I neglected to post this tear down video earlier, but this is how I opened up the first old Craftsman C3/Diehard extended capacity pack (XCP) to remove the batteries from the case. This pack was complicated by being stuffed full of stick, old insulating foam that essentially glued the batteries into the case. So I resorted to cutting open the sides of the case to release it. I was planning to grab the power post and top of the case to make an adapter I could plug into the C3 battery charger, so destroying this case was not a big deal. Also, the cut-away case proved to be useful in measuring clearance inside the case for sizing a replacement battery pack. It turns out the long screws, that I thought just attached the power post to the battery holder like in the compact C3 packs, actually went clear through the battery pack and into the bottom of the case. So those need to be removed first. Then you can carefully lever the pack out of the case, being careful to not short anything on the PCB and also lifting the pack straight up to clear those tall posts. These extended capacity packs are really designed to handle the extra battery cell weight. Likely one big market for these packs is with the trades and those workers will be carrying around battery packs every day. Drained packs get tossed into a tool box and fresh pack grabbed and shoved into power tools several times a day. So they needed a really solid case design to hold up to that sort of use. The 4 corner screws attach the top and bottom of the case together, same as the compact packs. But the center screws pass through the top of the case, then through the power post sides, through the PCB and then into posts in the case bottom. When tightened, those screws clamp the PCB and power post between the bottom and top of the case very securely. And the screws thread about an inch deep into those posts, unlike the quarter inch depth in the compact packs. In all 5 dead packs I purchase, none had any major breakage in the case, all screws were intact, no cracks and only a few scuff parks on the rubber case jacket. So I would say that case mechanical design is very robust. In the next video, I'll show you all the parts that make up the XCP battery pack, once I tear this one apart. Thanks for watching! ... https://www.youtube.com/watch?v=BwIBvFBxGI8

I was finally successful at trying to get serial data out of this air flow meter. I couldn't find any information on-line about how to get serial data out of this meter. General Tools, who sells an similar meter does sell a serial cable + data logging software package for about $100. That seemed a little steep for me seeing as I just want to see how it works. So I did some on-line research and found some links to similar hand-held meters with the 3.5 mm audio jack serial ports. I also found an old PDF file I must downloaded back when I purchased the meter that had some information about the serial port settings. I'll see if I can upload the file to my web server if folks are interested in seeing that. Then I set up my USB microscope and took a look around the connector. I could follow a trace or two over to a small surface mount transistor but that was about it. Looking at the on-line examples I found, none that exactly matched my setup, I surmised that the output needed the DTR line from the Data Terminal (or PC) for a high voltage reference, the GND line for a low voltage reference. Then the RxD line to the PC was connected to the output line from the meter with a pull down resistor to ground. Only problem is there appeared to be a 3 pole jack and all the on-line sources I found showed 2-pole jacks. So I set up a breadboard with a 5 volts on the high side and a resistor+LED on the low side and then soldered 3 wires to the audio cable and systematically went through trying all the combinations of the 3 wires until I found one that flashed the LED. It seems the meter has an output transistor that is running all the time, sending out data pulses ever 3 seconds or so. But that output connection is just floating, until an audio plug is inserted. The plug provides the high voltage (DTR) to one side of the transistor and another connection of the plug takes the other side of the transistor back out. Essentially you just have an output of the transistor connecting between the DTR line and then a pull down resistor to ground. When the transistor is turned on, it pulls the output high, when it is turned off, the output is pulled low. Quite a simple circuit and aside from setting the baud rate (2400 or 1200), there is no other configuration or handshaking needed. So, I plugged that into a DB-9 connector and over to my USB-serial adapter at the PC and fired up PuTTY and viola, strings of temperature/speed information. It also seems to reflect the units settings on the device. I'll need to check out the unit indicators for the other settings. So the next steps on this are to first clean up the connector wiring and get that all into a DB-9 shell so it is easy to plug into my PC or laptop when needed. Then, I would like to try to adapt it ... https://www.youtube.com/watch?v=fUKtoNidIhA