innards in general.

The hedge trimmer contained two switches. This is the second of the old switches (still works..just) and althouh not clear, also suffers from scorching internally. So probably did not have much life left.

The switch was more spongy in the old one (probably due to the bigger throw distance). The new one is much more firm and exact.

Still does not explain why the motor just buzzes somtimes as if it has an intermitant bad contact.

 

[ban-all-sheds]

So I wonder if it is somthing to do with the switch and the way it operates.

Or the mechanical linkage between the lever and the switch?

 

[dishman]

Or the mechanical linkage between the lever and the switch?

Good theory. In fact, it is probably the issue.

I used it for a good hour or so (not continuously) today and it only did it a few times. The mechanical lever that activates the switch is basically a plastic paddle (within the main lever armature) that flips up just enough (when the saftey lever is pulled) to press against the microswitches.

It is possible that the paddle is not pressing both switches evenly or at the same time, causing some form of false start.

In fact, the failing switch caused the same issue somtimes. So if one switch fails to activate the motor just buzzes.