Weller WSD81 vacuum pump mod

[lxd]

Hi guys.
This is my first post here so, a bit of information about me: I'm 21, looking to gain more knowledge about electronics. I am working in an A/V rental company and I need more expertise to be able, someday, to make my own hardware.

So.
For a few months I worked in a repair company that had a Weller WMD3, with a DSX80. (and a WSP80 but for some reasons I don't like it)
I loved this thing, it made recapping a lot easier. No more lifted traces, destroyed pads... You know the drill.

Wanting to have one at home, I started to look around for used units on the fleabay.
I love good tools, and boy o boy, you know they ain't cheap, but the WDD81 (the desoldering station) alone being 500$+, added its DSX80 iron which is going for around 200 bucks new on buy it now listings, was very cost prohibitive for me.
I started to look for cheaper options, but nothing gave me this impression of quality like the DSX80. So as it was not in my priority list, i skipped it for a little bit.

Someday, in a more or less recent past, I was wandering around on YouTube and I came across a video of Marco Reps about a WSF81D mod to add a vacuum pump.

This mod is using the solder feed output to drive the external pump (pretty clever I must say, this even allows the station to adjust the PWM duty directly via its interface)

This is great !
... Unless if nobody sells them.
Somewhat expected, as this kind of equipment is meant to be used in assembly plants.

So, i wander around a little more, and I found a listing for a WSD81 mainboard, bare. No casing, no transformer, nothing.
I quickly convince myself i'll figure something out, and as this was cheap, 30 bucks, i bought one.

One month later it shows up at the door, and here it is :





So it wasn't a scam, they scrapped WSD81s.
What do I do now ? I don't have anything to test it !

...

The DSX80, in all its glory, delivered in one piece by DHL. The seller didn't even use bubble wrap, the box was just wrapped in newspaper and packing tape. I'm glad I use PayPal sometimes...


All its accessories/consumables. I'm just missing the stand, which I will buy soon.


I may have gone a bit overboard on the transformer rating, but the iron and the controller themselves are eating around 90 watts.
If I want to be able to supply enough current to my 40 watt vacuum pump, I will need more than 130 VA. As 120 VA seemed a bit too small (maybe just right, I will never use the pump at max airflow anyway) I took a 160 VA one.


It is a Vigortronix VTX-146-160-212 for those who wonder. Quality and insulation seems ok.

I also bought the vacuum pump, a chinese™ VN-C4 which was surprisingly hard to find with a 24v motor.

The pump inside the WDD81V is a 35L/min, 55 kPa one.
This was the closest one that I found in terms of airflow, but it had a higher suction rate, 85 kPa. I'll take it, we'll see how it goes.

They even spelled "Model" wrong. Oh god what am I complaining about, that's the one and only Made in Chian quality seal.


Bent pin included for scale. Nothing a pair of pliers can't fix, right?

Anyways.
This is great but I don't even know if my motherboard works! And I know even less how will I drive my pump.
For the motherboard, it's simple, I just need to hook up the transformer to the controller and that should be it.
It will allow me to drive the iron, who should work even without the correct station. After all, it's just an expensive German-made resistor.
I'll do it. I'm just lazy. But i'm pretty confident that my controller should work.

For the pump driving part, that's a bit more complicated, but after a bit of Google-fu, I found this : Weller PU81 station mod for DSX80 desoldering handle

This is cool. That's what I want ! But unfortunately as this was made to fit inside the station, it will require some additional bodges and I don't want that. Also it didn't supply enough current for my pump.
So I decided that it was the time for me to take the plunge and learn how to design a PCB.

I fired up Eagle, watched tutorials, and started to re-trace the schematic that Futurist uploaded on hvforum.net. As he kindly provided his work as open hardware, and because my project is a fork of his, it will be a open hardware project too.

Here is Futurist schematic :


Here is my piss-poor redrawn schematic (i hope you do not mind some double traced nets, this is not OCD approved for the moment, i'll work on this later )


I needed to replace some components that weren't available for me. I guess Futurist did with what he had on hand for some things, but I may be wrong, that's where I need you

   - I replaced the DSF1J diodes who appear to be the part number for chinese made S1A-S1J series diodes. The choice of the F1J seems a bit weird to me, being used in D1 as a reverse polarity protection diode (?) and D2 & D3 as the astable multivibrator for the NE555 there is no need for a 400v diode.
D1 would need to be able to withstand the 1.5 amps for the 7805, D2 & D3 as they are for the astable, they need to be able to block Vcc, and be fast. Correct me if i'm wrong, S1B diode with 70V Vrms and 1 amp If should fit

I have seen that the 1N4148 is somewhat a better choice for astables, because it has a reverse recovery time in nanoseconds I guess. Is the diode speed related to how "sharp" will the PWM look?

   - For D4 and and D5, I need a schottky diode with Vrms greater than 24v and If greater than 2A (or should it be able to withstand all the current of the LM2596?). It seems to me that the MBRS340 would fit here.
Also, what is the purpose of D5?

   - I also need to replace the AP9985GM-HF 40V N-channel mosfet. I think that the DMN4026SK3-13 can do the job, 40V Vdss, it's Rds is higher than the AP9985 but I don't think that it will cause a problem, the higher the Rds, the higher the efficiency if I am correct?

Do I need to change the value of R2 here? As Rds is higher?

If someone could take the time to answer my questions, that would be really helpful.
I'll work on the schematics a bit more to get them right and i'll get on the routing this week end hopefully.
I will share the project files when they will be clean.

Many thanks in advance

[Hydron]

I've had a look at this circuit before for Futurist, it is a bit more complicated than required but did work for him. I'll have a proper look at your comments when I get some time.

I'm wondering if you bought your iron off the same seller as me and Futurist - mine arrived with thin newspaper and tape only, was OK thankfully. Did you also get a large number of tip number 6 included (the seller seemed to have a lot of them)?

I also built my station using a bare weller PCB (scraped from a 50W unit - PCB is the same as 80W), an 80VA toroidal transformer and a pump from a different scrapped desoldering station. I'll see if I can find some pictures to post.

[lxd]

Well, thank you for taking the time to help him, otherwise I would not have had his schematic to start my project

I bought it from a german seller, firestorm6 who still sells these :
eBay auction: #https://www.ebay.com/itm/Weller-DSX80-Entlotkolben-NEU-Orginal-Verpackt-sehr-viel-Zubehor/273597525448?hash=item3fb3aeedc8:g:g00AAOSwB-1Y4j6G:rk:3:pf:0
I picked it up for 165$ shipping included.

It was, as yours I guess, delivered with 10x 6# tips, a glass holder kit (tin can + one filter pre-fitted + kapton holder + glass tube), 10 filters and 2 o-rings, and the scraping tool for the tip holder.
The rest of the accessories were bought on another auction for 75$.

For the moment, this is what I have spent :
- WSD81 PCB 30$
- Vacuum pump 35$
- DSX80 165$
- Accessories 75$
- Toroidal trafo : 45$

At this point, i'm missing the stand which is 80$, all the components for the mod who should cost me under 100$, the PCBs let's say around 20$.
For the casing I will temporarly use a junction box because i want to design a custom laser cutted aluminium case for it, and as I want to build another station (a Unisolder, to drive a JBC C245) i will wait to have this one ready to send the parts to be cut.

I hope this project will stay below 600$ all complete, not so cheap but still that's 100$ less than what a WDD81 and a DSX80 alone would have cost me, and I have all the bits and bobs which would have been another 150$ if I had took the OEM weller route. For me it's a bargain.

I'm indeed very interested by your station, it would be cool if you could upload pics of it.
Thanks for everything!

[Hydron]

My suggestion to simplify it would be to remove the 555 section, and run the pump straight off the output of the LM2596. You can use the P2 pot to set the output voltage (I left mine at 24V, doesn't need to be changed after you have it correct), and the ON/OFF pin (pin 5) on the LM2596 to turn the pump on and off.
You can use the same 24V relay with the NC contact to pull the pin up to a voltage between 1.5 and 25V to turn it off when the button is not pressed, and disconnect it (which turns the LM2596 on) when the button is pressed. There are other ways that don't use a mechanical relay (I used a bridge rectifier and an optocoupler) but the relay is easiest.
Further simplification would be to remove the 12V reg entirely and replace with a zener + resistor (if you're only pulling the LM2596 pin high/low it needs very little current) but it's probably not worth bothering.

As for the questions about diodes:
D1 is to protect U1 from reverse conduction if the power is turned off but C4/C5 are still charged. Take a look at the datasheet for the 78-series regs - probably has it in there somwhere.
D4 and D5 - these are freewheeling/flyback diodes, and should be fast types, with schottky being ideal. D4 is obviously part of the buck converter circuit, but D5 actually does a similar task - the pump motor is an inductive load so the diode is needed to carry the current after the MOSFET turns off. (D5 would not be needed if the motor was directly driven from the buck converter, rather than from the 555).
D2 and D3 can be any small signal diode - 1N4148 is ideal as you mentioned.

As for my iron, it was indeed from the same seller, and see pics attached of the power unit I made. I used a similar buck converter on a salvaged PCB glued to the lid to drive the motor (I was _very_ short on space) and the weller PCB with potentiometer control is at the bottom of the enclosure (mostly hidden). Works rather well - am very happy with the purchase. I may also build a unisolder at some point, but I need to find some more time first!

[lxd]

Thanks for all the great suggestions, I will redraw this tomorrow or maybe sunday, i will ditch the relay and the 555 section as you did.
At this point i wonder if I should take the trouble to put a pot on the faceplate to adjust the pump voltage.
Wouldn't be very complicated though, keeping P2 but replacing it with a lower value pot, and placing a 10k pot in series with it on the frontplate should allow me to raise the lower value of the said pot with P2, to set it right where the pump starts.

Thanks for answering my questions aswell, it is much more clearer for me now. As I will ditch the linear reg and the 555 most of these won't be on the design, but i'll think of your comment when i'll see them elsewhere.

You have done a great job on your station, that's a tight fit ! What did you use to glue the PCB to the lid? It looks a lot like silicone gel but I have a doubt that it can hold onto polycarbonate cover with such a thin layer, is it epoxy?
Also, fun thing, the motor of your vacuum pump is made by Crouzet, their HQs are in Valence, not far from where I live
Their products aren't cheap though. In which station did you get it? It must have been a pretty good one to include such a quality part !

The unisolder is definitely my next project. It would be interesting to see if Sparkybg can create the profile for the DSX80 on it.
I seem to recall that the ceramic heating element of the WSP80 and the DSX80 share some similarities by the looks of it, I haven't measured them though, but maybe it can work with the WSP80 profile.

I'll post here as soon as I have progress. Cheers and ty again

[Hydron]

My pump came from an old JBC unit, so not surprised it's expensive!

I probably wouldn't bother with a pot for the pump voltage, but it's not hard to do if you'd like it.

You will need to have something like a relay or optocoupler still to switch the pump on/off - one wire of the button in the handle is shared with the heater. A 24VAC relay is the easiest way to deal with this - just put the coil between the switch pin and the unswitched as input.

WSP80 and DSX80 have compatible temperature sensors and heaters - they work with the same stations. You could probably use the WSP profile and maybe tweak the pid etc to deal with the larger thermal mass.

As for the glue, it's simply hot melt that's been smoothed while hot!