Does you soldering iron have grounded tip?

[Leo Bodnar]

I have been using ERSA soldering station that came to me with continental power plug (two prongs, no earth.)
Consequently it has a floating tip (it has linear power supply inside.)


Just before I stick on a UK plug with a ground connection, are there any reasons not to connect earth ground to the tip?


I never had a problem with floating tip before, comes useful to do a quick touch up to live low voltage circuits.
But somehow I don't think this is right.

I haven't paid attention to how soldering tip is connected to earth inside the soldering station (if at all.)
Personally, I'd probably ground the tip with 100k 1W resistor with 0.1uF 400V cap in parallel to create a low current DC discharge path.
Maybe there is more science to this?

[Kiriakos-GR]

My cheap soldering station, has also an Ground point ( female banana plug ) ,
but I had never use it , in the last 15 years. 

[Zero999]

Yes connecting to earth via a resistor is best for ESD. I wouldn't connect a capacitor in parallel though because it will bypass the resistor at high frequencies, i.e. short pulses of static electricity so the current will be high. I'd recommend a 1M to 10M resistor with no capacitor in parallel.

[Leo Bodnar]

Yes connecting to earth via a resistor is best for ESD. I wouldn't connect a capacitor in parallel though because it will bypass the resistor at high frequencies, i.e. short pulses of static electricity so the current will be high. I'd recommend a 1M to 10M resistor with no capacitor in parallel.

Duh! I just realised that capacitor does not really belong there.  It's purely for ESD purposes, not for low impedance EMI protection.

[Fraser]

I can also confirm that my Weller TCP PS2D soldering iron uses only a L & N connection to the mains plug but it provides a separate ESD connection point on the front panel (4mm banana socket). I presume this is done to enable bonding of the iron tip to the common ESD bonding point along with your anti-static mats, wrist strap etc. Using the mains earth in such a scenario could result in a p.d. if the ESD earth comes from a different location to that of the utility mains earth.   

In some countries that I have visited the earth pin may exist at the utility mains face plate, but in truth it is not a decent earth and should not be used for ESD protection or as a safety earth for that matter !  In one Middle East country I found the earth cable ran through the building and was then just buried under the concrete floor in the basement, no earth stake, carbon pit, copper mat or anything ! When tested for RF it actually made a pretty good HF antenna !!!! You should be fine in the UK though 

[Zero999]

An ESD earth is better being high impedance.

One room where I used to work had a large piece of sticky copper foil fixed to the building's brick wall for an ESD earth. I was sceptical so I measured the resistance between the ESD earth and mains earth and found it to be around 10M which was perfect for ESD protection. I suppose it was more convenient and deemed to be safer bonding to the wall than to the mains earth.

[ElektroQuark]

Yes, my METCAL (OKI) station has it.
It doesn't start if not properly grounded.

[tekfan]

Mine doesn't. I don't often care about ESD. Most of the time I just repair old electronics with ECL, TTL. Even when I work on old 4000 series CMOS logic I've never had a fauliure due to static discharge.

There are also times where a grounded iron is critical. Once I attempted to resolder a broken joint on a transformer's primary side. The circuit was live the entire time. I was amased to see the power LED glow without touching the power switch. I was amased I didn't receive a nasty shock (240VAC mains here).

A grounded soldering iron would have tripped the circuit breaker and but in this case I just continued soldering without knowing.

[gobblegobble]

It's a double insulated device and should not be grounded as per se, but assuming you don't modify the construction other than hooking up the tip to the ground through a 1M resistor you should be okay. Be aware though it will only work as ESD protection and will NOT trip the circuit breaker in any circumstances due to the added resistance. RCD should work perfectly fine though if you have one.

[ilikepez]

Why in gods name would you work on a live transformer like that?

[tekfan]

Why in gods name would you work on a live transformer like that?

I forgot to check the amplifier was turned off and unplugged from the mains. Definetly not the first time it happened.

[flolic]

I forgot to check the amplifier was turned off and unplugged from the mains. Definetly not the first time it happened.

What reminds me of flashes, bangs and burnt screwdrivers... Working on a live circuit, priceless  

[Slobodan]

My Ersa Multitip 15 has a grounded tip.

[KD0CAC John]

I like to confirm what I think I'm learning .
A thought I had on the subject , any conductor can acted like an antenna , and collect charge , or a capacitor ?
Much like , maybe my wrong idea on potential - the movement of charge ?     
Or without ESD grounding , the potential of damage

[mike_mike]

Hello,
I need help regarding the connection to the ground of the soldering iron and the connection to the ground of the electrostatic bracelet.
Can you show me a connection schematic ?

[Mortymore]

Hello,
I need help regarding the connection to the ground of the soldering iron and the connection to the ground of the electrostatic bracelet.
Can you show me a connection schematic ?

The big picture


Basically you should have a star connection. Each device that has to be ESD save must connect to a single convergence point, through a resistor between 100k and 1G Ohm

A connection board like this can be used, attached to the bench. Then the green cable goes to a ground connection in a wall socket, for instance.
 


As far as I know, typically the cables available in the market have 1M ohm resistor integrated. Being for wrist straps, ESD bench or floor mats, or to a soldering station



I have an Ersa RDS80 solder station that has a socket to connect an ESD wire. Between the tip of the iron and that socket there's a 200K Ohm resistance, so a direct cable could be used to connect to that convergence ground box. But I have my solder station connected through a cable with the 1M ohm resistance integrated.
That being said, the iron tip is not directly grounded. It's connected to ground but through a total resistance of 1.2M (0.2M from station + 1M from cable).

There must not be more than one concentration point to connect devices, in the bench.

EDIT to attach pictures in case the links get broke

[mike_mike]

I made the following schematic using the information that I found on the internet. The soldering iron that I will use is the Pensol IronE-N.
It is correct, or should I add a 1 MOhm resistor for the soldering iron also ?

[Mortymore]

It is correct, or should I add a 1 MOhm resistor for the soldering iron also ?

You have to add 1M Ohm resistor for the soldering iron

[Ian.M]

Unless the soldering station is designed to be double insulated, the tip typically needs to be directly grounded without a high value resistor in series.

This is because the ceramic insulation typically used for the heater element can become electrically leaky when hot, which typicaly couples half the element supply voltage to the tip, through the hot resistance of the ceramic which can be under 100K.   

See https://www.eevblog.com/forum/beginners/simple-fet-circuit-for-onewire-protocol-doesn_t-work-as-expected/msg1277272/#msg1277272 for a case when missing ground to a soldering station blew the s--t out of the poster's components. 

The same could happen if you inserted a 1Meg resistor in series with the tip ground connection on a soldering iron or station designed to have a directly grounded tip.

[mike_mike]

@Ian.M I read the messages from the suggested topic.
If I understood correctly, there needs to be direct contact between the soldering iron tip and earth. Is that correct ?
Also, it is correct to use 1 MOhm resistor between the electrostatic bracelet and earth ? Or there should also be direct contact ?

Thank you.

[Ian.M]

Yes, if the soldering iron element to bit leakage current is greater than a few uA it needs to be directly grounded to prevent damage to unprotected MOSFET gates.   

The wrist strap ground should always have approx 1Meg in series to prevent electrocution.  In 220V-240V mains supply countries, don't use a single resistor unless its rated for a voltage >=400V.  As 1/4W through hole resistors typically have a max voltage rating of around 200V (unless otherwise specified), I recommend 2x 560K in series.

[KL27x]

Mine had grounded tips. I inserted a 1Mohm resistor on all my 888's. I didn't even have to buy them; they are already there. A 1 Mohm resistor is connected between earth and the only N/C pin on the connector, so you just have to remove one connection and add a jumper. I have soldered more logic level mosfets than you could shake a stick at with no problems.

It occurred to me that I could add a switch to select between direct earth and 1M, but I never bothered.

[Ian.M]

Unless you are working with small discrete MOSFETs you are unlikely to see a problem as the leakage current must be sufficient to charge the gate capacitance to the gate oxide breakdown voltage in less than half a mains cycle (assuming line frequency AC power to the element).   Power MOSFETs typically have fairly large gate capacitance so more leakage current is required to reach the same gate voltage.

Most MOS ICs have ESD protection networks on their inputs which can easily handle the typical leakage currents involved, which protects the gate oxide of their input MOSFETs from overvoltage.

Most irons with mains elements have the tip hard grounded, for electrical safety and to protect components of the circuit being worked on.  Its less of a problem with low voltage irons, as, to maintain mechanical strength, the ceramic insulation thickness does not scale with the element voltage.  However as the element ages, and contamination (e.g from traces of flux vapour) builds up, possibly in micro-cracks, you can expect its insulation resistance to decrease.   If a low voltage soldering station was not designed for the bit to be grounded via a 1Meg resistor, it would be a good idea to occasionally check the voltage across the grounding resistor and either replace the element or switch to direct grounding if it ever exceeds a few volts with the iron at max temperature and actively heating.  Use a good DMM on AC V or a scope with a x10 probe, and the ground clip on the true ground end of the 1Meg resistor.

N.B. if the tip is hard grounded, it can be disastrous if you attempt to work on a circuit with charged capacitors or batteries present, if any other ground connection is present.  If in doubt, and especially when soldering PCB mount batteries, isolate the board or portable equipment you are working on by removing *ALL* external connections before soldering . . . .

[NiHaoMike]

Mine has a 100k or so resistor, added so that nothing dramatic would happen when soldering battery operated circuits if there's some unintended connection to ground.

[SiliconWizard]

On my Ersa station, there's a low-resistance connection from earth to the tip (like a couple ohm). Same on JBC stations.
Never had any issue with that. And yes, I always remove ALL connections to the circuits I'm working on before attempting to solder or unsolder.

For operator protection, a 1 Meg resistor or so to earth is warranted. Of course, you may notice that if you touch your soldering iron's tip (itself connected to earth with a low resistance),  you're going to lose this protection (but you'll also get burnt).

As Ian.M noted, this is justified but introduces a (minor IMO) potential safety concern, although the risk is probably higher with a high-resistance connection and a soldering station that doesn't have double insulation.

The ideal setup would probably be a double-insulated station and a 1 Meg resistor from tip to earth.