On PushButtons switches specs

[GordTheRogue]

:) Hello to all,

Which kind of specs must have pushbuttons for MIDIBox64??

I'm talking about two main things:

-  The ON-OFF states

-  Electric specs like contact resistance and so on

I've found this button http://www.e-switch.com/pdf/Series5500Pushbutton.pdf

maybe someone knows this mark or can say to me if they are right for MIDIBox.

Thanx, these info are very needed cause i'm going to order  and i don't want to buy useless things.

[illogik]

Yeah, these switches are ok; the thing with the midibox switches is that the have to be a momentary contact; it only needs to let the din/core know it has been pushed.

Then you can configure MB64(software-wise) so that this button for instance reacts as a toggle switch (for swithing fx on/off etc) or a pushbutton (note on/off).

contactresistance?

cheers, marcel

[GordTheRogue]

Thanx!!!!

about contact resistance as you can read on that link

"Contact Resistance: 10mΩ max. typical @ 2-4 VDC, 100mA"

What about Tactile Pushbuttons??

I've a lot of them desoldered from old TVs and other electric stuff... ;)

[illogik]

Hi,

Tact buttons are also momentary, so yes. And they are cheap too (for if you run out of tv's   ;)).

The other thing i forgot to mention; the buttuns you use must be nomally open (NO); meaning the contact points are connected when you push (opposed to NC where you break the connection when you push it). Most (all?) tact switches are NO, so your solid ;D.

cheers, marcel

[Echopraxia]

Does contact rating matter much when selecting switches? I am looking at rapid electronics omron b3f switches which have a contact rating of 24V DC 50mA. Does this have an effect on the whole power consumption of the midibox i.e ma rating of power supply? Would these draw alot of power? I see alot of switches with 12v DC. Do you know what the difference is between 12v and 24v switches?

[stryd_one]

That 'contact rating' is referring to the maximum amount of electricity you can put through the switch.

So if you have a 12V switch, and you put 15V through it, it'll fry. If it was a 24V switch, it'd be OK.

Likewise, if you have a 24VDC 50mA switch  and you give it 22V at 45mA, you'l be fine... but if you drew 22V at 100mA, you'd likely fry it.

The contact resistance is talking about the amount of resistance that the switch introduces when the circuit is closed (switch is ON/ pushed in).

Because of the metal parts, and the joins between them, the electrical current does not flow smoothly through the switch - it resists.

That resistance will vary depending on how much power you apply, which is why it says 10MOhm at 2-4VDC 100mA. if you gave it 1VDC, maybe the resistance would be higher, etc etc

Of course these two factors contribute to each other too....

For our purposes, we're putting 5V and very low amperage, so any of these you've listed (and well, pretty much anything designed for this kind of thing)

will be fine.

[Echopraxia]

Thanks stryd!  So all midibox cores only draw 5v from power supply which in turn send 5v to each button when pressed? I know you said that 24v dc 50ma switch should be ok but is it overkill concerning resistence or anything else? That type of switch is what I plan on getting.

[stryd_one]

Well, there's 5V of potential in the wire all the time, and when you push the button, that circuit is completed and the electricity flows. The current (amps) it draws will vary depending on the load you put on the circuit. In this case, it's just the switch and it's associated resistor, so not much. Yes, 24vdc 50mA is over kill. It shouldn't be a problem, but if you buy switches designed for heavier duty work, they might feel heavier too... Why not just link the switch?

[Echopraxia]

What do you mean link the switch? I am looking at the omron b3f tactile switches 12x12mm that they have at rapid electronics. Does anyone know if these are "heavy feeling" switches? I noticed they weight 3x as much as the 6x6mm switches. They have a "Switching capacity is 1 to 50 mA, 5 to 24 VDC (resistive load)" The core sends more than 1ma to the switches right?

[stryd_one]

I meant, give us a link to the switch - no need for that, I was lookig at those earlier this evening heheh

Those should be fine, but if you really want to know how they feel, that's what samples are for!

The amount of current that flows through the switch depends on the load attached to it (probably just the resistor in your case). Damned if I am doing the math at this hour, I'll leave it to you to find the V I R equation and punch the numbers in ;)

[bugfight]

I'll leave it to you to find the V I R equation and punch the numbers in

V = I R

aka ohms law.