EEVblog Electronics Community Forum
Products => Other Equipment & Products => Topic started by: Haggis McHaggis on April 29, 2019, 11:07:45 pm
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Hello,
i bought a T12 Quicko Mini soldering station and measured some voltage (0.5-3V) fluctuating (leakage current??) on the tip with my cheap DMM. Measured against the negative pole of stations DC input.
The station is a 24V DC version, which is powered via an old Lenovo laptop psu. The psu has PE on the primary, but only +/- on secondary side.
I want to solder some parts like a MCP1541. The respective datasheet says it's a CMOS. Thus i assume ESD safety is needed.
I read about earthing the tip could help, but i'm not sure how to do it correctly.
Any tips are welcome.
Thank you!
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Hello,
i bought a T12 Quicko Mini soldering station and measured some voltage (0.5-3V) fluctuating (leakage current??) on the tip with my cheap DMM. Measured against the negative pole of stations DC input.
The station is a 24V DC version, which is powered via an old Lenovo laptop psu. The psu has PE on the primary, but only +/- on secondary side.
I want to solder some parts like a MCP1541. The respective datasheet says it's a CMOS. Thus i assume ESD safety is needed.
I read about earthing the tip could help, but i'm not sure how to do it correctly.
Any tips are welcome.
Thank you!
The best thing is open and check what inside the device, but since you connect it with a DC charger it means no earthing on tip
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Odds are, because it has three pin power in with PE, the laptop PSU has the 0V (-) side of its DC out grounded. You can check that by checking for continuity, PE to 0V with the PSU totally disconnected.
If the tip's floating you can ground it, so with the iron cold and power off, check resistance between the tip and the 0V side of its DC in jack. If it reads open or very high resistance, its OK to ground the tip (via the barrel). If it shows as direct continuity, its already supposedly grounded so something else is going on e.g. your PSU doesn't have a grounded output so you'll need a seperate PE to 0V ground connection. As with all Chinese clone stuff, you'll probably have to do some resistance measurements with a DMM or even a teardown to figure out if the handpiece already has a ground wire fitted separate from the heater connections, so you can simply mod the station.
Once you've I.D'ed the tip ground wire at the connector, try a 1K resistor between there and 0V. Nearly all the stray voltage on the tip should go away. If so you can link the tip ground wire directly to 0V. If it doesn't, further investigation is required + possibly rewiring the handset.
N.B. After successfully grounding the tip, be *VERY* careful when working on circuits with charged capacitors or batteries. If you touch the grounded tip to a circuit node that's got a significant voltage on it, shorting it out, if the discharge current is high enough, you'll damage the bit and possibly also damage the controller in the station. If you've got no choice but to solder a battery terminal with the battery present, disconnect *ALL* other lead to the board or device to ensure there is no other ground connection to complete the circuit, and work on an ESD mat, *NOT* a grounded metal surface.
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Thank you very much.
Odds are, because it has three pin power in with PE, the laptop PSU has the 0V (-) side of its DC out grounded. You can check that by checking for continuity, PE to 0V with the PSU totally disconnected.
I just measured that. There is no connection between PE on the input to the DC output.
If the tip's floating you can ground it, so with the iron cold and power off, check resistance between the tip and the 0V side of its DC in jack. If it reads open or very high resistance, its OK to ground the tip (via the barrel). If it shows as direct continuity, its already supposedly grounded so something else is going on..
The resistance between DC in (-) and the tip is around 13Mohm, no direct continuity.
The handle is a T12-9501 and has a 4 pin plug. One of the pins is connected to the tip and is connected to some pin on the controller pcb. I'm not sure how to check if this is the ground wire or there for other purposes.
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I've attached a photo that shows a similar controller board, but with the same handle. On my unit there is no wire going to Earth (DC IN) on the board. It makes sense because there is no Earth input or terminal.
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I measured the resistance with the psu plugged in but with no connection to mains. Between PE and tip i get around 13MOhm (this value is ascending the longer i measure) and between PE and DC output (-) around 1MOhm.
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the odd is... its your laptop psu that is floating (not 0V relative to GND) i zapped few (new never been used) mosfets while connecting MK328 transistor checker with this type of smps psu, they are nasty arse when not earthed. my suggestion, ensure you laptop psu output is isolated from its mains input (using the smps transformer), if so, earth the DC- pin by shorting it to the gnd/earth pin or using some high value resistor if you want to be safe. this is my fix to my zapping smps psu. ymmv.
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Thanks for your input.
my suggestion, ensure you laptop psu output is isolated from its mains input (using the smps transformer),..
How do you do this?
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Here is a top view of the unit.
There is a 1KOhm resistor between on/off switch and DC in (-). I've no idea what the purpose of the resistor is.
The tip is connected via the green cable to the 4 pin connector (pin A1, pcb label 'E'). The 3 pin DC in connector has the mid green cable missing (pcb label 'E') unlike on the connection diagram posted earlier. I assume 'E' means Earth.
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If you have the one that has a 2.1mm DC input jack like the photo above shows, then the chances are that your power pack / wall wart will not have the earth connecting through to the soldering station. This can be checked easily enough with DMM to see if there is continuity between the earth pin of the power unit and the DC jack. Do you need to have the tip earthed? sometimes it can an advantage to have it floating, especially if the power supply uses a isolated transformer winding for the power.
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If you have the one that has a 2.1mm DC input jack like the photo above shows, then the chances are that your power pack / wall wart will not have the earth connecting through to the soldering station. This can be checked easily enough with DMM to see if there is continuity between the earth pin of the power unit and the DC jack. Do you need to have the tip earthed? sometimes it can an advantage to have it floating, especially if the power supply uses a isolated transformer winding for the power.
Yes, i have a 2.1mm DC input jack on my unit. I already measured some stuff (see above). The psu has no direct connection between the mains PE and the DC side.
Like mentioned in my first post, my primary goal is to avoid killing MCP1541's while soldering them in. Since i measured some voltage on the tip i concluded that i need to eliminate that first and then may look further at additional ESD safety measures.
I'm a noob, so i don't know whether i need to connect the station to mains PE or if its sufficient to connect the tip to DC (-).
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It's not so much the 3V you can measure but the 90V or so floating around off those laptop supplies to ground. That'll pop a CMOS IC in a second.
The typical laptop packs are floating. Most of them don't even have an earth pin in the cable. You would have to provide a separate ground path. Note that you don't want the tip connected directly to ground but via a 1M resistor. You don't want to whip all the electrons out of the thing you are soldering instantly or it'll blow up anyway.
My T12 exploded violently anyway so it's dead now. I slung it on my neighbour's garage roof. Now use the Metcal and the T12 is dead to me much like my wife :-DD
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lol, thanks for chiming in bd139
How do i measure that 90V floating?
I've attached a photo of my psu. It has 3 pins in and 2 out (signal pin is not connected, the cable has only 2 cores)
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Ahhh the old thinkpad 90W bricks. Good power supplies. Had a few of them! Try measuring AC volts between the barrel plug shield and something earthed. I actually used to get a tingle off my T420 when I had one of them.
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Why is the 90 or so floating voltage an issue here, surely if your soldering anything on a laptop especially something that is sensitive, you'd remove the battery and unplug the power brick from it as well so the laptop is dead?
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The 90V is the leakage in the Y capacitors between the primary and the secondary on the SMPS. So the tip is likely 90V or so with respect to ground. If you go poking around CMOS stuff it can be an issue as you are closer to ground so the circuit goes:
mains -> Y2 capacitor -> secondary -> DUT -> you -> ground.
This is incidentally the reason you get that tingling on some floating SMPS stuff when you touch the metal parts.
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The 90V is the leakage in the Y capacitors between the primary and the secondary on the SMPS. So the tip is likely 90V or so with respect to ground. If you go poking around CMOS stuff it can be an issue as you are closer to ground so the circuit goes:
mains -> Y2 capacitor -> secondary -> DUT -> you -> ground.
This is incidentally the reason you get that tingling on some floating SMPS stuff when you touch the metal parts.
Are saying then that the power cord is permanently attached to the laptop? The Y capacitors are located in the external SMPS and not in the laptop itself. If so then unplugging the DC power jack leaves the laptop totally isolated from the Y capacitors and this leakage so the problem goes away? [emoji848]
Sent from my POT-LX1 using Tapatalk
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Where has the laptop come from?
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Oh, I see, it's the iron that that is powered by the brick DOH, [emoji83]
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my suggestion, ensure you laptop psu output is isolated from its mains input (using the smps transformer),..
How do you do this?
There is a 1KOhm resistor between on/off switch and DC in (-). I've no idea what the purpose of the resistor is.
yes that 1KOhm resistor is probably meant to bring the DC- to same potential as as your soldering iron circuit GND, but looking at your picture i guess it will not do any good since there is no real earth wiring in there. the real earth wire only available in your laptop power brick. you need to modify your power brick that means opening it up. if there is no screw on the power brick you need to crack those glue open. if you dont want to do that, and dont want to zap your electronics component, then find another psu that is earthed, a classic 50/60Hz big transformer psu if you have one or have to. you wont appreciate the "floatness" until you zap your stock components for no apparent reason. that tinggling sensation bd139 is talking about? thats a early warning for you. you maybe lucky this time, or your lenovo power brick is not as bad as other smps psu so ymmv.
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I have 2 if the T12 soldering stations but there are powered by 230 to 24v internal SMPS which have a proper grounding connection and that us the only really effective way to remove the risks associated with sensetive parts. I have replaced many mosfets with zero losses using this system. If you really must have a portable soldering solution then maybe a battery operated or gas powered system is the option that you should explore?
Sent from my POT-LX1 using Tapatalk
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Ahhh the old thinkpad 90W bricks. Good power supplies. Had a few of them! Try measuring AC volts between the barrel plug shield and something earthed. I actually used to get a tingle off my T420 when I had one of them.
measured AC voltages between:
mains PE and DC- = 0.1V
mains PE and DC+ = 36V
* used a switched off 230V soldering irons tip as mains PE
** a second (newer) lenovo psu shows the same voltages
*** used a cheap DMM
Edit: i measured the psu only, no soldering station connected
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.. the real earth wire only available in your laptop power brick. you need to modify your power brick that means opening it up. if there is no screw on the power brick you need to crack those glue open.
Yeah, opening a glued psu will possibly look shitty afterwards. I thought about cracking it open and putting the guts into a larger soldering station case. But i'd have to order a larger case from seller which costs $$ and maybe don't fit in the end. What do you think about simply providing the PE by another device or a selfmade mains adapter? I could mount a 'earth' jack on the back panel and use this to connect to PE.
Edit: earth adapter img added
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I have 2 if the T12 soldering stations but there are powered by 230 to 24v internal SMPS which have a proper grounding connection and that us the only really effective way to remove the risks associated with sensetive parts. I have replaced many mosfets with zero losses using this system. If you really must have a portable soldering solution then maybe a battery operated or gas powered system is the option that you should explore?
I think/hope my controller board is the same they use for the build in psu versions. It looks like they simply didn't connect earth (pcb label 'E') to anything other than the pcb and the tip. In other words the DC in connector on the board has 3 pins and the middle ('E') pin has the green cable missing.
A portable station is not what i'm after.
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I have 2 if the T12 soldering stations but there are powered by 230 to 24v internal SMPS which have a proper grounding connection and that us the only really effective way to remove the risks associated with sensetive parts. I have replaced many mosfets with zero losses using this system. If you really must have a portable soldering solution then maybe a battery operated or gas powered system is the option that you should explore?
I think/hope my controller board is the same they use for the build in psu versions. It looks like they simply didn't connect earth (pcb label 'E') to anything other than the pcb and the tip. In other words the DC in connector on the board has 3 pins and the middle ('E') pin has the green cable missing.
A portable station is not what i'm after.
So if its not a portable version, you could perhaps sell the one you have on Ebay or something and buy a mains powered system with the built in psu? where the PE connection is taken right the way through to the iron tip?
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I have 2 if the T12 soldering stations but there are powered by 230 to 24v internal SMPS which have a proper grounding connection and that us the only really effective way to remove the risks associated with sensetive parts. I have replaced many mosfets with zero losses using this system. If you really must have a portable soldering solution then maybe a battery operated or gas powered system is the option that you should explore?
I think/hope my controller board is the same they use for the build in psu versions. It looks like they simply didn't connect earth (pcb label 'E') to anything other than the pcb and the tip. In other words the DC in connector on the board has 3 pins and the middle ('E') pin has the green cable missing.
A portable station is not what i'm after.
So if its not a portable version, you could perhaps sell the one you have on Ebay or something and buy a mains powered system with the built in psu? where the PE connection is taken right the way through to the iron tip?
The idea was to use an old psu i already had laying around and in addition hoping for a better quality psu this way.
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I have 2 if the T12 soldering stations but there are powered by 230 to 24v internal SMPS which have a proper grounding connection and that us the only really effective way to remove the risks associated with sensetive parts. I have replaced many mosfets with zero losses using this system. If you really must have a portable soldering solution then maybe a battery operated or gas powered system is the option that you should explore?
I think/hope my controller board is the same they use for the build in psu versions. It looks like they simply didn't connect earth (pcb label 'E') to anything other than the pcb and the tip. In other words the DC in connector on the board has 3 pins and the middle ('E') pin has the green cable missing.
A portable station is not what i'm after.
So if its not a portable version, you could perhaps sell the one you have on Ebay or something and buy a mains powered system with the built in psu? where the PE connection is taken right the way through to the iron tip?
The idea was to use an old psu i already had laying around and in addition hoping for a better quality psu this way.
I don't see any downside to using the supplied PSU, I ordered from AliExpress Quick Heating T12 soldering station electronic welding iron 2018 New version STC T12 OLED Digital Soldering Iron T12-952 QUICKO which is the larger case, a 24v 108w PSU, handle and and 5 tips with the standard controller all included and is currently 39.40 Euros. I did however improve on the earthing of the case itself to ensure that every part of the enclosure was grounded. I have had these now since Jan 2018 and very happy with them and fitted MOSFETs with them and never had a single problem with them.
On the the other hand, you and and bd139 both seem to have problems with the portable version which I suspect would be perfectly fine if it's fed with pure 24v from batteries.
Personally I'd be inclined to sell the one you have and purchase a complete new system from AliEx and sell what you have.
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Agree with buying one with the PSU inside it. Possibly with a Metcal badge on it :-DD
To work around it when I was using it, I plugged the negative into the earth on my bench PSU. Have to watch out you don't have an earth fault though otherwise things get interesting pretty quick.
(https://i.imgur.com/fC5UKLl.gif)
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Hmm, but what is difference between adding an earth jack versus using one with build in psu? Is this not the same technically?
One advantage of external psu would be more space on the workbench.
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It works out about the same at the end of the day electrically. Based on the fact you already have it, grounding it is best approach.
The tiny case on the low voltage one tends to get dragged around everywhere though so there's an advantage there.
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I have 2 if the T12 soldering stations but there are powered by 230 to 24v internal SMPS which have a proper grounding connection and that us the only really effective way to remove the risks associated with sensetive parts. I have replaced many mosfets with zero losses using this system. If you really must have a portable soldering solution then maybe a battery operated or gas powered system is the option that you should explore?
Is GND/DC- and earth bridged in your stations? I ask because in my station GND/DC- is connected to the case. I assume if i had a separate earth that would be connected to the case (and E pin on the board) instead of GND/DC-. Do i get that right?
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Found another T12 diy station with instructions. The first photo shows how to connect earth to DC-, leaving the E pin unconnected. I wonder why its not connected to the E pin.
https://www.aliexpress.com/store/product/Electric-Unit-LED-Digital-Soldering-Iron-Station-Temperature-Controller-DIY-Kits-use-for-HAKKO-T12-Handle/2954088_32836960037.html?spm=a2g1y.12024536.productList_5404174.pic_0 (https://www.aliexpress.com/store/product/Electric-Unit-LED-Digital-Soldering-Iron-Station-Temperature-Controller-DIY-Kits-use-for-HAKKO-T12-Handle/2954088_32836960037.html?spm=a2g1y.12024536.productList_5404174.pic_0)
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Found another T12 diy station with instructions. The first photo shows how to connect earth to DC-, leaving the E pin unconnected. I wonder why its not connected to the E pin.
https://www.aliexpress.com/store/product/Electric-Unit-LED-Digital-Soldering-Iron-Station-Temperature-Controller-DIY-Kits-use-for-HAKKO-T12-Handle/2954088_32836960037.html?spm=a2g1y.12024536.productList_5404174.pic_0 (https://www.aliexpress.com/store/product/Electric-Unit-LED-Digital-Soldering-Iron-Station-Temperature-Controller-DIY-Kits-use-for-HAKKO-T12-Handle/2954088_32836960037.html?spm=a2g1y.12024536.productList_5404174.pic_0)
Please do not connect Earth to DC- it is wrong for the Quicko system, I'll post some photos shortly for you of my Quicko T12-952 system and there is zero connection between DC - or + and Earth. The entire system has its own integral earth connection which grounds all of the metal enclosure and the iron tip which are all bonded together, using the Quicko supplied recommended power supply (24V 108W) and as already stated works perfectly and I have soldered many sensitive parts with it and 100% success rate.
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Thanks. It may be the best to copy that for my station.
A few days ago i contacted the quicko store service and asked for manual and schematics, but didn't get anything. :(
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As promised here are the photos of my system and I have identical systems apart from of them is built into a very slightly longer case.
It uses a 4 pin plug and socket for the connection of the iron handle and please note that I no longer use the standard handle as supplied with the system when purchased, although it does still work ok with it, I now use the T12-9501handle system as it provides better physical control over the tip, the standard handle has more of the tip exposed, otherwise they are same electrically.
I have confirmed that there is zero electrical connection between the DC supply and the Earth/GND connections using my DMM on continuity setting. As will see, I have provided a GND connection stud at the back of the enclosure to ensure that the enclosure is safely Earthed as the power supply is held in 2 rails on the bottom section and this does not provide a very good GND connection to the enclosure, hence my modification. This has been reported to Quicko so that may no longer be the case as I have had mine for 16 months now so they may have modified the earthing.
(https://i.imgur.com/MQax7FZl.jpg) (https://i.imgur.com/KygzHGpl.jpg) (https://i.imgur.com/xQ70Gk7h.jpg)
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Thank you for the photos.
T12-9501 handle here too.
I think i need to isolate my DC jack from the case first. Maybe using a plastic DC jack. Then use a M3 or M4 screw or a banana jack as Earth terminal connected to the case. I assume i then have to connect this Earth to the E pin on the board. Is this correct? Do i still need that 1K resistor (between DC+ DC-) in this scenario or can i remove it?
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I would think that you could do away with it if your going for a full on earthing.
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Did they fit the 1K resistor just to be funny and mess with you? Probably not! It provides a discharge path for the PSU's secondary side reservoir caps. Without it, the statiuon may not reboot cleanly if you turn it off then back on again at the wall without waiting several minutes in between.
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In this case, the unit does not come with a PSU, you have to provide that or use an existing one and as such surely, if the PSU needed that 1K resistor, it would have been built into the PSU brick?
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I'm not suggesting the 1K is a minimal load for the PSU (though if they found out their own PSU needed that, I can see it could be cheaper to fit it in the station rather than reworking a large batch of sealed PSUs), I'm suggesting it *MAY* there to make sure the input voltage goes all the way down to zero if its switched off at the wall for a second or so so the MCU in the station conroller gets a clean reset. Some types of MCU are known to have problems with POR if the supply voltage doesn't start from zero at switchon. If they've run into that issue, a resistor to guarantee residual charge is drained while off would be a cheap & easy fix
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Well, the PSU is not of their making, it is in fact one that the OP already had. Quicko don't make an external PSU for their solder stations, they offer them with internal ones, of which I have 2 of them, or like the one the OP has which uses a smaller enclosure and is fitted a 2.1 mm DC power jack so the user can use an existing laptop PSU or use 24v batteries, in which case the resistor is not required for a minimum load etc.
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I got a reply from Quicko that said i can wire it according to their diy kit wiring diagram (posted earlier in this thread or Specmaster's built in psu version, it's the same), BUT i'd need a power supply like theirs.
The question is whether my psu is like theirs or not? On my psu it looks like DC- is somehow coupled to PE through a 1M resistor. (i posted some measurements earlier) Has their psu a completely isolated PE with absolutely no connection to DC? @Specmaster Can you somehow determine if your built in psu has a coupling or isolation for PE?
Edit: @Specmaster
In your post with the photos of your station you wrote about continuity testing PE. Did you measure resistance too?
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Yes I did measure resistance too and there is NO connection between the DC output of the built in PSU and the Earth / Ground and neither is their a resistor between the DC and Ground either. Its 240VAC into the PSU via switch and a fuse, DC out to the iron controller and then DC via the iron controller to the iron tip. The main incoming Earth is directly connected to the PSU earth rails along the sides of the PCB, to enclosure and also to the Iron tip casing.
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Thanks Specmaster.
So my psu is not like theirs/yours. Should i then simply short DC- with the tip/E pin on the board? That way the tip would be connected to earth via 1M. But i'm not sure the 1M resistance between PE and DC is some kind of error in measurement.
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Thanks Specmaster.
So my psu is not like theirs/yours. Should i then simply short DC- with the tip/E pin on the board? That way the tip would be connected to earth via 1M. But i'm not sure the 1M resistance between PE and DC is some kind of error in measurement.
Let me get this straight, the photo of the PSU you posted, is that the one you're using? If so, is it one that you purchased specifically to power your soldering iron, or was one you already for a laptop? I say laptop because that is what Lenovo do, they make laptops and the PSU's to go with them.
Could you dismantle your solder station and take photos of the controller and post them here for me?
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Thanks Specmaster.
So my psu is not like theirs/yours. Should i then simply short DC- with the tip/E pin on the board? That way the tip would be connected to earth via 1M. But i'm not sure the 1M resistance between PE and DC is some kind of error in measurement.
Let me get this straight, the photo of the PSU you posted, is that the one you're using? If so, is it one that you purchased specifically to power your soldering iron, or was one you already for a laptop? I say laptop because that is what Lenovo do, they make laptops and the PSU's to go with them.
Could you dismantle your solder station and take photos of the controller and post them here for me?
Yes, the Lenovo psu on the photo is exactly what i use to power the soldering station. I didn't purchase it specifically, i had it laying around here. It is made for Lenovo laptops.
I already thought about disassmbling the station to have a better view on the board, but they glued the board connectors to the power switch on the backpanel. So not as easy to do as i'd like.
Meanwhile i made a test with a 1K resistor between DC- and the tip and measured the DC voltage over this resistor. The voltage drops to about 0.02 with the resistor (was fluctuating 0.5-3V, sometimes up to 10V before). Does that mean i can safely short DC- and tip and be done? If yes, i thought about putting a switch into the back panel to make grounding the tip switchable.
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If its a genuine Quicko station then the front and back plates are held in place by 4 cross point screws each, removing these screws will allow the the end plates to laid flat so you photograph them still connected. I'm keen to see if the actual controller is the same or not as mine. I understand that there are other versions of controller on sale and that some of them may not be fully compatible.
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I've attached some photos.
The board is not the same as yours, but has the same connectors. I think it is pin compatible.
ps ordered from quicko store @AliX
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So your 1K resistor is located there on the front panel rather than on the DC jack at the back? I think that I'd personally be tempted to try it with the resistor left in circuit and run a earth lead directly to the metal case or ever that 1K resistor is connected to and do a test of that way and see if it has any effect on the the way that the iron behaves and also measure the leakage to the tip.
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I'm a little confused. Do you mean the 1K resistor you can see on my photos above? That resistor was built in by Quicko and is connected between DC- and DC+.
The other 1K resistor, not seen on the photos, i used to test shorting DC- and the tip (aka earth), which seemed successfully eliminate the actual 'voltage on tip' issue.
I hope didn't confuse all of this even more.
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The soldering iron heater shell (tip) should be directly connected to protective earth-ground.
This is so a fault in the power supply could not make the soldering iron tip become hazardous live.
An ESD wrist-strap or mat is grounded through a 1MEG resistor, but not a mains-powered appliance unless it has double-insulation and no Y-capacitor in the PSU, which is not the case here.
The KSGER STM32 controllers and irons use a 5-pin GX12-5 connector and 5 conductor cable, one pin for the safety ground and another for the heater return. They have two grounds.
Quicko has used a 4-pin GX12-4 and 4-cond. cable. I'm not sure where or how they safety-ground the heating element shell.
On the Quicko controller PCB, the two green wires (to PSU, to wand) should have continuity between them unless the PCB has a mistake. They should also have continuity with DC(-) and the soldering station chassis.
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OK, then, the best think to do here is to remove all modifications that you have done and return to a standard Quicko product, i.e. as it left the factory. Then try and connect an earth lead directly to the green earth lead on the Quicko unit and then do further measurement tests and see if the iron functions correctly and if the leakage that you measured before has disappeared. If it is working OK and there is no leakage detected it would then seem to be suitable for use.
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Sorry, i'm a noob and this getting more complicated the more i read about it :)
Do you say i absolutely have to get a direct separate PE connection from mains into the case? I thought i can use DC- as connection to earth (though with 1M resistance to PE) via the psu. It seemd to work here.
I haven't modified anything yet, i did tests using measurement clips and cables.
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That's correct then that way you'll be as close to the same kind of set up as I have. You know I still can't quite get my head around why you never went for the self powered version like mine, all of this problem would have gone because it worked perfectly straight from the box. As ,mentioned, the only modification I've made to mine was ensure that the metal enclosure was also well bonded to the PE for safety reasons in the event of a fault occurring internally between the PSU and the enclosure as the 240v supply is on the PSU PCB.
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It sure would have been easier, but the mini station was cheaper and i had two lenovo psu's laying around. In addition i thought not having 230VAC in the controller is a good thing. My hope is that the Lenovo psu is designed well and doesn't do much damage in case of failure.
Regarding tip/earth connection i read some soldering stations have that 1M resistor too. If i'm correct i would have the same in the end.
I have another question about the case. Since it is coated or anodized i'm not sure whether there is electrical connection between all the pices of the case or not. There is for example no connection between the DC jack (-) and the metall enclosure of the 4 pole aviation jack although there should be a connection if the case would be raw/uncoated.
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Yes, its cheaper its true, but the cost of the parts in kit form is not that much more, its only the PSU, enclosure and power lead, but then you probably have other spare power leads, and then the whole kit is guaranteed to work together correctly, using other parts and this is no longer a certainty.
Yes the case is anodised and what I did was to scrap this off at points where the various parts join together, at least at one corner of the top and bottom at front and rear as well drilling a hole in the base and mounting a earth stud there as well for added safety.
I would not worry about the 1M resistor as that is red herring, 1M resistors are used in some cases on antistatic mats and also to discharge capacitors but 1M in earth loop means that high voltages will still occur at the tip which is precisely what you don't want to happen, which was your original reason for raising this thread.
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I think I have same T12 station as Haggis McHaggis. My station is dead after several uses, do not power anymore. The inside pictures of Quicko T12-943 are on this link: https://www.eevblog.com/forum/beginners/soldering-station-quicko-t12-943-problem/ (https://www.eevblog.com/forum/beginners/soldering-station-quicko-t12-943-problem/)
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The linear voltage regulator overheats, because it's dropping 24V to 3.3V and powering MCU/OLED.
Some controller boards have a bad PCB layout, no extra copper for cooling that IC.
Others show a buck-converter which could be better but more noisy for the thermocouple amplifier.
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I'm a little worried about the controller after reading draza's unit suddenly stopped working.
Nonetheless i've another question about grounding. I've attached a schematic which shows what i want to modify on my unit. I thought about adding a banana jack, a toggle switch and replace the DC in jack with a insulated one. The switch would toggle the tip to either DC- or case/PE. Do you think it will work this way?
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I don't think that will work because you still need DC(-) going to PE.
If you are using a two-prong (ungrounded) DC power (laptop) brick, you must have a PE connection to DC(-) or it will float up to 60-100VAC (due to Y-capacitor) which can damage parts when you solder them. If you are using a battery pack for DC power, there is nowhere for ESD to go.
I would keep the case, DC(-), PE, banana jack all connected together. The ESD mat and wrist-strap should have 1MEG resistors.
draza's T12-943 unit I'm not sure why the controller failed - it could be his 30V bench PSU has overshoot problems and gave it say a 25V spike...
Yes, Quicko says T12-943 must be limited to 25VDC max. input voltage :palm:
I think some of the 24VDC power supplies have poor regulation or overshoot which might be too much. 1V margin is pretty small.
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I don't think that will work because you still need DC(-) going to PE.
If you are using a two-prong (ungrounded) DC power (laptop) brick, you must have a PE connection to DC(-) or it will float up to 60-100VAC (due to Y-capacitor) which can damage parts when you solder them. If you are using a battery pack for DC power, there is nowhere for ESD to go.
I would keep the case, DC(-), PE, banana jack all connected together. The ESD mat and wrist-strap should have 1MEG resistors.
My laptop psu has a 3 prong AC input. I measured 1MOhm between PE and DC- while the psu was off all connections and powered off. So it already has some kind of PE reference. Should i connect it directly to PE nonetheless in this case?
Edit: do you think my Lenovo laptop psu (posted an image of it earlier in this thread) can overshoot its output and can damage the controller? I hope it's a good psu with built in voltage peak protection. But what do i know.
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I think I have same T12 station as Haggis McHaggis. My station is dead after several uses, do not power anymore. The inside pictures of Quicko T12-943 are on this link: https://www.eevblog.com/forum/beginners/soldering-station-quicko-t12-943-problem/ (https://www.eevblog.com/forum/beginners/soldering-station-quicko-t12-943-problem/)
There is a high risk if the DC adapter (or bench PSU) is already on and then you plug it (DC) into the soldering station, a surge occurs that can make an overvoltage spike and damage the controller. It's due to the cable inductance and capacitors. Best to plug in AC power last.
The Quicko T12-943 controller is only rated to 25V max.
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My laptop psu has a 3 prong AC input. I measured 1MOhm between PE and DC- while the psu was off all connections and powered off. So it already has some kind of PE reference. Should i connect it directly to PE nonetheless in this case?
Edit: do you think my Lenovo laptop psu (posted an image of it earlier in this thread) can overshoot its output and can damage the controller? I hope it's a good psu with built in voltage peak protection. But what do i know.
Three-prong laptop adapters can have the DC side connected to PE ground, and others have a Y-capacitor and sometimes a 1 megohm resistor, instead of a direct connection.
I would say having a 1MEG resistor (inside the adapter) is not good enough. Because the adapter has leakage currents which can put some potential on the DC(-). If your tip has 36V stray charge on it, that can matter.
For me, I want my soldering iron earth grounded to ensure no stray charge can happen on the tip, no matter what. You need a ground-wire run for the ESD mat anyway. It's your choice.
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I would say having a 1MEG resistor (inside the adapter) is not good enough. Because the adapter has leakage currents which can put some potential on the DC(-). If your tip has 36V stray charge on it, that can matter.
I did a test in which i connected the tip to DC-. The stray voltage on the tip went away. But i'm not sure if there are other scenarios i did not measure. I simply measured it with my DMM for a short time.
I've attached some more wiring diagrams. Which would one you prefer?
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What is the switch for?
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What is the switch for?
Tip earthing on/off (floating on/off) I probably don't need this switch at all.
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I would ground everything together and check with an ohmmeter every few months. No switch needed.
Once my ESD mat ground went open-circuit and the mat had stray AC voltage from other junk on my bench.
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I've attached a new diagram.
green marked = 1MEG resistance measured
red marked = questionable connection
I read advice against connecting DC- with PE, because the galvanic isolation gets ineffective and there is risk of transient voltage flow for fractions of seconds when the psu is switched on/off. In my case there is already some kind of link between them (marked green).
Or should i simply connect the tip to DC- without an additional PE input jack to the controller as already mentioned in this thread? I then would connect the ESD mat and wristband through its own connection to PE and have it separated from the soldering station.
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For me, I want my soldering iron earth grounded to ensure no stray charge can happen on the tip, no matter what. You need a ground-wire run for the ESD mat anyway. It's your choice.
You don't specifically want the soldering iron tip to be connected to mains earth directly - this is why most production quality units will have a separate terminal on the station. You want the soldering iron tip connected to the same potential as the ESD equipotential zone. Nothing in an ESD equipotential zone should be tied hard to mains earth as you can still get an ESD strike in that case.
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You don't specifically want the soldering iron tip to be connected to mains earth directly - ..
I was wondering that too. Should i use the psu's link to PE as ground for everything? (see attachment)
Edit: there wouldn't be a connection to PE if the psu is not plugged in, so maybe not the best idea.
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All I can say is this, I don't have an ESD mat but I do have an ESD wrist band that wear when handling sensitive parts. My T12 irons use the makers proper PSU's, neither have any connection from the DC-ve to the tip directly or via any resistor to ground and the only grounding it does have is from the IEC inlet socket directly to the tip and the enclosure, so with the iron plugged in with the power lead plugged in the mains out on the wall or bench etc, the iron tip is connected directly to the mains PE.
I have replaced may sensitive parts, IC's and MOSFETS etc with this setup and not lost any of them due zapping them. Of course it goes without saying that the equipment being worked on is switched off and disconnected and any power filtering caps discharged before attempting to solder anything.
You are having the problem because of the cheap PSU that your using, which was designed in the first instance to power a laptop. Your PSU is leaking enough power that you may be able to feel a tingle when touching the DC output. With the proper built in Quicko PSU, there is no high voltage leak through to the DC.
This is the way to go in reality if your going to be working on sensitive gear, use the right tool for the right job, or of course, get yourself a 24v battery and the you will only have pure DC which should not leak.
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For me, I want my soldering iron earth grounded to ensure no stray charge can happen on the tip, no matter what. You need a ground-wire run for the ESD mat anyway. It's your choice.
You don't specifically want the soldering iron tip to be connected to mains earth directly - this is why most production quality units will have a separate terminal on the station. You want the soldering iron tip connected to the same potential as the ESD equipotential zone. Nothing in an ESD equipotential zone should be tied hard to mains earth as you can still get an ESD strike in that case.
Mains-powered soldering stations must have the tip (directly) grounded per safety standards, so I'm not sure what you are talking about. Please don't confuse people on this.
Grounding through a 1MEG resistor has it's own problems, there is no guarantee the tip is at zero volts potential due to leakage currents in the station's PSU.
On my ESD mat I monitor ground currents and find that even a mains power cord lying on across the mat can induce several few volts of mains hum, due to capacitive coupling and the 1MEG resistor.
Production-quality soldering stations can offer a front panel banana jack, which connects internally to mains-earth. The expectation is a mat or wrist-strap with 1MEG resistor is then plugged in.
An "ESD equipotential zone" has to have a reference, such as earth ground. You would never leave it floating because something grounded will inevitably touch the zone.
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For me, I want my soldering iron earth grounded to ensure no stray charge can happen on the tip, no matter what. You need a ground-wire run for the ESD mat anyway. It's your choice.
You don't specifically want the soldering iron tip to be connected to mains earth directly - this is why most production quality units will have a separate terminal on the station. You want the soldering iron tip connected to the same potential as the ESD equipotential zone. Nothing in an ESD equipotential zone should be tied hard to mains earth as you can still get an ESD strike in that case.
Mains-powered soldering stations must have the tip (directly) grounded per safety standards, so I'm not sure what you are talking about. Please don't confuse people on this.
Grounding through a 1MEG resistor has it's own problems, there is no guarantee the tip is at zero volts potential due to leakage currents in the station's PSU.
On my ESD mat I monitor ground currents and find that even a mains power cord lying on across the mat can induce several few volts of mains hum, due to capacitive coupling and the 1MEG resistor.
Production-quality soldering stations can offer a front panel banana jack, which connects internally to mains-earth. The expectation is a mat or wrist-strap with 1MEG resistor is then plugged in.
An "ESD equipotential zone" has to have a reference, such as earth ground. You would never leave it floating because something grounded will inevitably touch the zone.
Agreed, maybe the reason the 952 does not show any leakage of AC on the DC is because PSU is inside of a screened and grounded metal enclosure and the also the leads from the PSU to the controller are no more 50mm long so not a lot of capacitive coupling can take place there, unlike with a laptop PSU brick which typically has around 1 to 2 meters of cable to the DC jack.
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I made another diagram :)
In this one there is a banana jack for the tip isolated from the enclosure. DC- is connected to the enclosure. What do you think?
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Personally I'd connect the PE directly to the tip and enclosure and forego the banana plug, this could get accidentally pulled out and they your right back zapping the things that your trying to protect. Likewise ESD mat and wrist band, should be connected to PE via another route for safety.
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I would not float the soldering iron tip. Any bad connection or loose wire would cause a big problem. Just keep DC(-) and the tip and enclosure grounded together to PE, like soldering stations have been doing for many decades.
I don't suggest daisy-chaining the ground for the ESD mat and wrist-strap.
That way, one open connection at the mains PE wire would make the mat, wristband and soldering iron all float up together.
In production environments, after years the wires get broken or screws loose and it is possible to have a bad ground.
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I would not float the soldering iron tip. Any bad connection or loose wire would cause a big problem. Just keep DC(-) and the tip and enclosure grounded together to PE, like soldering stations have been doing for many decades.
I don't suggest daisy-chaining the ground for the ESD mat and wrist-strap.
That way, one open connection at the mains PE wire would make the mat, wristband and soldering iron all float up together.
In production environments, after years the wires get broken or screws loose and it is possible to have a bad ground.
The following notice ignored >:D
"Warning: this topic has not been posted in for at least 120 days.
Unless you're sure you want to reply, please consider starting a new topic."
Yeah, I know, but what'yer gonna do about it? ::)
I started reading this thread after following a link from the "Cheap T12 clone soldering stations" thread I'd stumbled upon in my search for a T12-9501 soldering handle wiring diagram to positively confirm which way round to best wire in the ball bearing shake sensor switch.
I'd already made a diagram from two months back when I'd rewired the supplied handle of a KSGER T12 soldering station with oled display (proper aluminium cased version) but hadn't noted that this switch actually had a 'polarity' (I hadn't actually had to remove it from the earth tag in the handle so had missed this little fact of its construction).
I did finally come across a posted diagram in that other thread and duly voted a 'thank you' to Zanga for his Reply #148 on: September 18, 2018
https://www.eevblog.com/forum/reviews/cheap-t12-clone-soldering-stations/msg1832351/#msg1832351 (https://www.eevblog.com/forum/reviews/cheap-t12-clone-soldering-stations/msg1832351/#msg1832351).
In hindsight, I suppose I could have worked it out for myself with a continuity test as I did once I'd confirmed that the 'gold' wire end is meant to connect to that tag and the blue wire to the 'silver' wire end (in case anyone's curious - the glass thermistor, btw, can go either way round). Basically, you want the ball resting against the disk contact (gold wire end) so that it makes an intermittent contact to the cup contact whilst soldering (ie the gold end pointing down). If you fit it the other way round, you'll land up having to rely on allowing the station's buzzer to remind you to tilt it up on every time out to reset whatever time out period you had chosen. Anyway, I digress...
What caught my attention here was this issue of "Touch Voltage" which virtually all small to medium power smpsus are afflicted with. Firstly (at least in the EU) we can blame the EMC directive in mandating the use of the dreaded Y cap measure to mitigate conducted common mode interference along the low voltage dc cable as a result of coupling via the high frequency isolation/stepdown transformer's inter-winding capacitance from the 150 or (in my case) 300 volt high frequency spikes produced by the HT switching of the 170 or (again in my case) 350 volts dc produced by directly rectifying the incoming mains and smoothing it (fvsvo 'smoothing') with a BFO 400 or 450 VDC rated cap to the tune of ~1μF per watt's worth of power rating (universal 90 to 265 vac mains voltage rating case), the idea being (like Brexiteer's demands on immigration) to send these unwanted voltage spikes back to where they had originated.
It works to a limited extent, perhaps by as much as 20dB's worth of attenuation if you're very lucky. It's less of the Aldididdle's "Once it's Gone, it's gone" slogan so much as Asda's "Every Little Helps." sort of a measure. However, this "20dB if you're lucky" prize does come with an unfortunate side effect, "Touch voltage" tingle (the classic 50 to 90 vac high impedance voltage seen with a typical DMM - it's actually half whatever the mains voltage supply happens to be, your 10MR DMM just loads the 1M6R typical of a 10W rated wallwart leakage voltage down to the 50 or 90 volt reading typically observed).
This is commonly seen in the case of class II wallwarts and cheap laptop charging bricks which forego the sheer unadulterated luxury of a PE connection. It's worth noting that even when an earthed laptop charging brick is plugged into an earthed outlet, it may still have this half live voltage if they've neglected to either connect the barrel (normally negative of the 19vdc output) to the PE or at least linked it to the PE via a 3 to 10KR 'bleed resistor' to bog down this leakage voltage to just a volt or less.
Incredibly, these aluminium cased oled KSGER stations aren't earthed despite the iron tips being connected to the PE tag of the C14 mains socket. Of course, mine is now well and truly earthed, but only after I'd modified the BFO diode heatsink which bridges the HV/LV isolation slot to stop it resting on the solder resist mask which had been its only form of insulation from a circuit trace carrying the 350VDC from the BFO 68μF 400VDC rated smoothing cap!!! :wtf:
TBH, I never tested to see whether this half live voltage was present on the DC output. The accursed Y cap which is typically wired in parallel with (often alongside of) the opto-isolator that provides the required voltage negative feedback to stabilise the voltage is still present in this smpsu board's circuitry. I can only conclude that it must have suffered this detriment but since I've linked the negative rail to the case and PE, I don't really care any more - it's not a signal generator where such a direct link between the BNC shields and mains earth is not a good idea[1].
In theory, as long as the tip itself remains connected to the PE, it shouldn't matter whether or not the DC supply is floating at half mains live voltage. However, as most of us know full well, theory and practice are often at odds with each other and in this case, prudence suggests that it would be a most excellent idea to also independently ground the DC output (negative common rail point) so theory and practice are in full agreement (even if it's merely a 10KR to reduce this leakage voltage to just a volt or so - in this case, it not being a signal generator, a full zero ohms connection to the PE is the best and cheapest choice).
The OP's problem here appears to stem from the use of a mini station being powered off a laptop supply that suffers from this half mains live voltage issue. A simple test to verify that this voltage is merely the usual half mA or less from a 4n7F (max - it's more typically a 1nF cap) Y class EMC RFI suppression cap (typically 80μA in the case of the 1nF used in a 10W rated wallwart), would be to wire a 10KR resistor across the DMM voltage input terminals to verify that the voltage drops to around the 2 volts or less mark (and doesn't blow the resistor to kingdom come! :-DD).
Once this leakage voltage has been proved to be the normal condition (as opposed to a nasty fault condition - Y caps are designed to failsafe, ie never ever go short but only open circuit), the common negative terminal can be tied to the PE connection alongside of the tip's ground connection to eliminate the risk of ESD damage to sensitive components.
[1] This reference to signal generators stems from the troublesome effects of ground loops you can let yourself in for if you do what Feeltech so foolishly did in response to customer moans about this half live mains touch voltage issue through the use of a non earthed (IEC C8 two wire mains cord socket) class II 10W rated smpsu board in the FY6600 model when they evolved it into the FY6800 model with its "Tail Wags Dog" BFO C14 mains socket on a 700 gram plastic boxed cheap arbitrary wave/function signal generator and hard wired the chassis ground to the PE by stealing one of the two ground wires in the ribbon cable, which links the smpsu board's +5 and +/-12 volt rails to the main board, as a ready to hand length of wire to solder directly onto the C14's PE tag. :palm: :palm: :palm: :palm: IDIOTS! feckin utter IDIOTS for perpetrating such IDIOCITY >:(
My solution to the original problem with the earlier FY6600 model had been to completely give up the notion that I could find a two wire mains lead based solution and, by way of a compromise re the tail wags dog effect, fit an IEC C6 (trefoil or clover leaf) three pole mains socket to provide access to the PE by which to link the chassis ground via a 10KR "drain" resistor to squash the 90 odd volts down to a mere half volt ac of leakage.
The class II smpsu used in these signal generators doesn't actually require a hard connection to the PE which was only needed in this case as a means of killing the nasty touch voltage stone dead with a 3 to 10KR "drain" resistor which attenuates any unwanted signal/noise flows to and from the mains earth by some 50 to 60dB (including any undesired galvanic voltages and mains frequency interference from volt drops in the neutral wire due to running heavy domestic loads).
JBG
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Thanks everyone who has contributed to this insightful topic.
I want to purchase a Quicko T12-942 unit from Banggood soon. To power the mini station, I would like to use a universal notebook power supply I found at home (see attachment). Unfortunately, the power supply's manufacturer spared the ground prong. To make sure that the station is ESD safe, I plan to connect a wire from a mains outlet PE prong to the case, ground of the soldering station and the tip of the station. Could anybody please confirm that this is the correct way to do it? Is this what you ended up doing Haggis McHaggis?
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Another 120 day topic warning... but since no one responded, well.
Yes, powerline ground is the standard way to do this. Should read under 2 ohms. NASA agrees.
http://www.dccguy.com/wp-content/uploads/2017/07/OpenForumHandtoolsPrass08.pdf (http://www.dccguy.com/wp-content/uploads/2017/07/OpenForumHandtoolsPrass08.pdf)