A few notes that i forgot to include in the docs...
First of all, the values i have given in the docu for adjustment are just general pointers to get things to work. Of course they can be tweaked.
For example, the maximum output voltage adjusted by R32. You could set it higher, so that it will dump more energy into the tip when heating up initially. However, i have no idea how much they can handle, so be careful. Of course you could also set it lower, which would increase heatup time a bit, but at the same time reduces stress on the coil in the tip and the output driver. Generally, the higher the voltage there the higher the current consumption, naturally.
The adjustment of the idle voltage using R19 can also be tweaked. Higher idle voltage means higher idle tip temp and faster thermal recovery. Again, lower idle voltage means a bit lower idle temp and a slower thermal recovery.
The OpAmp feedback network R23/R24 defines the gain of that stage. Since this is what is in the feedback loop, tweaking these values can give you a harder/deeper or softer/shallower response for thermal recovery when using the tip.
Greetings,
Chris
Nice
I just got a Metcal handle, tweezer and a pile of unused tips for free.
With this project I can get them into use
If anyone wants a set of PCB's, i still have 6 sets. One set consists of the main RF PCB and the supply/controller PCB. I'm happy to give them away without profit, that is, for the same price that i paid, plus shipping. So it comes down to 10 Euro for a set, plus whatever shipping cost is (depends on where it has to go and by what method).
So, if anyone wants a set, drop me an eMail and we'll figure out how to proceed.
Greetings,
Chris
Nice
I just got a Metcal handle, tweezer and a pile of unused tips for free.
With this project I can get them into use
That's great! Just make sure that the stuff is for the 13.56 MHz system. They also have a 455 kHz system, those things will not work on this supply.
Since i don't have such a system myself, i also can't adapt this circuit for it. My guess is that basically just the oscillator need to be changed and the xformer and filter section adapted to the lower frequency.
If anyone wants to jump in and work on that it would be great.
Greetings,
Chris
Nice
I just got a Metcal handle, tweezer and a pile of unused tips for free.
With this project I can get them into use
That's great! Just make sure that the stuff is for the 13.56 MHz system. They also have a 455 kHz system, those things will not work on this supply.
Since i don't have such a system myself, i also can't adapt this circuit for it. My guess is that basically just the oscillator need to be changed and the xformer and filter section adapted to the lower frequency.
If anyone wants to jump in and work on that it would be great.
Greetings,
Chris
They are for MX-500 so should work.
Is the connector some standard model or Metcal proprietary?
Nice
I just got a Metcal handle, tweezer and a pile of unused tips for free.
With this project I can get them into use
That's great! Just make sure that the stuff is for the 13.56 MHz system. They also have a 455 kHz system, those things will not work on this supply.
Since i don't have such a system myself, i also can't adapt this circuit for it. My guess is that basically just the oscillator need to be changed and the xformer and filter section adapted to the lower frequency.
If anyone wants to jump in and work on that it would be great.
Greetings,
Chris
They are for MX-500 so should work.
Is the connector some standard model or Metcal proprietary?
I's a standard F type, as used on cable/sat Tv so easily obtainable.
A few typos in instructions :
Inductor is SRR1260 not SSR1260
Full partno for IC1 is LM22676TJ-ADJ
What tolerance would you suggest for the NPO caps?
A few typos in instructions :
Inductor is SRR1260 not SSR1260
Full partno for IC1 is LM22676TJ-ADJ
What tolerance would you suggest for the NPO caps?
Ahh, thanks for the corrections!
As for the caps, i used RS# 391-038, which is spec's ad +/- 10% tolerance.
Note to everyone about the caps:In the instructions i said that that C20 and C30 are not used. For C20 this is still true. However, C30 should be installed _plus_ another one on top of it, so that in total there are 4 x 56p at the output of L5. This has improved has the output voltage by +10V (from 91Vampl to 101Vampl) when the tip is heated up and idling. I also reduced the number of turn on L5 from 10 to 8, which initially increased the output to 91Vampl. Reducing the turns on L3 also increases the output a bit, but also degrades the waveform itself a little. So i'm not sure if it is a good idea to do that or not. If you want to check for yourself, simply use only 10 or 9 turns instead of the original 11.
Since i am not a RF guy, the output filter is something that probably can be refined somewhat. If anyone has the proper knowledge and wants to build such a unit, it would be great if you could look into that. The goal is to get the maximum possible output voltage swing for a given supply voltage from the buck converter, while keeping the output waveform as sine-like as possible.
Greetings,
Chris
For what it's worth:
I used RS# 723-6596 for C14 to C19, and instead of one 33n for C13 i used 3 x 723-6593 in parallel.
Greetings,
Chris
Just for fun i did a small comparison run now.
I took 2 fresh cartridges, STTC-036. 1 mm from the tip end i placed 1 turn of solder wire on each. On my original Metcal supply, the STSS-PS2V-002, it took 10 seconds until the solder was molten. With my RF-Gen it only took 8 seconds. Repeated that several times after cooling down the tips to room temp (20°), same results always.
I have a peak voltage of 23.5 volts, and an idle voltage of 19.5 volts on my circuit. Dunno what the STSS has.
The Vampl values i gave above are probably not really correct. As already mentioned, i have a really lousy probe and a half-broken scope. From the timing results i got here it seems that my unit dumps a bit more power (and thus higher peak voltage) into the tip than what my scope tells me.
Greetings,
Chris
Since i am not a RF guy, the output filter is something that probably can be refined somewhat. If anyone has the proper knowledge and wants to build such a unit, it would be great if you could look into that. The goal is to get the maximum possible output voltage swing for a given supply voltage from the buck converter, while keeping the output waveform as sine-like as possible.
I would think max power as opposed to max peak-to-peak would be the optimum, depending on how far the waveform shape deviates from a sine.
I'd guess you may also get more power with no filter at all, as well as a ton of noise!
Once I start playing I'll hook up a specrtum analyser - this may be a useful away to tweak filters.
I would think max power as opposed to max peak-to-peak would be the optimum, depending on how far the waveform shape deviates from a sine.
I'd guess you may also get more power with no filter at all, as well as a ton of noise!
Yes, but since the load is the same, a higher peak voltage automatically means higher power. And indeed, the current draw from the overall circuit rises with that as well. [Edit: the voltages i got were on the output while a tip was connected, of course.]
BTW, still had no chance to measure the current consumption on the 12V rail. But if it of any help, my circuit consumes about 40mA when powered with 30V, when the RF part is turned off. Disconnecting the FET's drain, and powering up the driver, has it rise to 100mA. All that according to my bench supply.
I should really get some fresh fuses to have some meaningful measurements there....
Once I start playing I'll hook up a specrtum analyser - this may be a useful away to tweak filters.
Indeed. A network analyzer would be great as well, to figure out what impedance those tips have when cold and hot.
Greetings,
Chris
Just a quick update.
The boards are all gone, thanks to all who were interested in them.
As for the supply/controller board and firmware, i hope to get back to it in a week or two. I'm rather busy with a customers project at the moment and thus don't really have the time to do much on this one. However, i added some functions to the firmware, as well as the core of a state-machine to handle power-up, sleep, power-down, etc. with various options. It will be fully user configurable as well.
What it can do is to start at different power up modes, normal, limited and boost. "Limited" means to limit power uptake during initial heatup, "boost" means increased power during that. After a given time the unit can go into sleep, at which point it will go into "limited" mode, reducing power consumption. It will auto-detect any thermal load changes, and upon reaching a threshold will wake-up again, optionally in "boost" mode to decrease recovery time from sleep. Also, after staying a given amount of time in sleep, it will shut-down the RF stage completely.
Wakeup is then done by pushing/handling the encoder. Of course the state-machine also restarts when the tip is changed. What's left to do is to implement some software-based protection features, for example against too high SWR, supply, etc. And finally, of course, packaging it all together with a decent UI. Al settings will be stored in the internal EEPROM of the µC. Speaking of which, for development i currently use the PIC 18F2620. It can probably be scaled down later, once i know what the final memory usage will be. Also, i added a RS232 interface to the board, so that the µC can later be updated through the bootloader (i use TinyBLD here) without needing a PIC programmer. Of course the BL has still to be programmed using a regular programmer.
Greetings,
Chris
Can you sign me up for a set of boards when you get more?
Can you sign me up for a set of boards when you get more?
Thanks, but i'm not sure that i will get another batch done. My main goal was to get myself another supply for my Metcal handpieces, and also to get a usable circuit out in the open. Considering what it had cost me so far i could have gone and bought a used STSS, or even two of them, but where would be the fun in that
In any case, the current supply/controller board would have to change then anyways. Right now i used parts that i had at hand. The result is that the DC/DC converter circuits there for the +5 and +12 volt rails are extremely oversized. On a redesign i would go for a 12V switcher followed by a 5 volt linear regulator. Also i made a stupid mistake on them. I connected the boost/limit trimpots to GND on one side, while it should have been open there. Plus i forgot two series resistors after them. While all that can be corrected on the actual boards, it's something that should change for the next version.
But as said, not sure if i will get another batch produced. If anyone is willing to jump in on that, be my guest. I will definitely change the circuitry/layout to reflect these changes, so that someone else can have batch done. After all it's not that expensive, it was 35 US$ per 10 boards in red at iTead, plus a bit over 30 US$ for the DHL express shipping. Oh, and plus taxes of course...
If i should decide to have another batch done, i'll surely give some notice here
Greetings,
Chris
I was looking for enclosure and found WAG 100.
http://www.fischerelektronik.de
Hey, that's a great find! Thanks very much, i'll check where i can get one here. Shouldn't be too big of a problem, since Fischer Elektronik is a german company.
Greetings,
Chris
Can you sign me up for a set of boards when you get more?
Thanks, but i'm not sure that i will get another batch done. My main goal was to get myself another supply for my Metcal handpieces, and also to get a usable circuit out in the open. Considering what it had cost me so far i could have gone and bought a used STSS, or even two of them, but where would be the fun in that
In any case, the current supply/controller board would have to change then anyways. Right now i used parts that i had at hand. The result is that the DC/DC converter circuits there for the +5 and +12 volt rails are extremely oversized. On a redesign i would go for a 12V switcher followed by a 5 volt linear regulator. Also i made a stupid mistake on them. I connected the boost/limit trimpots to GND on one side, while it should have been open there. Plus i forgot two series resistors after them. While all that can be corrected on the actual boards, it's something that should change for the next version.
But as said, not sure if i will get another batch produced. If anyone is willing to jump in on that, be my guest. I will definitely change the circuitry/layout to reflect these changes, so that someone else can have batch done. After all it's not that expensive, it was 35 US$ per 10 boards in red at iTead, plus a bit over 30 US$ for the DHL express shipping. Oh, and plus taxes of course...
If i should decide to have another batch done, i'll surely give some notice here
Greetings,
Chris
Thanks for sharing the project! Sounds like a really challenging job so I'm sure you were really satisfied when you melted some solder for the first time
If you make the mods and release the gerbers I'll get a batch done at itead and sell the rest to any aussies interested, I think it is only fair I add $5 to the cost of each board set and send the proceeds to you. Do you have a paypal account?
Any ideas for a switch? I would like to have two connectors and a switch between them.
The schematic got multiple sheets. Is it done with eagle hobby or standard/pro license?
I could do a fixed version with eagle. Just need to go trough the thread for all changes/bugs.
Thanks for sharing the project! Sounds like a really challenging job so I'm sure you were really satisfied when you melted some solder for the first time
If you make the mods and release the gerbers I'll get a batch done at itead and sell the rest to any aussies interested, I think it is only fair I add $5 to the cost of each board set and send the proceeds to you. Do you have a paypal account?
Yes, it was indeed quite satisfying. The biggest challenge wasn't so much the circuitry, but the fact that i have almost no suitable equipment to make proper measurements. So it was a lot of trial&error here.
Would be fantastic if you had another batch of boards produced. Most of the changes/bugs i have already fixed in the schematics and layouts, since i usually fix such stuff while building/testing the prototypes. Just have to drop the 5V dc/dc converter section and put a linear one in there. Then i'll recheck everything and prepare the files to upload them here. Should be able to do that rather quickly, since it's only little stuff/changes, and as such can do it in the evening hours. Yes, i do have PayPal.
Greetings,
Chris
Any ideas for a switch? I would like to have two connectors and a switch between them.
The schematic got multiple sheets. Is it done with eagle hobby or standard/pro license?
I could do a fixed version with eagle. Just need to go trough the thread for all changes/bugs.
Basically any switch will do, as long as it has sufficient current and voltage handling capacity. Just run the coax from the board to the switch, and from there to the connectors. Make sure to have a good ground connection throughout, but you only need to switch the "hot" one, however. You could also use a suitable relay if you want. There are two pins available from the µC that otherwise end up on the ICSP header, one of them could be used to toggle the relay then (using a small signal N-FET or NPN for switching).
I use a standard license for Eagle here, and Eagle version is the old 4.16. Never came around to update it to the newer version, since it still does all i want it to do and thus have no requirement to spend money on the newest version update.
But as said to cwalex, i have most of the changes already done, so you don't really need to work on that. I'll look forward to get the updated stuff uploaded here ASAP.
Greetings,
Chris
But as said to cwalex, i have most of the changes already done, so you don't really need to work on that. I'll look forward to get the updated stuff uploaded here ASAP.
Awesome! Thanks a lot for sharing all this. I'll order them from itead (snailmail to keep cost down) and sell the pcbs I don't use at my cost + $5 (our community donation to you for your trouble). Hopefully there will be enough interest for the boards to sell them all otherwise no big deal
Always handy to have spares! If there is going to be lots of interest from ausies hopefully they will all chime in here so I know to order more than the standard 10qty.
