Hi everybody!
I'm building a 3V powered portable headphone amplifier. Next to the power switch there are 2x1000uF Panasonic FM caps. In spite my switch is rated 50A peak (AC, unfortunately...) This could create an arc that could damage the switch contacts in the long run. Anyone has a suggestion for a capacitor (value, type) to be placed across the switch to protect the contacts?
Thanks very much in the anticipation,
Massimo
P.S. I searched Google as well, but... no answer.
I'm building a 3V powered portable headphone amplifier. Next to the power switch there are 2x1000uF Panasonic FM caps. In spite my switch is rated 50A peak (AC, unfortunately...) This could create an arc that could damage the switch contacts in the long run. Anyone has a suggestion for a capacitor (value, type) to be placed across the switch to protect the contacts?
Thanks very much in the anticipation,
Massimo
P.S. I searched Google as well, but... no answer.
Maybe it is a stupid idea to protect from the side effects of the reservoir caps adding another cap...😕
Maybe a limiter resistor? or a lamp?
Humblest apologies if my question was really stupid.
Massimo
Maybe a limiter resistor? or a lamp?
Humblest apologies if my question was really stupid.
Massimo
Hi Massimo,
for sure placing an antiarc cap on the switch (in parallel) is very well done: in the long term all that little arc on the switch contacts will deteriorate them. I always use a 10 nano cap, ceramic 1kVolt or polyester X2 class at least 250 Volts AC. Solder it on the switch, and if the switch has 2 poles, you have to use 2 caps.
for sure placing an antiarc cap on the switch (in parallel) is very well done: in the long term all that little arc on the switch contacts will deteriorate them. I always use a 10 nano cap, ceramic 1kVolt or polyester X2 class at least 250 Volts AC. Solder it on the switch, and if the switch has 2 poles, you have to use 2 caps.
Grazie!
Ciao Claudio and thanks very very much for your kind answer.
From your answer I got the impression that your use a cap to protect your AC power switch. My situation is bit different, because I have DC (worse than your situation), lower voltage (better) and higher current (worse).
Do you think this could make any difference, e.g. in capacitor value? would it be appropriate to use an Epcos stacked COG capacitor, e.g. RS code 211-5047?
Thanks once again and have a nice evening. 🙂
Massimo.
P.S. I don't wanna be indiscreet, but... may I ask the name of your city? 😱
Ciao Claudio and thanks very very much for your kind answer.
From your answer I got the impression that your use a cap to protect your AC power switch. My situation is bit different, because I have DC (worse than your situation), lower voltage (better) and higher current (worse).
Do you think this could make any difference, e.g. in capacitor value? would it be appropriate to use an Epcos stacked COG capacitor, e.g. RS code 211-5047?
Thanks once again and have a nice evening. 🙂
Massimo.
P.S. I don't wanna be indiscreet, but... may I ask the name of your city? 😱
Prego Massimo!
Here's a document to calculate the values, which refers to a snubber (RC in series): http://docs-europe.electrocomponents.com/webdocs/073b/0900766b8073b055.pdf
A snubber is more efficient, but at an higher cost. RS code: 209-213
PS: I am in Bari, pretty far from Torino!
Here's a document to calculate the values, which refers to a snubber (RC in series): http://docs-europe.electrocomponents.com/webdocs/073b/0900766b8073b055.pdf
A snubber is more efficient, but at an higher cost. RS code: 209-213
PS: I am in Bari, pretty far from Torino!
Claudio, thanks a lot for the great reference. 🙂
Bari... I remember when I was young... great raw seafood dinners and great music at the "Time Zones" festival.
Hope those wonders are still there 😀
Ciao!
Massimo
Bari... I remember when I was young... great raw seafood dinners and great music at the "Time Zones" festival.
Hope those wonders are still there 😀
Ciao!
Massimo
I've seen 100nF caps in a lot of audio gear across the AC switch.
Of course there are many ways to deal with arcing.
Of course there are many ways to deal with arcing.
Personally I would use Y-rated capacitor, as they are guaranteed to fail open-circuit. But I guess for you not switching mains it's not so critical.
antomas said:
uncooked Seafood...yes, it's still here!🙂)
Time Zones, I still remember the Fripp-Sylvian concert....
If its just 3 volts I wouldn't be too worried about arcing since the voltage is too low to cause any significant arcing damage. If you mean 300Volts than I would consider taking some measures.
Placing the cap across the switch will permit a small amout of AC current to pass through if your using an AC source. This could result in some nasty surprises, especially since there are some large caps on the other side. Another option would be to use a choke to limit the current inrush when the switch is turned on. A choke would work with both AC and DC sources. I would be concerned with a cap across the switch if your using a SMPS or Linear PS, since its possible that AC could be generated if the PS's output filter is crappy. I would probably included a high value resistor across the caps to discharge them for safety measures.
Placing the cap across the switch will permit a small amout of AC current to pass through if your using an AC source. This could result in some nasty surprises, especially since there are some large caps on the other side. Another option would be to use a choke to limit the current inrush when the switch is turned on. A choke would work with both AC and DC sources. I would be concerned with a cap across the switch if your using a SMPS or Linear PS, since its possible that AC could be generated if the PS's output filter is crappy. I would probably included a high value resistor across the caps to discharge them for safety measures.
Yeap, not a problem with 3volts and low power headphone amplifier with relatively low filtering capacitance.TechGuy said:
3v 2000A load could be different, or 20F (20000000uF) powercapacitors.
Gentlemen, thanks a lot for your answers.
To be precise, source is 2xAA NiMH. Caps are 2x1000uF 10 or 16V Panasonic FM, each connected to the supply pins of a buffer chip. Load should not be more than 10 mA.
Techguy and Mzzj,
In the meanwhile I found some other references on the net and, apparently, 3V seems too low to build an arc 🙂
One of the documents I found recommends a limiter resistor in series to the switch to cope with capacitive loads. Maybe the internal resistance of the NiMH batteries is already high enough, also considering that I plan to use a mains-rated switch and not one of these tiny lever switches used to switch signals.
Thanks once again,
Massimo
To be precise, source is 2xAA NiMH. Caps are 2x1000uF 10 or 16V Panasonic FM, each connected to the supply pins of a buffer chip. Load should not be more than 10 mA.
Techguy and Mzzj,
In the meanwhile I found some other references on the net and, apparently, 3V seems too low to build an arc 🙂
One of the documents I found recommends a limiter resistor in series to the switch to cope with capacitive loads. Maybe the internal resistance of the NiMH batteries is already high enough, also considering that I plan to use a mains-rated switch and not one of these tiny lever switches used to switch signals.
Thanks once again,
Massimo
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