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Thread: Momentary switches question

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    Momentary switches question

    I realize this is not a keyboard forum but these switches look like the ones in a DoD pedal.
    It is in an alesis keyboard. They switch the midi choices.

    It has 4 legs. My question is this when pushing the button should I have continuity from both left legs to both right legs? I know the left top and bottom on both sides has continuity.
    Thanks,
    NosajClick image for larger version. 

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    Supporting Member Jazz P Bass's Avatar
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    I believe that what you saw is correct.

    Look at the voltages on it.

    They are usually 'pulled down' when the switch is depressed.

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    Lifetime Member Enzo's Avatar
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    Those are common tactile switches. Yes, two pins on ione side are together, and the remaining two are together. Press the switch and the two sides connect so all four are together.

    Rather than use the ohm meter, I find it easier to watch voltages go up and down as I press the switch. If it is a strobed matrix circuit, I( can watch it on a scope. On the keyboard they are likely strobed, at least not surprising if they were.

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    Quote Originally Posted by Enzo View Post
    Those are common tactile switches. Yes, two pins on ione side are together, and the remaining two are together. Press the switch and the two sides connect so all four are together.

    Rather than use the ohm meter, I find it easier to watch voltages go up and down as I press the switch. If it is a strobed matrix circuit, I( can watch it on a scope. On the keyboard they are likely strobed, at least not surprising if they were.
    Some of them were not working which is why I asked. I took some out of circuit and tested continuity.But I will hook it up to a scope So I can see what you mean by strobed or not. I will need to order some either way as I have some non working ones. Any one have a handy mouser number for them?

    Thanks,
    nosaj

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    Lifetime Member Enzo's Avatar
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    Measure them, they are 6mm or 8mm or 12mm or some other number of mm on a side. Look up tactile switches in MOuser in the size. The little round black dot is the actuator or shaft, whatever they call it. Those can be the slightest little sliver up to a thing 3/8" tall, typically measured as height from the bottom of the switch, not counting the legs. determine which you need. In some low clearance things, a half millimeter can matter, in other things, just get close. They also come in force - ie how hard you have to push. I get middle range ones unless I know for sure. Your photo four legged ones, but they also come in two legged, so make sure. SO I can't give you a Mouser number, becasue I don't know just which ones you need.

    If they don't close on a meter, that is good enough for me, but in circuit it is hard to clip a meter lead to the switch leg, so I go to the circuit function. I am sure you can detemine a bad switch in your own way.

    These things cost like 20 cents. If some are worn out, just replace them all, why go through this again in six months for the ones we left? or if there are forty of them, perhaps teh commonly used ones, replace all, but leave the master edit MIDI dump ones we used rarely. (I made that function up, don't look for it)

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    Quote Originally Posted by Enzo View Post
    Measure them, they are 6mm or 8mm or 12mm or some other number of mm on a side. Look up tactile switches in MOuser in the size. The little round black dot is the actuator or shaft, whatever they call it. Those can be the slightest little sliver up to a thing 3/8" tall, typically measured as height from the bottom of the switch, not counting the legs. determine which you need. In some low clearance things, a half millimeter can matter, in other things, just get close. They also come in force - ie how hard you have to push. I get middle range ones unless I know for sure. Your photo four legged ones, but they also come in two legged, so make sure. SO I can't give you a Mouser number, becasue I don't know just which ones you need.

    If they don't close on a meter, that is good enough for me, but in circuit it is hard to clip a meter lead to the switch leg, so I go to the circuit function. I am sure you can detemine a bad switch in your own way.

    These things cost like 20 cents. If some are worn out, just replace them all, why go through this again in six months for the ones we left? or if there are forty of them, perhaps teh commonly used ones, replace all, but leave the master edit MIDI dump ones we used rarely. (I made that function up, don't look for it)
    I found these that I believe will work. Thing I'm unclear on is the operating force says 1n. What does that mean? How much is 1 Newton of force? Or better yet what would middle of the road be ? You said you choose Medium right?

    Thanks,
    nosaj http://www.mouser.com/ProductDetail/...4OczhfSxKpE%3d

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    Lifetime Member Enzo's Avatar
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    I chose medium if more than one is offered. I have no idea what 1 newton means in the real world, but if I have the option of 0.8, 1 and 1.2 newtons, I choose the middle one. If your dimensions only have one, then use it. In the panel of a keyboard it won;t really matter if one button requires a little more force to activate. it isn;t like you;d need to stand on it. The information says 100 grams. How that translates into newtons, I couldn't tell you.

    The example you link is probably fine. Open the data sheet from that page to see the options for that model switch.

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    don't forget the joker g1's Avatar
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    1 newton is roughly 9 inch/pounds.

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    Quote Originally Posted by Enzo View Post
    The information says 100 grams. How that translates into newtons, I couldn't tell you.
    It's nearly 1 newton. 1 newton is the gravitational force on a British Standard apple resting on the earth's surface. An apple weighs about 100 gram so 1 newton is about 100 gram force.

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    Lifetime Member Enzo's Avatar
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    Is that a red apple or a green one?

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    Supporting Member eschertron's Avatar
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    Quote Originally Posted by Enzo View Post
    Is that a red apple or a green one?
    If you remember the logo for "apple records" it was a green apple, with a slice taken out. I can see now that the slice was taken to bring the mass of the apple down to British standards. 100g is a pretty small apple, after all.

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    Quote Originally Posted by eschertron View Post
    If you remember the logo for "apple records" it was a green apple, with a slice taken out. I can see now that the slice was taken to bring the mass of the apple down to British standards. 100g is a pretty small apple, after all.
    That's not what you'd say if YOU were Newton lying under the tree when the little &*(%er whacked you one as it fell.

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