Happy new year everybody!
I know it’s been a while and wow! what a year so far! On a personal side it looks like we’re going to move sometime soon. We have put the house for sale and a looking at buying a farm instead. A farm you ask? Yes, Wouldn’t it be great to have space for a proper workshop and maybe even a pick and place machine??
Last time I wrote was to let you know that I now had 5 pens in the wild for beta-testing. So far I have only gained little more knowledge about the workings of the pen – the beta testers might not be the most active solderers (is that even a word?) in the world.
This has put me a bit back. I knew what I had to do but I kept pushing it in front of me. I needed to assemble some new boards so I could carry on the firmware development. I know I have to implement a PID regulator instead of the P-regulator I have now. that brings me to the code right away. I will give out the code for the current version when the next is ready. I know it sounds a bit harsh but IF this soldering pen is really good I don’t want it copied right from the beginning. Also that will give users some code that works but not as good as it could be.. uhm.. let me know if that is just plain stupid.
Okay, time for news. I struggled with the pen only working at 12V.
Above is a picture of the top layer where the SOIC is a huge P-FET and the single pin is the gate that connects to a pull-up resistor. It is also connected to a smaller N-FET (SOT-23 casing) that controls the bigger P-FET. the error might not be physical BUT it is there nonetheless. The N-FET was only graded for a Vds of 20V. Usually, semiconductor technology has the bad habit of failing to short. can you see what is happening then? N-Fet fails to short means that the P-FET is fully ON allowing the tip to heat without control which means a ruined tip. Those are EXPENSIVE! I was bummed out when I burned out the 4th one.
I will of course make some dummy-load next time so I don’t waste anymore tips but this means that it could still work at maybe 24V. I will definitely try this out when I get some new N-FETs.
Next I have been looking into some nice cable for the pen. The current is what I could find in my drawer. I have found some really nice looking cable but I haven’t tried it yet. It is also expensive :/
Lastly I will give away some information. Here’s the current schematic for all your nerdy needs! Drop me a line if you have comments or thoughts about this