Dear all,
Recently I am choosing a miniature toggle switch to power up a 3.3V, 200mA power circuit. But those rating just made me confusing.
For example :
NKK Series M2100 Switch
Power Level (silver) : 6A @ 125V aC or 3A @ 250 V AC or 3A @ 30V DC
Logic Level (gold) : 0.4VA maximum @ 28V AC/DC maximum
Do this meant that the gold contact's 0.4VA is the maximum power capability of the contact that can stand of? Or it mean that due to the resistance of the gold contact, the contact only capable to reach 0.4VA @ 28V, which is just around 14mA.
While in another case,
AE101MD1AQ04
This Switch rated at just 0.4VA(Power Rating), but it rated that it can goes beyond 3A @ 250V AC too.
I just simple can't brain this rated value at all, anyone can enlighten me?
Recently I am choosing a miniature toggle switch to power up a 3.3V, 200mA power circuit. But those rating just made me confusing.
For example :
NKK Series M2100 Switch
Power Level (silver) : 6A @ 125V aC or 3A @ 250 V AC or 3A @ 30V DC
Logic Level (gold) : 0.4VA maximum @ 28V AC/DC maximum
Do this meant that the gold contact's 0.4VA is the maximum power capability of the contact that can stand of? Or it mean that due to the resistance of the gold contact, the contact only capable to reach 0.4VA @ 28V, which is just around 14mA.
While in another case,
AE101MD1AQ04
This Switch rated at just 0.4VA(Power Rating), but it rated that it can goes beyond 3A @ 250V AC too.
I just simple can't brain this rated value at all, anyone can enlighten me?
Switching DC current tends to draw an arc as the contacts open, that's why there is such a huge difference between AC and DC ratings.
I think the logic level aspect is that maximum level of current that will ensure no pitting of the surfaces over many thousands of cycles of operation. Pitted contacts equal indeterminate logic levels and contact bounce.
I think the logic level aspect is that maximum level of current that will ensure no pitting of the surfaces over many thousands of cycles of operation. Pitted contacts equal indeterminate logic levels and contact bounce.
Still not very clear about it.
Is it true that if those toggle switches with power rating that rated at just 0.4VA with gold contact cannot be used under my application? Which is 3.3V @ 200mA, plus minus 0.7VA.
Because from what i searched from the mouser, most of the toggle switches was rated at just 0.4VA.
Is it true that if those toggle switches with power rating that rated at just 0.4VA with gold contact cannot be used under my application? Which is 3.3V @ 200mA, plus minus 0.7VA.
Because from what i searched from the mouser, most of the toggle switches was rated at just 0.4VA.
If that is the only rating given for the gold then I would have to say it is not suitable.
Switching "high" current at low voltage can show up contact problems. Another approach, could you use an FET as the switch. Modern FET's have on resistances in the sub 10 milliohm region and more importantly, its consistent and non varying.
Switching "high" current at low voltage can show up contact problems. Another approach, could you use an FET as the switch. Modern FET's have on resistances in the sub 10 milliohm region and more importantly, its consistent and non varying.
Quite often switches have a thin gold plating over the silver, when used for logic switching the figures quoted will not damage the gold, when used for power switching the gold will disappear due to the sparking, so one switch can do two functions. Relys also do this it save having to stock two parts.
"Quite often switches have a thin gold plating over the silver..." - Quite true. If the switch or relay is only going to be used in what the telephone industry called a "dry circuit" (negligable power, no arcing), then the gold is good and is preserved. If the contacts arc, then the gold erodes, exposing the silver alloy, which is good for power contacts. The silver oxidizes, however, making the contacts then useless for dry circuits. The silver contacts rely on some arcing to break through the oxide.
This makes using used switches or relays dicey for dry circuits, since you don't know how they have been used in the past. I learned this the hard way when I used some beefy used toggle switches to switch signals in a preamp, and found that they were hopelessly noisy and intermittent. Later on I used them for power switches, and they worked great.
- John Atwood
This makes using used switches or relays dicey for dry circuits, since you don't know how they have been used in the past. I learned this the hard way when I used some beefy used toggle switches to switch signals in a preamp, and found that they were hopelessly noisy and intermittent. Later on I used them for power switches, and they worked great.
- John Atwood
I had similar problems with new dip relays which seemed suitable for switching audio, but were not. (10mA minimum rating) I did not then understand the distinction between dry switching applications and low power, but figured it out rather quickly having experienced exactly the problems described by John.
+1.
There is also the difficulty of understanding what happens if ratings are exceeded. In general there is a total lack of data on switch (and relay) test methods in data sheets. Most beginners do not get to read thick tomes by serious engineers on the subject.
So what happens if my switch rated at 32vDC and 1amp gets used in a 48v circuit at 1amp? Does it explode? Weld? Fail to switch? Die early? etc
In many situations an easy cop-out is to wildly over-specify the ratings. Simple in small quantity DIY .....
There is also the difficulty of understanding what happens if ratings are exceeded. In general there is a total lack of data on switch (and relay) test methods in data sheets. Most beginners do not get to read thick tomes by serious engineers on the subject.
So what happens if my switch rated at 32vDC and 1amp gets used in a 48v circuit at 1amp? Does it explode? Weld? Fail to switch? Die early? etc
In many situations an easy cop-out is to wildly over-specify the ratings. Simple in small quantity DIY .....
So let me guess, for this model : Multicomp
The contacts come with brass with gold plated. If it stressed below 0.4VA, it can use as high frequency signal transmission contact and operate just fine.While if once stressed beyond 0.4VA, the gold will "oxidized" and left the brass that will just continue to conduct normally, but just the brass is poor in signal transmission, but still good enough for power conductivity.
Right? Correct me if I am wrong.
The contacts come with brass with gold plated. If it stressed below 0.4VA, it can use as high frequency signal transmission contact and operate just fine.While if once stressed beyond 0.4VA, the gold will "oxidized" and left the brass that will just continue to conduct normally, but just the brass is poor in signal transmission, but still good enough for power conductivity.
Right? Correct me if I am wrong.
Yes,it's basically that way.
You are using it as a *power* switch and under "silver" ratings it's perfect.
The thin gold layer will dissapear, no big deal because under it you have (relatively) thick silver.
*If* you used it for audio signal switching it would also work, because you have a thin gold plating which under those conditions will last a lot.
You must avoid what John Atwood says: switches used for power later become unsuitable if recycled for audio.
You are using it as a *power* switch and under "silver" ratings it's perfect.
The thin gold layer will dissapear, no big deal because under it you have (relatively) thick silver.
*If* you used it for audio signal switching it would also work, because you have a thin gold plating which under those conditions will last a lot.
You must avoid what John Atwood says: switches used for power later become unsuitable if recycled for audio.
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