• Had a bit of fun converting a DC locomotive to DCC

    01/20/2021 at 21:34 0 comments

    I decided to take on the small project of converting a cheap HO scale DC locomotive to DCC.  I chose a locomotive that used discrete wires vs a split frame loco (the frame halves being used to carry current) with springs and clips as having to do things such as isolating the motor from the frame on a split frame would have been a pain. Anyways for a decoder I chose a DN136D.

    Here's the loco I chose to do the conversion:

    Inside of the loco (with the decoder to be installed sitting on top):

    I then disconnected one of the leads on a light and checked that the current didn't exceed the 80mA max without a series resistor as specified in the decoder manual:

    Now it was time to start desoldering leads from the loco PCB and wire up the decoder leads.  Since the PCB was single sided without any plated thu-holes a manual solder sucker would work fine (solder wick would also work), and that is what I chose as although I do have a Hakko FR-301, I didn't want to have to clean it out afterwords. What needed to be desoldered from the PCB were the light leads, and the motor leads. The leads going to the wheels for electrical pickup would remain soldered to the PCB (some were actually in the same holes as the leads for the lights so actually they got desoldered and then resoldered.) Now it was time to create a rats nest of connections.  The manual for the decoder was thankfully clear on what to connect what to what, but I did have to reverse the motor leads. I used some heatshrink tubing along with some hot glue.

    I later spotted a pickup lead broken off.  I soldered that back down.  It wasn't my best work, but I wanted to minimize melting the nearby plastic.

    I then tidied things up using some Kapton tape (I did this after testing it on the track.)

    This was where things were going to end, but thanks to me  dropping it on the floor, the front light broke off.  I didn't have any incandescent replacement bulbs on hand and was too cheap to pay around $10 USD for a replacement, so I grabbed and LED and put a 2K ohm resistor in series (I wanted to under drive the LED and I measured around 12 volts from the bulb leads open circuit.)  I bodged that in and held it to the frame with copious amounts of hot glue.

    It worked fine.  I later learned that the decoder provides constant current to the lights and also by default limits current to ~30mA for use with LEDs, so I didn't actually to wire in a series resistor. It didn't come out half bad.

    With the shell back on.

    It looks quite nice.  Perhaps in the future I'll replace the other bulb with an LED, so they match.  

    Overall, things went well. The decoder ended up costing more than the locomotive itself, so I would love to find a viable open-source decoder design and make my own so I can convert a few more locomotives without spending a wad of cash in the process.

    Almost forgot to share an image of the DCC controller I made, I'll have to do a project page on that sometime.

  • Finally found out the root cause of problems transferring large files(1GB+) with Samba shares

    06/15/2020 at 14:04 0 comments

    I've been using flash drives on my Raspberry Pi's for Samba shares. Whenever I tried to copy large files to a share from a Windows machine it would hang for a bit and eventually fail.  I tried reformatting a flash drive to exfat (vs fat32.) Still the same issue.  Interesting enough, this issue doesn't occur with Linux clients. I eventually found this thread. It mentioned the underlying issue being using exfat/fat32, and to try using ext4. So I did. It worked! Everything now transfers fine, big or small.

  • Detergent 8, does it really work?

    06/12/2020 at 17:27 0 comments

    Someone mentioned on Hackaday a while back of using Detergent 8 to remove flux from PCBs.  I looked the product up and found the product page here. There was a link to order a sample so I did. A little time later an 8 oz. sample bottle arrived.

    I first tried a 3% solution on a PCB I had lying around, the before picture was a bit blurry so I didn't post the before and after of that. It got most of the flux off but there was still some stubborn traces of flux left. 

    I decided to try it again, this time making a ~6% solution (instructions specify a 3-5% solution for manual soaking.) I measured it out in a graduated cylinder. 

    The test subject was a PCB I soldered together in the morning (I didn't solder in the crystal as I didn't want it to be submerged.)

    I poured the solution in a bowl, heated it in the microwave for about 20 seconds and then placed the PCB in the bowl.

    I let it soak for about half an hour and then removed the board.  Just about all of the flux was removed!  I didn't even have to scrub the board.  I'm impressed!

    The good news: it beats having to use isopropyl alcohol and having to brush the crap out of the board with a toothbrush. The bad news: It's not cheap. A one gallon bottle costs over $100 USD.  Fortunately, the 8 oz. sample bottle will last me quite a while.

    Some tips to make things easier. Use a dropper the get the concentrate out of the bottle and put it in a dropper bottle. Don't try pouring directly out of the bottle like I did as some likes to run down the side of the bottle.