Weller WE1010 Solder Station: OK to replace power switch with lighted switch?

[vanwerk]

Hi all! First time posting here. I bought a Weller WE1010 soldering station earlier this year, and am wanting to replace the default power switch with one that is illuminated. I opened the case up and removed the original switch, and think I found a suitable replacement in terms of current rating and physical dimensions: https://www.digikey.com/en/products/detail/c-k/DA102J3GS215QF7/566770

Based on the circuit of the original power switch, is it OK to add this switch in serial, or will this affect the operation of the step-down transformer? I drew up the section of the circuit in question, original on top and my proposed mod on bottom. The pasted diagram is from the datasheet, hence my interpretation of a lamp & resistor in series with the switch.

[bob91343]

It won't work.  The neon lamp and the 33k resistor need to be across the primary of the transformer.  The lamp and resistor will be in series and the switch will apply power to the transformer and lamp-resistor combination.

[vanwerk]

It won't work.  The neon lamp and the 33k resistor need to be across the primary of the transformer.  The lamp and resistor will be in series and the switch will apply power to the transformer and lamp-resistor combination.

I agree. After thinking about it longer, it seems like the transformer and the series-resistor-lamp should be in parallel, which is exactly what you said, correct?



I guess I'm a little confused by the illuminated switch circuit in the datasheet.

[Nusa]

First off, I hope the switch is actually on the LINE and not the NEUTRAL, and you just have them backward on your diagram. Yeah, it'll work the other way around, but it's less safe. Ideally, there should also be a fuse. If there really isn't one there, consider adding one.

Otherwise, you're overthinking it. The datasheet diagram is indicating that the resistor and lamp are internal (you won't see them, but they're there) inside the switch connected between terminals 2 and 3, and the switch is connected between terminals 1 and 2. They're actually numbered on the switch, so it does matter which way around you have them on diagrams. So you connect terminal 1 to LINE, terminal 2 to the transformer, and terminal 3 to NEUTRAL (where NEUTRAL connects to the transformer is fine).

[NiHaoMike]

If there isn't already a fuse, add one just before the switch. Weller is infamous for leaving it out.

Also, adding additional resistance will allow the neon bulb inside to last longer, something like 10-22k would be a good value for your case. Maybe not so important for something like a soldering iron that is only used for short times.

[vanwerk]

First off, I hope the switch is actually on the LINE and not the NEUTRAL, and you just have them backward on your diagram. Yeah, it'll work the other way around, but it's less safe.

I hate to dash your hopes, but the switch is on NEUTRAL. I admit that I rarely work with mains connectors, but I'm fairly confident in my diagram. Here's a photo of the quick connect terminals on the inside of the AC inlet/IEC-320 C-14 connector, followed by a wide shot of the transformer circuit (click for full-size):

Ideally, there should also be a fuse. If there really isn't one there, consider adding one.

There isn't one on the primary side, unfortunately. I would love to put one in; I am open to suggestions on how to pick an appropriate fuse (current rating, fast/slow "blow", etc)!

Otherwise, you're overthinking it. The datasheet diagram is indicating that the resistor and lamp are internal (you won't see them, but they're there) inside the switch connected between terminals 2 and 3, and the switch is connected between terminals 1 and 2. They're actually numbered on the switch, so it does matter which way around you have them on diagrams. So you connect terminal 1 to LINE, terminal 2 to the transformer, and terminal 3 to NEUTRAL (where NEUTRAL connects to the transformer is fine).

I threw together a symbol in KiCad to hopefully clear up any confusion. Here's my interpretation of your proposal, with a fuse included on LINE:

Also, adding additional resistance will allow the neon bulb inside to last longer, something like 10-22k would be a good value for your case. Maybe not so important for something like a soldering iron that is only used for short times.

Thanks for the tip. I'm looking at Mfg Part Number DA102J3GS215QF7 for the switch that I chose; according to the datasheet, a P/N ending in 7 like mine already has an internal resistance of 33kΩ; is that sufficient? Excited to replace the lame stock switch with a glowing green one

[NiHaoMike]

2A slow blow would probably be a good start, definitely way better than nothing. You can also measure the highest current it draws during use (most likely while warming up) and add at least 25% for margin. Using slow blow means you won't have to account for inrush.

The 10-22k is in series with the 33k already in the switch, that will reduce the current so the bulb lasts longer.

[vanwerk]

2A slow blow would probably be a good start, definitely way better than nothing. You can also measure the highest current it draws during use (most likely while warming up) and add at least 25% for margin. Using slow blow means you won't have to account for inrush.

The 10-22k is in series with the 33k already in the switch, that will reduce the current so the bulb lasts longer.

Right on, thanks. Last Q: watt rating on that extra 10-22kΩ resistor? 1W? Not seeing the lamp's current draw, etc. anywhere on the datasheet.

I'm starting to think I might need to put all these extra components on a little PCB or something! Maybe put together a WE1010 "upgrade kit"

[bob91343]

The current drawn by the lamp is miniscule, maybe a milliampere or two so the power rating of the resistor is almost immaterial.  Figure 67 Volts across the lamp and the rest across the resistor.  Derate the resistor by at least 2:1.

[Ian.M]

There's no need to make a PCB as you can simply use an appropriately rated fully insulated inline fuseholder.  That also avoids the need to mount a PCB carrying mains safely.   The extra resistor is gilding the lily for a neon indicator that isn't going to be on 24/7.  Neons run at or below their rated current typically have an expected lifespan in excess of 20K hours.  If you do 20 hours soldering a week, you are unlikely to have to worry about the bulb wearing out for the next 20 years! 

If you *MUST* fit an extra series resistor for the neon, you can simply use a 1/2W through-hole one to get one that has thicker, more mechanically robust leads and so it runs cool, loop the leads to form eyelets to anchor the wire through before you solder them, file down any sharp spikes and cover the resistor, solder joints and 1/2" of the lead insulation with heatshrink sleeving with a drop of superglue on the wire insulation before shrinking to bond it to the heatshrink, then apply another layer of heatshrink over the top without superglue, extending 1/2" past the ends of the first layer. 

Don't forget to secure your new wiring with small cable ties so it cant flap around and short to anything on the secondary side of the transformer if any single connection comes loose.

[Nusa]

You can fix the Line/Neutral issue just by swapping those connectors at the IEC socket. Push the Earth connector all the way on while you're at it. And of course you'll need a new wire for the lamp. I tend to agree that you don't need to worry about the life of the lamp.

The advice above sounds good on fuses.

[vanwerk]

Thanks for the valuable input, all! This turned out to be a little bit more involved than anticipated, but I think it's a good idea to add in a fuse while I have it open.

We'll see what Radioshack has to offer today, if you can believe my town still has one.

[docsalr]

I modded it this weekend.  Added a red illuminated switch and an external fuse rated for 1A.  Hakko X-888D with similar specs has a 2A fuse and I am still scratching my head if 1A should be the right size?

[vanwerk]

Let’s go!!! I just realized I never posted pics of my final mod. Will update my post here when I get a chance!

[floobydust]

I modded it this weekend.  Added a red illuminated switch and an external fuse rated for 1A.  Hakko X-888D with similar specs has a 2A fuse and I am still scratching my head if 1A should be the right size?

It depends on the particular safety standard and size of the transformer, but primary fusing is generally 167-300% of the transformer's rated VA.
Assume it's an 80VA transformer (it would never see 100% duty-cycle and likely a bit undersized), 120VAC gives 1.11A to 2A for a fuse.

[docsalr]

Green switch also looks nice but I opted for a red one to warn anyone that it needs to be turned off!