• A review of my experience with Digitspace

    12/18/2019 at 14:14 0 comments

    A few weeks ago, I was approached by a representative from Digitspace hat offered to provide some tools in return for mentioning them in a project.  I haven't done business with them as a normal customer.   While they didn't ask for a review, I thought I would provide one.

    I got my package in about a week after the order was shipped via DHL.  It was well packed as a styrofoam "box" was made within the box and everything was placed with ESD bags (even if some of the items didn't need an ESD bag.)  The name-brand official Raspberry Pi 4 usb-C power supply appears to be genuine.  

    Ordering a microSD card from a non-established retailer worried me a bit as fake SD cards are a thing. The Sandisk microSD card that I received appears to be the real deal at least on first impressions. The packaging is designed for the Asian market with little English, but enough to know the important bits.  

    The person that I spoke with could actually speak English proficiently which is a major plus as it can be next to impossible to resolve something when the rep speaks "Chinglish" (been there, done that.)  The website layout is need and clean.  Some items at the time of this writing do lack some needed descriptions but the rep I spoke with says they plan to fix this.  Overall prices weren't bad.  In summary, I would consider ordering from them as a normal customer.  

  • Fixing an old RC boat

    09/24/2019 at 22:01 0 comments

    Today I planned to mount an SQ12 camera on an old RC boat to make for some interesting footage.  I pulled out the old boat, put in the batteries for both the boat itself and the controller, turned it on . . .

    . . . and you guessed it nothing!  I had an almost identical extra boat and controller (the only difference was the frequency it operated on.) I put in batteries, got nothing.   I checked to make sure the batteries were good and they were.  

    I this point I feared the worse case scenario, the PCBs on both boats were ruined by the water.  Seeing that I was unable to turn them on, I decided to take them apart!  Sadly I had to damage the stickers to get to the screws to take the top off, but there was no other way.  I did have one screw well snap on me due to the fact the screws were torqued down so hard. Inside I found a a few styrofoam pieces and an internal box that likely housed the PCB and motors.

     I pressed on and opened the inner box.  Sure enough, it contained the PCB and motors.  I couldn't find any obvious signs of damage to the PCB.  Interesting to note is that some sort of grease was used to actually mitigate any water ingress, didn't expect to see any effort given as it was a cheapo product.  It would have been better if it used a greased o-ring but can you expect.  The grease was a bit cracked in areas, so I would need to fix that later before I closed everything back up.

    Seeing as everything looked fine in the PCB and motor box, I started thinking. Could it really something stupid simple as the power switch not working? I decided to short out the power switch leads.  It came to life!  I didn't open the other one and see if its power switch also failed (will likely do that in the future) but it's likely what happened to it as well.

    Upon reflection, the failure isn't too surprising.  The boat sits very low in the water and of course the points where the propeller shafts enter the boat means that water gets in the boat very easily, hence the sealed PCB and motor box and the styrofoam pieces.  The instructions mention every so often pulling the boat out of the water and holding it vertically with the bow pointed up to let the water drain out.  Just slightly above where the drain is located is the power switch, hence an easy point of failure.  

    My fix was to simply bypass the switch and solder the leads together.  I tried some contact cleaner on the switch, but that failed to work.

    Now came the resealing of the inner PCB and motor box.  The old cracked grease wasn't going to do.  I thought of what I could use that I had on hand and came up with petroleum jelly.  There are likely better options out there but as it's non-conductive and it was what I had on hand, it's what I used.  I used q tips to apply it (after removing the much of the old grease that could be easily removed.)

    After that I closed everything up. and made sure it still worked.  I then forgot about the styrofoam pieces and had to open it back up to put them back in.

    Anyways here's some footage I took. As light as the camera is, it weighed down the boat too much and had to put it at an odd angle to reduce the chances of the boat tipping over.

  • Attempting to get a PBX phone to power up without a PBX

    09/12/2019 at 15:21 0 comments

    Backstory: A relative's workplace has recently upgraded their phone system and I got handed an old Panasonic KX-T7636 desk phone that was going to be thrown out.

    The desk phone has a POTS jack in addition to the PBX line jack.  It didn't come with a wall wort so my suspicion was that it was powered from the PBX line.  I tried connecting it up to a phone jack and as I suspected, nothing.  

    I then decided to tear it down, find the voltage rail(s) and figure out what voltage(s) were needed,  and rig up something to feed  the voltage(s) into those rail(s).  After I cracked it open I studied the PCB carefully for hints.  I found something marked 3.3V on the silkscreen. I probed around a bit with my multimeter and it appeared to be the main and only voltage rail (with the exception of the circuitry for interfacing the PBX and POTS lines.) I also looked up the part numbers of the chips, and the one that I found a datasheet for, showed that it used 3.3V for the supply.

    I found an unpopulated SMD capacitor footprint that was connected to the rail and decided to use that as the point to feed the rail.  I macgyvered a power supply using an Ebay adjustable buck converter powered by a 13.8V linear power supply (can you tell that I need a proper bench power supply?) I soldered some speaker wire to the capacitor footprint leads.  Powered everything up. Still no external signs of life.  

    At this point I wondered if the phone was trying to communicate with a PBX before it would show anything externally.  Lacking an oscilloscope, I put my multimeter in AC mode and probed the PBX jack. I did get some AC voltages, so my guess appears to be right. The phone isn't going to play nice, until it can connect to the PBX.  I probed around a bit more I found that the lines that fed into the bridge rectifier that feeds the internal power supply only came from the PBX jack.

    At this point things have hit a wall. I could try to get more info on the PBX signaling and try to fudge it with a microcontroller, but perhaps that's going down quite a rabbit hole.  I'm not a phone system expert by any stretch of the imagination, just someone that was a bit curious.  Would love to hear from phone nerds if they happen to know anyway to hack it to make it operate as a normal POTS phone, but I imagine it would likely take more effort than it's worth.