I believe I've settled on a design for this. The schematic is shown here in pdf format: http://www.obddiag.net/prog/pickit2.pdf This uses all through-hole parts and resuces the original PicKit2 complexity be eliminating the EEPROMs used for the ToGo programming (which I don't need). I had planned to do this on breadboard, but I've decided instead to make it more permanent. I want to take a retro approach on this so I'll be building it on perf board using wire wrap for the connections.
Does anyone have any suggested modification to this setup?
The controller will help the reflow process. As for the stencil, I'll be manually dispensing dabs of solder paste for a while. I have considered etched aluminum pop cans. As you can see, I like the DIY on the cheap method. :) It always makes me laugh a little when I look at old tech, what it took, and what it cost to do just 20-30 years ago, only to do it in my kitchen for not much more cost than a cheese burger. I love it. :D
Awesome, thanks! I wasn't sure if it made sense in 'projects' or 'tools of the trade' since it's both... more a project to built the tool I suppose. :)
I recently built a BPv4 from parts and need to flash the bootloader. Unfortunately I only have a JDM2 currently. I do have a handful of PICs laying around, such at PIC18F4550 (code compatible with the PIC18F2550). Can anyone recommend a simple circuit I could build on a breadboard using common parts. I really only need it to last long enough to flash the BPv4 so simple is best here and I'd prefer to avoid having to order any odd parts. As noted, I do have a JDM2, so I can flash code to the PIC18F4550 as needed. Does anyone have a suggestion on a simple design for this? I'm not necessarily stuck on the PikKit design and would be happy with any ICSP that is simple and has readily available software that can flash a PIC24FJ256GB106.
When I received the Big Box of Parts USA a few months ago I found an unpolulated Bus Pirate v4.0c board. I've been wanting a BP for some time and enjoy building whatever I can, so I grabbed this board and set off ordering parts. I was able to source all parts through Mouser (almost, explained later). I've been wanting to try my hand at reflow using a toaster oven as well, so why not pull two projects into one. The parts arrived, but to my dismay I realized the CD4066 chip I ordered was SO-14 (as noted on the wiki parts list) instead of TSSOP14, as this board required. Also, the shrouded header I received was not quite what I had expected so I tossed it in the parts bin and decided to use a normal unshrouded header instead. Everything else was as expected. I taped each of the part strips onto a printout of the parts list for easy identification while populating the board.
The next hurdle was going to be solder paste. I didn't want to spend money on a "custom" stencil for this one-off, and I didn't want to make a project out of making a stencil, either laser cut or etched. I decided to hand dispense solder paste on the cheap, so I ordered a tub of Mechanic paste from ebay. I also acquired a 5ml syringe and blunt tip. I knew with some of the smaller pads this would be tough. I carefully began placing the beads of paste on the pads. I had several spots where the paste bridged onto adjacent pads, but I hoped it would sort itself out during reflow. For the PIC and USB connections, I used a thin strip of paste instead of trying to keep to the individual pads. Due to the fact that I used a plunger-style syringe, the dabs of solder paste were inconsistent in size from one pad to another, some getting what appeared to be too much, others too little. Once complete, parts were hand placed using tweezers, and tapped or pressed gently into the paste to hold them down and hopefully avoid tombstoning.
The next hurdle was the reflow itself. I've been wanting to build a toaster reflow controller for some time now but wasn't sure how well it would do the job. For this project I decided to use a K-Type thermocuple digital thermometer to monitor temp in the oven, a stopwatch for timing, and my hand for on/off control of the oven to maintain the reflow profile. A few times the temp began coasting past my desired temp, so I cracked open the oven door a bit to bleed off a few degrees. This was not that hard to control, even manually. Once the temps got into the 210-220*C range parts started popping into place. I let it climb to 230*C at the peak and held it for about 20 seconds while watching to make sure the larger pads like the USB grounds reflowed, then I turned the oven off and let it cool to 180*C, then opened the door until about 150*C, and finally pulled the board out for final cooldown and inspection.
Everything reflowed very nicely considering the crude process I had followed. I had no tombstones, deformed connectors, or part-to-part solder bridging, but there were a few issues. Several of my pads had too much paste. This was hard to judge before reflow as the paste loses some mass when the flux cooks off but I wasn't sure how much. I wicked a bit of the excess solder from them using copper braid and a 25-watt pencil iron. A few other pads were connected, but had "too little" solder on them. The PIC had only a few bridges which were easy to wick away. The biggest issue though was with the PIC orientation. One side was perfect, the two adjacent sides were very good, but the last side was shifted about a pin's width out of line. The connections were held in place between the pads instead of being on the pads. As I don't have a hot air tool (now justified and added to my list), this would be an issue. I decided to pop the board back into the oven and redo the process. I also added a bit more paste to a few pads that seemed lacking. When the board hit a sweet spot around 230*C I popped the door open and tapped the PIC in hopes of shifting it into place. This was harder than expected and took several tries. Once satisfied, I ramped back to 230 and followed the proper cooldown to ensure no cold joints. The chip still wasn't aligned quite right, but had moved enough to eliminate the shorts.
At this point, the reflow work was done, so I hand soldered the headers in place, then connected the USB cable to see if it'd light up. It did! This was a good sign after all the board had gone through up to this point. Now, I still need to await the CD4066 IC, which I'll hand solder into place. I also need to get a boot loader onto the PIC. Unfortunately I only have a JDM2, so I'll be building a PicKit2 clone to flash the bootloader.
All in all, this project was a success! The process worked well enough to repeat and the reflow toaster puts an end to my fears of QFN and BGA chips. It looks like I'll be moving forward on the reflow controller project now that I've seen the results of an off the shelf kitchen toaster. I'll also have a BPv4 to add to my toolbox along side my OLS. Pretty sweet for a free PCB!
I can certainly see value in temp control... we're not cavemen. Still, a solder pot is for melting solder. The cheap units do this. I was talking to a friend about these and he suggested saving the money and just using a muffin tin on the stove. Based on the teardown, it's only a few steps past this due to portability. I've decided for now to postpone the purchase. I have a thought that I could build a controller for one of these that includes a K-Type thermocouple to get a nice controlled unit, using the cheap pot for the hardware of the build. Unfortunately, I've given myself way too many projects so this one will likely have to wait until the need becomes more pressing.
Nice! I have a pickup on the way from China for exactly this project. It appears to be the same used here. The valve is a good idea and will likely save me some time and trouble once mine arrives. Thanks for sharing this.
Scary stuff! Thanks for the link. This makes me want to tear into a few of my pieces of gear. I usually take things apart over their life, but usually only once dead, or if modding... seldom when new and working as expected. I may change that habit to 'always before plugging in', at least for those 'I can't believe it's that cheap' buys.
Thanks Ian. I think this new tools forum will be very helpful.
bearmos: Thanks for the explanation. I guess the numbers have spoken, no go on the 220 version. I'll think things over for the 110 version. I had an idea for a DIY pot I might try out also.
Any idea if there are any differences in the 110 unit aside from the plug? I appreciate your honest assesment of the product. I'll certainly keep this in mind. As they say, you get what you pay for. :) Still, for such a low cost, I'm sure I could get a few uses out of it.
I've been looking for a solder pot on ebay and found a few very cheap. The catch is that the cheap ones are all listed as 220 and have the China/Australia plug style. Is anyone familiar enough with these to know if I could do a simple cord/plug swap to US style cord for use on 110? Any issues I might encounter? Insufficient voltage causing low/half temp, control circuit damage, something else? I'm hopeful it would work on 110 without modification. What do you think?
[quote author="rwinscot"]Any rules against custom PCBs? I have a whole bunch of stuff I'd like to throw in the pot for consideration: peristatic motors, missle gyros, various solar bits, etc. I'm new to the forum - but I'd love to participate.[/quote] Missle gyros? Happen to have a picture of one of yours? If nobody wants them in the box, I'd take one off your hands. ;)
Just a heads up to those who are watching/waiting, I messaged Sal_The_Tiller last Saturday to make sure the box arrived ok. He confirmed that it did and said he'll be posting soon.
