HP (@banjohat)It's been a while since I got the soldering pen to work.
Now I'm back with more good news. I've printed the first casing for the electronics! Yes it might not be much but it's there! Looking more pen-ish than ever.
What do you think?
I haven't added buttons yet - they will go in the two hoels farthest from the tip.
The hole closes to the tip is for a small light-pipe so the LED can shine through the casing. I was thinking some white PLA in 3mm would suffice.
I'm still working on buttons. I'm not convinced that my initial idea will work so adding the buttons as small pieces of plastic might be the solution.
Here the pen is heating. The red LED is really bright!!
Next step is to convert all parts to 0603 so I maybe can have it produced locally. Also I will be extending the PCB beyond the 50mm limit I was currently working on, making room for a barrel jack connector for the 12V.
I should make a gif.. the green is pulsing, indicating that working temperature has been reached.
The biggest problem is now that the mini-jack connector is only rated for 1A and the tip is requiring 2A.. The connector gets warm.. I don't think I will have any luck finding a high-current low-profil mini-jack connector..
Any thoughts?
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Good news - I've just contacted a local company for a quote for production.. Let's hope for the best :)
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Thats a great solution, with higher voltages the tip will probably heat up faster as well, so even less time spent with high amps running. Being able to run it on a powerbank or stash of LiPo cells (put a few in series and off you go!) would be awesome. What form factors are you considering for the power input?
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I was looking for a co-planar barrel-jack connector but I couldn't find anything small enough :( Instead I'm thinking of just leaving it to the end-user although it's not the prettiest solution. To make it easy I will just add a piece of wire and some stress relief.
Any suggestions?
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Well, I'd guess a pair of wires would be fine indeed, maybe a bit of wire, which will be needed anyway, with a female barrel connector?
For me just a pair of wires would be fine as well, I use these things a lot to experiment: https://www.sparkfun.com/products/10288
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I've considered that. I have a 12V outlet with banana connectors on my desk so I have just the connectors in the end of the wire and then I can connect the pen when I need it. I'm thinking that the barrel connector is a bit big and heavy?
Nice solution with the adapter!
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Yes, a barrel connector is a bit bulky indeed, though it depends on the cable length whether it gets in your way or not. Have you considered micro-USB? They should be able to handle currents up to 2A as well and are quite a bit smaller.
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hmm, I can see what you mean but I really(!) don't like the idea of making a 24V power supply (that could be sold along the pen) with a micro USB connector. I feel that would get me in big trouble ;)
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Well, USB Power Delivery allows 20 V, but I'm not sure the additional hardware to negotiate that would be a good idea either.
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Definitely true that a 24V to USB adapter cable wouldn't be fool-proof (enough). Let's say it's a suggestion for a line of thought ;-).
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About the mini jack getting warm; is there a way to determine whether it is mainly the current causing this, or the conducted heat from the tip?
On the other side, the 2A current is probably running only for short periods (i.e. during warm up), keeping the tip at the set temperature should require a lot less current, and there is always a safety margin.
Not quite surprising there are no 3.5mm connectors suited for >1A, when using this with headphones your ears will probably get hurt... ;-)
Another thing, is the pen able to run on 19/20VDC as well? Would be ideal as most laptop adapters run at 16/19V --> there's always one around these days.
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The solution is (of course) to use 24V, so the wattage matches the rated amperage. It will work fine with 12V I just can't warrant that. I've changed the LDO so it can handle up to 36V, which will lower the current in the connector. It should even work with 5V so it would work with USB power banks.
Also I've decided to discard the barrel-jack because I can't find any that mathes the size constraints.
This leaves just the 0402 -> 0603 update, which I'm doing right now and a firmware update.
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