EMI filtering on power cord
Jim N6OTQ:
>If your power cord is round and has a diameter of 1/4" or less, these guys will? >work:? < https://mgs4u.com/product/double-ferrite-beads/>
>You'll need to cut the cord to get these ferrite beads on, and then splice the cord? >back together?
Instead of cutting the power cord why not use these clamp on devices instead:
https://www.aliexpress.com/item/1005003686552253.html?gatewayAdapt=Msite2Pc
I have used the clamp on ferrite devices for more than 30 years now and they are very? good and exceptionally easy to use.
Please, be aware that you can easily put as many as needed on a cable by just putting? them on and on in series to add filtering as needed.
Cheap too.
------- Best regards, Goran Finnberg The Mastering Room AB Goteborg Sweden E-mail: mastering@... Learn from the mistakes of others, you can never live long enough to make them all yourself.??? -?? John Luther (\__/) (='.'=) (")_(") Ranglet, Aron, VovVov, Nero & Smurfen:RIP
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Re: EMI filtering on power cord
Very cool. Does this script use an internal PC Slot Card or a USB (like a National Instruments USB), Host device? ? Ross ?
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From: [email protected] < [email protected]> On Behalf Of Wilko Bulte Sent: Thursday, August 03, 2023 11:02 AM To: [email protected]Subject: Re: [Test Equipment Design & Construction] EMI filtering on power cord ? "Because I could": my home grown EMI probe in (isolated..) contact with the lead of a Metcal close to the handpiece For the curious: the Python script used is here
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Re: EMI filtering on power cord
"Because I could": my home grown EMI probe in (isolated..) contact with the lead of a Metcal close to the handpiece
For the curious: the Python script used is here
Wilko
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Re: EMI filtering on power cord
I own two Metcal 13.5MHz ISM bans soldering stations. Both are housed in extruded aluminium cases, and (IIRC) they have a netfilter integrated inside the IEC mains entry.
The silicone cable to the hand piece is a coaxial cable (no surprise), from dismantling a broken one it looked like serious and tighly woven shielding, probably silvered too.
Might be interesing to try my RF probes on the SA to see what RF leaks (or not).
As a soldering iron these things are absolutely brilliant!
Wilko
PA1WBU
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Re: EMI filtering on power cord
If your power cord is round and has a diameter of 1/4" or less, these guys will work: ?<>
You'll need to cut the cord to get these ferrite beads?on, and then splice the cord back together?(beware OSHA regulations) -- one of these beads is electrically almost identical to the ferrites molded onto data cables...you can stack several of these on your cord, and with one properly placed splice, add beads on both ends of the cord.? As they say, measure twice, cut once. ??
Looks like I just found tomorrow afternoon's project when it's 103Foutdoors.? I have some received noise problems in my shack with my primary transceiver,?and this might help.
73
On Thu, Aug 3, 2023 at 2:27?AM Adrian Godwin < artgodwin@...> wrote: The wired chokes Ross describes are available in a package that includes an IEC inlet connector. If your controller has an unfiltered connector and the extra depth required, you can substitute a filtered one fairly easily.
Hi, ? The Common Mode Choke that I was referring to is one that is “wired into” the EMI Filter. It has two counter-wound coils on a Ferrite Core (donut), and is wired into the AC Power path generally near the load side. Many EMI Filters have one, two or three of them in series with the Power path of the product. There is generally an X Capacitor between them if there are multiple frequency poles or even the same frequency pole. There generally one or more Y Capacitors in an EMI Filter. The values need to be selected to provide the amount of suppression desired and not exceed Leakage Current requirements. Below is a schematic of the Corcom 6EF1F Filter that I recommended… ? 
? The Common mode Choke is 465uH, the X Capacitor (Line-to-Line), is 0.01uF, the Y Capacitors (Line-to-Chassis Ground), are 0.0049uF, the X Capacitor Discharge Resistor is 1.5Meg. The suppression values shown are for a 50 Ohm System. Rarely, have I ever seen a 50 Ohm System except when the Line is connected to a MIL-STD-461 LISN. The Load side is almost certainly much lower than 50 Ohms. ? A real good Filter has Multiple Pole sections. The more Poles, generally the better suppression. The schematic below is from the Corcom Catalog and is a Corcom 20EJT1 Filter. The values are 91uH Common Mode Chokes, 0.1uF X Capacitor and two sets of 0.0056uF Y Capacitors. ? It has two sections and filters very well as it creates a controlled High Impedance in (Line), and out (Load), of the Filter with Inductance (read that as High Series Impedance), on both sides. Each Common Mode Choke makes a high Impedance, each X Capacitor Makes a Low Impedance. The Y Capacitors sink Common Mode currents to a common low Impedance reference (Chassis Ground). Note that this filter includes two sets of Y Capacitors so they are each smaller in value to meet Leakage requirements.? Notice that we get some decent suppression including some Differential Mode suppression. ? 
? ? One caution when using High Impedance Filtering is that you need to make sure your Power Impedance presented to the Load is low enough and meets your Middlebrook Criteria Impedance (Impedance at Low Frequencies), to prevent Lop Stability in Switching Regulators. ? ? Ross ? ? ? ? The only soldering irons that are relatively emission-free are the old fashioned heaters that just go when plugged in, or flame heated types. Ever since temperature controlled ones emerged, they have become EMI sources. So, you can't entirely escape EMI trouble just by changing irons, unless you take some steps back in the technology, or spend quite a bit of time and money.
The most common irons nowadays I think, are variable temperature-regulated types, typically using a phase-controlled TRIAC circuit for the power part - same as a light dimmer for incandescent lamps. So, you've got lots of EMI crap around all the line frequency harmonics, plus RF from the relatively fast edges of the device switching, with line harmonics surrounding each RF spur. It's really quite a mess. I'd think there would be at least a little filtering included in most products for sale, but just barely enough to meet certain regulatory specs. And some items probably just ignore the specs. Anyway, some may be much better than others, but you'd have to compare specs, which may be non-existent or false, or compare actual units.
So, you're kind of on your own, but there are plenty of very basic things that could have been built into these products (making them more expensive), that you can add. The first and easiest line of defense is common-mode chokes. Look into "clip-on EMI chokes" and such, which are split ferrite cores surrounded by a plastic clamp/holder thing. On a soldering iron for instance, you'd want chokes at the control box first - one at the line cord entry, and one at the power output to the iron cord. As Ross explained, the cordage makes great antennas for certain frequency ranges, so swamping that effect goes a long way toward peace and quiet.
Chances are that you'll get very noticeable reduction in interference. If you've never dealt with common-mode chokes, you'll see right away why you'd want "clip-on" types, so you don't have to worry about fitting over connectors and such. If you just have to pass a wire through, then a solid toroid is best, but usually you'll have cables with connectors. Look for clip ones big enough to fit on the cables, and with as much L as you can get. Typically 1-10 uH is available in common size ranges.
If you still need more suppression, you can try more CM chokes, and in different spots. You can get more improvement by adding more types of filtering, and figuring out how the junk gets out and around, as Ross explained.
Lastly, for situations needing very low interference, you may have to turn off any offending items of all types, not just irons. They'll never be perfect.
Ed
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Re: EMI filtering on power cord
The wired chokes Ross describes are available in a package that includes an IEC inlet connector. If your controller has an unfiltered connector and the extra depth required, you can substitute a filtered one fairly easily.
Hi, ? The Common Mode Choke that I was referring to is one that is “wired into” the EMI Filter. It has two counter-wound coils on a Ferrite Core (donut), and is wired into the AC Power path generally near the load side. Many EMI Filters have one, two or three of them in series with the Power path of the product. There is generally an X Capacitor between them if there are multiple frequency poles or even the same frequency pole. There generally one or more Y Capacitors in an EMI Filter. The values need to be selected to provide the amount of suppression desired and not exceed Leakage Current requirements. Below is a schematic of the Corcom 6EF1F Filter that I recommended… ? 
? The Common mode Choke is 465uH, the X Capacitor (Line-to-Line), is 0.01uF, the Y Capacitors (Line-to-Chassis Ground), are 0.0049uF, the X Capacitor Discharge Resistor is 1.5Meg. The suppression values shown are for a 50 Ohm System. Rarely, have I ever seen a 50 Ohm System except when the Line is connected to a MIL-STD-461 LISN. The Load side is almost certainly much lower than 50 Ohms. ? A real good Filter has Multiple Pole sections. The more Poles, generally the better suppression. The schematic below is from the Corcom Catalog and is a Corcom 20EJT1 Filter. The values are 91uH Common Mode Chokes, 0.1uF X Capacitor and two sets of 0.0056uF Y Capacitors. ? It has two sections and filters very well as it creates a controlled High Impedance in (Line), and out (Load), of the Filter with Inductance (read that as High Series Impedance), on both sides. Each Common Mode Choke makes a high Impedance, each X Capacitor Makes a Low Impedance. The Y Capacitors sink Common Mode currents to a common low Impedance reference (Chassis Ground). Note that this filter includes two sets of Y Capacitors so they are each smaller in value to meet Leakage requirements.? Notice that we get some decent suppression including some Differential Mode suppression. ? 
? ? One caution when using High Impedance Filtering is that you need to make sure your Power Impedance presented to the Load is low enough and meets your Middlebrook Criteria Impedance (Impedance at Low Frequencies), to prevent Lop Stability in Switching Regulators. ? ? Ross ? ? ? ? The only soldering irons that are relatively emission-free are the old fashioned heaters that just go when plugged in, or flame heated types. Ever since temperature controlled ones emerged, they have become EMI sources. So, you can't entirely escape EMI trouble just by changing irons, unless you take some steps back in the technology, or spend quite a bit of time and money.
The most common irons nowadays I think, are variable temperature-regulated types, typically using a phase-controlled TRIAC circuit for the power part - same as a light dimmer for incandescent lamps. So, you've got lots of EMI crap around all the line frequency harmonics, plus RF from the relatively fast edges of the device switching, with line harmonics surrounding each RF spur. It's really quite a mess. I'd think there would be at least a little filtering included in most products for sale, but just barely enough to meet certain regulatory specs. And some items probably just ignore the specs. Anyway, some may be much better than others, but you'd have to compare specs, which may be non-existent or false, or compare actual units.
So, you're kind of on your own, but there are plenty of very basic things that could have been built into these products (making them more expensive), that you can add. The first and easiest line of defense is common-mode chokes. Look into "clip-on EMI chokes" and such, which are split ferrite cores surrounded by a plastic clamp/holder thing. On a soldering iron for instance, you'd want chokes at the control box first - one at the line cord entry, and one at the power output to the iron cord. As Ross explained, the cordage makes great antennas for certain frequency ranges, so swamping that effect goes a long way toward peace and quiet.
Chances are that you'll get very noticeable reduction in interference. If you've never dealt with common-mode chokes, you'll see right away why you'd want "clip-on" types, so you don't have to worry about fitting over connectors and such. If you just have to pass a wire through, then a solid toroid is best, but usually you'll have cables with connectors. Look for clip ones big enough to fit on the cables, and with as much L as you can get. Typically 1-10 uH is available in common size ranges.
If you still need more suppression, you can try more CM chokes, and in different spots. You can get more improvement by adding more types of filtering, and figuring out how the junk gets out and around, as Ross explained.
Lastly, for situations needing very low interference, you may have to turn off any offending items of all types, not just irons. They'll never be perfect.
Ed
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Re: EMI filtering on power cord
Hi, ? The Common Mode Choke that I was referring to is one that is “wired into” the EMI Filter. It has two counter-wound coils on a Ferrite Core (donut), and is wired into the AC Power path generally near the load side. Many EMI Filters have one, two or three of them in series with the Power path of the product. There is generally an X Capacitor between them if there are multiple frequency poles or even the same frequency pole. There generally one or more Y Capacitors in an EMI Filter. The values need to be selected to provide the amount of suppression desired and not exceed Leakage Current requirements. Below is a schematic of the Corcom 6EF1F Filter that I recommended… ? 
? The Common mode Choke is 465uH, the X Capacitor (Line-to-Line), is 0.01uF, the Y Capacitors (Line-to-Chassis Ground), are 0.0049uF, the X Capacitor Discharge Resistor is 1.5Meg. The suppression values shown are for a 50 Ohm System. Rarely, have I ever seen a 50 Ohm System except when the Line is connected to a MIL-STD-461 LISN. The Load side is almost certainly much lower than 50 Ohms. ? A real good Filter has Multiple Pole sections. The more Poles, generally the better suppression. The schematic below is from the Corcom Catalog and is a Corcom 20EJT1 Filter. The values are 91uH Common Mode Chokes, 0.1uF X Capacitor and two sets of 0.0056uF Y Capacitors. ? It has two sections and filters very well as it creates a controlled High Impedance in (Line), and out (Load), of the Filter with Inductance (read that as High Series Impedance), on both sides. Each Common Mode Choke makes a high Impedance, each X Capacitor Makes a Low Impedance. The Y Capacitors sink Common Mode currents to a common low Impedance reference (Chassis Ground). Note that this filter includes two sets of Y Capacitors so they are each smaller in value to meet Leakage requirements. ?Notice that we get some decent suppression including some Differential Mode suppression. ? 
? ? One caution when using High Impedance Filtering is that you need to make sure your Power Impedance presented to the Load is low enough and meets your Middlebrook Criteria Impedance (Impedance at Low Frequencies), to prevent Lop Stability in Switching Regulators. ? ? Ross ? ? ?
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From: [email protected] < [email protected]> On Behalf Of Ed Breya via groups.io Sent: Wednesday, August 02, 2023 2:00 PM To: [email protected]Subject: Re: [Test Equipment Design & Construction] EMI filtering on power cord ? The only soldering irons that are relatively emission-free are the old fashioned heaters that just go when plugged in, or flame heated types. Ever since temperature controlled ones emerged, they have become EMI sources. So, you can't entirely escape EMI trouble just by changing irons, unless you take some steps back in the technology, or spend quite a bit of time and money.
The most common irons nowadays I think, are variable temperature-regulated types, typically using a phase-controlled TRIAC circuit for the power part - same as a light dimmer for incandescent lamps. So, you've got lots of EMI crap around all the line frequency harmonics, plus RF from the relatively fast edges of the device switching, with line harmonics surrounding each RF spur. It's really quite a mess. I'd think there would be at least a little filtering included in most products for sale, but just barely enough to meet certain regulatory specs. And some items probably just ignore the specs. Anyway, some may be much better than others, but you'd have to compare specs, which may be non-existent or false, or compare actual units.
So, you're kind of on your own, but there are plenty of very basic things that could have been built into these products (making them more expensive), that you can add. The first and easiest line of defense is common-mode chokes. Look into "clip-on EMI chokes" and such, which are split ferrite cores surrounded by a plastic clamp/holder thing. On a soldering iron for instance, you'd want chokes at the control box first - one at the line cord entry, and one at the power output to the iron cord. As Ross explained, the cordage makes great antennas for certain frequency ranges, so swamping that effect goes a long way toward peace and quiet.
Chances are that you'll get very noticeable reduction in interference. If you've never dealt with common-mode chokes, you'll see right away why you'd want "clip-on" types, so you don't have to worry about fitting over connectors and such. If you just have to pass a wire through, then a solid toroid is best, but usually you'll have cables with connectors. Look for clip ones big enough to fit on the cables, and with as much L as you can get. Typically 1-10 uH is available in common size ranges.
If you still need more suppression, you can try more CM chokes, and in different spots. You can get more improvement by adding more types of filtering, and figuring out how the junk gets out and around, as Ross explained.
Lastly, for situations needing very low interference, you may have to turn off any offending items of all types, not just irons. They'll never be perfect.
Ed
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Re: EMI filtering on power cord
I still have one of those. ?
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From: [email protected] < [email protected]> On Behalf Of Ed Breya via groups.io Sent: Wednesday, August 02, 2023 7:45 PM To: [email protected]Subject: Re: [Test Equipment Design & Construction] EMI filtering on power cord ? Harvey, I've had the WTCPs almost forever. They don't make a lot of CW, but they are amazingly noisy when the thermostat cycles (off especially, dumping the transformer's stored energy). I've had lots of situations where the impulses cause large interference, even sometimes popping GFCIs. There is no added EMI suppression in these at all.
I've even used them to quick-check sensitive circuits to make sure if they're properly shielded and such - if the iron is on, you can hear the thermostat click, which is the trigger to look for bad behavior.
Ed
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Re: EMI filtering on power cord
Hi, ? Ferrite Cores come in different materials for different frequency ranges of suppression. Some are specifically made for Low Frequency and some are made specifically for High Frequency. ? The best all-around Frequency Curve is something like Fair-Rite Corp #43 Material. It is a Nickel-Zinc Material that covers the Frequency Range of 20MHz to 250MHz. From their Catalog, the following curve shows it usefulness in the Frequency Range you are probably having issues with. It has been the standard of the industry for decades. See the Curve below… ? 
? ? Another Alternative material is Steward #28 Material. Laird owns them now. Below is a set of curves from their catalog that gives you an idea of how the materials provide suppression. ? 
? ? By the way, usually, the bigger the core, the more suppression (lower Impedance over Frequency – especially under Dc Bias conditions). ? You can also purchase cores big enough to put a couple of turns through the center of them. That increases their suppression by nearly double – same frequency range. That works with any core so long as it does not saturate it with any DC Bias or too high of currents passing through it. ? TDK also makes good Clamp-on Ferrite Cable Cores too. ? As you will note, most Video and some Keyboard and Mouse cables have a Ferrite Core molded into their cables. They do that to meet FCC Class-B or CE-Mark EN55022 Class-B requirements. You may also notice that there might be one on each end of a Video cable. That’s because the Display vendor or Video Card vendor doesn’t know if it will be connected to a compliant device and they don’t want to be blamed for a violation. ? Ross ?
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From: [email protected] < [email protected]> On Behalf Of Ed Breya via groups.io Sent: Wednesday, August 02, 2023 7:45 PM To: [email protected]Subject: Re: [Test Equipment Design & Construction] EMI filtering on power cord ? Harvey, I've had the WTCPs almost forever. They don't make a lot of CW, but they are amazingly noisy when the thermostat cycles (off especially, dumping the transformer's stored energy). I've had lots of situations where the impulses cause large interference, even sometimes popping GFCIs. There is no added EMI suppression in these at all.
I've even used them to quick-check sensitive circuits to make sure if they're properly shielded and such - if the iron is on, you can hear the thermostat click, which is the trigger to look for bad behavior.
Ed
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Re: EMI filtering on power cord
OK, the interference seems odd, but I can't really explain it.
What about Metcal, in your experience?? I know they are about 13 Mhz, but I do have to wonder how well shielded they are.
What this suggests is that a standard 24 volt system with a variac might be the optimal for low noise.
Harvey
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On 8/2/2023 9:45 PM, Ed Breya via groups.io wrote: Harvey, I've had the WTCPs almost forever. They don't make a lot of CW, but they are amazingly noisy when the thermostat cycles (off especially, dumping the transformer's stored energy). I've had lots of situations where the impulses cause large interference, even sometimes popping GFCIs. There is no added EMI suppression in these at all.
I've even used them to quick-check sensitive circuits to make sure if they're properly shielded and such - if the iron is on, you can hear the thermostat click, which is the trigger to look for bad behavior.
Ed
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Re: EMI filtering on power cord
Harvey, I've had the WTCPs almost forever. They don't make a lot of CW, but they are amazingly noisy when the thermostat cycles (off especially, dumping the transformer's stored energy). I've had lots of situations where the impulses cause large interference, even sometimes popping GFCIs. There is no added EMI suppression in these at all.
I've even used them to quick-check sensitive circuits to make sure if they're properly shielded and such - if the iron is on, you can hear the thermostat click, which is the trigger to look for bad behavior.
Ed
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Re: EMI filtering on power cord
Ross, Ed, Harvey, Thank you very much for your very thoughtful?and elaborate responses. This is?very helpful.
In my initial approach to this, I was thinking?more of electrical, not magnetic field filters ("radiated emissions"). I've opened the case a while back and - to be noted - there's absolutely nothing on the IEC connector of the cord coming in. Which is sort of why I didn't really think of ferrite cores, so that's a great?point for me to look into. Plus, they're cheap, and very easy to try and see if they cure or at least diminish this issue. The garbage thrown out is so bad, even an FM tuner is being disturbed enough to not present a listenable reception (with antenna in close proximity, so grain of salt with that).?
Anyway, I think I'll have a phased?approach and I have some "clip-on" cores coming in tomorrow. This is cheap and quick.?
Then I'll probably look into stuff like the?Tripp-Lite Isobar 2-6 or sym. I'm pretty sure I'll want to cure this in all ways it can manifest,?for the sake of my bench instrumentation and... fm tuners.?
Thank you, Radu.?
On Wed, Aug 2, 2023 at 1:40?PM Harvey White < madyn@...> wrote: Have a look at the WTCP series by weller.? Don't get the ones with a
temperature control.
You change the tip to change the temperature.
The tip is magnetic and attracts the heating element.? A little past the
tip's curie point, the tip becomes non-magnetic and the heating element
is pushed away by the spring.? As it cools down it becomes magnetic and
the heating element contacts the tip.
Not the most elegant (I prefer Metcal), but it's a 24 volt AC solution
without SCRs and 13 Mhz oscillators.
Harvey
On 8/2/2023 4:00 PM, Ed Breya via wrote:
> The only soldering irons that are relatively emission-free are the old
> fashioned heaters that just go when plugged in, or flame heated types.
> Ever since temperature controlled ones emerged, they have become EMI
> sources. So, you can't entirely escape EMI trouble just by changing
> irons, unless you take some steps back in the technology, or spend
> quite a bit of time and money.
>
> The most common irons nowadays I think, are variable
> temperature-regulated types, typically using a phase-controlled TRIAC
> circuit for the power part - same as a light dimmer for incandescent
> lamps. So, you've got lots of EMI crap around all the line frequency
> harmonics, plus RF from the relatively fast edges of the device
> switching, with line harmonics surrounding each RF spur. It's really
> quite a mess. I'd think there would be at least a little filtering
> included in most products for sale, but just barely enough to meet
> certain regulatory specs. And some items probably just ignore the
> specs. Anyway, some may be much better than others, but you'd have to
> compare specs, which may be non-existent or false, or compare actual
> units.
>
> So, you're kind of on your own, but there are plenty of very basic
> things that could have been built into these products (making them
> more expensive), that you can add. The first and easiest line of
> defense is common-mode chokes. Look into "clip-on EMI chokes" and
> such, which are split ferrite cores surrounded by a plastic
> clamp/holder thing. On a soldering iron for instance, you'd want
> chokes at the control box first - one at the line cord entry, and one
> at the power output to the iron cord. As Ross explained, the cordage
> makes great antennas for certain frequency ranges, so swamping that
> effect goes a long way toward peace and quiet.
>
> Chances are that you'll get very noticeable reduction in interference.
> If you've never dealt with common-mode chokes, you'll see right away
> why you'd want "clip-on" types, so you don't have to worry about
> fitting over connectors and such. If you just have to pass a wire
> through, then a solid toroid is best, but usually you'll have cables
> with connectors. Look for clip ones big enough to fit on the cables,
> and with as much L as you can get. Typically 1-10 uH is available in
> common size ranges.
>
> If you still need more suppression, you can try more CM chokes, and in
> different spots. You can get more improvement by adding more types of
> filtering, and figuring out how the junk gets out and around, as Ross
> explained.
>
> Lastly, for situations needing very low interference, you may have to
> turn off any offending items of all types, not just irons. They'll
> never be perfect.
>
> Ed
>
|
Re: EMI filtering on power cord
Have a look at the WTCP series by weller.? Don't get the ones with a temperature control.
You change the tip to change the temperature.
The tip is magnetic and attracts the heating element.? A little past the tip's curie point, the tip becomes non-magnetic and the heating element is pushed away by the spring.? As it cools down it becomes magnetic and the heating element contacts the tip.
Not the most elegant (I prefer Metcal), but it's a 24 volt AC solution without SCRs and 13 Mhz oscillators.
Harvey
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On 8/2/2023 4:00 PM, Ed Breya via groups.io wrote: The only soldering irons that are relatively emission-free are the old fashioned heaters that just go when plugged in, or flame heated types. Ever since temperature controlled ones emerged, they have become EMI sources. So, you can't entirely escape EMI trouble just by changing irons, unless you take some steps back in the technology, or spend quite a bit of time and money.
The most common irons nowadays I think, are variable temperature-regulated types, typically using a phase-controlled TRIAC circuit for the power part - same as a light dimmer for incandescent lamps. So, you've got lots of EMI crap around all the line frequency harmonics, plus RF from the relatively fast edges of the device switching, with line harmonics surrounding each RF spur. It's really quite a mess. I'd think there would be at least a little filtering included in most products for sale, but just barely enough to meet certain regulatory specs. And some items probably just ignore the specs. Anyway, some may be much better than others, but you'd have to compare specs, which may be non-existent or false, or compare actual units.
So, you're kind of on your own, but there are plenty of very basic things that could have been built into these products (making them more expensive), that you can add. The first and easiest line of defense is common-mode chokes. Look into "clip-on EMI chokes" and such, which are split ferrite cores surrounded by a plastic clamp/holder thing. On a soldering iron for instance, you'd want chokes at the control box first - one at the line cord entry, and one at the power output to the iron cord. As Ross explained, the cordage makes great antennas for certain frequency ranges, so swamping that effect goes a long way toward peace and quiet.
Chances are that you'll get very noticeable reduction in interference. If you've never dealt with common-mode chokes, you'll see right away why you'd want "clip-on" types, so you don't have to worry about fitting over connectors and such. If you just have to pass a wire through, then a solid toroid is best, but usually you'll have cables with connectors. Look for clip ones big enough to fit on the cables, and with as much L as you can get. Typically 1-10 uH is available in common size ranges.
If you still need more suppression, you can try more CM chokes, and in different spots. You can get more improvement by adding more types of filtering, and figuring out how the junk gets out and around, as Ross explained.
Lastly, for situations needing very low interference, you may have to turn off any offending items of all types, not just irons. They'll never be perfect.
Ed
|
Re: EMI filtering on power cord
The only soldering irons that are relatively emission-free are the old fashioned heaters that just go when plugged in, or flame heated types. Ever since temperature controlled ones emerged, they have become EMI sources. So, you can't entirely escape EMI trouble just by changing irons, unless you take some steps back in the technology, or spend quite a bit of time and money.
The most common irons nowadays I think, are variable temperature-regulated types, typically using a phase-controlled TRIAC circuit for the power part - same as a light dimmer for incandescent lamps. So, you've got lots of EMI crap around all the line frequency harmonics, plus RF from the relatively fast edges of the device switching, with line harmonics surrounding each RF spur. It's really quite a mess. I'd think there would be at least a little filtering included in most products for sale, but just barely enough to meet certain regulatory specs. And some items probably just ignore the specs. Anyway, some may be much better than others, but you'd have to compare specs, which may be non-existent or false, or compare actual units.
So, you're kind of on your own, but there are plenty of very basic things that could have been built into these products (making them more expensive), that you can add. The first and easiest line of defense is common-mode chokes. Look into "clip-on EMI chokes" and such, which are split ferrite cores surrounded by a plastic clamp/holder thing. On a soldering iron for instance, you'd want chokes at the control box first - one at the line cord entry, and one at the power output to the iron cord. As Ross explained, the cordage makes great antennas for certain frequency ranges, so swamping that effect goes a long way toward peace and quiet.
Chances are that you'll get very noticeable reduction in interference. If you've never dealt with common-mode chokes, you'll see right away why you'd want "clip-on" types, so you don't have to worry about fitting over connectors and such. If you just have to pass a wire through, then a solid toroid is best, but usually you'll have cables with connectors. Look for clip ones big enough to fit on the cables, and with as much L as you can get. Typically 1-10 uH is available in common size ranges.
If you still need more suppression, you can try more CM chokes, and in different spots. You can get more improvement by adding more types of filtering, and figuring out how the junk gets out and around, as Ross explained.
Lastly, for situations needing very low interference, you may have to turn off any offending items of all types, not just irons. They'll never be perfect.
Ed
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Re: EMI filtering on power cord
Hi Radu, ? There are two kinds of emissions that can be emitted from a product. Those are Conducted and Radiated Emissions and Conducted Emissions. ? The Conducted Emissions are those (as you said), emissions from the product that are induced into the Power Line (Mains), and those may be Common Mode or Differential Mode emissions. Those emissions may be generated (also said by you), by the off-line Switching Regulator internal to the product. ? The Common Mode Emissions are present on both AC Line Conductors and even possibly Ground. Those are controlled by Common Mode Chokes and Y Capacitors in EMI Filters. The Differential Mode Emissions are Emissions that are not the same on the AC Line Conductors. Those are controlled by the X Capacitors in the EMI Filter. ? ? The Radiated Emissions are emissions that are radiated into the local environment. Those could be coming from the Soldering Iron Base to Soldering Iron Handle – it’s a long antenna, right? ? ? Recommendations: - Unplug the Soldering Iron, move it 3 to 6 feet away, plug it into an outlet (preferably on another power source not common to the rest of your Lab setup), or ideally to an off-line AC-to-DC-to-AC UPS. Turn the Soldering Iron on and see if you still have the same problem.
- Soldering Iron Cable Radiated Emissions.
Move the Soldering Iron Handle (stretching the cable out vertically, then horizontally close to and approximating the same distance to your susceptible devices. The Vertical and Horizontal cable orientation is because E-H Radiated Fields are polarized. ? If you have a Loop Probe (it is easy to make one), and a Spectrum Analyzer or sensitive meter like an HP 3400A, you can “sniff” the Cable and localize the Emission Source. ? Don’t Rule out the Power Cord yet, we will get to that. If there are Conducted Emissions, they will likely be re-radiated off of the Power Cord and still cause the problem to some degree – that is, if they are not filtered correctly. If you still have a problem, take the Soldering Iron Power Cord and Z-fold it on top of itself with a length of 8”. This has the effect of making the Radiated Length of the Power Cord only 8” in length, pushing the ? wavelength much higher and less efficient to radiate the emission frequencies that the Soldering Iron Power Station is radiating. If that is not the problem, do the same with the Soldering Iron Cable from the Base to the Handle. ? If none of these show a big change in the problem, you likely do not have a Radiated Emission issue and it is (as you said), a conducted issue. ? - With the cables Z-folded as in step 1, plug the Soldering Iron back into the power outlet on the Lab Bench. Turn it on, does the problem come back? If yes, you likely have (as you said), a Conducted Emission Issue. The only way to fix that is to Filter the Soldering Iron Power Input Leads. They didn’t put in enough Conducted Emissions suppression.
? It is possible that a Capacitor in their EMI Filter has deteriorated and needs to be replaced. If that is the case it needs to be replaced with the same value and safety rating and type (an X Capacitor and a Y Capacitor have different safety ratings like X1, X2 and Y1, Y2). It is very unlikely that the Common Mode Choke has failed unless the Soldering Iron Base has been dropped and it became cracked. You might find one to replace it with the same value, wire gauge and safety rating. ? - A good External IEC-22 EMI Filter for this would one constructed with a Corcom 6EF1F EMI Filter in a small metal box. If you construct one, you will need to follow UL construction rules.
? - There may be other Filters out there that come in a box that will help. I have a Tripp-Lite Isobar 2-6 that I use to isolate noisy stuff under test. There is one on ebay now for $16.50 plus shipping. That would work for you – you would only plug your Soldering Iron into it. It would filter off the Conducted Emissions from contaminating the rest of your power to the rest of the bench. You may still have to Z-fold the cable because the re-radiated emissions are coming from the Soldering Iron Base.
? - If the offending emissions are from the Soldering Iron Cable, you would need to fix that in the Soldering Iron Base. The emissions are not likely coming from the Soldering Iron Heating Element in the Handle – it could though if it is a Resonant Heating Type, though. Remember, you are trying to suppress the emissions at the source not the destination.
? If it is a bad Capacitor, you can replace it with the same type and safety rated components. If you need to modify it, (add additional X and Y Capacitors in the Soldering Iron Base that supply power to the Soldering Iron Element in the Handle, that would likely violate the safety of the product and that must be considered too. ? - Last option, buy a new Soldering Iron.
? ? Hope this helps you solve the issue, ? Ross ?
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From: [email protected] < [email protected]> On Behalf Of Radu Bogdan Dicher Sent: Wednesday, August 02, 2023 10:53 AM To: [email protected]Subject: [Test Equipment Design & Construction] EMI filtering on power cord ? Hi all,
Not sure this is the right home for this topic, but here it goes.?
I've been very happy using one of these clone soldering stations and handpieces that accept Hakko cartridge tips. And the tips are amazing, they changed my soldering life.?
Now, the station is a small aluminum box with fine control circuitry etc., but it spews all sort of switching noise and whatnot into the lab/bench. It's so bad, I've seen it disturb measurements, or very sensitive signal setups such as those used when aligning FM tuners.?
I guess I'm looking for - maybe?... - an inline EMI filter? One that would have a female (one end) and (male) the other end IEC sockets? I don't know what's available out there and some research didn't return much in terms of great options.?
Welcoming any ideas of curing this issue.?
Thank you,
Radu.?
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EMI filtering on power cord
Hi all,
Not sure this is the right home for this topic, but here it goes.?
I've been very happy using one of these clone soldering stations and handpieces that accept Hakko cartridge tips. And the tips are amazing, they changed my soldering life.?
Now, the station is a small aluminum box with fine control circuitry etc., but it spews all sort of switching noise and whatnot into the lab/bench. It's so bad, I've seen it disturb measurements, or very sensitive signal setups such as those used when aligning FM tuners.?
I guess I'm looking for - maybe?... - an inline EMI filter? One that would have a female (one end) and (male) the other end IEC sockets? I don't know what's available out there and some research didn't return much in terms of great options.?
Welcoming any ideas of curing this issue.?
Thank you,
Radu.?
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Re: Open-hardware power rail oscilloscope probe
LTspice may be helpful for all this ... I'm not volunteering to do it :) but I'm doing my first serious low-noise design in it now. Like any simulator, the garbage in-garbage out phenomenon is always hanging over you, but it could be instructive and help verify analytical analysis. One need not have the design-intended opamps and transistors, just something reasonably in the same realm, and swapping in & out other models can give an idea of how sensitive a component / circuit section is to overall noise levels.
Have fun ...
J
Gary Johnson via groups.io wrote:
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The originator was mystified by the fact that the measured noise was much higher than expected. The mistake in his noise estimate was assuming that the gain of the first stage is 1. While that’s true for the signal path, the *noise gain* of that stage is about 12. So the voltage noise of the op amp is multiplied by 12, not 1.
At least that’s what I saw after quickly skimming the article. Mighta missed something along the way…
Gary NA6O
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Re: Open-hardware power rail oscilloscope probe
The originator was mystified by the fact that the measured noise was much higher than expected. The mistake in his noise estimate was assuming that the gain of the first stage is 1. While that’s true for the signal path, the noise gain of that stage is about 12. So the voltage noise of the op amp is multiplied by 12, not 1.?
At least that’s what I saw after quickly skimming the article. Mighta missed something along the way…
Gary NA6O
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Re: Open-hardware power rail oscilloscope probe
Interleaved, please: On 7/31/2023 2:42 PM, Patrick Coleman wrote: Sorry about this - I realised this afternoon that KiCanvas is still in alpha and doesn't work everywhere yet (eg, mobile!). I added an old-fashioned PDF schematic to , see -
Oh, I have a copy of Kicad, and just opened the file in that. Since I really haven't used it for anything yet (EAGLE in my configuration works for me), running it on a laptop has some interesting features. Hi, this is a pretty neato thing, if you commercialize your design
I'd be interested in buying one! tx!
Thanks Jesse! I'll update here as soon as I've got a prototype ready (I'm hoping to slide it in with another order early next week).
Harvey, John - I really appreciate the comments. I wanted to think about them a bit more (and run the different configurations through my noise calculation spreadsheet), and I'll respond tomorrow. John, my instinct was to avoid diodes in the low-noise section but you may well be right that the input voltage is too high on one end of the potentiometer. I'll take another look.
My thought would be to have the gain stage without an input offset adjustment.? As long as the offset is not too bad, it can be compensated for by simply sending the pot voltage to the inverting output driver.? Noise on the pot would not be amplified by the gain stage.? This almost suggests a 20 turn trimpot to adjust a "zero" reference and then a front panel offset (you may want steps and the like). I'd also consider putting in an isolated supply running off the USB inputs.? They're surprisingly inexpensive.? Not sure how good the noise figure is, but if that were a problem, then plugin to charge, but the grounds are now isolated. Harvey Kind regards
*Patrick Coleman*
Technical Director
BLINKENLIGHT Ltd
mob. +44 7709 045 513
web. <>
Sent from Front
On July 31, 2023 at 5:30 PM GMT+1 roy.thistle@... wrote:
On Sun, Jul 30, 2023 at 05:57 PM, Patrick Coleman wrote:
You can find the schematic
yup... can't view the schematic with anything but your link (doesn't load anything in Altium 365, or directly on the Kicanvas Webpage.)
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Re: Open-hardware power rail oscilloscope probe
Sorry about this - I realised this afternoon that KiCanvas is still in alpha and doesn't work everywhere yet (eg, mobile!). I added an old-fashioned PDF schematic to?, see -
Hi, this is a pretty neato thing, if you commercialize your design I'd be interested in buying one! tx!
Thanks Jesse! I'll update here as soon as I've got a prototype ready (I'm hoping to slide it in with another order early next week).
Harvey, John - I really appreciate the comments. I wanted to think about them a bit more (and run the different configurations through my noise calculation spreadsheet), and I'll respond tomorrow. John, my instinct was to avoid diodes in the low-noise section but you may well be right that the input voltage is too high on one end of the potentiometer. I'll take another look.
Kind regards |
| Patrick Coleman |
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| Technical Director |
| BLINKENLIGHT Ltd |
mob. +44 7709 045 513 |
| web. |
 On July 31, 2023 at 5:30 PM GMT+1 roy.thistle@... wrote:
On Sun, Jul 30, 2023 at 05:57 PM, Patrick Coleman wrote:
You can find the schematic
yup... can't view the schematic with anything but your link (doesn't load anything in Altium 365, or directly on the Kicanvas Webpage.)
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