• DIY female to female jumper wires for when the cheapie ones crap out in terms of providing power

    03/18/2021 at 15:33 0 comments

    Like many, I often buy the Shenzhen special when it comes to jumper wires.  They often do good enough when it comes to signaling, but when using them to deliver power to anything requiring more than a minute amount of power you start to have problems.  The two problems with them is the wire diameter tends to be extremely small and connector resistance. 

    On account of being too cheap to buy more expensive ones, I decided to try my hand at making my own.

    Materials needed:

    24 AWG speaker wire

    single pin press-fit female pin headers (can of course use press-fit male pin headers for male ends)

    heat shrink tubing

    of course normal soldering equipment/supplies

    I specifically chose press-fit pin headers as they have "needle eyes" on them vs. just a straight section of metal.  The "needle eye" allows one to "thread" the speaker wire and thus keeps it nicely held in place so one doesn't have to hold the wire in place for soldering.  The the on-label purpose of the "needle eyes" are to compress when pushed in a plated thru-hole and expand on the other-side, holding the pin headers in-place.

    After soldering it in place:

    And with some heat-shrink tubing:

    I did experiment with putting an additional piece of heat-shrink tubing over part of the pin-header housing and wire to make it more robust, but as I expected it the additional thickness causes issues when being plugged in side-by-side:

    The pin headers that I got were more rectangular than square.  That could cause problems when plugging in to double-row headers.  Going to look around and see if I can find some completely square ones.

    Based on some very crude testing, there does seem to be an improvement over the cheapie dupont connectors.

  • 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.